Time course of recovery following resistance training leading or not to failure

Qualified fitness trainers practice scientifically based judgement in prescribing exercise programs

Fitness trainers are widely in demand by both commercial fitness centres and individual people. They serve members in one-to-one personal training (PT) or group training (GX) in commercial fitness centres. However, the services provided by fitness trainers have not been consistent across the industry. This service inconsistency has led to an increased doubt about professionalism in conducting safe and correct exercise for the public. No studies have evaluated how fitness trainers make decisions when they curate exercise programs for members. This research utilized a qualitative semi-structured interview method to collect data from 16 fitness trainers in Greater Kuala Lumpur, Malaysia. Inverview data was verbatim transcribed and analyzed using a theory-driven analysis. The study investigated fitness training professional decision-making processes when they design and precribe fitness execise programming to clients. Using Cognitive Continuum Theory (CCT) as a lens to explore the decision-making processes revealed a dichotomy of decision-making processes for curating personal training and group training. Feedback mechanism in the implementation of personal training was proven to be more personalized than group training. There are four themes in decision-making processed discovered to be impreative characteristics for fitness trainers. The application of CCT allowed further understanding of the implementation of exercise programs for PT and GX training when fitness trainers modified exercise programs.

Exploring the Dose-Response Relationship Between Estimated Resistance Training Proximity to Failure, Strength Gain, and Muscle Hypertrophy: A Series of Meta-Regressions

BACKGROUND

The proximity to failure in which sets are terminated has gained attention in the scientific literature as a potentially key resistance training variable. Multiple meta-analyses have directly (i.e., failure versus not to failure) or indirectly (e.g., velocity loss, alternative set structures) evaluated the effect of proximity to failure on strength and muscle hypertrophy outcomes categorically; however, the dose-response effects of proximity to failure have not been analyzed collectively in a continuous manner.

OBJECTIVE

To meta-analyze the aforementioned areas of relevant research, proximity to failure was quantified as the number of repetitions in reserve (RIR). Importantly, the RIR associated with each effect in the analysis was estimated on the basis of the available descriptions of the training interventions in each study. Data were extracted and a series of exploratory multilevel meta-regressions were performed for outcomes related to both strength and muscle hypertrophy. A range of sensitivity analyses were also performed. All models were adjusted for the effects of load, method of volume equating, duration of intervention, and training status.

RESULTS

The best fit models for both strength and muscle hypertrophy outcomes demonstrated modest quality of overall fit. In all of the best-fit models for strength, the confidence intervals of the marginal slopes for estimated RIR contained a null point estimate, indicating a negligible relationship with strength gains. However, in all of the best-fit models for muscle hypertrophy, the marginal slopes for estimated RIR were negative and their confidence intervals did not contain a null point estimate, indicating that changes in muscle size increased as sets were terminated closer to failure.

CONCLUSIONS

The dose-response relationship between proximity to failure and strength gain appears to differ from the relationship with muscle hypertrophy, with only the latter being meaningfully influenced by RIR. Strength gains were similar across a wide range of RIR, while muscle hypertrophy improves as sets are terminated closer to failure. Considering the RIR estimation procedures used, however, the exact relationship between RIR and muscle hypertrophy and strength remains unclear. Researchers and practitioners should be aware that optimal proximity to failure may differ between strength and muscle hypertrophy outcomes, but caution is warranted when interpreting the present analysis due to its exploratory nature. Future studies deliberately designed to explore the continuous nature of the dose-response effects of proximity to failure in large samples should be considered.

No Effect of Breakfast Consumption Observed for Afternoon Resistance Training Performance in Habitual Breakfast Consumers and Nonconsumers: A Randomized Crossover Trial

BACKGROUND

Pre-exercise meal frequency is commonly believed to impact exercise performance, but little is known about its impact on resistance training.

OBJECTIVE

This study investigated the impact of breakfast consumption on afternoon resistance training performance in habitual breakfast consumers and nonconsumers.

DESIGN

A randomized, crossover study was conducted in Lubbock, TX between November 2021 and May 2022.

PARTICIPANTS

Thirty-nine resistance-trained male (n = 20) and female (n = 19) adults (mean ± SD age 23.0 ± 4.7 years) who habitually consumed (≥5 d/wk; n = 19) or did not consume (≥5 d/wk; n = 20) breakfast completed the study.

INTERVENTION

After the establishment of 1-repetition maximums at the first visit, participants completed 2 additional visits, each of which included 4 sets of barbell back squat, bench press, and deadlift, using 80% of their 1-repetition maximum after either consuming breakfast and lunch or the same food at lunch only.

MAIN OUTCOME MEASURES

Repetitions, along with average and peak average concentric velocity and power, were measured for all repetitions throughout each exercise session. Visual analog scales were used to assess feelings of fatigue, energy, focus, hunger, desire to eat, and fullness throughout each exercise session.

STATISTICAL ANALYSES PERFORMED

Data were analyzed using linear mixed-effects models.

RESULTS

No interactions or main effects involving condition or habitual breakfast consumption were observed for resistance training outcomes, although sex differences were noted. Male participants performed significantly fewer repetitions on sets 2, 3, and 4 (P < .014) for total repetitions, on sets 2 and 4 for barbell back squat (P < .023), and set 4 for deadlift (P = .006), with no observed differences between sexes for bench press repetitions. Male participants displayed reductions in average power across all sets and exercises except deadlift.

CONCLUSIONS

These data suggest that alterations in pre-exercise meal frequency may not influence afternoon resistance training performance provided similar total nutritional intake is consumed.

Fatigue and Performance Rates as Decision-Making Criteria in Pacing Control During CrossFit®

We investigated fatigue and performance rates as decision-making criteria in pacing control during CrossFit®. Thirteen male regional-level competitors completed conditions of all-out (maximum physical work from beginning to end) and controlled-split (controlled physical work in the first two rounds but maximum work in the third round) pacing throughout the Fight Gone Bad workout separated by one week. We assessed benchmarks, countermovement jumps and ratings of fatigue after each round. Benchmarks were lower in round 1 (99 vs. 114, p < .001) but higher in rounds 2 (98 vs. 80, p < .001) and 3 (97 vs. 80, p < .001) for controlled-split compared with all-out pacing. Reductions in countermovement jumps were higher after rounds 1 (-12.6% vs. 1.6%, p < .001) and 2 (-12.7% vs. -4.0%, p = .014) but similar after round 3 (-13.2% vs. -11.3%, p = .571) for all-out compared with controlled-split pacing. Ratings of fatigue were higher after rounds 1 (7 vs. 5 a.u., p < .001) and 2 (8 vs. 7 a.u, p = .023) but similar after round 3 (9 vs. 9 a.u., p = .737) for all-out compared with controlled-split pacing. During all-out pacing, countermovement jump reductions after round 2 correlated with benchmark drops across rounds 1 and 2 (r = .78, p = .002) and rounds 1 and 3 (r = -.77, p = .002) and with benchmark workout changes between pacing strategies (r = -.58, p = .036), suggesting that the larger the countermovement jump reductions the higher the benchmark drops across rounds and workouts. Therefore, benchmarks, countermovement jumps and ratings of fatigue may assess exercise-induced fatigue as decision-making criteria to improve pacing strategy during workouts performed for as many repetitions as possible.

Combined Accentuated Eccentric Loading and Rest Redistribution in High-Volume Back Squat: Acute Stimulus and Fatigue

ABSTRACT

Chae, S, Long, SA, Lis, RP, McDowell, KW, Wagle, JP, Carroll, KM, Mizuguchi, S, and Stone, MH. Combined accentuated eccentric loading and rest redistribution in high-volume back squat: Acute stimulus and fatigue. J Strength Cond Res 38(4): 648-655, 2024-The purpose of this study was to examine acute stimulus and fatigue responses to combined accentuated eccentric loading and rest redistribution (AEL + RR). Resistance-trained men ( n = 12, 25.6 ± 4.4 years, 1.77 ± 0.06 m, and 81.7 ± 11.4 kg) completed a back squat (BS) 1 repetition maximum (1RM) and weight releaser familiarization session. Three BS exercise conditions (sets × repetitions × eccentric-concentric loading) consisted of (a) 3 × (5 × 2) × 110/60% (AEL + RR 5), (b) 3 × (2 × 5) × 110/60% (AEL + RR 2), and (c) 3 × 10 × 60/60% 1RM (traditional sets [TS]). Weight releasers (50% 1RM) were attached to every first repetition of each cluster set (every first, third, fifth, seventh, and ninth repetition in AEL + RR 5 and every first and sixth repetition in AEL + RR 2). The AEL + RR 5 resulted in greater total volume load (sets × repetitions × eccentric + concentric loading) (6,630 ± 1,210 kg) when compared with AEL + RR 2 (5,944 ± 1,085 kg) and TS (5,487 ± 1,002 kg). In addition, AEL + RR 5 led to significantly ( p < 0.05) greater rating of perceived exertion (RPE) after set 2 and set 3 and lower blood lactate (BL) after set 3 and 5, 15, and 25 minutes postexercise than AEL + RR 2 and TS. There was a main effect of condition for BL between AEL + RR 5 (5.11 ± 2.90 mmol·L -1 ), AEL + RR 2 (6.23 ± 3.22 mmol·L -1 ), and TS (6.15 ± 3.17 mmol·L -1 ). In summary, AEL + RR 5 results in unique stimulus and fatigue responses. Although it may increase perceived exertion, coaches could use AEL + RR 5 to achieve greater back squat total volume load while reducing BL accumulation.

Accuracy of Intraset Repetitions-in-Reserve Predictions During the Bench Press Exercise in Resistance-Trained Male and Female Subjects

ABSTRACT

Refalo, MC, Remmert, JF, Pelland, JC, Robinson, ZP, Zourdos, MC, Hamilton, DL, Fyfe, JJ, and Helms, ER. Accuracy of intraset repetitions-in-reserve predictions during the bench press exercise in resistance-trained male and female subjects. J Strength Cond Res 38(3): e78-e85, 2024-This study assessed the accuracy of intraset repetitions-in-reserve (RIR) predictions to provide evidence for the efficacy of RIR prescription as a set termination method to inform proximity to failure during resistance training (RT). Twenty-four resistance trained male ( n = 12) and female ( n = 12) subjects completed 2 experimental sessions involving 2 sets performed to momentary muscular failure (barbell bench press exercise) with 75% of 1 repetition maximum (1RM), whereby subjects verbally indicated when they perceived to had reached either 1 RIR or 3 RIR. The difference between the predicted RIR and the actual RIR was defined as the "RIR accuracy" and was quantified as both raw (i.e., direction of error) and absolute (i.e., magnitude of error) values. High raw and absolute mean RIR accuracy (-0.17 ± 1.00 and 0.65 ± 0.78 repetitions, respectively) for 1-RIR and 3-RIR predictions were observed (including all sets and sessions completed). We identified statistical equivalence (equivalence range of ±1 repetition, thus no level of statistical significance was set) in raw and absolute RIR accuracy between (a) 1-RIR and 3-RIR predictions, (b) set 1 and set 2, and (c) session 1 and session 2. No evidence of a relationship was found between RIR accuracy and biological sex, years of RT experience, or relative bench press strength. Overall, resistance-trained individuals are capable of high absolute RIR accuracy when predicting 1 and 3 RIR on the barbell bench press exercise, with a minor tendency for underprediction. Thus, RIR prescriptions may be used in research and practice to inform the proximity to failure achieved upon set termination.

