Potential mechanisms for a role of metabolic stress in hypertrophic adaptations to resistance training

Acute Effect of Fixed vs. Self-Selected Rest Interval Between Sets on Physiological and Performance-Related Responses

Background: Although the comparison between self-managed rest and fixed rest periods in subjects experienced in lower-limb strength training has been investigated, the results remain unclear due to controversies among some studies. Therefore, the present study aimed to analyze the role of self-managed rest versus fixed rest in athletic performance, mean propulsive velocity, velocity loss, muscle oxygen saturation, and rest time in trained subjects; Methods: Thirteen subjects with a minimum of one year of training experience (age (years): 26.31 ± 3.84; height (cm): 175.46 ± 5.61; weight (kg): 79.24 ± 6.83) were randomly assigned to two groups (self-selected rest group [SR] = 7 and fixed rest group [FR] = 6). The subjects underwent a session for evaluation (one maximum repetition (1RM) estimation, familiarization, and data collection) and another day for a traditional strength training session for the back squat, consisting of five sets of four repetitions at 80% of 1RM. One group took a fixed 2 min break, while the other group managed their breaks autonomously (resuming when they felt ready to perform the next set at maximum velocity). Mean propulsive velocity (MPV) was monitored using a linear position transducer, and muscle oxygen saturation (SmO2) was measured with a near-infrared spectroscopy device; Results: Significant differences between the groups were found for the rest time between the first and second sets (SR 97.29 ± 23.70 seg vs. FR 120 ± 0.00 seg). However, no differences were found for MPV, velocity loss, or SmO2; Conclusions: Given the similarities in performance and physiological outcomes between fixed and self-selected rest conditions, both can be used equally depending on the preferences and training goals of coaches and athletes.

Effects of aerobic, resistance, and combined exercise training on body fat and glucolipid metabolism in inactive middle-aged adults with overweight or obesity: a randomized trial

METHOD

Twenty inactive males (BMI 27.67 ± 0.88 kg/m2, age 49.15 ± 2.58 years) participated in an eight-week were randomly assigned to one of three intervention groups (combined (CT), resistance (RT), and aerobic (AT)) exercise modalities to assess within-subject and between group changes in glycolipid profile. Data were analyzed using repeated measures ANCOVA.

RESULT

Pre-post mean values of body fat percentage (%BF), area under the curve (AUC), low density lipoprotein (LDL), high density lipoprotein (HDL) and total cholesterol (TC) decreased in all three groups. The main effect of exercise modality on the AUC (F (2, 26) = 10.577, P = 0.001, η2 = 0.569) was significant. Post-hoc analyses revealed that the RT group (-30.653 ± 6.766, p = 0.001) with 11.53% and the CT group (M = -0.896, SE = 3.347, P = 0.015) with 3.79% exhibited significantly greater reductions in AUC compared to the AT group. LDL levels showed significant different between groups (F (2, 26) = 6.33, p = 0.009, η2 = 0.442), specially significantly 3.7% lowered in AT (MD = 4.783, SE = 1.563, P = 0.002) and 3.79% lower in CT (MD = 4.57, SE = 1.284, P = 0.008) groups compared to the RT group. AT significantly reduced TC by 17.716 ± 5.705 mg/dL (p = 0.02) compared to RT, representing a 7.97% decrease.

CONCLUSION

Exercise type significantly influences lipid profiles and glycemic control. Notably, both aerobic and combined training demonstrated a superior ability to modulate the lipid profile, and resistance training and combined training were more effective in reducing the AUC.

TRIAL REGISTRATION

May, 31st 2024.

REGISTRATION NO

PACTR202405463745521 "Retrospectively registered".

Anabolic myokine responses and muscular performance following 8 weeks of autoregulated compared to linear resistance exercise in recreationally active males

BACKGROUND

To date, no studies, to our knowledge, have compared the efficacy of autoregulated periodized and linear resistance exercises on anabolic myokines and muscular performance among recreationally active individuals. This study aimed to compare the effects of an 8-week autoregulated periodized resistance exercise (APRE) program with a linear resistance exercise (LRE) program on insulin-like growth factor-1 (IGF-1), follistatin (FST), myostatin (MST), body composition, muscular strength, and power in recreationally active males.

METHODS

Thirty males were randomly assigned to either the APRE group (n = 15) or the LRE group (n = 15). Participants completed training three times a week for 8 weeks. The outcome measures included serum IGF-1, FST, MST, muscular strength (isometric knee extension and handgrip), power (vertical jump), lean body mass, and fat mass.

RESULTS

IGF-1 circulating levels increased over time following APRE (34%) and with no significant change following LRE (~-1%). There were no significant differences over time or between groups for FST or MST. Muscular strength (knee extension [21.5 vs. ~16%] and handgrip [right: 31 vs. 25%; left: 31.7 vs. 28.8%]) and power (~ 33 vs. ~26%) significantly increased to a greater extent following APRE compared to LRE. Interestingly, the results revealed that lean body mass increased over time only after APRE (~ 3%), but not LRE.

CONCLUSION

These findings suggest that APRE may be more effective than LRE in increasing muscular strength, power, and lean body mass, as well as circulating IGF-1 levels, in recreationally active males. The observed differences may be attributed to the increased training volume associated with APRE. However, further research is needed to directly assess muscle protein synthesis.

Hypoxia matters: comparison of external and internal training load markers during an 8-week resistance training program in normoxia, normobaric hypoxia and hypobaric hypoxia

PURPOSE

To compare external and internal training load markers during resistance training (RT) in normoxia (N), intermittent hypobaric hypoxia (HH), and intermittent normobaric hypoxia (NH).

METHODS

Thirty-three volunteers were assigned an 8-week RT program in either N (690 m, n = 10), HH (2320 m, n = 10), or NH (inspired fraction of oxygen = 15.9%; ~ 2320 m, n = 13). The RT program (3x/week) consisted of six exercises, with three sets of six to 12 repetitions at ~ 70% of one repetition maximum (1RM) with the first session of each week used for analysis. 1RM in back squat and bench press was used to evaluate muscle strength before and after the program. External load was assessed by the volume load relative to body mass (RVL, kg·kg-1). Internal load was assessed by the ratings of perceived exertion (RPE) and heart rate (HR).

RESULTS

Smaller relative improvements were found for the back squat in the N group (11.5 ± 8.8%) when compared to the NH group (22.2 ± 8.2%, P = 0.01) and the HH group (22 ± 8.1%, P = 0.02). All groups showed similar RVL, HR responses and RPE across the program (P˃0.05). However, reduced HR recovery values, calculated as the difference between the highest HR value (HRpeak) and the resting heart rate after a two min rest, were seen in the N and NH groups across the program (P < 0.05).

CONCLUSION

It seems that 8 weeks of intermittent RT in hypoxic environments could maximize time-efficiency when aiming to improve strength levels in back squat without evoking higher levels of physiological stress. Performing RT at hypobaric hypoxia may improve the cardiorespiratory response, which in turn could speed recovery.

Change in Femoral Cartilage Cross-Sectional Area After Aerobic and Resistance Exercise

We compared the immediate response and recovery of femoral cartilage morphology following aerobic or resistance exercise to a control condition. Fifteen healthy young males (23.9 years; 170.1 cm; 69.7 kg) visited the laboratory three separate days and randomly performed one of the 30-min exercise aerobic exercises (treadmill running), resistance exercises (leg presses, back squats, and knee extensions), or seated rest as the control, each followed by the 50-min recovery. Ultrasonographic images of the femoral cartilage cross-sectional area (CSA) were obtained before and after exercise and every 5 min thereafter. To test exercise effects over time, a mixed model analysis of variance and Tukey-Kramer post-hoc tests were performed (p<0.05). The femoral cartilage CSA was different (condition×time: F34,742=4.30, p<0.0001) and the femoral cartilage CSA was decreased after the aerobic (-5.8%, p<0.0001) and the resistance (-3.4%, p=0.04) exercises compared to the pre-exercise levels. Deformed femoral cartilage CSA took 35 and 10 min to return to the pre-exercise levels after aerobic and resistance exercises (p+>+0.09), respectively. Thirty minutes of moderate exertion performing aerobic or resistance exercises immediately reduced the femoral cartilage CSA. A rest period ranging from 10 to 35 min was required for cartilage recovery after weight-bearing exercises.

Microvascular Reactivity Is Greater Following Blood Flow Restriction Resistance Exercise Compared with Traditional Resistance Exercise

ABSTRACT

Perlet, MR, Hosick, PA, Licameli, N, and Matthews, EL. Microvascular reactivity is greater following blood flow restriction resistance exercise compared with traditional resistance exercise. J Strength Cond Res XX(X): 000-000, 2024-Chronic blood flow restriction (BFR) resistance exercise can improve muscular strength, hypertrophy, and microvasculature function, but the acute microvascular effects are unknown. We aimed to test the effects of acute BFR resistance exercise on postexercise microvascular reactivity in an exercising muscle and nonexercising muscle compared with traditional resistance exercise (TRE). Twenty-five adults (men = 14, women = 11, age: 22 ± 3 years, body mass: 71.69 ± 14.49 kg, height: 170 ± 10 cm) completed barbell back squat 1-repetition maximum (1RM) testing followed by 2 randomized and counterbalanced resistance exercise visits separated by ≥48 hours. The 2 visits involved either BFR (4 sets of 30-15-15-15 repetitions at 30% 1RM, with 60-second rest intervals) or TRE (4 sets of 10 repetitions at 70% 1RM, 60-second rest intervals). During each exercise visit, a pre- and postbarbell back squat vascular occlusion test was performed using near-infrared spectroscopy to measure skeletal muscle oxygen (SmO2) in the vastus lateralis (VL) and flexor carpi radialis (FCR). Two-way repeated-measures ANOVA found an interaction effect (p = 0.020) for SmO2 reactivity in the VL. Post hoc analysis found greater reactive hyperemia postexercise in the VL for the BFR condition (p < 0.001) but not the TRE condition (p ≥ 0.05). There were no time, condition, or interaction effects (all p > 0.05) for the same analysis in the FCR. This analysis suggests that BFR, but not TRE, lead to acutely improved microvasculature function. Moreover, it suggests that the effects of BFR resistance exercise are local to the exercised or occluded limb and not systemic.