Hypoxia Does Not Impair Resistance Exercise Performance or Amplify Post-Exercise Fatigue

Purpose: To determine whether performing resistance exercise in hypoxia acutely reduces performance and increases markers of fatigue, and whether these responses are exaggerated if exercising at high versus low work rates (i.e., exercising to failure or volume matched non-failure). Methods: Following a within-subject design, 20 men completed two trials in hypoxia (13% oxygen) and two in normoxia (21% oxygen). The first session for hypoxic and normoxic conditions comprised six sets of bench press and shoulder press to failure (high work rate), while subsequent sessions involved the same volume distributed over 12 sets (low work rate). Physical performance (concentric velocity) and perceptual responses were measured during exercise and for 72 hr post-exercise. Neuromuscular performance (bench throw velocity) was assessed pre- and post-session. Results: Hypoxia did not affect physical performance, neuromuscular performance, and perceptual recovery when exercising at high or low work rates. Higher work rate exercise caused greater acute decrements in physical performance and post-exercise neuromuscular performance and increased perceived exertion and muscle soreness (p ≤ 0.006), irrespective of hypoxia. Conclusions: Hypoxia does not impact on resistance exercise performance or increase markers of physical and perceptual fatigue. Higher exercise work rates may impair physical performance, and exaggerate fatigue compared to low work rate exercise, irrespective of environmental condition. Practitioners can prescribe hypoxic resistance exercise without compromising physical performance or inducing greater levels of fatigue. For athletes who are required to train with high frequency, decreasing exercise work rate may reduce post-exercise markers of fatigue for the same training volume.

The Effects and Reproducibility of 10, 20, and 30% Velocity Loss Thresholds on Acute and Short-Term Fatigue and Recovery Responses

ABSTRACT

Weakley, J, Johnston, RD, Cowley, N, Wood, T, Ramirez-Lopez, C, McMahon, E, and García-Ramos, A. The effects and reproducibility of 10, 20, and 30% velocity loss thresholds on acute and short-term fatigue and recovery responses. J Strength Cond Res 38(3): 465-473, 2024-This study aimed to establish the effects and reproducibility of implementing 10, 20, and 30% velocity loss thresholds (VLTs) during the free-weight barbell back squat on acute and short-term perceived soreness, neuromuscular fatigue, and physical performance. Using a repeated, counterbalanced, crossover design, 12 team-sport athletes completed on separate sessions 5 sets of the free-weight barbell back-squat until reaching VLTs of either 10, 20, or 30%. Outcomes were measured immediately postexercise and 24 hours after each session. To assess reproducibility, the same sessions were repeated after 4 weeks. Immediately postexercise, small differences in countermovement jump (CMJ) and 10-m sprint performance were observed between VLT conditions, whereas small to moderate differences in differential ratings of perceived exertion were reported (10% < 20% < 30%). At 24 hours, trivial differences in CMJ outcomes were found but small differences in 10-m sprint performance were detected between conditions (10% < 20% < 30%). In addition, at 24 hours, a single small difference in radial deformation using tensiomyography was found between 10 and 30% conditions, whereas large to very large differences in perceived soreness were reported between conditions (10% < 20% < 30%). Finally, the standard error of measurement of all outcome measures at 24 hours were of a similar magnitude to those reported in tightly controlled, short-term studies. Collectively, these findings demonstrate that VLTs help control the fatigue outcomes that occur as a response to resistance training and that they are reproducible. Therefore, for practitioners who wish to prescribe resistance training and be confident in the subsequent fatigue response, it is strongly advised that VLTs are implemented.

The Importance of Recovery in Resistance Training Microcycle Construction

Systemic resistance training aims to enhance performance by balancing stress, fatigue and recovery. While fatigue is expected, insufficient recovery may temporarily impair performance. The aim of this review was to examine evidence regarding manipulation of resistance training variables on subsequent effects on recovery and performance. PubMed, Medline, SPORTDiscus, Scopus and CINAHL were searched. Only studies that investigated recovery between resistance training sessions were selected, with a total of 24 articles included for review. Training to failure may lengthen recovery times, potentially impairing performance; however, it may be suitable if implemented strategically ensuring adequate recovery between sessions of similar exercises or muscle groups. Higher volumes may increase recovery demands, especially when paired with training to failure, however, with wide variation in individual responses, it is suggested to start with lower volume, monitor recovery, and gradually increase training volume if appropriate. Exercises emphasising the lower body, multi-joint movements, greater muscle recruitment, eccentric contractions, and/or the lengthened position may require longer recovery times. Adjusting volume and frequency of these exercises can affect recovery demands depending on the goals and training logistics. Daily undulating programming may maximise performance on priority sessions while maintaining purposeful and productive easy days. For example, active recovery in the form of training opposing muscle groups, light aerobic cardio, or low-volume power-type training may improve recovery and potentially elicit a post activation potentiation priming effect compared to passive recovery. However, it is possible that training cessation may be adequate for allowing sufficient recovery prior to sessions of importance.

Time Course of Recovery From Different Velocity Loss Thresholds and Set Configurations During Full-Squat Training

ABSTRACT

Cornejo-Daza, PJ, Villalba-Fernández, A, González-Badillo, JJ, and Pareja-Blanco, F. Time course of recovery from different velocity loss thresholds and set configurations during full-squat training. J Strength Cond Res 38(2): 221-227, 2024-The aims of the research were to examine the effects of (a) velocity loss (VL) thresholds and (b) set configuration, traditional or cluster, on time-course recovery. A randomized cross-over research design was conducted, in which 15 resistance-trained men performed 4 protocols consisting of 3 sets of 70% 1RM in full squat (SQ), differing in the VL incurred during the set assessed with a linear velocity transducer: (a) 20% (70-20), (b) 30% (70-30), (c) 40% (70-40), and in the set configuration (d) 20% of VL using a cluster methodology (70-CLU). Movement velocity against the load that elicited a 1 m·s -1 velocity at baseline measurements (V1-load) in SQ, countermovement jump (CMJ) height, and sprint time in 20 m (T20) were assessed at baseline (Pre) and postintervention (Post, 6 hour-Post, 24 hour-Post, and 48 hour-Post). The 70-20 protocol resulted in fewer total repetitions than the other protocols ( p = 0.001), whereas 70-CLU, 70-30, and 70-40 completed similar total repetitions. The 70-30 protocol significantly worsened T20 at 6 hours-Post, CMJ at 48 hours-Post, and V1-load at 6 hours-Post ( p < 0.05). The 70-40 protocol significantly impaired T20 at 6 hours-Post, and CMJ and V1-load at 24 hours-Post ( p < 0.05). No significant performance reductions were observed for 70-20 and 70-CLU at 6 hours-Post, 24 hours-Post, and 48 hours-Post. Protocols with higher VL resulted in more pronounced fatigue and a slower rate of recovery. Cluster sets (70-CLU) resulted in higher volume than protocols with a similar level of fatigue (70-20) and a quicker recovery than protocols with a similar volume (70-30 and 70-40).

The Connection Between Resistance Training, Climbing Performance, and Injury Prevention

BACKGROUND

Climbing is an intricate sport composed of various disciplines, holds, styles, distances between holds, and levels of difficulty. In highly skilled climbers the potential for further strength-specific adaptations to increase performance may be marginal in elite climbers. With an eye on the upcoming 2024 Paris Olympics, more climbers are trying to maximize performance and improve training strategies. The relationships between muscular strength and climbing performance, as well as the role of strength in injury prevention, remain to be fully elucidated. This narrative review seeks to discuss the current literature regarding the effect of resistance training in improving maximal strength, muscle hypertrophy, muscular power, and local muscular endurance on climbing performance, and as a strategy to prevent injuries.

MAIN BODY

Since sport climbing requires exerting forces against gravity to maintain grip and move the body along the route, it is generally accepted that a climber`s absolute and relative muscular strength are important for climbing performance. Performance characteristics of forearm flexor muscles (hang-time on ledge, force output, rate of force development, and oxidative capacity) discriminate between climbing performance level, climbing styles, and between climbers and non-climbers. Strength of the hand and wrist flexors, shoulders and upper limbs has gained much attention in the scientific literature, and it has been suggested that both general and specific strength training should be part of a climber`s training program. Furthermore, the ability to generate sub-maximal force in different work-rest ratios has proved useful, in examining finger flexor endurance capacity while trying to mimic real-world climbing demands. Importantly, fingers and shoulders are the most frequent injury locations in climbing. Due to the high mechanical stress and load on the finger flexors, fingerboard and campus board training should be limited in lower-graded climbers. Coaches should address, acknowledge, and screen for amenorrhea and disordered eating in climbers.

CONCLUSION

Structured low-volume high-resistance training, twice per week hanging from small ledges or a fingerboard, is a feasible approach for climbers. The current injury prevention training aims to increase the level of performance through building tolerance to performance-relevant load exposure and promoting this approach in the climbing field.

The velocity of resistance exercise does not accurately assess repetitions-in-reserve

This study assessed the reliability of mean concentric bar velocity from 3- to 0-repetitions in reserve (RIR) across four sets in different exercises (bench press and prone row) and with different loads (60 and 80% 1-repetition maximum; 1RM). Whether velocity values from set one could be used to predict RIR in subsequent sets was also examined. Twenty recreationally active males performed baseline 1RM testing before two randomised sessions of four sets to failure with 60 or 80% 1RM. A linear position transducer measured mean concentric velocity of repetitions, and the velocity associated with each RIR value up to 0-RIR. For both exercises, velocity decreased between each repetition from 3- to 0-RIR (p ≤ 0.010). Mean concentric velocity of RIR values was not reliable across sets in the bench press (mean intraclass correlation coefficient [ICC] = 0.40, mean coefficient of variation [CV] = 21.3%), despite no significant between-set differences (p = 0.530). Better reliability was noted in the prone row (mean ICC = 0.80, mean CV = 6.1%), but velocity declined by 0.019-0.027 m·s-1 (p = 0.032) between sets. Mean concentric velocity was 0.050-0.058 m·s-1 faster in both exercises with 60% than 80% 1RM with (p < 0.001). At the individual level, the velocity of specific RIR values from set one accurately predicted RIR from 5- to 0-RIR for 30.9% of repetitions in subsequent sets. These findings suggest that velocity of specific RIR values vary across exercises, loads and sets. As velocity-based RIR estimates were not accurate for 69.1% of repetitions, alternative methods to should be considered for autoregulating of resistance exercise in recreationally active individuals.

Time to consider the potential role of alternative resistance training methods in cancer management?

Exercise has emerged as fundamental therapeutic medicine in the management of cancer. Exercise improves health-related outcomes, including quality of life, neuromuscular strength, physical function, and body composition, and it is associated with a lower risk of disease recurrence and increased survival. Moreover, exercise during or post cancer treatments is safe, can ameliorate treatment-related side effects, and may enhance the effectiveness of chemotherapy and radiation therapy. To date, traditional resistance training (RT) is the most used RT modality in exercise oncology. However, alternative training modes, such as eccentric, cluster set, and blood flow restriction are gaining increased attention. These training modalities have been extensively investigated in both athletic and clinical populations (e.g., age-related frailty, cardiovascular disease, type 2 diabetes), showing considerable benefits in terms of neuromuscular strength, hypertrophy, body composition, and physical function. However, these training modes have only been partially or not at all investigated in cancer populations. Thus, this study outlines the benefits of these alternative RT methods in patients with cancer. Where evidence in cancer populations is sparse, we provide a robust rationale for the possible implementation of certain RT methods that have shown positive results in other clinical populations. Finally, we provide clinical insights for research that may guide future RT investigations in patients with cancer and suggest clear practical applications for targeted cancer populations and related benefits.

Interference Effects of Different Resistance-Training Protocols on Rowing Ergometer Performance: A Study on Semiprofessional Rowers

PURPOSE

To evaluate the interference effects of various resistance-training (RT) protocols on rowing ergometer performance.

METHODS

Fourteen semiprofessional male rowers randomly completed 5 protocols in separate sessions: (1) control-no RT session was performed, (2) upper-body high-fatigue-4 sets to failure during the bench pull exercise, (3) upper-body low-fatigue-4 sets of 6 repetitions during the bench pull exercise, (4) lower-body high-fatigue-4 sets to failure during the leg-press exercise, and (5) lower-body low-fatigue-4 sets of 6 repetitions during the leg-press exercise. All sets were performed against the 12-repetition-maximum load with 2 minutes of interset rest. Following the completion of the protocols, subjects performed an all-out 1000-m rowing ergometer test.

RESULTS

Compared with the control condition, rowing ergometer performance was not significantly affected after the low-fatigue RT protocols (upper body: P ≥ .487; Δ = 0.0%-0.2%; lower body: P ≥ .200; Δ = -0.2%-0.5%), while it significantly declined following high-fatigue RT protocols (upper body: P ≤ .001; Δ = 1.0%-2.0%; lower body: P ≤ .002; Δ = 2.1%-2.5%). The average heart rate was significantly lower for the control condition compared with all RT protocols (P ≤ .043; Δ = 1.0%-1.5%).

CONCLUSIONS

To minimize interference on rowing performance, coaches should prioritize the level of effort in RT protocols over specific exercises, specifically avoiding high-fatigue protocols that lead to failure before rowing practice.

Changes in Intraset Repetitions in Reserve Prediction Accuracy During Six Weeks of Bench Press Training in Trained Men

In this study we investigated whether the accuracy of intraset repetitions in reserve (RIR) predictions changes over time. Nine trained men completed three bench press training sessions per week for 6 weeks (following a 1-week familiarization). The final set of each session was performed until momentary muscular failure, with participants verbally indicating their perceived 4RIR and 1RIR. RIR prediction errors were calculated as raw differences (RIRDIFF), with positive and negative values indicating directionality, and absolute RIRDIFF (absolute value of raw RIRDIFF) indicating error scores. We constructed mixed effect models with time (i.e., session) and proximity to failure as fixed effects, repetitions as a covariate, and random intercepts per participant to account for repeated measures, with statistical significance set at p ≤ .05. We observed a significant main effect for time on raw RIRDIFF (p < .001), with an estimated marginal slope of -.077 repetitions, indicating a slight decrease in raw RIRDIFF over time. Further, the estimated marginal slope of repetitions was -.404 repetitions, indicating a decrease in raw RIRDIFF as more repetitions were performed. There were no significant effects on absolute RIRDIFF. Thus, RIR rating accuracy did not significantly improve over time, though there was a greater tendency to underestimate RIR in later sessions and during higher repetition sets.

Time Course of Jump Recovery and Performance After Velocity-Based Priming and Concurrent Caffeine Intake

Purpose: Morning priming exercise and caffeine intake have been previously suggested as an effective strategy to increase within-day performance and readiness. However, the concurrent effect of both strategies is unknown. The present research aimed to map the within-day time course of recovery and performance of countermovement jump (CMJ) outcomes, kinetics, and strategy and readiness after priming alone and in combination with caffeine. Methods: Eleven participants performed a control, a priming exercise (Priming) and a priming with concurrent caffeine intake (PrimingCaf) in a double-blind randomized, crossover design. CMJ metrics were assessed before, post, and 2 h, 4 h, and 6 h after each condition while readiness was assessed at 6 h. Results: Perceived physical, mental performance capability and activation balance were higher at 6 h after Priming and PrimingCaf conditions. Immediate reductions in jump height (5.45 to 6.25%; p < .046), concentric peak velocity (2.40 to 2.59%; p < .041) and reactive strength index-modified (RSImod) (9.06 to 9.23% p < .051) after Priming and PrimingCaf were observed, being recovered at 2 h (p > .99). Concentric impulse was restored in PrimingCaf (p > .754; d = -0.03 to-0.08) despite lower concentric mean force/BM (p < .662; d = -0.18 to -0.26) as concentric duration was increased (p > .513; d = 0.15 to 0.21). Individual analysis revealed that some participants benefit from both strategies as they showed increases in jump height over the smallest worthwhile change while others did not. Conclusions: Psychological readiness was increased after both priming conditions at 6 h; however, it seems necessary to consider individual changes to achieve the positive effects of the priming or the priming in combination with caffeine on jumping outcomes.

Maximizing Strength: The Stimuli and Mediators of Strength Gains and Their Application to Training and Rehabilitation

ABSTRACT

Spiering, BA, Clark, BC, Schoenfeld, BJ, Foulis, SA, and Pasiakos, SM. Maximizing strength: the stimuli and mediators of strength gains and their application to training and rehabilitation. J Strength Cond Res 37(4): 919-929, 2023-Traditional heavy resistance exercise (RE) training increases maximal strength, a valuable adaptation in many situations. That stated, some populations seek new opportunities for pushing the upper limits of strength gains (e.g., athletes and military personnel). Alternatively, other populations strive to increase or maintain strength but cannot perform heavy RE (e.g., during at-home exercise, during deployment, or after injury or illness). Therefore, the purpose of this narrative review is to (a) identify the known stimuli that trigger gains in strength; (b) identify the known factors that mediate the long-term effectiveness of these stimuli; (c) discuss (and in some cases, speculate on) potential opportunities for maximizing strength gains beyond current limits; and (d) discuss practical applications for increasing or maintaining strength when traditional heavy RE cannot be performed. First, by conceptually deconstructing traditional heavy RE, we identify that strength gains are stimulated through a sequence of events, namely: giving maximal mental effort, leading to maximal neural activation of muscle to produce forceful contractions, involving lifting and lowering movements, training through a full range of motion, and (potentially) inducing muscular metabolic stress. Second, we identify factors that mediate the long-term effectiveness of these RE stimuli, namely: optimizing the dose of RE within a session, beginning each set of RE in a minimally fatigued state, optimizing recovery between training sessions, and (potentially) periodizing the training stimulus over time. Equipped with these insights, we identify potential opportunities for further maximizing strength gains. Finally, we identify opportunities for increasing or maintaining strength when traditional heavy RE cannot be performed.

Predicting Total Back Squat Repetitions from Repetition Velocity and Velocity Loss

The purpose of this investigation was to determine if average concentric velocity (ACV) of a single repetition at 70% of one-repetition maximum (1RM), ACV of the first repetition of a set to failure at 70% of 1RM, or the velocity loss during the set could predict the number of repetitions performed in the back squat. Fifty-six resistance-trained individuals participated in the study (male = 41, age = 23 ± 3 yrs, 1RM = 162.0 ± 40.0 kg; female = 15, age = 21 ± 2 yrs, 1RM = 81.5 ± 12.5 kg). After 1RM testing, participants performed single repetition sets with 70% of 1RM and a set to failure with 70% of 1RM. ACV was recorded on all repetitions. Regression model comparisons were performed, and Akaike Information Criteria (AIC) and Standard Error of the Estimate (SEE) were calculated to determine the best model. Neither single repetition ACV at 70% of 1RM (R2 = 0.004, p = 0.637) nor velocity loss (R2 = 0.011, p = 0.445) were predictive of total repetitions performed in the set to failure. The simple quadratic model using the first repetition of the set to failure (Y = β 0 + β 1 X A C V F i r s t + β 2 Z + ε ) was identified as the best and most parsimonious model (R2 = 0.259, F = 9.247, p < 0.001) due to the lowest AIC value (311.086). A SEE of 2.21 repetitions was identified with this model. This average error of ~2 repetitions warrants only cautious utilization of this method to predict total repetitions an individual can perform in a set, with additional autoregulatory or individualization strategies being necessary to finalize the training prescription.

Repeatability of Brain Activity as Measured by a 32-Channel EEG System during Resistance Exercise in Healthy Young Adults

Electroencephalography (EEG) is attracting increasing attention in the sports and exercise fields, as it provides insights into brain behavior during specific tasks. However, it remains unclear if the promising wireless EEG caps provide reliable results despite the artifacts associated with head movement. The present study aims to evaluate the repeatability of brain activity as measured by a wireless 32-channel EEG system (EMOTIV flex cap) during resistance exercises in 18 apparently healthy but physically inactive young adults (10 men and 8 women). Moderate-intensity leg press exercises are performed with two evaluations with 48 h. between. This intensity allows enough time for data analysis while reducing unnecessary but involuntary head movements. Repeated measurements of EEG during the resistance exercise show high repeatability in all frequency bands, with excellent ICCs (>0.90) and bias close to zero, regardless of sex. These results suggest that a 32-channel wireless EEG system can be used to collect data on controlled resistance exercise tasks performed at moderate intensities. Future studies should replicate these results with a bigger sample size and different resistance exercises and intensities.