Endocrine Responses to Heated Resistance Exercise in Men and Women

ABSTRACT

Pryor, JL, Sweet, DK, Rosbrook, P, Qiao, J, Looney, DP, Mahmood, S, and Rideout, T. Endocrine responses to heated resistance exercise in men and women. J Strength Cond Res 38(7): 1248-1255, 2024-We examined the endocrine responses of 16 (female = 8) resistance trained volunteers to a single bout of whole-body high-volume load resistance exercise in hot (HOT; 40° C) and temperate (TEMP; 20° C) environmental conditions. Thermoregulatory and heart rate (HR) data were recorded, and venous blood was acquired before and after resistance exercise to assess serum anabolic and catabolic hormones. In men, testosterone increased after resistance exercise in HOT and TEMP ( p < 0.01), but postexercise testosterone was not different between condition ( p = 0.51). In women, human growth hormone was different between condition at pre-exercise ( p = 0.02) and postexercise ( p = 0.03). After controlling for pre-exercise values, the between-condition postexercise difference was abolished ( p = 0.16). There were no differences in insulin-like growth factor-1 for either sex ( p ≥ 0.06). In women, cortisol increased from pre-exercise to postexercise in HOT ( p = 0.04) but not TEMP ( p = 0.19), generating a between-condition difference at postexercise ( p < 0.01). In men, cortisol increased from pre-exercise to postexercise in HOT only ( p < 0.01). Rectal temperature increased to a greater extent in HOT compared with TEMP in both men ( p = 0.01) and women ( p = 0.02). Heart rate increased after exercise under both conditions in men and women ( p = 0.01), but only women experience greater postexercise HR in HOT vs. TEMP ( p = 0.04). The addition of heat stress to resistance exercise session did not overtly shift the endocrine response toward an anabolic or catabolic response. When acute program variables are prescribed to increase postresistance exercise anabolic hormones, adding heat stress is not synergistic but does increase physiologic strain (i.e., elevated HR and rectal temperature).

Resistance Training in the Heat: Mechanisms of Hypertrophy and Performance Enhancement

ABSTRACT

Pryor, JL, Sweet, D, Rosbrook, P, Qiao, J, Hess, HW, and Looney, DP. Resistance training in the heat: Mechanisms of hypertrophy and performance enhancement. J Strength Cond Res 38(7): 1350-1357, 2024-The addition of heat stress to resistance exercise or heated resistance exercise (HRE) is growing in popularity as emerging evidence indicates altered neuromuscular function and an amplification of several mechanistic targets of protein synthesis. Studies demonstrating increased protein synthesis activity have shown temperature-dependent mammalian target of rapamycin phosphorylation, supplemental calcium release, augmented heat shock protein expression, and altered immune and hormone activity. These intriguing observations have largely stemmed from myotube, isolated muscle fiber, or rodent models using passive heating alone or in combination with immobilization or injury models. A growing number of translational studies in humans show comparable results employing local tissue or whole-body heat with and without resistance exercise. While few, these translational studies are immensely valuable as they are most applicable to sport and exercise. As such, this brief narrative review aims to discuss evidence primarily from human HRE studies detailing the neuromuscular, hormonal, and molecular responses to HRE and subsequent strength and hypertrophy adaptations. Much remains unknown in this exciting new area of inquiry from both a mechanistic and functional perspective warranting continued research.

The relation between autophagy modulation by intermittent fasting and aquaporin 2 expression in experimentally induced diabetic nephropathy in albino rat

Polyuria is an early sign of diabetic nephropathy (DN) that produces dehydration in diabetic patients. This could be caused by alteration of renal aquaporin 2 (AQP2) expression. This study aimed to describe the relation between autophagy modulation via intermittent fasting (IF) and renal AQP2 expression and polyuria in case of DN. We divided the rats into control, DN and IF groups. After 2 and 4 weeks of diabetes induction, blood glucose (BG), serum creatinine (Scr), urine volume, and 24 hours urine protein (UP) were examined. Diabetic nephropathy histopathological index (DNHI) was calculated to evaluate histopathological changes. Immunohistochemistry and real-time PCR were performed to measure the levels of AQP2 and the autophagy marker; LC3 in kidney tissue. DNHI was correlated to the PCR and immunoexpression of AQP2 and LC3. Intermittent fasting significantly decreased the BG, Scr, urine volume, 24 hours UP, and DNHI as compared diabetes. Diabetes significantly elevated the immunoreactivity and mRNA expression levels of AQP2 and LC3 as compared to the control. However, the IF decreased AQP2 and stimulated autophagy in cyclic fashion. Our data revealed significant positive correlations between AQP2 and LC3 at the level of immunoexpression and mRNA at 2nd weeks. Taken together, these data showed that autophagy stimulation didn't regulate AQP2 expression in case of diabetic nephropathy, however IF decreased polyuria through improvement of glycemic state.

Blood flow restriction therapy with exercise are no better than exercise alone in improving athletic performance, muscle strength, and hypertrophy: a systematic review and meta-analysis

BACKGROUND

The benefits of Blood Flow Restriction Therapy (BFRT) have gained attention in recent times.

OBJECTIVE

This review aimed to evaluate the immediate (up to 24 hours), intermediate (up to 6 weeks), and long term (6-10 weeks) effects of BFRT plus exercises (EX) compared to EX only on athletic performance (sprint and jump performance), muscle strength, and hypertrophy in athletes and physically active population.

METHODS

A literature search was conducted to select randomized controlled trials across four electronic databases from inception till April 2021. The search yielded twenty-seven studies in total.

RESULTS

Based on eligibility criteria, twenty-one studies were analyzed. No differences were found between both groups for immediate (standardized mean difference [SMD] -0.02, 95% confidence interval [CI] -0.31, 0.27) and long-term effects (SMD -0.30, 95%CI -0.90, 0.30) on sprint performance. For jump performance, no significant effect was observed immediately (SMD -0.02 (95% CI -1.06, 1.02) and long term (SMD -0.40 (95% CI -1.46, 0.67). Similarly, muscle torque at intermediate (SMD 0.90 (95% CI -1.01, 2.81) and long term (SMD -0.54 (95% CI -1.19, 0.12), muscle strength at intermediate (SMD 1.12 (95% CI 0.20, 2.04), and long term (SMD -0.07 (95% CI -0.56, 0.42) also showed non-significant effects. Muscle hypertrophy at intermediate (SMD 0.16 (95% CI -0.31, 0.63) and long term (SMD -0.20 (95% CI -0.90, 0.50) were not statistically significant.

CONCLUSIONS

There was no significant difference observed in BFRT plus EX group compared to the EX-group on athletic performance, muscle strength, and muscle hypertrophy.

Associations Between Object Control Skills and Cognitive Functions in Boys, Younger and Older Men: Across-Sectional Study

Purpose: This study aimed to explore the association of cognitive function and process- as well product-oriented outcomes of object control skills (OCS) in boys, younger and older men. Methods: A total of 77 male participants took part in this study, including 35 primary school children (9.04 ± 0.53 years), 22 younger adults (23.5 ± 2.34 years), and 20 older adults (69.5 ± 4.43 years). We assessed the process-oriented performance of throwing, kicking, and catching performance using the component approach. For the product-oriented performance, throwing and kicking velocity was recorded with a STALKER SOLO 2.0 radar gun. For catching, the number of caught balls was assessed. Cognitive function was evaluated using the Trail-Making-Test (TMT) one day later. Results: Younger adults performed better in both domains than the other two groups. The results of the children and older adults were comparable in the motor and cognitive domains. However, the older adults yielded significantly better results for the process-oriented catching and product-oriented throwing performances. Moderate to strong correlations exist between OCS- and TMT performance, with significant correlations predominantly between product-oriented OCS results and TMT in children. Conclusion: The results of both domains support a hypothetical lifespan developmental trajectory with a progression from childhood to younger adult age and a degression in older adults. Furthermore, our results suggest that the suspected relationship between motor and cognitive function depends on age, the analyzed cognitive and motor skills, and the applied methodological approach (process-oriented vs. product-oriented).

Potential Moderators of the Effects of Blood Flow Restriction Training on Muscle Strength and Hypertrophy: A Meta-analysis Based on a Comparison with High-Load Resistance Training

BACKGROUND

While it has been examined whether there are similar magnitudes of muscle strength and hypertrophy adaptations between low-load resistance training combined with blood-flow restriction training (BFR-RT) and high-load resistance training (HL-RT), some important potential moderators (e.g., age, sex, upper and lower limbs, frequency and duration etc.) have yet to be analyzed further. Furthermore, training status, specificity of muscle strength tests (dynamic versus isometric or isokinetic) and specificity of muscle mass assessments (locations of muscle hypertrophy assessments) seem to exhibit different effects on the results of the analysis. The role of these influencing factors, therefore, remains to be elucidated.

OBJECTIVES

The aim of this meta-analysis was to compare the effects of BFR- versus HL-RT on muscle adaptations, when considering the influence of population characteristics (training status, sex and age), protocol characteristics (upper or lower limbs, duration and frequency) and test specificity.

METHODS

Studies were identified through database searches based on the following inclusion criteria: (1) pre- and post-training assessment of muscular strength; (2) pre- and post-training assessment of muscular hypertrophy; (3) comparison of BFR-RT vs. HL-RT; (4) score ≥ 4 on PEDro scale; (5) means and standard deviations (or standard errors) are reported or allow estimation from graphs. In cases where the fifth criterion was not met, the data were requested directly from the authors.

RESULTS

The main finding of the present study was that training status was an important influencing factor in the effects of BFR-RT. The trained individuals may gain greater muscle strength and hypertrophy with BFR-RT as compared to HL-RT. However, the results showed that the untrained individuals experienced similar muscle mass gains and superior muscle strength gains in with HL-RT compared to BFR-RT.

CONCLUSION

Compared to HL-RT, training status is an important factor influencing the effects of the BFR-RT, in which trained can obtain greater muscle strength and hypertrophy gains in BFR-RT, while untrained individuals can obtain greater strength gains and similar hypertrophy in HL-RT.

Effect of Step Load Based on Time under Tension in Hypoxia on the ACL Pre-Operative Rehabilitation and Hormone Levels: A Case Study

The aim of the study was to determine the effect of step load in hypoxia on the effectiveness of preoperative rehabilitation (PR) and hormone levels based on a case study. Introduction: We assessed the impact of variables such as rate of movement and time under tension (TUT) in normobaric hypoxia on the levels of growth hormone (GH), insulin-like growth factor 1 (IGF-1), and erythropoietin (EPO). Additionally, the impact of step load on the hypertrophy and strength of knee extensors and flexors was assessed. Methods: The work uses a case study, the research subject of which was a 23-year-old female professional handball player. The tests included an isokinetic assessment of the peak torque of knee extensors and flexors as well as body composition analysis. Results: The results showed a more than (10.81-fold) increase in GH after the microcycle with time under tension (TUT). The deficit between the lower limbs was also reduced. Conclusions: Using a hypoxic environment based on an appropriate altitude, combined with changes such as a short rest break between sets and a controlled tempo of movement with an eccentric phase, TUT may offer an alternative to the PR process, especially among athletes who care about fast RTS.

Differences in knee flexor and extensor force and kinematic variables in rural versus urban area female students in Romania

The study aimed to identify and explain the typical differences in low-intensity high-volume resistance training (LIHV-RT) performances for major muscle groups between rural versus urban young female students to establish the relevant set of quantitative and qualitative resistance training parameters. The study sample included 46 recreational active female students at the Transilvania University of Brașov, (mean ± SD age, 20 ± 1 year; body mass, 60 ± 3 kg; height, 160 ± 4 cm) grouped urban vs. rural. The study used modified resistance exercise machines for the hamstring- and quadricep-group muscles, equipped with a dynamometer and sensors for identifying developed forces and accelerations. A number of 368 tests were performed, representing two attempts for each subject, for knee flexion and knee extension exercises, with two different loads. For the performance analysis some variables were considered: the maximum number of repetition until failure, maximum force developed, maximum acceleration, the duration of the set and the mean time per repetition. The maximum number of repetition to failure shows a significant higher value for rural than urban in case of knee flexion (d = 0.98 [0.32, 1.54] for load 1(L1) and d = 0.65 [0.03, 1.21] for load 2(L2)) and in case of knee extension (d = 1.89 [1.11, 2.48] for L1 and d = 1.67 [0.92, 2.25] for L2). The total duration of the sets shows a significant higher value for rural than urban in case of knee flexion (d = 0.84 [0.19, 1.39] for L2) and in case of knee extension (d = 1.46 [0.74, 2.03] for L1 and d = 1.56 [0.98, 2.14] for L2). Additionally we found differences in the quality of the relevant repetitions execution and in the impulse developed during the LIHV- MNRF sets. The study's main finding was that there are differences in LIHV-RT performances knee flexion and knee extension antagonistic exercises, between rural and urban female students. We concluded that the obtained results allow teachers to understand the optimal design of RT programs for the different groups of participants, in order to adapt their teaching techniques so that their final objectives are achieved, insisting on particular aspects of the theoretical or practical contents.

A meta-analysis on the impact of resistance training on phase angle in middle-aged and older individuals

PURPOSE

To determine the impact of resistance training (RT) on phase angle (PhA) in middle-aged and older individuals via meta-analysis, explore effects in subgroups, and identify optimal RT protocol.

MATERIALS AND METHODS

We searched five databases using predefined criteria, assessed literature quality per Cochrane 5.1 Handbook, and used Revman 5.3 for effect size aggregation, bias assessment, sensitivity analysis, and subgroup analysis.

RESULTS

RT improved PhA in middle-aged and older individuals (d = 0.34, 95 % CI: 0.27-0.40, P < 0.05). Effective subgroups included Suspension (d = 0.62, 95 % CI: 0.33-0.90, P < 0.05), free-weights and machine (d = 0.36, 95 % CI: 0.28-0.45, P < 0.05), equipment training (d = 0.24, 95 % CI: 0.13-0.36, P < 0.05), and moderate-intensity RT (d = 0.34, 95 % CI: 0.27-0.42, P < 0.05). RT was conducted 2-3 times/week (d = 0.20, 95 % CI: 0.01-0.38, P < 0.05) or (d = 0.38, 95 % CI: 0.30-0.47, P < 0.05). PhA improved after 8 weeks (d = 0.37, 95 % CI: 0.23-0.51, P < 0.05), 12 weeks (d = 0.35, 95 % CI: 0.26-0.44, P < 0.05), and ≥ 24 weeks (d = 0.26, 95 % CI: 0.11-0.41, P < 0.05) of RT in aged and older individuals. Low- and high-intensity RT, elastic band training, and weekly exercises did not significantly improve PhA.

CONCLUSIONS

RT enhances PhA in middle-aged and older adults. For optimal results, we recommend 2-3 weekly sessions of free weights and machine training lasting at least 8 weeks.

Fatigue and Metabolic Responses during Repeated Sets of Bench Press Exercise to Exhaustion at Different Ranges of Motion

This study compared the acute effects of different ranges of motion (ROM) on fatigue and metabolic responses during repeated sets of bench press exercise. Ten resistance trained men performed three sets to momentary failure with two-min rest intervals at three different ROM: full ROM (FULL), and partial ROM in which the barbell was moved either at the bottom half (BOTTOM) or the top half (TOP) of the full barbell vertical displacement. In TOP, a higher load was lifted, and a higher total number of repetitions was performed compared to FULL and BOTTOM (130 ± 17.6 vs. 102.5 ± 15.9 vs. 98.8 ± 17.5 kg; 55.2 ± 9.8, 32.2 ± 6.5 vs. 49.1 ± 16.5 kg, respectively p < 0.01). Work per repetition was higher in FULL than TOP and BOTTOM (283 ± 43 vs. 205 ± 32 vs. 164 ± 31 J/repetition, p < 0.01). Mean barbell velocity at the start of set 1 was 21.7% and 12.8% higher in FULL compared to TOP and BOTTOM, respectively. The rate of decline in mean barbell velocity was doubled from set 1 to set 3 (p < 0.01) and was higher in FULL than both TOP and BOTTOM (p < 0.001). Also, the rate of mean barbell velocity decline was higher in BOTTOM compared to TOP (p = 0.045). Blood lactate concentration was similarly increased in all ROM (p < 0.001). Training at TOP ROM allowed not only to lift a higher load, but also to perform more repetitions with a lower rate of decline in mean barbell velocity. Despite the lower absolute load and work per repetition, fatigue was higher in BOTTOM than TOP and this may be attributed to differences in muscle length.

Effect of Resistance Training Programs With Equated Power on Older Adults' Functionality and Strength: A Randomized Controlled Trial

ABSTRACT

Fraga-Germade, E, Carballeira, E, and Iglesias-Soler, E. Effect of resistance training programs with equated power on older adults' functionality and strength: a randomized controlled trial. J Strength Cond Res 38(1): 153-163, 2024-This study aimed to compare the effect of 2 training programs of equated power but differing in load intensity on older adults' functionality, strength, performance, and body composition. Forty-four active (23 female) older adults (66.3 ± 4.5 years) were randomly assigned to low-load high-velocity (LL-HV), high-load low-velocity (HL-LV), and control (CON) groups. Low-load high-velocity and HL-LV performed, twice weekly for 5 weeks, a resistance training program at 95% of their individual peak power (PP) but with different load intensities for 3 exercises: chest press (CHP), leg press (LP), and seated row (SR). Before and after the intervention, body composition, functional performance, maximal voluntary isokinetic force (MVF), PP, and a relative load-power profile (L-PP) were evaluated for every exercise. PP similarly improved in the experimental groups for SR and LP (p < 0.05). Both groups increased their MVF for the 3 exercises (p < 0.05). Positive effects on L-PP were observed in LL-HV for SR (p = 0.009) and HL-LV for LP (p < 0.001). CON decreased its global power performance in SR (p = 0.009) and CHP (p = 0.031) compared with the baseline. Both experimental groups improved Timed Up and Go performance (p < 0.05), but only HL-LV increased 6-minute walking performance (pre: 514.3 ± 89.0 m, post: 552.6 ± 65.4 m; p < 0.05). In conclusion, adding short-term power training (i.e., 10 sessions throughout 5 weeks) with loads slightly above the optimal load to nonsupervised multicomponent training might improve active older adults' functional performance and cardiovascular endurance.

Molecular profiling of high-level athlete skeletal muscle after acute endurance or resistance exercise - A systems biology approach

OBJECTIVE

Long-term high-level exercise training leads to improvements in physical performance and multi-tissue adaptation following changes in molecular pathways. While skeletal muscle baseline differences between exercise-trained and untrained individuals have been previously investigated, it remains unclear how training history influences human multi-omics responses to acute exercise.

METHODS

We recruited and extensively characterized 24 individuals categorized as endurance athletes with >15 years of training history, strength athletes or control subjects. Timeseries skeletal muscle biopsies were taken from M. vastus lateralis at three time-points after endurance or resistance exercise was performed and multi-omics molecular analysis performed.

RESULTS

Our analyses revealed distinct activation differences of molecular processes such as fatty- and amino acid metabolism and transcription factors such as HIF1A and the MYF-family. We show that endurance athletes have an increased abundance of carnitine-derivates while strength athletes increase specific phospholipid metabolites compared to control subjects. Additionally, for the first time, we show the metabolite sorbitol to be substantially increased with acute exercise. On transcriptional level, we show that acute resistance exercise stimulates more gene expression than acute endurance exercise. This follows a specific pattern, with endurance athletes uniquely down-regulating pathways related to mitochondria, translation and ribosomes. Finally, both forms of exercise training specialize in diverging transcriptional directions, differentiating themselves from the transcriptome of the untrained control group.

CONCLUSIONS

We identify a "transcriptional specialization effect" by transcriptional narrowing and intensification, and molecular specialization effects on metabolomic level Additionally, we performed multi-omics network and cluster analysis, providing a novel resource of skeletal muscle transcriptomic and metabolomic profiling in highly trained and untrained individuals.

Effect of resistance training programs differing in set structure on muscular hypertrophy and performance in untrained young men

Purpose: This study aimed to compare the effects on muscle hypertrophy and muscular performance of two resistance training (RT) programs that differed only in set structure: traditional set structure (TS) vs. rest redistribution set structure (RR). Methods: Thirty untrained young men were pair-matched and randomly assigned to a TS (n = 15) or an RR (n = 15) protocol based on individual baseline measures. Participants trained for 8 weeks using the same total body RT routines performed twice weekly. The TS protocol comprised four sets of 10 repetitions per exercise with 120-s interset rest, and the RR involved eight sets of five repetitions per exercise with 51-s interset rest. Participants were tested pre- and post-intervention for body composition, regional muscle thickness, upper- and lower-body muscle maximal strength [1-repetition maximum (1RM)], mean power output and velocity at 75% 1RM and muscular endurance (repetitions to failure at 70% 1RM). Results: Compared to baseline, both groups exhibited equally significantly decreased body fat mass (p < 0.05), increased fat-free mass (p < 0.001), muscle thickness (p < 0.05), upper and lower-body muscular maximal strength (p < 0.001) and endurance performance (p < 0.001). However, both groups only increase the lower-body power output (p < 0.001) but not the upper-body (p > 0.05). No significant differences existed between groups for all measurements (p > 0.05). Conclusion: These results suggest that RR and TS groups have similar effects for improving muscle hypertrophy and performance in untrained young men.