Effects of Resistance Priming Exercise on Within-day Jumping Performance and its Relationship with Strength Level

This study aimed to identify the effects of same-day resistance priming exercise on countermovement jump parameters and subjective readiness, and to identify whether baseline strength level influenced these outcomes. Fourteen participants performed two separate conditions (Priming [2 sets high-load parallel squats with a 20% velocity loss cut-off] and Control) in a randomized, counterbalanced crossover design. Countermovement jump was assessed at pre, post and 6 h while readiness was assessed at pre and at 6 h only. All countermovement jump force-time metrics were similar between conditions (p>0.05), but different individual responses were noted 6 h after priming. Jump height was increased for 4/14, decreased for another 4/14, and maintained for 6/14 participants at 6 h. Higher perceived physical performance capability (p<0.001) and activation balance (p=0.005) were observed after priming only. Positive relationships were observed between strength and the percentage change in jump height (r=0.47-0.50; p=0.033-0.042), concentric peak velocity (r=0.48-0.51; p=0.030-0.041) and impulse (r=0.47; p=0.030-0.045) at post and 6 h after priming exercise. These findings suggest that velocity-based high-load low-volume priming exercise has potential to positively impact jump performance and subjective readiness later that day in certain individuals. Participant absolute strength level may influence this response but should be confirmed in subsequent studies.

Acute Mechanical and Metabolic Responses to Different Resistance Training Protocols With Equated Volume Load

PURPOSE

To investigate the effect of different resistance training protocols with equated volume load on acute mechanical and metabolic responses.

METHODS

In a randomized order, 18 men performed 8 different training protocols in the bench press exercise consisting of (sets, repetitions, intensity, and interset recoveries) 3 × 16, 40% 1-repetition maximum (1RM), 2 and 5 minutes; 6 × 8, 40% 1RM, 2 and 5 minutes; 3 × 8, 80% 1RM, 2 and 5 minutes; and 6 × 4, 80% 1RM, 2 and 5 minutes. Volume load was equalized between protocols (1920 arbitrary units). Velocity loss and effort index were calculated during the session. Movement velocity against the 60% 1RM and blood lactate concentration pre-post exercise were used to assess the mechanical and metabolic responses, respectively.

RESULTS

Resistance training protocols performed with heavy load (80% 1RM) resulted in a lower (P < .05) total number of repetitions (effect size = -2.44) and volume load (effect size = -1.79) than the scheduled ones when longer set configurations and shorter rest periods were used in the same protocol (ie, higher-training-density protocols). Protocols including a higher number of repetitions per set and shorter rest times induced higher velocity loss, effort index, and lactate concentrations than the rest of the protocols.

CONCLUSIONS

Our results suggest that resistance training protocols with similar volume load but different training variables (ie, intensity, number of sets and repetitions, rest between sets) produce different responses. Implementing a lower number of repetitions per set and longer rest intervals is recommended to reduce the intrasession and postsession fatigue.

Acute Effects of Heavy Strength Training on Mechanical, Hemodynamic, Metabolic, and Psychophysiological Parameters in Young Adult Males

This study analyzed the acute effects of heavy strength training on mechanical, hemodynamic, metabolic, and psychophysiological responses in adult males. Thirteen recreational level males (23.3 ± 1.5 years) randomly performed two heavy strength training sessions (3 sets of 8 repetitions at 80% of one repetition maximum [1RM]) using the bench press (HST-BP) or full squat (HST-FS)). The repetition velocity was recorded in both sessions. Moreover, before and after the sessions, the velocity attained against the ~1.00 m·s−1 load (V1Load) in the HST-BP, countermovement jump (CMJ) height in the HST-FS, blood pressure, heart rate, blood lactate, and psychophysiological responses (OMNI Perceived Exertion Scale for Resistance Exercise) were measured. There were differences between exercises in the number of repetitions performed in the first and third sets (both <8 repetitions). The velocity loss was higher in the HST-BP than in the HST-FS (50.8 ± 10.0% vs. 30.7 ± 9.5%; p < 0.001). However, the mechanical fatigue (V1Load vs. CMJ height) and the psychophysiological response did not differ between sessions (p > 0.05). The HST-FS caused higher blood pressure and heart rate responses than the HST-BP (p < 0.001 and p = 0.02, respectively) and greater blood lactate changes from pre-training to post-set 1 (p < 0.05). These results showed that the number of maximal repetitions performed in both sessions was lower than the target number and decreased across sets. Moreover, the HST-BP caused a higher velocity loss than the HST-FS. Finally, the HST-FS elicited higher hemodynamic and metabolic demand than the HST-BP.

Effect of High-Volume Cluster Sets vs. Lower-Volume Traditional Sets on Accuracy of Estimated Repetitions to Failure

ABSTRACT

Davies, TB, Li, J, and Hackett, DA. Effect of high-volume cluster sets vs. lower-volume traditional sets on accuracy of estimated repetitions to failure. J Strength Cond Res XX(X): 000-000, 2022-This study investigated the effects of resistance training using cluster (CLUS) vs. traditional (TRAD) set structures on the accuracy of estimated repetitions to failure (ERF). Nineteen healthy male resistance trainers (age 21.0 ± 4.4 years) were randomized into 1 of the 2 bench press training routines performed for 6 weeks. Cluster (n = 10) performed 6 sets of 5 repetitions at 85% of 1 repetition maximum (1RM) with 30-second interrepetition rest and 3 minutes of interset rest. Traditional (n = 9) performed 3 sets of 5 repetitions at 85% 1RM with 5 minutes of interset rest. Maximum repetitions at 85% 1RM was performed before and after intervention to assess error in ERF and mean concentric velocity (MCV). The ERF, rating of perceived exertion, and maintenance of MCV were assessed throughout the intervention. Rating of perceived exertion was lower for sets 1-3 in CLUS compared with TRAD from weeks 1 to 4 (effect size [ES] = 0.8-2.4, p ≤ 0.04). The ERF was greater for sets 1-3 in CLUS than in TRAD during all intervention weeks (ES = 1.0-5.1, p ≤ 0.04). Maintenance of MCV was greater in CLUS compared with TRAD for all sets at week 1 (ES = 0.76, p = 0.002) and sets 4-6 at week 6 (ES = 0.77, p = 0.006). After the intervention, error in ERF did not change, and no differences were found between the groups. Findings indicate that accuracy of ERF does not improve after resistance training using set structures that induce different transient fatigue-related effects when using high loads in experienced resistance trainers.

Training Specificity for Athletes: Emphasis on Strength-Power Training: A Narrative Review

Specificity has two major components: A strength-endurance continuum (S-EC) and adherence to principles of Dynamic Correspondence. Available evidence indicates the existence of the S-EC continuum from two aspects. Indeed, the S-EC exists, particularly if work is equated as a high load low repetition scheme at one end (strength stimulus) and high volume (HIEE stimulus) at the other. Furthermore, some evidence also indicates that the continuum as a repetition paradigm with high-load, low repetition at one end (strength stimulus) and a high repetition, low load at the other end. The second paradigm is most apparent under three conditions: (1) ecological validity-in the real world, work is not equated, (2) use of absolute loads in testing and (3) a substantial difference in the repetitions used in training (for example 2-5 repetitions versus ≥10 repetitions). Additionally, adherence to the principles and criteria of dynamic correspondence allows for greater "transfer of training" to performance measures. Typically, and logically, in order to optimize transfer, training athletes requires a reasonable development of capacities (i.e., structure, metabolism, neural aspects, etc.) before more specific training takes place.

Repetitions in Reserve Is a Reliable Tool for Prescribing Resistance Training Load

ABSTRACT

Lovegrove, S, Hughes, L, Mansfield, S, Read, P, Price, P, and Patterson, SD. Repetitions in reserve is a reliable tool for prescribing resistance training load. J Strength Cond Res 36(10): 2696-2700, 2022-This study investigated the reliability of repetitions in reserve (RIR) as a method for prescribing resistance training load for the deadlift and bench press exercises. Fifteen novice trained men (age: 17.3 ± 0.9 years, height: 176.0 ± 8.8 cm, body mass: 71.3 ± 10.7 kg) were assessed for 1 repetition maximum (1RM) for deadlift (118.1 ± 27.3 kg) and bench press (58.2 ± 18.6 kg). Subsequently, they completed 3 identical sessions (one familiarization session and 2 testing sessions) comprising sets of 3, 5, and 8 repetitions. For each repetition scheme, the load was progressively increased in successive sets until subjects felt they reached 1-RIR at the end of the set. Test-retest reliability of load prescription between the 2 testing sessions was determined using intraclass correlation coefficient (ICC) and coefficient of variation (CV). A 2-way analysis of variance with repeated measures was used for each exercise to assess differences in the load corresponding to 1-RIR within each repetition scheme. All test-retest comparisons demonstrated a high level of reliability (deadlift: ICC = 0.95-0.99, CV = 2.7-5.7% and bench press: ICC = 0.97-0.99, CV = 3.8-6.2%). Although there were no differences between time points, there was a difference for load corresponding to 1-RIR across the 3 repetition schemes (deadlift: 88.2, 84.3, and 79.2% 1RM; bench press: 93.0, 87.3, and 79.6% 1RM for the 3-, 5-, and 8-repetition sets, respectively). These results suggest that RIR is a reliable tool for load prescription in a young novice population. Furthermore, the between-repetition scheme differences highlight that practitioners can effectively manipulate load and volume (repetitions in a set) throughout a training program to target specific resistance training adaptations.

Neuromuscular Fatigue and Metabolic Stress during the 15 Minutes of Rest after Carrying Out a Bench Press Exercise Protocol

Background: Velocity loss (VL) at 1 m·s−1 can help to determine neuromuscular fatigue after performing an exercise protocol. The aim of this study was to analyse muscle fatigue and metabolic stress during the 15 min that follow the execution of a bench press (BP) exercise protocol. Methods: Forty-four healthy male students of sports science performed two exercise sessions separated by one week of rest. In the first week, the participants carried out a test with progressive loads in the (BP) exercise until reaching the one-repetition maximum (1RM) in order to obtain the load−velocity relationship of each participant. In the second week, each participant conducted three BP exercise sets at an intensity of 70% of 1RM, determining this load through the mean propulsive velocity (MPV) obtained from the individual load−velocity relationship, with the participants performing the maximum number of repetitions (MNR) to muscle failure. Two minutes of rest were allocated between sets. MPV at 1 m·s−1 and blood lactate concentrations were recorded before executing the exercise and at minute 0, 5, 10 and 15 after performing the exercise protocol. Results: A two-factor repeated measures ANOVA was performed. MPV at 1 m·s−1 in minute 0 post-exercise was −33.3% (p < 0.05), whereas in minute 10 and 15 post-exercise, it was ≈−9% (p > 0.05). Regarding the blood lactate levels, significant differences were observed in all measurements before and after the exercise protocol (p < 0.001), obtaining ≈7 mmol·L−1 at minute 10 post-exercise and 4.3 mmol·L−1 after 15 min of recovery. Conclusions: MPV with medium or moderate loads shows a certain recovery from minute 10 of rest. However, the blood lactate levels are still high (>5 mmol·L−1). Therefore, although there seem to be certain conditions to reach a similar maximum MPV peak, the residual fatigue at the neuromuscular level and the non-recovery of metabolic homeostasis would hinder the reproduction of these protocols, both at the level of applied stimulus and from a methodological perspective, since a long recovery time would be required between sets and exercises.