Muscular Adaptations and Psychophysiological Responses in Resistance Training Systems

Purpose: We investigated the effect of drop-set (DS) and rest-pause (RP) systems compared to traditional (TRAD) resistance training on muscular adaptations and psychophysiological responses. Methods: Twenty-seven trained men (age: 23.4 ± 3.4 years; resistance training experience: 5.1 ± 1.7 years) were assigned to experimental groups (DS: n = 9, 3 × 10 repetitions at 75% with 6 additional repetitions at 55% 1RM; RP: n = 9, 3 × 16 repetitions at 75% 1RM; TRAD: n = 9, 4 × 12 repetitions at 70% 1RM) and performed lower-limb training sessions twice a week for 8 weeks. Maximum dynamic strength (1RM) and localized muscular endurance (LME) tests were performed in 45° leg press at baseline and post intervention. Session-RPE was assessed 15 min after the end of each training session. Results: A significant time vs. group interaction was observed for 1RM (p = .012) and LME (p < .0001). Post hoc comparisons revealed that RP elicited greater gains in muscular strength than DS (p = .044) but not TRAD (p = .116); and DS elicited greater LME than RP (p < .001) and TRAD (p = .001). No statistical differences were observed in Session-RPE and training strain between conditions; however, RP promoted higher training monotony (p = .036) than DS and TRAD. Conclusions: The DS and RP systems have a potential role in training programs aiming to promote muscle strength and localized muscular endurance adaptations, respectively. However, RP may promote higher training monotony than DS and TRAD, even though the other psychophysiological responses are similar.

Exploring the acute muscle fatigue response in resistance trained individuals during eccentric quasi-isometric elbow flexions-a cross-sectional comparison of repetition and sex

Eccentric quasi-isometrics (EQIs) are a novel, low-velocity resistance exercise technique that incorporates a holding isometric contraction to positional fatigue, followed by voluntary resistance of the resulting eccentric muscle action. As females are typically more fatigue resistant than males during isometric and low-velocity dynamic muscle actions, this study explored sex-differences in the muscle fatigue response to an EQI protocol. Twenty-five (n = 12 female) participants completed 4 unilateral EQI elbow flexions. Absolute and relative surface electromyography (sEMG) amplitude (iEMG, LE peak), mean power frequency (MPF), angular impulse (aIMP), and elbow angle were compared across repetitions and between sexes using discrete values and statistical parametric/non-parametric mapping. There were significant and substantial sex and repetition differences in absolute iEMG, MPF, and aIMP, however, males and females had statistically similar absolute aIMP by repetition 4. When expressed relatively, there were no significant sex-differences. Additionally, there were significant between repetition changes in sEMG amplitude and elbow angle with an increasing number of repetitions, largely in the first-two thirds of repetition time. The current study suggests that there are absolute, but not relative sex-differences in EQI induced muscle fatigue, and the effects across repetitions occur predominately in the first two-thirds of repetition time.

Effects of a Perioperative Blood Flow Restriction Therapy Program on Early Quadriceps Strength and Patient-Reported Outcomes After Anterior Cruciate Ligament Reconstruction

Background

Quadriceps muscle atrophy remains a limiting factor in returning to activity after anterior cruciate ligament reconstruction (ACLR). Blood flow restriction (BFR) therapy may accelerate quadriceps strengthening in the perioperative period.

Purpose

To evaluate postoperative isometric quadriceps strength in patients who underwent ACLR with a perioperative BFR program.

Study Design

Randomized controlled trial; Level of evidence, 1.

Methods

Patients indicated for ACLR were randomized into 2 groups, BFR and control, at their initial clinic visit. All patients underwent 2 weeks of prehabilitation preoperatively, with the BFR group performing exercises with a pneumatic cuff set to 80% limb occlusion pressure placed over the proximal thigh. All patients also underwent a standardized postoperative 12-week physical therapy protocol, with the BFR group using pneumatic cuffs during exercise. Quadriceps strength was measured as peak and mean torque during seated leg extension and presented as quadriceps index (percentage vs healthy limb). Patient-reported outcomes (PROs), knee range of motion, and quadriceps circumference were also gathered at 6 weeks, 3 months, and 6 months postoperatively, and adverse effects were recorded.

Results

Included were 46 patients, 22 in the BFR group (mean age, 25.4 ± 10.6 years) and 24 in the control group (mean age, 27.5 ± 12.0 years). At 6 weeks postoperatively, the BFR group demonstrated significantly greater strength compared with the controls (quadriceps index: 57% ± 24% vs 40% ± 18%; P = .029), and the BFR group had significantly better Patient-Reported Outcomes Measurement Information System-Physical Function (42.69 ± 5.64 vs 39.20 ± 5.51; P = .001) and International Knee Documentation Committee (58.22 ± 7.64 vs 47.05 ± 13.50; P = .011) scores. At 6 weeks postoperatively, controls demonstrated a significant drop in the peak torque generation of the operative versus nonoperative leg. There were no significant differences in strength or PROs at 3 or 6 months postoperatively. Three patients elected to drop out of the BFR group secondary to cuff intolerance during exercise; otherwise, no other severe adverse events were reported.

Conclusion

Integrating BFR into perioperative physical therapy protocols led to improved strength and increased PROs at 6 weeks after ACLR. No differences in strength or PROs were found at 3 and 6 months between the 2 groups.

Registration

NCT04374968 (ClinicalTrials.gov identifier).

Acute Effects of Continuous and Intermittent Blood Flow Restriction on Sprint Interval Performance and Muscle Oxygen Responses

ABSTRACT

Wizenberg, AM, Gonzalez-Rojas, D, Rivera, PM, Proppe, CE, Laurel, KP, Stout, JR, Fukuda, DH, Billaut, F, Keller, JL, and Hill, EC. Acute effects of continuous and intermittent blood flow restriction on sprint interval performance and muscle oxygen responses. J Strength Cond Res 37(10): e546-e554, 2023-This investigation aimed to examine the acute effects of continuous and intermittent blood flow restriction (CBFR and IBFR, respectively) during sprint interval training (SIT) on muscle oxygenation, sprint performance, and ratings of perceived exertion (RPE). Fifteen men (22.6 ± 2.4 years; 176 ± 6.3 cm; 80.0 ± 12.6 kg) completed in random order a SIT session with CBFR, IBFR (applied during rest), and no blood flow restriction (NoBFR). Each SIT session consisted of two 30-second all-out sprint tests separated by 2 minutes. Peak power (PP), total work (TW), sprint decrement score (S dec ), RPE, and muscle oxygenation were measured during each sprint. A p value ≤0.05 was considered statistically significant. PP decreased to a greater extent from sprint 1 to sprint 2 during CBFR (25.5 ± 11.9%) and IBFR (23.4 ± 9.3%) compared with NoBFR (13.4 ± 8.6%). TW was reduced similarly (17,835.6 ± 966.2 to 12,687.2 ± 675.2 J) from sprint 1 to sprint 2 for all 3 conditions, but TW was lower (collapsed across time) for CBFR (14,320.7 ± 769.1 J) than IBFR (15,548.0 ± 840.5 J) and NoBFR (15,915.4 ± 771.5 J). There were no differences in S dec (84.3 ± 1.7%, 86.1 ± 1.5%, and 87.2 ± 1.1% for CBFR, IBFR, and NoBFR, respectively) or RPE, which increased from sprint 1 (8.5 ± 0.3) to sprint 2 (9.7 ± 0.1). Collective muscle oxygenation responses increased across time and were similar among conditions, whereas increases in deoxy[heme] and total[heme] were greatest for CBFR. Applying BFR during SIT induced greater decrements in PP, and CBFR resulted in greater decrements in work across repeated sprints. The larger increases in deoxy[heme] and total[heme] for CBFR suggested it may induce greater metabolite accumulation than IBFR and NoBFR when combined with SIT.

Beneficial Effects of Asparagus officinalis Extract Supplementation on Muscle Mass and Strength following Resistance Training and Detraining in Healthy Males

The phytoecdysteroid 20-hydroxyecdysone (20E) is widely used for resistance training (RT). Little is known about its potential ergogenic value and detraining effects post-RT. This study aimed to examine the effects of 20E extracted from Asparagus officinalis (A. officinalis) on muscle strength and mass, as well as anabolic and catabolic hormones following RT and detraining. Twenty males, aged 20.1 ± 1.1 years, were matched and randomly assigned to consume double-blind supplements containing either a placebo (PLA) or 30 mg/day of 20E for 12 weeks of RT and detraining. Before and after RT and detraining, muscle strength and mass and anabolic and catabolic hormones were measured. This study found that 20E reduced cortisol levels significantly (p < 0.05) compared to the PLA, yet no effect was observed on muscle mass, strength, or anabolic hormones after RT. Subsequent to 6 weeks of detraining, the 20E demonstrated a lower percentage change in 1RM bench press/FFM than the PLA (p < 0.05). Compared to the PLA, detraining throughout the 12 weeks resulted in a lower percentage change in thigh (p < 0.05) and chest (p < 0.01) circumferences, as well as reduced cortisol levels (p < 0.01), with 20E. Our findings demonstrate that 20E supplementation is a promising way to maintain muscle mass and strength during detraining. Accordingly, 20E may prevent muscle mass and strength loss due to detraining by lowering catabolic hormone levels.

Resistance Training for Older Women: Do Adaptive Responses Support the ACSM and NSCA Position Stands?

PURPOSE

The optimal intensity of resistance training (RT) to improve muscular, physical performance, and metabolic adaptations still needs to be well established for older adults. Based on current position statements, we compared the effects of two different RT loads on muscular strength, functional performance, skeletal muscle mass, hydration status, and metabolic biomarkers in older women.

METHODS

One hundred one older women were randomly allocated to perform a 12-wk whole-body RT program (eight exercises, three sets, three nonconsecutive days a week) into two groups: 8-12 repetitions maximum (RM) and 10-15RM. Muscular strength (1RM tests), physical performance (motor tests), skeletal muscle mass (dual-energy X-ray absorptiometry), hydration status (bioelectrical impedance), and metabolic biomarkers (glucose, total cholesterol, HDL-c, HDL-c, triglycerides, and C-reactive protein) were measured at baseline and posttraining.

RESULTS

Regarding muscular strength, 8-12RM promoted higher 1RM increases in chest press (+23.2% vs +10.7%, P < 0.01) and preacher curl (+15.7% vs +7.4%, P < 0.01), but not in leg extension (+14.9% vs +12.3%, P > 0.05). Both groups improved functional performance ( P < 0.05) in gait speed (4.6%-5.6%), 30 s chair stand (4.6%-5.9%), and 6 min walking (6.7%-7.0%) tests, with no between-group differences ( P > 0.05). The 10-15RM group elicited superior improves in the hydration status (total body water, intracellular and extracellular water; P < 0.01), and higher gains of skeletal muscle mass (2.5% vs 6.3%, P < 0.01), upper (3.9% vs 9.0%, P < 0.01) and lower limbs lean soft tissue (2.1% vs 5.4%, P < 0.01). Both groups improved their metabolic profile. However, 10-15RM elicited greater glucose reductions (-0.2% vs -4.9%, P < 0.05) and greater HDL-c increases (-0.2% vs +4.7%, P < 0.01), with no between-group differences for the other metabolic biomarkers ( P > 0.05).

CONCLUSIONS

Our results suggest that 8-2RM seems more effective than 10-15RM for increasing upper limbs' muscular strength, whereas the adaptative responses for lower limbs and functional performance appear similar in older women. In contrast, 10-15RM seems more effective for skeletal muscle mass gains, and increased intracellular hydration and improvements in metabolic profile may accompany this adaptation.

Influence of Practice Periodization and Sleep Duration on Oxidative Stress in High School Judo Athletes

Numerous research studies have investigated the relationship between exercise, oxidative stress level, and condition in athletes who engage in intense training on a daily basis. However, it is known that oxidative stress is affected by exercise, sleep, and the psychological state, but there are only a few studies that have comprehensively examined oxidative stress based on the actual practice periods and living conditions of athletes. Therefore, our study aimed to explore the influence of three distinct training periods (short training period, intensive training period, and pre-competition periods) as well as life situations (sleep and number of steps) on oxidative stress levels (diacron reactive oxygen metabolites: d-ROMs) in high school judo athletes. The results showed that, among the three periods, the level of oxidative stress increased the most during the pre-competition period, and the value was higher than during the training period, when the intensity of training was highest. The levels of the d-ROMs values during the pre-competition period were negatively correlated with the amount of sleep on the previous day. The findings suggest that, besides the exercise intensity, factors such as sleep duration and other life situations should be regarded as critical considerations for high school judo athletes.

Effects of Drop Sets on Skeletal Muscle Hypertrophy: A Systematic Review and Meta-analysis

BACKGROUND

One of the most popular time-efficient training methods when training for muscle hypertrophy is drop sets, which is performed by taking sets to concentric muscle failure at a given load, then making a drop by reducing the load and immediately taking the next set to concentric or voluntary muscle failure. The purpose of this systematic review and meta-analysis was to compare the effects of drop sets over traditional sets on skeletal muscle hypertrophy.

METHODS

This systematic review followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. The SPORTDiscus and MEDLINE/PubMed databases were searched on April 9, 2022, for all studies investigating the effects of the drop set training method on muscle hypertrophy that meets the predefined inclusion criteria. Comprehensive Meta-Analysis Version 3 (Biostat Inc., Englewood Cliffs, NJ, USA) was used to run the statistical analysis. Publication bias was assessed through visual inspection of the funnel plots for asymmetry and statistically by Egger's regression test with an alpha level of 0.10.

RESULTS

Six studies met the predefined inclusion criteria. The number of participants in the studies was 142 (28 women and 114 men) with an age range of 19.2-27 years. The average sample size was 23.6 ± 10.9 (range 9-41). Five studies were included in the quantitative synthesis. Meta-analysis showed that both the drop set and traditional training groups increased significantly from pre- to post-test regarding muscle hypertrophy (drop set standardized mean difference: 0.555, 95% CI 0.357-0.921, p < 0.0001; traditional set standardized mean difference: 0.437, 95% CI 0.266-0.608, p < 0.0001). No significant between-group difference was found (standardized mean difference: 0.155, 95% CI - 0.199 to - 0.509, p = 0.392).

CONCLUSIONS

The results of this systematic review and meta-analysis indicate that drop sets present an efficient strategy for maximizing hypertrophy in those with limited time for training. There was no significant difference in hypertrophy measurements between the drop set and traditional training groups, but some of the drop set modalities took half to one-third of the time compared with traditional training.

Muscle Swelling of the Triceps Surae in Response to Straight-Leg and Bent-Leg Calf Raise Exercises in Young Women

ABSTRACT

Kassiano, W, Costa, B, Kunevaliki, G, Soares, D, Stavinski, N, Francsuel, J, Carneiro, MAS, Tricoli, I, Nunes, JP, Ribeiro, AS, and Cyrino, ES. Muscle swelling of the triceps surae in response to straight-leg and bent-leg calf raise exercises in young women. J Strength Cond Res 37(7): e438-e443, 2023-Triceps surae muscle swelling in response to different resistance exercises remains to be determined. This study compared the effects of straight-leg (STRA-leg) calf raise vs. bent-leg (BENT-leg) calf raise exercises on triceps surae muscle swelling. Seventeen young women (23.7 ± 4.0 years; 67.4 ± 16.0 kg; and 163.5 ± 7.2 cm) performed 2 resistance training sessions; in one, they performed the STRA-leg calf raise, and in another, they performed the BENT-leg calf raise. A randomized, cross-over, and counterbalanced design was adopted for this investigation. The subjects performed 4 sets of 20 repetitions maximum until concentric muscular failure. The muscle thickness of the gastrocnemius medial (GM), gastrocnemius lateral (GL), and soleus (SOL) was taken through B-mode ultrasound before and immediately after the calf raise exercises. STRA-leg calf raise elicited greater increases in muscle thickness of GM (+8.8% vs. -0.9%, p < 0.001) and GL (+14.5% vs. +7.0%, p < 0.001) than BENT-leg calf raise. Conversely, BENT-leg calf raise elicited greater increases in SOL muscle thickness than STRA-leg calf raise (+15.4% vs. +7.7%, p < 0.001). From a practical perspective, the STRA-leg calf raise should be preferred if the aim is stimulating the 3 muscles that comprise the triceps surae, whereas the BENT-leg calf raise should be prioritized if the target muscle is the SOL.

Effects of lipodystrophy and physical exercise on bioimpedance parameters in people living with HIV: A cross-sectional study

OBJECTIVE

The aim of this study was to evaluate the effects of lipodystrophy and physical exercise on the parameters of bioimpedance spectroscopy (BIS) and bioimpedance vector analysis (BIVA) of people living with HIV (PLWHIV).

METHODS

Seventy patients were divided into two groups: PLWHIV with lipodystrophy (PLWHIV-L) and PLWHIV without lipodystrophy (PLWHIV-NL). The phase angle (PhA) and the BIVA were determined from the values of resistance and reactance collected by the BIS. The percentage of fat mass and lean soft tissue (LST) were determined by dual-energy x-ray absorptiometry. For comparisons between the PLWHIV-L and PLWHIV-NL groups, the t test for independent samples or the Mann-Whitney test was used. From the BIVA, the average of the impedance vectors of the two groups was calculated with the 95% confidence ellipse, and the individual vectors of the patients divided by sex were also compared with the tolerance ellipses of 50%, 75%, and 95% of the healthy reference population. The relationships between the variables of interest were determined by the Pearson or Spearman correlation coefficient and the coefficient of determination. Analysis of covariance was used for comparisons between groups, adjusted for possible confounding variables.

RESULTS

PLWIV-L showed better hydration conditions (P <0.01), higher LST (P <0.01), and lower percent of fat mass (P <0.01). No differences in PhA were observed between PLWHIV who practiced or did not practice physical exercise. There was a significant difference between the impedance vectors of the groups with and without lipodystrophy (T = 42.4 and P <0.01). Additionally, most of the patients who were positioned beyond the ellipse limits of 50% of tolerance fell into the areas of edema and cachexia. The extracellular to intracellular water ratio explained 81% of the PhA variations. When PhA was adjusted for height², fat mass/height² and LST, it was significantly different between groups of the female sex (PhA: P <0.01).

CONCLUSION

Lipodystrophy and the practice of physical exercise do not present direct involvement in the PhA values, with sex, body composition, and hydration variables being the main influences on this variable. BIVA was able to show differences in the body composition of the groups even when the PhA values were similar.

Application of blood flow restriction in hypoxic environment augments muscle deoxygenation without compromising repeated sprint exercise performance

NEW FINDINGS

What is the central question of this study? Does applying blood flow restriction during the rest periods of repeated sprint exercise in a hypoxic environment lead to greater local hypoxia within exercising muscles without compromising training workload? What is the main finding and its importance? Repeated sprint exercise with blood flow restriction administered during rest periods under systemic hypoxia led to severe local hypoxia within the exercised muscles without a reduction in power output. The maintained power output might be due to elevated neuromuscular activation. Accordingly, the proposed repeated sprint exercise in the current study may be an effective training modality.

ABSTRACT

Repeated sprint exercise (RSE) is a popular training modality for a wide variety of athletic activities. The purpose of this study was to assess the combined effects of systemic hypoxia and blood flow restriction (BFR) on muscle deoxygenation and RSE performance. Twelve healthy young men performed a standard RSE training modality (five sets of 10 s maximal sprint with a 60 s rest) under four different conditions: (1) normoxic control (NC), normoxia (N, 20.9%) + control BFR (C, 0 mmHg); (2) normoxic BFR (NB), normoxia (N, 20.9%) + BFR (B, 140 mmHg); (3) hypoxic control (HC), hypoxia (H, 13.7%) + control BFR (C, 0 mmHg); and (4) hypoxic BFR (HB): hypoxia (H, 13.7%) + BFR (B, 140 mmHg). BFR was only administered during the rest period of the respective RSE trials. In the local exercising muscles, muscle oxygen saturation (Sm O 2 $\textit{Sm}{O}_{2}$ ) and neuromuscular activity were measured using near-infrared spectroscopy and surface electromyography, respectively. SmO2 was lower in systemic hypoxia conditions relative to normoxia conditions (P < 0.05). A rther decrease in SmO2 was observed in HB relative to HC (Set 1: HC 70.0 ± 17.5 vs. HB 57.4 ± 11.3%, P = 0.001; Set 4: HC 67.5 ± 14.6 vs. HB 57.0 ± 12.0%, P = 0.013; Set 5: HC 61.0 ± 15.3 vs. HB 47.7 ± 11.9%, P < 0.001). No differences in RSE performance were observed between any of the conditions (P > 0.05). Interestingly, an elevated neuromuscular activity was seen in response to the BFR, particularly during conditions of systemic hypoxia (P < 0.05). Thus, RSE with BFR administered during rest periods under systemic hypoxia led to severe local hypoxia without compromising training workload.