Toward a New Paradigm in Resistance Training by Means of Velocity Monitoring: A Critical and Challenging Narrative

For more than a century, many concepts and several theories and principles pertaining to the goals, organization, methodology and evaluation of the effects of resistance training (RT) have been developed and discussed between coaches and scientists. This cumulative body of knowledge and practices has contributed substantially to the evolution of RT methodology. However, a detailed and rigorous examination of the existing literature reveals many inconsistencies that, unless resolved, could seriously hinder further progress in our field. The purpose of this review is to constructively expose, analyze and discuss a set of anomalies present in the current RT methodology, including: (a) the often inappropriate and misleading terminology used, (b) the need to clarify the aims of RT, (c) the very concept of maximal strength, (d) the control and monitoring of the resistance exercise dose, (e) the existing programming models and (f) the evaluation of training effects. A thorough and unbiased examination of these deficiencies could well lead to the adoption of a revised paradigm for RT. This new paradigm must guarantee a precise knowledge of the loads being applied, the effort they involve and their effects. To the best of our knowledge, currently this can only be achieved by monitoring repetition velocity during training. The main contribution of a velocity-based RT approach is that it provides the necessary information to know the actual training loads that induce a specific effect in each athlete. The correct adoption of this revised paradigm will provide coaches and strength and conditioning professionals with accurate and objective information concerning the applied load (relative load, level of effort and training effect). This knowledge is essential to make rational and informed decisions and to improve the training methodology itself.

Towards an improved understanding of proximity-to-failure in resistance training and its influence on skeletal muscle hypertrophy, neuromuscular fatigue, muscle damage, and perceived discomfort: A scoping review

While proximity-to-failure is considered an important resistance training (RT) prescription variable, its influence on physiological adaptations and short-term responses to RT is uncertain. Given the ambiguity in the literature, a scoping review was undertaken to summarise evidence for the influence of proximity-to-failure on muscle hypertrophy, neuromuscular fatigue, muscle damage and perceived discomfort. Literature searching was performed according to PRISMA-ScR guidelines and identified three themes of studies comparing either: i) RT performed to momentary muscular failure versus non-failure, ii) RT performed to set failure (defined as anything other than momentary muscular failure) versus non-failure, and iii) RT performed to different velocity loss thresholds. The findings highlight that no consensus definition for "failure" exists in the literature, and the proximity-to-failure achieved in "non-failure" conditions is often ambiguous and variable across studies. This poses challenges when deriving practical recommendations for manipulating proximity-to-failure in RT to achieve desired outcomes. Based on the limited available evidence, RT to set failure is likely not superior to non-failure RT for inducing muscle hypertrophy, but may exacerbate neuromuscular fatigue, muscle damage, and post-set perceived discomfort versus non-failure RT. Together, these factors may impair post-exercise recovery and subsequent performance, and may also negatively influence long-term adherence to RT.KEY POINTS This scoping review identified three broad themes of studies investigating proximity-to-failure in RT, based on the specific definition of set failure used (and therefore the research question being examined), to improve the validity of study comparisons and interpretations.There is no consensus definition for set failure in RT, and the proximity-to-failure achieved during non-failure RT is often unclear and varies both within and between studies, which together poses challenges when interpreting study findings and deriving practical recommendations regarding the influence of RT proximity-to-failure on muscle hypertrophy and other short-term responses.Based on the limited available evidence, performing RT to set failure is likely not superior to non-failure RT to maximise muscle hypertrophy, but the optimal proximity to failure in RT for muscle hypertrophy is unclear and may be moderated by other RT variables (e.g., load, volume-load). Also, RT performed to set failure likely induces greater neuromuscular fatigue, muscle damage, and perceived discomfort than non-failure RT, which may negatively influence RT performance, post-RT recovery, and long-term adherence.

Sex Differences May Exist for Performance Fatigue but Not Recovery After Single-Joint Upper-Body and Lower-Body Resistance Exercise

ABSTRACT

Lewis, MH, Siedler, MR, Lamadrid, P, Ford, S, Smith, T, SanFilippo, G, Waddell, B, Trexler, ET, Buckner, S, and Campbell, BI. Sex differences may exist for performance fatigue but not recovery after single-joint upper-body and lower-body resistance exercise. J Strength Cond Res 36(6): 1498-1505, 2022-This study evaluated sex differences in performance recovery and fatigue during dynamic exercise. Twenty-eight resistance-trained males (n = 16) and females (n = 12) completed a repeated-measures, randomized, parallel-groups design. The protocol consisted of a baseline assessment, a recovery period (4, 24, or 48 hours), and a postrecovery assessment. The assessments were identical consisting of 4 sets of 10 repetition maximum (10RM) bicep curls and 4 sets of 10RM leg extensions to failure. Recovery was quantified as the number of total repetitions completed in the postrecovery bout. Fatigue was quantified as the number of repetitions completed set to set within the session. For analysis, we set the level of significance at p ≤ 0.05. No sex differences in performance recovery were observed across any of the investigated time periods for either exercise modality. Regarding fatigue, significant effects were observed for set (p < 0.001) and sex (p = 0.031) for bicep curls. Repetitions dropped in later sets, and females generally completed a greater number of repetitions than males (8.8 ± 0.5 vs. 7.2 ± 0.5). For leg extension, a significant sex × set interaction was observed (p = 0.003), but post hoc tests revealed these sex differences as marginal. Our results suggest that in dynamic bicep curls and leg extensions, other factors unrelated to sex may be more impactful on performance recovery. To optimize an athlete's desired adaptations, it may be more important to consider other variables unrelated to sex such as volume, perceived exertion, and training history when formulating training prescriptions for single-joint exercises.

Effects of Velocity Loss Threshold during Resistance Training on Strength and Athletic Adaptations: A Systematic Review with Meta-Analysis

This study aimed to systematically review the effects of the different velocity loss (VL) thresholds during resistance training (RT) on strength and athletic adaptations. The VL was analyzed as both a categorical and continuous variable. For the categorical analysis, individual VL thresholds were divided into Low-ModVL (≤ 25% VL) or Mod-HighVL (> 25% VL). The efficacy of these VL thresholds was examined using between-group (Low-ModVL vs. Mod-HighVL) and within-group (pre–post effects in each group) analyses. For the continuous analysis, the relationship (R2) between each individual VL threshold and its respective effect size (ES) in each outcome was examined. Ten studies (308 resistance-trained young men) were finally included. The Low-ModVL group trained using a significantly (p ≤ 0.001) lower VL (16.1 ± 6.2 vs. 39.8 ± 9.0%) and volume (212.0 ± 102.3 vs. 384.0 ± 95.0 repetitions) compared with Mod-HighVL. Between-group analyses yielded higher efficacy of Low-ModVL over Mod-HighVL to increase performance against low (ES = 0.31, p = 0.01) and moderate/high loads (ES = 0.21, p = 0.07). Within-group analyses revealed superior effects after training using Low-ModVL thresholds in all strength (Low-ModVL, ES = 0.79–2.39 vs. Mod-HighVL, ES = 0.59–1.91) and athletic (Low-ModVL, ES = 0.35–0.59 vs. Mod-HighVL, ES = 0.05–0.36) parameters. Relationship analyses showed that the adaptations produced decreased as the VL threshold increased, especially for the low loads (R2 = 0.73, p = 0.01), local endurance (R2 = 0.93, p = 0.04), and sprint ability (R2 = 0.61, p = 0.06). These findings prove that low–moderate levels of intra-set fatigue (≤25% VL) are more effective and efficient stimuli than moderate–high levels (> 25% VL) to promote strength and athletic adaptations.

Improvement of Oxidative Stress in Older Women Is Dependent on Resistance Training Volume: Active Aging Longitudinal Study

ABSTRACT

Cunha, PM, Ribeiro, AS, Padilha, C, Nunes, JP, Schoenfeld, BJ, Cyrino, LT, Tomeleri, CM, Nascimento, MA, Antunes, M, Fernandes, RR, Barbosa, DS, Venturini, D, Burini, RC, Sardinha, LB, and Cyrino, ES. Improvement of oxidative stress in older women is dependent on resistance training volume: Active aging longitudinal study. J Strength Cond Res 36(4): 1141-1146, 2022-The purpose of the present study was to investigate the effects of resistance training (RT) performed with a higher versus lower training volume on oxidative stress (OS) biomarkers in older women. Thirty-eight older women (≥60 years) were randomly assigned to 1 of 2 groups: a group that performed 1 set per exercise (low volume [LV], n = 18) or 3 sets per exercise (high volume [HV], n = 20). The whole-body RT consisted of a 12-week RT program involving 8 exercises performed with sets of 10-15 repetitions maximum, 3 days per week. Advanced oxidation protein products (AOPP), total radical-trapping antioxidant parameter (TRAP), and ferrous oxidation-xylenol orange (FOX) were used as OS biomarkers. The composite Z-score of the percentage changes from pre- to posttraining of OS biomarkers according to groups was calculated. A significant main effect of time (p < 0.05) was found for AOPP (LV = -7.3% vs. HV = -12.2%) and TRAP (LV = +1.5% vs. HV = +15.5%) concentrations, without a statistical difference between the groups (p > 0.05). A significant group vs. time interaction (p < 0.001) was revealed for FOX (LV = +6.4% vs. HV = -8.9%). The overall analysis indicated higher positive changes for HV than LV (composed Z-score: HV = 0.41 ± 1.22 vs. LV = -0.37 ± 1.03; p < 0.05). Our results suggest that a greater volume of RT seems to promote superior improvements on OS biomarkers in older women.

Methods for Controlling and Reporting Resistance Training Proximity to Failure: Current Issues and Future Directions

Resistance training variables such as volume, load, and frequency are well defined. However, the variable proximity to failure does not have a consistent quantification method, despite being defined as the number of repetitions in reserve (RIR) upon completion of a resistance training set. Further, there is between-study variability in the definition of failure itself. Studies have defined failure as momentary (inability to complete the concentric phase despite maximal effort), volitional (self-termination), or have provided no working definition. Methods to quantify proximity to failure include percentage-based prescription, repetition maximum zone training, velocity loss, and self-reported RIR; each with positives and negatives. Specifically, applying percentage-based prescriptions across a group may lead to a wide range of per-set RIR owing to interindividual differences in repetitions performed at specific percentages of 1 repetition maximum. Velocity loss is an objective method; however, the relationship between velocity loss and RIR varies set-to-set, across loading ranges, and between exercises. Self-reported RIR is inherently individualized; however, its subjectivity can lead to inaccuracy. Further, many studies, regardless of quantification method, do not report RIR. Consequently, it is difficult to make specific recommendations for per-set proximity to failure to maximize hypertrophy and strength. Therefore, this review aims to discuss the strengths and weaknesses of the current proximity to failure quantification methods. Further, we propose future directions for researchers and practitioners to quantify proximity to failure, including implementation of absolute velocity stops using individual average concentric velocity/RIR relationships. Finally, we provide guidance for reporting self-reported RIR regardless of the quantification method.

Analysis of the Use and Applicability of Different Variables for the Prescription of Relative Intensity in Bench Press Exercise

Simple Summary

The aim of this research is to analyze the different variables that influence the prescription of resistance training (one-repetition maximum (1RM) and number of maximal repetitions (xRM)) through the velocity of execution, with the aim of approaching the precise definition and control of intensity in bench press exercise. Fifty male physical education students were divided into four groups according to their relative strength ratio (RSR) and performed a 1RM bench press test, and two maximum number of repetitions (MNR) tests one week apart, using a relative load corresponding to 70% 1RM determined through the mean propulsive velocity (MPV) obtained from the individual load–velocity relationship. Regarding MPV, the best (fastest) repetition of the set values were similar between groups (0.62 m·s⁻¹–0.64 m·s⁻¹). The average MNR was 12.38 ± 2.51, with significant variation between groups with regards to MNR (CV:13–29%), and greater variability in the group corresponding to the lowest RSR values (CV: 29%). The use of variables such as the 1RM or a MNR do not allow an adequate degree of precision to prescribe and control the relative intensity of resistance training. Besides, execution velocity control can offer an adequate alternative to guarantee an accurate prescription of intensity with regard to resistance training.

Abstract

Background: The aim of the study was to analyze the use of variables such as % of one-repetition maximum (1RM) and number of maximal repetitions (xRM) with execution velocity to define and control the intensity of resistance training in bench press exercise. Hence, exercise professionals will achieve better control of training through a greater understanding of its variables. Methods: In this cross-sectional study, fifty male physical education students were divided into four groups according to their relative strength ratio (RSR) and performed a 1RM bench press test (T1). In the second test, participants performed repetitions to exhaustion (T2), using a relative load corresponding to 70% 1RM determined through the mean propulsive velocity (MPV) obtained from the individual load–velocity relationship. This same test was repeated a week later (T3). Tests were monitored according to the MPV of each repetition and blood lactate values (LACT). Results: Regarding MPV, the best (fastest) repetition of the set (MPVrep Best) values were similar between groups (0.62 m·s⁻¹–0.64 m·s⁻¹), with significant differences in relation to the high RSR group (p < 0.001). The average maximum number of repetitions (MNR) was 12.38 ± 2.51, with no significant differences between the RSR groups. Nonetheless, significant variation existed between groups with regards to MNR (CV: 13–29%), with greater variability in the group corresponding to the lowest RSR values (CV: 29%). The loss of velocity in the MNR test in the different groups was similar (p > 0.05). Average LACT values (5.72 mmol·L⁻¹) showed significant differences between the Medium RSR and Very Low RSR groups. No significant differences were found (p > 0.05) between T2 and T3 with regards to MNR, MPVrep Best, or MPVrep Last, with little variability seen between participants. Conclusions: The use of variables such as the 1RM, estimated using an absolute load value, or an MNR do not allow an adequate degree of precision to prescribe and control the relative intensity of resistance training. Besides, execution velocity control can offer an adequate alternative to guarantee an accurate prescription of intensity with regard to resistance training.

The Effect of Load and Volume Autoregulation on Muscular Strength and Hypertrophy: A Systematic Review and Meta-Analysis

Background

Autoregulation has emerged as a potentially beneficial resistance training paradigm to individualize and optimize programming; however, compared to standardized prescription, the effects of autoregulated load and volume prescription on muscular strength and hypertrophy adaptations are unclear. Our objective was to compare the effect of autoregulated load prescription (repetitions in reserve-based rating of perceived exertion and velocity-based training) to standardized load prescription (percentage-based training) on chronic one-repetition maximum (1RM) strength and cross-sectional area (CSA) hypertrophy adaptations in resistance-trained individuals. We also aimed to investigate the effect of volume autoregulation with velocity loss thresholds ≤ 25% compared to > 25% on 1RM strength and CSA hypertrophy.

Methods

This review was performed in accordance with the PRISMA guidelines. A systematic search of MEDLINE, Embase, Scopus, and SPORTDiscus was conducted. Mean differences (MD), 95% confidence intervals (CI), and standardized mean differences (SMD) were calculated. Sub-analyses were performed as applicable.

Results

Fifteen studies were included in the meta-analysis: six studies on load autoregulation and nine studies on volume autoregulation. No significant differences between autoregulated and standardized load prescription were demonstrated for 1RM strength (MD = 2.07, 95% CI – 0.32 to 4.46 kg, p = 0.09, SMD = 0.21). Velocity loss thresholds ≤ 25% demonstrated significantly greater 1RM strength (MD = 2.32, 95% CI 0.33 to 4.31 kg, p = 0.02, SMD = 0.23) and significantly lower CSA hypertrophy (MD = 0.61, 95% CI 0.05 to 1.16 cm², p = 0.03, SMD = 0.28) than velocity loss thresholds > 25%. No significant differences between velocity loss thresholds > 25% and 20–25% were demonstrated for hypertrophy (MD = 0.36, 95% CI – 0.29 to 1.00 cm², p = 0.28, SMD = 0.13); however, velocity loss thresholds > 25% demonstrated significantly greater hypertrophy compared to thresholds ≤ 20% (MD = 0.64, 95% CI 0.07 to 1.20 cm², p = 0.03, SMD = 0.34).

Conclusions

Collectively, autoregulated and standardized load prescription produced similar improvements in strength. When sets and relative intensity were equated, velocity loss thresholds ≤ 25% were superior for promoting strength possibly by minimizing acute neuromuscular fatigue while maximizing chronic neuromuscular adaptations, whereas velocity loss thresholds > 20–25% were superior for promoting hypertrophy by accumulating greater relative volume.

Protocol Registration The original protocol was prospectively registered (CRD42021240506) with the PROSPERO (International Prospective Register of Systematic Reviews).

Supplementary Information

The online version contains supplementary material available at 10.1186/s40798-021-00404-9.

The Validity of Perceived Recovery Status as a Marker of Daily Recovery Following a High-Volume Back-Squat Protocol

Although a variety of tools to monitor recovery have been developed, many are impractical for daily use due to cost, time, and challenges with interpretation. The Perceived Recovery Status (PRS) scale was recently developed as an expeditious, noninvasive tool to assess recovery status. While PRS has been strongly associated with repeated sprinting performance, a paucity of research exists relating PRS and performance recovery following resistance exercise. Purpose: The purpose of this study was to evaluate the sensitivity of PRS as a subjective marker of recovery up to 72 hours after a high-volume back-squat protocol. Methods: Eleven resistance-trained men reported to the laboratory on 5 separate occasions (1 familiarization session and 4 testing sessions). The first testing session was considered the baseline session and consisted of a nonfatiguing performance assessment (ie, countermovement jumps and back squats) and a fatiguing back-squat protocol of 8 sets of 10 at 70% 1-repetition maximum separated by 2 minutes of recovery. Participants returned 24, 48, and 72 hours following baseline to provide a PRS rating and complete the performance assessment. Results: Repeated-measures correlations revealed strong associations between PRS countermovement jump (r = .84) and mean bar velocity (r = .80) (both P < .001). Conclusions: The current findings suggest that PRS can be used as a method to effectively assess daily recovery following a fatiguing bout of resistance exercise. Practitioners are cautioned that the relationship between PRS and performance recovery is individualized, and equivalent PRS scores between individuals are not indicative of similar recovery.

Methodological Proposal for Strength and Power Training in Older Athletes: A Narrative Review

INTRODUCTION

Within the adult population, it is not uncommon to meet older athletes who challenge the negative stereotypes associated with aging. Although their physical performance is superior to their sedentary counterparts, they are not immune to impaired neuromuscular function, leading to a decreased physical capacity and an increased risk of injuries. Despite the abundant information about the benefits of strength/power training in advanced ages, there are no methodological proposals that guide physical activity professionals to program this type of training.

OBJECTIVE

This study aimed to review the factors related to the decrease in sports performance within older athletes and the benefits of a strength/power program in order to provide a methodological proposal to organize training in this population.

METHODS

This is a review article. First, databases from PubMed, Science Direct, and SPORTSDiscus and search engines, namely Google Scholar and Scielo, were reviewed, using standard keywords such as strength and power training, evaluation of physical performance, neuromuscular function, and risk of injury in the elderly athlete. All related articles published during the period 1963 to 2020 were considered. A total of 1837 documents were found. By removing 1715 unrelated documents, 122 articles were included in the study after revision control.

RESULTS

Strength/power training is key to alleviating the loss of performance in older athletes and the benefits in neuromuscular function, which helps reduce the rate of serious injuries, maintaining sports practice for a longer period of time. In order to design an appropriate program, a prior evaluation of the individual's physical-technical level must be carried out, respecting the biologicalpedagogical principles and safety regulations.

CONCLUSION

The methodological proposal delivered in this review can serve as a technical guide for physical activity professionals, which will be able to structure the strength/power training and thus preserve the sports practice in older athletes for a longer time.