National Strength and Conditioning Association Position Statement on Weightlifting for Sports Performance

ABSTRACT

Comfort, P, Haff, GG, Suchomel, TJ, Soriano, MA, Pierce, KC, Hornsby, WG, Haff, EE, Sommerfield, LM, Chavda, S, Morris, SJ, Fry, AC, and Stone, MH. National Strength and Conditioning Association position statement on weightlifting for sports performance. J Strength Cond Res XX(X): 000-000, 2022-The origins of weightlifting and feats of strength span back to ancient Egypt, China, and Greece, with the introduction of weightlifting into the Olympic Games in 1896. However, it was not until the 1950s that training based on weightlifting was adopted by strength coaches working with team sports and athletics, with weightlifting research in peer-reviewed journals becoming prominent since the 1970s. Over the past few decades, researchers have focused on the use of weightlifting-based training to enhance performance in nonweightlifters because of the biomechanical similarities (e.g., rapid forceful extension of the hips, knees, and ankles) associated with the second pull phase of the clean and snatch, the drive/thrust phase of the jerk and athletic tasks such as jumping and sprinting. The highest force, rate of force development, and power outputs have been reported during such movements, highlighting the potential for such tasks to enhance these key physical qualities in athletes. In addition, the ability to manipulate barbell load across the extensive range of weightlifting exercises and their derivatives permits the strength and conditioning coach the opportunity to emphasize the development of strength-speed and speed-strength, as required for the individual athlete. As such, the results of numerous longitudinal studies and subsequent meta-analyses demonstrate the inclusion of weightlifting exercises into strength and conditioning programs results in greater improvements in force-production characteristics and performance in athletic tasks than general resistance training or plyometric training alone. However, it is essential that such exercises are appropriately programmed adopting a sequential approach across training blocks (including exercise variation, loads, and volumes) to ensure the desired adaptations, whereas strength and conditioning coaches emphasize appropriate technique and skill development of athletes performing such exercises.

Acute Effects of Low-intensity Isometric Exercise at Long and Short Muscle-tendon Unit Lengths

Low-intensity training at long muscle-tendon unit lengths with a greater passive force may cause muscle swelling, which may be related to hypertrophy, even if the active force production is lower than that at short muscle-tendon unit lengths. This study compared muscle swelling after low-intensity torque-matched isometric exercises at long and short muscle-tendon unit lengths. Twenty-six volunteers performed isometric knee flexion exercises (30% of maximal voluntary contraction× 5 seconds×10 repetitions×9 sets) either at long or short lengths of the hamstrings (90° hip flexion and 30° knee flexion, or 90° hip and knee flexion, respectively). Active torque was calculated by subtracting passive torque from the total torque generated during exercise. Swelling-induced changes in cross-sectional area was assessed before and after exercise using ultrasonography. There was no between-group difference in the total torque during exercise; however, the active torque was significantly lower in the group trained at long than in the group trained at short muscle-tendon unit lengths. Muscle swelling occurred in both groups. The results suggest that exercise at long muscle-tendon unit lengths can cause similar muscle swelling as exercise at short muscle-tendon unit lengths, even in cases where active torque production is lower than that at short lengths.

Efficacy of resistance training in hypoxia on muscle hypertrophy and strength development: a systematic review with meta-analysis

A systematic review and meta-analysis was conducted to determine the effects of resistance training under hypoxic conditions (RTH) on muscle hypertrophy and strength development. Searches of PubMed-Medline, Web of Science, Sport Discus and the Cochrane Library were conducted comparing the effect of RTH versus normoxia (RTN) on muscle hypertrophy (cross sectional area (CSA), lean mass and muscle thickness) and strength development [1-repetition maximum (1RM)]. An overall meta-analysis and subanalyses of training load (low, moderate or high), inter-set rest interval (short, moderate or long) and severity of hypoxia (moderate or high) were conducted to explore the effects on RTH outcomes. Seventeen studies met inclusion criteria. The overall analyses showed similar improvements in CSA (SMD [CIs] = 0.17 [- 0.07; 0.42]) and 1RM (SMD = 0.13 [0.0; 0.27]) between RTH and RTN. Subanalyses indicated a medium effect on CSA for longer inter-set rest intervals and a small effect for moderate hypoxia and moderate loads favoring RTH. Moreover, a moderate effect for longer inter-set rest intervals and a trivial effect for severe hypoxia and moderate loads favoring RTH was found on 1RM. Evidence suggests that RTH employed with moderate loads (60-80% 1RM) and longer inter-set rest intervals (≥ 120 s) enhances muscle hypertrophy and strength compared to normoxia. The use of moderate hypoxia (14.3-16% FiO2) seems to be somewhat beneficial to hypertrophy but not strength. Further research is required with greater standardization of protocols to draw stronger conclusions on the topic.

Two vs. One Resistance Exercise Sessions in One Day: Acute Effects on Recovery and Performance

Purpose: The purpose of this study was to compare the recovery response of one resistance training session (1TRS) vs. two resistance training sessions (2TRS) performed in 1 day, on upper body performance, muscle morphology and muscle soreness in trained men. Methods: Twenty-four resistance trained men were randomly assigned into a 1TRS group (N = 12; age = 25.0 ± 2.4 years; body mass = 87.6 ± 14.0 kg; height = 177.1 ± 4.9 cm) or into a 2TRS group (N = 10; age = 24.4 ± 1.6 years; body mass = 81.1 ± 5.6 kg; height = 176.6 ± 6.7 cm). 1TRS performed one training session involving eight sets of 10 reps at 70% of 1RM at the bench press, while 2TRS group divided the same training volume in two workouts, with a recovery time of 4 hr. Performance [bench press throw power (BTP) and isometric bench press (IBP)] and muscle thickness of pectoralis major (PECMT) were assessed at baseline (BL), 15-min, 24-hr and 48-hr post-exercise. Results: Training intensity was significantly higher in 2TRS compared to 1TRS (p < .001). Faster recovery rates were detected for BTP (p = .039) and PECMT (p = .05) in 2TRS compared to 1TRS. Both BTP and PECMT were significantly more affected (p < .05) in 1TRS than in 2TRS at 24 h. Conclusions: Results indicate that the recovery process may be accelerated by splitting a high resistance training volume into two different training sessions performed in 1 day.

Serum Metabolites Associated with Muscle Hypertrophy after 8 Weeks of High- and Low-Load Resistance Training

The mechanisms responsible for the similar muscle growth attained with high- and low-load resistance training (RT) have not yet been fully elucidated. One mechanism is related to the mechanical stimulus and the level of motor unit recruitment; another mechanism is related to the metabolic response. We investigated the electromyographic signal amplitude (sEMG) and the general metabolic response to high-load RT (HL) and low-load resistance training (LL). We measured muscle thickness by ultrasound, sEMG amplitude by electromyography, and analysis of metabolites expressed through metabolomics. No differences were observed between the HL and LL groups for metabolic response and muscle thickness. A greater amplitude of sEMG was observed in the HL group. In addition, a correlation was observed between changes in muscle thickness of the vastus lateralis muscle in the HL group and levels of the metabolites carnitine, creatine, 3-hydroxyisovalerate, phenylalanine, asparagine, creatine phosphate, and methionine. In the LL group, a correlation was observed between changes in muscle thickness of the vastus lateralis muscle and levels of the metabolites acetoacetate, creatine phosphate, and oxypurinol. These correlations seem to be related to the characteristics of activated muscle fibers, the metabolic demand of the training protocols used, and the process of protein synthesis.

Effects of Different Isometric Training Programs on Muscle Size and Function in the Elbow Flexors

It remains unknown whether a regimen of a combination of high- and low-intensity resistance training increases muscle size and maximal voluntary isometric contraction (MVC) simultaneously. This study aimed to clarify the effect of the combination of high- and low-intensity resistance training on muscle size and neuromuscular function in the elbow flexors. Sixteen male adults participated in a 9-week isometric training regimen in elbow joint flexion of each arm. We randomly assigned two different training regimens to left and right arms: one aiming to strengthen maximal strength (ST) and the other aiming to develop muscle size as well as maximal strength, which consists of one contraction to volitional failure with 50% of MVC added to ST (COMB). Following the 3-week training to volitional failure as familiarization, the participants conducted the 6-week ST and COMB training in each arm. Before the intervention, and at the third (Mid) and ninth (Post) weeks, MVC and muscle thickness in the anterior part of the upper arm (ultrasound) were measured. Muscle cross-sectional area (mCSA) was derived from the obtained muscle thickness. From Mid to Post, the relative change in MVC was similar in both arms. The COMB regimen increased muscle size, but no significant change was found in ST. Following the 3-week isometric training to volitional failure, the 6-week training regimen for developing maximal voluntary and muscle hypertrophy increased MVC, with increasing mCSA, and the training-induced change in MVC was similar to that for developing maximal voluntary strength alone.

Phase angle, muscle tissue, and resistance training

The biophysical response of the human body to electric current is widely appreciated as a barometer of fluid distribution and cell function. From distinct raw bioelectrical impedance (BIA) variables assessed in the field of body composition, phase angle (PhA) has been repeatedly indicated as a functional marker of the cell's health and mass. Although resistance training (RT) programs have demonstrated to be effective to improve PhA, with varying degrees of change depending on other raw BIA variables, there is still limited research explaining the biological mechanisms behind these changes. Here, we aim to provide the rationale for the responsiveness of PhA determinants to RT, as well as to summarize all available evidence addressing the effect of varied RT programs on PhA of different age groups. Available data led us to conclude that RT modulates the cell volume by increasing the levels of intracellular glycogen and water, thus triggering structural and functional changes in different cell organelles. These alterations lead, respectively, to shifts in the resistive path of the electric current (resistance, R) and capacitive properties of the human body (reactance, Xc), which ultimately impact PhA, considering that it is the angular transformation of the ratio between Xc and R. Evidence drawn from experimental research suggests that RT is highly effective for enhancing PhA, especially when adopting high-intensity, volume, and duration RT programs combining other types of exercise. Still, additional research exploring the effects of RT on whole-body and regional BIA variables of alternative population groups is recommended for further knowledge development.

Twelve Weeks Rest–Pause and Traditional Resistance Training: Effects on Myokines and Performance Adaptations among Recreationally Trained Men

A rest–pause (RP) technique involves performing one or more repetitions at high resistance to failure, followed by a short rest before performing one or more repetitions. These techniques can affect neuromuscular conditions and fatigue by changing the rest time between repetitions. This study compared the effect of 12 weeks of RP and traditional resistance training (TRT) on myokines (myostatin (MSTN), follistatin (FLST) and insulin-like growth factor-1 (IGF-1)) and functional adaptations. The study recruited 29 men between the ages of 20 and 30 who had performed resistance training for at least 6 to 12 months. Participants were randomly divided into three groups: RP, TRT, and control; resistance training was performed 3 days per week for 12 weeks. The training methods of the two groups were largely similar. The results showed that RP increased IGF-1 and FLST/MSTN more than the TRT group (% change = 19.04, % change = 37.71), and only the RP and TRT groups had significant changes in the FLST/MSTN ratio compared to the control group (p < 0.001 and p = 0.02, respectively). In addition, FLST levels increased and MSTN decreased in the RP and TRT groups, but the rate of change in FLST was significant in the RP and TRT groups compared to the control group (p = 0.002 and p = 0.001, respectively). Leg press and bench press strength, and arm and thigh muscular cross-sectional area (MCSA) increased more in the RP group than in the others, and the percentage of body fat (PBF) decreased significantly. The change between strength and MCSA was significant (p ≤ 0.05), and the PBF change in RP and TRT compared to the control (ES RP group = 0.43; ES TRT group = 0.55; control group ES = 0.09) was significant (p = 0.005, p = 0.01; respectively). Based on the results, the RP training technique significantly affects strength and muscle hypertrophy more than the TRT method, which can be included in the training system to increase strength and hypertrophy.

Training in the Initial Range of Motion Promotes Greater Muscle Adaptations Than at Final in the Arm Curl

OBJECTIVE

The effects of ROM manipulation on muscle strength and hypertrophy response remain understudied in long-term interventions. Thus, we compared the changes in strength and regional muscle hypertrophy after training in protocols with different ranges of motion (ROM) in the seated dumbbell preacher curl exercise using a within-participant experimental design.

DESIGN AND METHODS

Nineteen young women had one arm randomly assigned to train in the initial ROM (INITIALROM: 0°-68°; 0° = extended elbow) while the contralateral arm trained in the final ROM (FINALROM: 68°-135°), three times per week over an eight-week study period. Pre- and post-training assessments included one repetition maximum (1RM) testing in the full ROM (0°-135°), and measurement of biceps brachii cross-sectional area (CSA) at 50% and 70% of humerus length. Paired t-tests were used to compare regional CSA changes between groups, the sum of CSA changes at 50% and 70% (CSAsummed), and the strength response between the training protocols.

RESULTS

The INITIALROM protocol displayed a greater CSA increase than FINALROM protocol at 70% of biceps length (p = 0.001). Alternatively, we observed similar increases between the protocols for CSA at 50% (p = 0.311) and for CSAsummed (p = 0.111). Moreover, the INITIALROM protocol displayed a greater 1RM increase than FINALROM (p < 0.001).

CONCLUSIONS

We conclude that training in the initial angles of elbow flexion exercise promotes greater distal hypertrophy of the biceps brachii muscle in untrained young women. Moreover, the INITIALROM condition promotes a greater dynamic strength increase when tested at a full ROM compared to the FINALROM.

Blood Flow Restriction Therapy for 2 Weeks Prior to Anterior Cruciate Ligament Reconstruction Did Not Impact Quadriceps Strength Compared to Standard Therapy

PURPOSE

To evaluate the efficacy of a 2-week home-based blood flow restriction (BFR) prehabiliation program on quadriceps strength and patient-reported outcomes prior to anterior cruciate ligament (ACL) reconstruction.

METHODS

Patients presenting with an ACL tear were randomized into two groups, BFR and control, at their initial clinic visit. Quadriceps strength was measured using a handheld dynamometer in order to calculate peak force, average force, and time to peak force during seated leg extension at the initial clinic visit and repeated on the day of surgery. All patients were provided education on standardized exercises to be performed 5 days per week for 2 weeks between the initial clinic visit and date of surgery. The BFR group was instructed to perform these exercises with a pneumatic cuff set to 80% of limb occlusion pressure placed over the proximal thigh. Patient-Reported Outcome Measurement System Physical Function (PROMIS-PF), knee range of motion, and quadriceps circumference were gathered at the initial clinic visit and day of surgery, and patients were monitored for adverse effects.

RESULTS

A total 45 patients met inclusion criteria and elected to participate. There were 23 patients randomized to the BFR group and 22 patients randomized into the control group. No significant differences were noted between the BFR and control groups in any demographic characteristics (48% vs 64% male [P = .271] and average age 26.5 ± 12.0 vs 27.0 ± 11.0 [P = .879] in BFR and control, respectively). During the initial clinic visit, there were no significant differences in quadriceps circumference, peak quadriceps force generation, time to peak force, average force, pain, and PROMIS scales (P > .05 for all). Following completion of a 2-week home prehabilitation protocol, all patients indeterminant of cohort demonstrated decreased strength loss in the operative leg compared to the nonoperative leg (P < .05 for both) However, there were no significant differences in any strength or outcome measures between the BFR and control groups (P > .05 for all). There were no complications experienced in either group, and both were compliant with the home-based prehabilitation program.

CONCLUSIONS

A 2-week standardized prehabilitation protocol preceding ACL reconstruction resulted in a significant improvement in personal quadriceps peak force measurements, both with and without the use of BFR. No difference in quadriceps circumference, strength, or patient reported outcomes were found between the BFR and the control group. The home-based BFR prehabiliation protocol was found to be feasible, accessible, and well tolerated by patients.

LEVEL OF EVIDENCE

Level II, randomized controlled trial with small effect size.

The impact of leg position on muscle blood flow and oxygenation during low-intensity rhythmic plantarflexion exercise

PURPOSE

Resistance training (RT) is an effective countermeasure to combat physical deconditioning whereby localized hypoxia within the limb increases metabolic stress eliciting muscle adaptation. The current study sought to examine the influence of gravity on muscle oxygenation (SmO₂) alongside vascular hemodynamic responses.

METHODS

In twelve young healthy adults, an ischemic occlusion test and seven minutes of low-intensity rhythmic plantarflexion exercise were used alongside superficial femoral blood flow and calf near-infrared spectroscopy to assess the microvascular vasodilator response, conduit artery flow-mediated dilation, exercise-induced hyperemia, and SmO₂ with the leg positioned above or below the heart in a randomized order.

RESULTS

The microvascular vasodilator response, assessed by peak blood flow (798 ± 231 mL/min vs. 1348 ± 290 mL/min; p < 0.001) and reperfusion slope 10 s of SmO₂ after cuff deflation (0.75 ± 0.45%.s-1 vs.2.40 ± 0.94%.s-1; p < 0.001), was attenuated with the leg above the heart. This caused a blunted dilatation of the superficial femoral artery (3.0 ± 2.4% vs. 5.2 ± 2.1%; p = 0.008). Meanwhile, blood flow area under the curve was comparable (above the heart: 445 ± 147 mL vs. below the heart: 474 ± 118 mL; p = 0.55) in both leg positions. During rhythmic exercise, the increase in femoral blood flow was lower in the leg up position (above the heart: 201 ± 94% vs. below the heart: 292 ± 114%; p = 0.001) and contributed to a lower SmO₂ (above the heart: 41 ± 18% vs. below the heart 67 ± 5%; p < 0.001).

CONCLUSION

Positioning the leg above the heart results in attenuated peak vascular dilator response and exercise-induced hyperemia that coincided with a lower SmO₂ during low-intensity plantarflexion exercise.

Haemodynamics and oxygenation in the lower-limb muscles of young ambulatory adults with cerebral palsy

AIM

To evaluate muscle haemodynamics and oxygen metabolism in adults with cerebral palsy (CP) at rest and during exercise.

METHOD

This cross-sectional study included 12 adults with spastic CP (four females, eight males; mean age [SD] 29 years 6 months [7 years 10.8 months]) and 13 typically developing individuals (seven females, six males; mean age [SD] 26 years 6 months [1 year 1.9 months]). Near-infrared spectroscopy was used to assess changes in muscle blood flow (mBF), muscle oxygen consumption (mVO₂ ), and muscle oxygen saturation in the vastus lateralis and rectus femoris muscles during three conditions: rest, low load at 20% maximum voluntary contraction (MVC), and high load at 80% MVC.

RESULTS

MBF was lower in participants with CP than in typically developing participants at rest (p < 0.001) and at 20% MVC (p = 0.007) in both muscles. Increased load caused a reduction in mBF in typically developing participants and an increase in CP. MVO₂ in typically developing participants increased from rest to 20% MVC and was reduced at 80% MVC compared with 20% MVC. In participants with CP, there was no change with load in the rectus femoris muscle; however, there was an increase in the vastus lateralis muscle from rest to 20% MVC, and 80% MVC had a similar value. Muscle saturation was higher in participants with CP across all conditions (vastus lateralis, p < 0.001; rectus femoris, p = 0.0518).

INTERPRETATION

Oxidative metabolism in CP is not limited by oxygen delivery (mBF), because high muscle saturation suggests oxygen availability. Adults with CP demonstrate muscular responses to exercise that are inconsistent with typical high-workload activation, probably because of inefficient fibre recruitment and secondary anomalies.