Effect of the Repetitions-In-Reserve Resistance Training Strategy on Bench Press Performance, Perceived Effort, and Recovery in Trained Men

ABSTRACT

Mangine, GT, Serafini, PR, Stratton, MT, Olmos, AA, VanDusseldorp, TA, and Feito, Y. Effect of the repetitions-in-reserve resistance training strategy on bench press performance, perceived effort, and recovery in trained men. J Strength Cond Res 36(1): 1-9, 2022-This study examined the effects of the repetitions-in-reserve (RIR) strategy on resistance exercise performance, perceived effort, and recovery. Fourteen resistance-trained men (24.6 ± 3.0 years, 176 ± 5 cm, 85.7 ± 14.0 kg) completed 2 bench press protocols in a randomized crossover fashion. The protocols consisted of 4 sets at 80% of 1 repetition maximum (1RM) to a self-reported 3-RIR and a fifth set to failure or all 5 sets to failure (0-RIR). Barbell kinetics (velocity, rate of force development, and impulse), repetition volume, total work, and ratings of perceived exertion (RPE) were quantified on each set. Barbell kinetics were reassessed during one set of 3 repetitions at 80% 1RM completed at 24-hour, 48-hour, and 72-hour postexercise. Blood samples were collected before and after exercise at 6 hours, 24 hours, 48 hours, and 72 hours and analyzed for concentrations of creatine kinase (CK). Separate, 2-way repeated-measures analysis of variance revealed significant interactions (p < 0.001) where 3-RIR better maintained repetitions and work at greater average velocity (+0.6 m·s-1) and lower RPE (0-RIR = 10; 3-RIR = 8.2) across all sets. No differences were seen between conditions for CK at 6 hours postexercise (3-RIR: 32.2 ± 55.3%; 0-RIR: 40.8 ± 66.0%) or for CK and barbell kinetics at 24 hours to 72 hours postexercise. Although no differences were seen for recovery, the RIR strategy enabled work to be better sustained across sets at a lower perceived effort and higher average velocity. This strategy could be used to manage fatigue and better sustain effort and volume during a resistance training session.

Acute and delayed effects of strength training in ball velocity and accuracy in young competition tennis players

This study aimed to investigate the acute and delayed effects of medicine ball throws and resistance training in ball velocity and accuracy of serve, forehand and backhand in young competition tennis players. A crossover-randomized design was used with 10 competition tennis players (6 girls and 4 boys between 14 and 18 years old). The subjects performed 6 stroke test sessions, 3 for each strength protocol. The velocity and accuracy of strokes were measured before (basal situation), 3 minutes, 24 and 48 hours after the protocol. Medicine ball throws protocol was performed by accomplishing 3 sets of 6 repetitions using a 2 kg ball, throwing it at maximal speed. Resistance training protocol was performed by accomplishing 3 sets of 6 repetitions at 75% one-repetition maximum, lifting the load at maximal speed of bench press, dead lift, one hand row and half squat. There were no significant (p > 0.05) differences in all strokes, regarding ball velocity and accuracy after each method and each recovery time, compared to the basal situation. These results suggest that medicine ball throws and resistance training methods have no acute and delayed detrimental effects on stroke velocity and accuracy in young competition tennis players.

Effects of Resistance Training to Muscle Failure on Acute Fatigue: A Systematic Review and Meta-Analysis

BACKGROUND

Proper design of resistance training (RT) variables is a key factor to reach the maximum potential of neuromuscular adaptations. Among those variables, the use of RT performed to failure (RTF) may lead to a different magnitude of acute fatigue compared with RT not performed to failure (RTNF). The fatigue response could interfere with acute adaptive changes, in turn regulating long-term adaptations. Considering that the level of fatigue affects long-term adaptations, it is important to determine how fatigue is affected by RTF versus RTNF.

OBJECTIVE

The aim of this systematic review and meta-analysis was to compare the effects of RTF versus RTNF on acute fatigue.

METHODS

The search was conducted in January 2021 in seven databases. Only studies with a crossover design that investigated the acute biomechanical properties (vertical jump height, velocity of movement, power output, or isometric strength), metabolic response (lactate or ammonia concentration), muscle damage (creatine kinase activity), and rating of perceived exertion (RPE) were selected. The data (mean ± standard deviation and sample size) were extracted from the included studies and were either converted into the standardized mean difference (SMD) or maintained in the raw mean difference (RMD) when the studies reported the results in the same scale. Random-effects meta-analyses were performed.

RESULTS

Twenty studies were included in the systematic review and 12 were included in the meta-analysis. The main meta-analyses indicated greater decrease of biomechanical properties for RTF compared with RTNF (SMD - 0.96, 95% confidence interval [CI] - 1.43 to - 0.49, p < 0.001). Furthermore, there was a larger increase in metabolic response (RMD 4.48 mmol·L^-1, 95% CI 3.19-5.78, p < 0.001), muscle damage (SMD 0.76, 95% CI 0.31-1.21, p = 0.001), and RPE (SMD 1.93, 95% CI 0.87-3.00, p < 0.001) for RTF compared with RTNF. Further exploratory subgroup analyses showed that training status (p = 0.92), timepoint (p = 0.89), load (p = 0.10), and volume (p = 0.12) did not affect biomechanical properties; however, greater loss in the movement velocity test occurred on upper limbs compared with lower limbs (p < 0.001). Blood ammonia concentration was greater after RTF than RTNF (RMD 44.66 μmol·L^-1, 95% CI 32.27-57.05, p < 0.001), as was 48 h post-exercise blood creatine kinase activity (SMD 0.86, 95% CI 0.33-1.42, p = 0.002). Furthermore, although there was considerable heterogeneity in the overall analysis (I² = 83.72%; p < 0.01), a significant difference in RPE after RTF compared with RTNF was only found for studies that did not equalize training volumes.

CONCLUSIONS

In summary, RTF compared with RTNF led to a greater decrease in biomechanical properties and a simultaneous increase in metabolic response, higher muscle damage, and RPE. The exploratory analyses suggested a greater impairment in the velocity of movement test for the upper limbs, more pronounced muscle damage 48 h post-exercise, and a greater RPE in studies with non-equalized volume after the RTF session compared with RTNF. Therefore, it can be concluded that RTF leads to greater acute fatigue compared with RTNF. The higher acute fatigue after RTF can also have an important impact on chronic adaptive processes following RT; however, the greater acute fatigue following RTF can extend the time needed for recovery, which should be considered when RTF is used.

PROTOCOL REGISTRATION

The original protocol was prospectively registered (CRD42020192336) in the International Prospective Register of Systematic Reviews (PROSPERO).

Is there Evidence for the Suggestion that Fatigue Accumulates Following Resistance Exercise?

It has been suggested that improper post-exercise recovery or improper sequence of training may result in an 'accumulation' of fatigue. Despite this suggestion, there is a lack of clarity regarding which physiological mechanisms may be proposed to contribute to fatigue accumulation. The present paper explores the time course of the changes in various fatigue-related measures in order to understand how they may accumulate or lessen over time following an exercise bout or in the context of an exercise program. Regarding peripheral fatigue, the depletion of energy substrates and accumulation of metabolic byproducts has been demonstrated to occur following an acute bout of resistance training; however, peripheral accumulation and depletion appear unlikely candidates to accumulate over time. A number of mechanisms may contribute to the development of central fatigue, postulating the need for prolonged periods of recovery; however, a time course is difficult to determine and is dependent on which measurement is examined. In addition, it has not been demonstrated that central fatigue measures accumulate over time. A potential candidate that may be interpreted as accumulated fatigue is muscle damage, which shares similar characteristics (i.e., prolonged strength loss). Due to the delayed appearance of muscle damage, it may be interpreted as accumulated fatigue. Overall, evidence for the presence of fatigue accumulation with resistance training is equivocal, making it difficult to draw the conclusion that fatigue accumulates. Considerable work remains as to whether fatigue can accumulate over time. Future studies are warranted to elucidate potential mechanisms underlying the concept of fatigue accumulation.

Lighter-Load Exercise Produces Greater Acute- and Prolonged-Fatigue in Exercised and Non-Exercised Limbs

Purpose: The present study compared the fatigue and perceptual responses to volume-load matched heavier- and lighter- load resistance exercise to momentary failure in both a local/exercised, and non-local/non-exercised limb. Methods: Eleven resistance-trained men undertook unilateral maximal voluntary contraction (MVC) testing for knee extension prior to and immediately, 24 hr- and 48 hr- post heavier (80% MVC) and lighter  (40% MVC) load dynamic unilateral knee extension exercise. Only the dominant leg of each participant was exercised to momentary failure using heavier and lighter loads, and perceptions of discomfort were measured immediately upon exercise cessation. Results: Point estimates and confidence intervals suggested that immediately post-exercise there was greater fatigue in both the exercised and non-exercised legs for the lighter- load condition. At 24 hr the exercised leg under the heavier-load condition had recovered to pre-exercise strength; however, the exercised leg under lighter- load condition had still not fully recovered by 48 hr. For the non-exercised leg, only the lighter-load condition induced fatigue; however, recovery had occurred by 48 hr. Median discomfort ratings were statistically significantly different (Z = -2.232, p = .026) between lighter and heavier loads (10 [IQR = 0] and 8 [IQR = 3], respectively). Conclusions: This study suggests that lighter-load resistance exercise induces greater fatigue in both the exercised- and non-exercised limbs, compared to heavier-load resistance exercise. These findings may have implications for exercise frequency as it may be possible to engage in heavier-load resistance exercise more frequently than a volume-load matched protocol using lighter loads.Abbreviations CI: Confidence intervals: ES: Effect size: MVC: Maximum voluntary contraction; Nm:Newton meters; RM: Repetition maximum; SD: Standard deviation; SI: Strength index.

Periodization and Block Periodization in Sports: Emphasis on Strength-Power Training-A Provocative and Challenging Narrative

ABSTRACT

Stone, MH, Hornsby, WG, Haff, GG, Fry, AC, Suarez, DG, Liu, J, Gonzalez-Rave, JM, and Pierce, KC. Periodization and block periodization in sports: emphasis on strength-power training-a provocative and challenging narrative. J Strength Cond Res 35(8): 2351-2371, 2021-Periodization can be defined as a logical sequential, phasic method of manipulating fitness and recovery phases to increase the potential for achieving specific performance goals while minimizing the potential for nonfunctional over-reaching, overtraining, and injury. Periodization deals with the micromanagement of timelines and fitness phases and is cyclic in nature. On the other hand, programming deals with the micromanagement of the training process and deals with exercise selection, volume, intensity, etc. Evidence indicates that a periodized training process coupled with appropriate programming can produce superior athletic enhancement compared with nonperiodized process. There are 2 models of periodization, traditional and block. Traditional can take different forms (i.e., reverse). Block periodization has 2 subtypes, single goal or factor (individual sports) and multiple goals or factors (team sports). Both models have strengths and weaknesses but can be "tailored" through creative programming to produce excellent results for specific sports.

Acute Effects of Parallel Back Squat Performed in Different Set Configurations on Neuromuscular Performance

We compared the acute effects of parallel back squat performed from different resistance training configurations on neuromuscular performance. Twenty-eight young adults underwent 4 experimental conditions: inter-repetition rest, traditional, traditional to failure, and rest-pause in the parallel back squat in a randomized, counterbalanced, and cross-over design. The neuromuscular performance was assessed through peak torque of knee extensors and flexors at two angular velocities (90 and 120 º/s) in three moments (before, post, and post-30 min). The peak torque of the knee extensors and flexors at 90 and 120 º/s decreased immediately after training for traditional, traditional to failure, and rest-pause (-8.1% to -17.7%, P<0.001). A greater reduction in the extensor peak torque was found at 120 º/s (P<0.05) in the rest-pause (-17.7%) when compared to traditional (-10.8%). The peak torque returned to baseline values only at post-30 min for the traditional configuration for the knee flexion action at 120 º/s. The peak torque remained similar for the muscular actions and angular velocities for the inter-repetition rest (P>0.05). Our results suggest the inter-repetition rest configuration seems to be a more appropriate strategy for maintaining the lower limb neuromuscular performance after a resistance training session.