The study of the effect of drinks based on extracts of herbal adaptogens on the functional status of athletes during physical activity

Adverse environmental factors, stress, lack of sleep and rest, and heavy physical exertion, deplete the human body. In particular, the reserves of the main metabolites, water, and oxygen, are very limited. People, especially athletes, need to take special dietary supplements with adaptogenic properties to adapt to stressful extreme loads. In this study, the influence of using extracts of leuzea, ginseng, and Eleutherococcus on athletes' performance, endurance, strength, and emotional state is carried out. The studies were conducted on four groups of male athletes aged from 19 to 25 years. For three weeks, diagnostics of vital lung capacity, Stange, and Genchi tests are carried out, and data on the general impressions of athletes are collected. According to the research results, the use of adaptogens leads to an increase in physical performance. After the first week of the study, a positive effect on the human body are noticed: improve well-being and increased athletic performance. When using Eleutherococcus, there was a change in the work of the central nervous system (motor functions): tasks begin to be performed in an organized and accelerated manner without deterioration of well-being, but the volume of strength exercises remained the same. When using the drug leuzea, muscle strength was noted, which allowed to increase the load. There is a positive effect of phytopreparations on the body, namely on the functions of the cardiovascular, central nervous and endocrine systems. In 4 participants who took leuzea, the performance in power competitions improved by 18.5% compared to the control group. The intake of Eleutherococcus and ginseng is accompanied by an increase in the activity of neurotransmitter cells, i.e., the effect on the mesolimbic system.  In addition, a study of hematological blood parameters and hormonal statuses at the beginning and end of the study was conducted with the subjects who took leuzea extract. So, the use of the drug leuzea leads to the following positive changes: a more significant increase in ESR, a more significant increase in hemoglobin, compared with the control group. The conclusion is made about the practicality of taking biologically active additives based on some plant adaptogens.

Application and progress of blood flow restriction training in improving muscle mass and strength in the elderly

As an emerging training method, blood flow restriction training has been proved to promote the growth of muscle mass and strength. In recent years, it has been gradually applied in different populations. However, there are few studies on how blood flow restriction training affects muscle mass and strength in the elderly. The relevant literature is compiled and summarized in this study. Through the comparison of blood flow restriction training with traditional training methods and its application in the elderly, it shows that blood flow restriction training can effectively increase muscle mass and strength, prevent muscle atrophy, improve cardiopulmonary function, facilitate injury and postoperative rehabilitation, and intervene in related degenerative diseases as a training method suitable for the elderly,. The main mechanism of blood flow restriction training promoting muscle mass and strength growth is metabolic stress response, including muscle fiber recruitment, protein synthesis signal pathway activation, hormone secretion, etc., and is also related to cell swelling caused by pressure. At present, although the application of blood flow restriction training in the elderly population is increasing, there is a lack of personalized programs. In the future, more research on the dose effect and safety of blood flow restriction training is needed to develop more accurate personalized training programs.

Acute changes in motor unit discharge property after concentric versus eccentric contraction exercise in knee extensor

This study aimed to investigate the motor unit firing property immediately after concentric or eccentric contraction exercise. Eighteen healthy men performed repetitive maximal isokinetic knee extension exercises with only concentric or eccentric contraction until they exerted less than 80% of the baseline strength. Before and after the fatiguing exercise, high-density surface electromyography of the vastus lateralis was recorded during submaximal ramp-up isometric contraction and individual motor units were identified. Only motor units that could be tracked before and after exercise were analyzed. Muscle cross-sectional area of the vastus lateralis was measured using ultrasound, and electrically evoked torque was recorded before and after the exercise. Sixty-five and fifty-three motor units were analyzed before and after the concentric and eccentric contractions, respectively. The results showed that motor units with moderate to high recruitment thresholds significantly decreased recruitment thresholds under both conditions, and the motor unit discharge rates significantly increased after concentric contraction compared to eccentric contraction. A greater muscle cross-sectional area was observed with concentric contraction. The evoked torque was significantly decreased under both conditions, but no difference between the conditions. These results suggest that fatiguing exercise with concentric contraction contributes to greater neural input to muscles and metabolic responses than eccentric contraction.

Immediate association of navicular bone height and plantar intrinsic muscle size with toe flexion task: An ultrasound-based study

BACKGROUND: Intrinsic foot muscle (IFM) dysfunction and poor foot arch are associated with various foot conditions. Toe flexor exercise (TFE) has been used to improve it; however, the immediate effects of TFE on each IFM and how it relates to changes in navicular bone height (NH) are unclear. OBJECTIVE: This study aimed to investigate acute muscle swelling in the IFM after TFE and the association between changes in NH and IFM size. METHODS: Fourteen adults participated in this study. NH and cross-sectional area (CSA) of the IFM were acquired pre and post- TFE. The CSA of the IFM, including the abductor hallucis (AbH), flexor hallucis brevis, flexor digitorum brevis, and quadratus plantae, was acquired with ultrasonography. In the TFE, each participant completed five sets of eight repetitions with maximum strength. RESULTS: The NH and CSA of all IFM significantly increased significantly post-TFE (p< 0.01). Only the increase in AbH was moderately and positively correlated with the change in NH (r= 0.54, p< 0.01). CONCLUSION: This study suggests that the acute swelling of AbH after TFE is associated with an immediate increase in NH, supporting the important role of AbH in the formation of foot arch.

Effects of exercise programs on phase angle in older adults: A systematic review and meta-analysis

The purpose of this study was to calculate the effects of exercise programs on phase angle (PhA) in older people. A systematic review was undertaken in multiple electronic databases in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-analyses statement guidelines for the purposes of selecting randomized controlled trials that measured the effects of the exercise programs on PhA in older adults on 31 March 2022. We carried out a random-effect meta-analysis for the effects of exercise programs on PhA. Additionally, we analysed the differences between subgroups in terms of weekly frequency, number of sets and repetitions, and duration of interventions. Studies were methodological assessed through the PEDro scale where one had excellent, ten had good, and three had poor methodological quality. For the purposes of the study, fourteen studies met the criteria for inclusion. However, four studies did not have enough information to be included in the quantitative analysis. The remaining ten articles revealed moderate effects on PhA in favour of intervention groups (p=0.009, SMD=0.72 [0.46-0.99], I2=54%). The meta-analysis also showed that interventions lasting twelve weeks are more successful in generating positive effects on PhA as opposed to eight weeks (SMD's=0.79 vs. 0.64, respectively). These results indicate that resistance training (RT) is an effective and safe to improve PhA in the older people, especially through RT programs lasting from eight to twelve weeks. A novel finding of this study was that RT is the most used type of exercise by authors when assessing the PhA in older adults.

Blood flow restriction training promotes functional recovery of knee joint in patients after arthroscopic partial meniscectomy: A randomized clinical trial

Purpose: To explore the effect of blood flow restriction training (BFRT) on the recovery of knee function in patients after arthroscopic partial meniscectomy (APM).

Methods: Forty patients undergoing APM surgery were included in this parallel group, two-arm, single-assessor blinded, randomized clinical trial. The subjects were randomly divided into two groups: routine rehabilitation group (RR Group, n = 20) and routine rehabilitation + blood flow restriction training group (RR + BFRT Group, n = 20). One subject in each group dropped out during the experiment. All patients received 8 weeks of routine rehabilitation starting from the second day after APM. In addition, patients in the RR + BFRT group required additional BFRT twice a week. Visual analogue scale (VAS) score, range of motion (ROM), one-leg standing test (OLST) score, Lysholm knee score, quadriceps muscle strength, quadriceps thickness, and thigh circumference were evaluated at preoperative, postoperative, 4 and 8 weeks after surgery. SPSS 25.0 software was used for statistical analysis of the data. Repeated measures ANOVA was used if the data were normally distributed and had homogeneity of variance. Generalized estimating equations were chosen if the data were not normally distributed or had homogeneity of variance.

Results: There were no significant differences in VAS score, ROM, OLST score, Lysholm knee score, quadriceps muscle strength, quadriceps thickness, and thigh circumference between the two groups before surgery (p > 0.05). Compared with postoperative, VAS score, ROM, OLST score, Lysholm knee score, and thigh circumference were significantly improved in the RR group (p < 0.05), while quadriceps muscle strength and quadriceps thickness were not significantly enhanced at 8 weeks postoperatively (p > 0.05). However, VAS score, ROM, OLST score, Lysholm knee score, quadriceps muscle strength, quadriceps thickness, and thigh circumference were all significantly improved in the RR + BFRT group at 8 weeks postoperatively (p < 0.05). Furthermore, compared with the RR group, VAS score (50% vs. 86%), ROM (7.9% vs. 16.0%), OLST score (57.3% vs. 130.1%), Lysholm knee score (38.4% vs. 55.7%), relative peak torque (11.0% vs. 84.7%), mean power (20.6% vs. 88.1%), rectus femoris thickness (0.40% vs. 13.0%), vastus medialis (0.29% vs. 5.32%), vastus lateralis (0% vs. 6.2%), vastus internus (0% vs. 5.8%), and thigh circumference (2.7% vs. 5.8%) in the RR + BFRT group were significantly improved at 4 and 8 weeks postoperatively (p < 0.05).

Conclusion: BFRT combined with routine rehabilitation training can better promote the recovery of knee joint function in patients after APM, especially the improvement of quadriceps muscle strength and thickness.

Beyond Mechanical Tension: A Review of Resistance Exercise-Induced Lactate Responses & Muscle Hypertrophy

The present review aims to explore and discuss recent research relating to the lactate response to resistance training and the potential mechanisms by which lactate may contribute to skeletal muscle hypertrophy or help to prevent muscle atrophy. First, we will discuss foundational information pertaining to lactate including metabolism, measurement, shuttling, and potential (although seemingly elusive) mechanisms for hypertrophy. We will then provide a brief analysis of resistance training protocols and the associated lactate response. Lastly, we will discuss potential shortcomings, resistance training considerations, and future research directions regarding lactate's role as a potential anabolic agent for skeletal muscle hypertrophy.

Blood Flow Restriction Therapy: An Evidence-Based Approach to Postoperative Rehabilitation

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Blood flow restriction therapy (BFRT) involves the application of a pneumatic tourniquet cuff to the proximal portion of the arm or leg. This restricts arterial blood flow while occluding venous return, which creates a hypoxic environment that induces many physiologic adaptations.

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BFRT is especially useful in postoperative rehabilitation because it produces muscular hypertrophy and strength gains without the need for heavy-load exercises that are contraindicated after surgery.

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Low-load resistance training with BFRT may be preferable to low-load or high-load training alone because it leads to comparable increases in strength and hypertrophy, without inducing muscular edema or increasing pain.