Effect of resistance training with blood flow restriction on muscle damage markers in adults: A systematic review

Background

The purpose of this review was to systematically analyze the evidence regarding the occurrence of muscle damage (changes in muscle damage markers) after resistance training with blood flow restriction sessions.

Materials and methods

This systematic review was conducted in accordance with the PRISMA recommendations. Two researchers independently and blindly searched the following electronic databases: PubMed, Scopus, Web of Science, CINAHL, LILACS and SPORTdicus. Randomized and non-randomized clinical trials which analyzed the effect of resistance training with blood flow restriction on muscle damage markers in humans were included. The risk of bias assessment was performed by two blinded and independent researchers using the RoB2 tool.

Results

A total of 21 studies involving 352 healthy participants (men, n = 301; women, n = 51) were eligible for this review. The samples in 66.6% of the studies (n = 14) were composed of untrained individuals. All included studies analyzed muscle damage using indirect markers. Most studies had more than one muscle damage marker and Delayed Onset Muscle Soreness was the measure most frequently used. The results for the occurrence of significant changes in muscle damage markers after low-load resistance training with blood flow restriction sessions were contrasting, and the use of a pre-defined repetition scheme versus muscle failure seems to be the determining point for this divergence, mainly in untrained individuals.

Conclusions

In summary, the use of sets until failure is seen to be determinant for the occurrence of significant changes in muscle damage markers after low-load resistance training with blood flow restriction sessions, especially in individuals not used to resistance exercise.

Trial registration

Register number: PROSPERO number: CRD42020177119.

Effect of velocity loss during squat training on neuromuscular performance

This study aimed to compare the effects of three resistance training (RT) programs differing in the magnitude of velocity loss (VL) allowed in each exercise set: 10%, 30%, or 45% on changes in strength, vertical jump, sprint performance, and EMG variables. Thirty-three young men were randomly assigned into three experimental groups (VL10%, VL30%, and VL45%; n = 11 each) that performed a velocity-based RT program for 8 weeks using only the full squat exercise (SQ). Training load (55-70% 1RM), frequency (2 sessions/week), number of sets (3), and inter-set recovery (4 min) were identical for all groups. Running sprint (20 m), countermovement jump (CMJ), 1RM, muscle endurance, and EMG during SQ were assessed pre- and post-training. All groups showed significant (VL10%: 6.4-58.6%; VL30%: 4.5-66.2%; VL45%: 1.8-52.1%; p < 0.05-0.001) improvements in muscle strength and muscle endurance. However, a significant group × time interaction (p < 0.05) was observed in CMJ, with VL10% showing greater increments (11.9%) than VL30% and VL45%. In addition, VL10% resulted in greater percent change in sprint performance than the other two groups (VL10%: -2.4%; VL30%: -1.8%; and VL45%: -0.5%). No significant changes in EMG variables were observed for any group. RT with loads of 55-70% 1RM characterized by a low-velocity loss (VL10%) provides a very effective and efficient training stimulus since it yields similar strength gains and greater improvements in sports-related neuromuscular performance (jump and sprint) compared to training with higher velocity losses (VL30%, VL45%). These findings indicate that the magnitude of VL reached in each exercise set considerably influences the observed training adaptations.

Strengthening the Case for Cluster Set Resistance Training in Aged and Clinical Settings: Emerging Evidence, Proposed Benefits and Suggestions

Resistance training (RT) is a fundamental component of exercise prescription aimed at improving overall health and function. RT techniques such as cluster set (CS) configurations, characterized by additional short intra-set or inter-repetition rest intervals, have been shown to maintain acute muscular force, velocity, and 'power' outputs across a RT session, and facilitate positive longer-term neuromuscular adaptations. However, to date CS have mainly been explored from a human performance perspective despite potential for application in health and clinical exercise settings. Therefore, this current opinion piece aims to highlight emerging evidence and provide a rationale for why CS may be an advantageous RT technique for older adults, and across several neurological, neuromuscular, cardiovascular and pulmonary settings. Specifically, CS may minimize acute fatigue and adverse physiologic responses, improve patient tolerance of RT and promote functional adaptations (i.e., force, velocity, and power). Moreover, we propose that CS may be a particularly useful exercise rehabilitation technique where injury or illness, persistent fatigue, weakness and dysfunction exist. We further suggest that CS offer an alternative RT strategy that can be easily implemented alongside existing exercise/rehabilitation programs requiring no extra cost, minimal upskilling and/or time commitment for the patient and professional. In light of the emerging evidence and likely efficacy in clinical exercise practice, future research should move toward further direct investigation of CS-based RT in a variety of adverse health conditions and across the lifespan given the already demonstrated benefits in healthy populations.

Acute Physiological Response to Light- and Heavy-load Power-oriented Exercise in Older Adults

This study investigated the acute responses to volume-load-matched heavy-load (80% 1RM) versus light-load (40% 1RM) power-oriented resistance training sessions in well-functioning older adults. Using a randomized cross-over design, 15 volunteers completed each condition on a leg press. Neuromuscular (maximal isometric force and rate of force development) and functional performance (power during sit-to-stand test), lactate, and muscle damage biochemistry (creatine kinase, lactate dehydrogenase and C-reactive protein serum concentration) were assessed pre- and post-exercise. Performance declines were found after heavy-load (Cohen's d effect size (d); maximal isometric force=0.95 d; rate of force development=1.17 d; sit-to-stand power =0.38 d, all p<0.05) and light-load (maximal isometric force=0.45 d; rate of force development=0.9 d; sit-to-stand power=1.17 d, all p<0.05), while lactate concentration increased only after light-load (1.7 d, p=0.001). However, no differences were found between conditions (all p>0.05). Both conditions increased creatine kinase the day after exercise (marginal effect=0.75 d, p<0.001), but no other blood markers increased (all, p>0.05). Irrespective of the load used, power training induced non-clinically significant decreases in sit-to-stand performance, moderate declines in maximal isometric force, but pronounced decreases in the rate of force development. Furthermore, the metabolic stress and muscle damage were minor; both sessions were generally well tolerated by well-functioning older adults without previous experience in resistance training.

Resistance Training to Failure vs. Not to Failure: Acute and Delayed Markers of Mechanical, Neuromuscular, and Biochemical Fatigue

ABSTRACT

González-Hernández, JM, García-Ramos, A, Colomer-Poveda, D, Tvarijonaviciute, A, Cerón, J, Jiménez-Reyes, P, and Márquez, G. Resistance training to failure vs. not to failure: acute and delayed markers of mechanical, neuromuscular, and biochemical fatigue. J Strength Cond Res 35(4): 886-893, 2021-This study aimed to compare acute and delayed markers of mechanical, neuromuscular, and biochemical fatigue between resistance training sessions leading to or not to failure. Twelve resistance-trained men completed 2 sessions that consisted of 6 sets of the full-squat exercise performed against the 10 repetitions maximum load. In a randomized order, in one session the sets were performed to failure and in the other session the sets were not performed to failure (5 repetitions per set). Mechanical fatigue was quantified through the recording of the mean velocity during all repetitions. The neuromuscular function of the knee extensors was assessed through a maximal voluntary contraction and the twitch interpolation technique before training, immediately after each set, and 1, 24, and 48 hours post-training. Serum creatine kinase (CK) and aspartate aminotransferase (AST) were measured before training and 1, 24, and 48 hours post-training to infer muscle damage. Alpha was set at a level of 0.05. A higher velocity loss between sets was observed during the failure protocol (-21.7%) compared with the nonfailure protocol (-3.5%). The markers of peripheral fatigue were generally higher and long lasting for the failure protocol. However, the central fatigue assessed by the voluntary activation was comparable for both protocols and remained depressed up to 48 hours post-training. The concentrations of CK and AST were higher after the failure protocol revealing higher muscle damage compared with the nonfailure protocol. These results support the nonfailure protocol to reduce peripheral fatigue and muscle damage, whereas the central fatigue does not seem to be affected by the set configuration.

Proximity to Failure and Total Repetitions Performed in a Set Influences Accuracy of Intraset Repetitions in Reserve-Based Rating of Perceived Exertion

ABSTRACT

Zourdos, MC, Goldsmith, JA, Helms, ER, Trepeck, C, Halle, JL, Mendez, KM, Cooke, DM, Haischer, MH, Sousa, CA, Klemp, A, and Byrnes, RK. Proximity to failure and total repetitions performed in a set influences accuracy of intraset repetitions in reserve-based rating of perceived exertion. J Strength Cond Res 35(2S): S158-S165, 2021-The aim of this study was to assess the accuracy of predicting repetitions in reserve (RIR) intraset using the RIR-based rating of perceived exertion (RPE) scale. Twenty-five men (age: 25.3 ± 3.3 years, body mass: 89.0 ± 14.7 kg, height: 174.69 ± 6.7 cm, and training age: 4.7 ± 3.2 years) reported to the laboratory. Subjects performed a 1 repetition maximum (1RM) squat followed by one set to failure at 70% of 1RM. During the 70% set, subjects verbally indicated when they believed they were at a 5RPE (5RIR), 7RPE (3RIR), or 9RPE (1RIR), and then continued to failure. The difference between actual repetitions performed and participant-predicted repetitions was calculated as the RIR difference (RIRDIFF). The average load used for the 70% set was 123.10 ± 24.25 kg and the average repetitions performed were 16 ± 4. The RIRDIFF was lower (RPEs were more accurate) closer to failure (RIRDIFF at 9RPE = 2.05 ± 1.73; RIRDIFF at 7RPE = 3.65 ± 2.46; and RIRDIFF at 5RPE = 5.15 ± 2.92 repetitions). There were significant relationships between total repetitions performed and RIRDIFF at 5RPE (r = 0.65, p = 0.001) and 7RPE (r = 0.56, p = 0.004), but not at 9RPE (r = 0.01, p = 0.97). Thus, being farther from failure and performing more repetitions in a set were associated with more inaccurate predictions. Furthermore, a multiple linear regression revealed that more repetitions performed per set was a significant predictor of RIR prediction inaccuracy at the called 5 (p = 0.003) and 7 (p = 0.011) RPEs, while training age (p > 0.05) was not predictive of rating accuracy. These data indicate RIR predictions are improved during low to moderate repetition sets and when there is close proximity to failure.