Resistance training modalities: comparative analysis of effects on physical fitness, isokinetic muscle functions, and core muscle biomechanics

Introduction

This study aimed to evaluate the effects of varied resistance training modalities on physical fitness components, body composition, maximal strength assessed by one-repetition maximum (1RM), isokinetic muscle functions of the shoulder and knee joints, and biomechanical properties of core muscles.

Methods

Forty participants were randomly assigned to four groups: control group (CG, n = 10), compound set training group (CSG, n = 10), pyramid set training group (PSG, n = 10), and superset training group (SSG, n = 10). Excluding the CG, the other three groups underwent an 8-week resistance training program, three sessions per week, at 60%-80% of 1RM intensity for 60-90 min per session. Assessments included body composition, physical fitness components, 1RM, isokinetic muscle functions, and biomechanical properties (muscle frequency, stiffness, etc.) of the rectus abdominis and external oblique muscles.

Results

The PSG demonstrated the most significant improvement in relative peak torque during isokinetic testing of the shoulder and knee joints. Compared to the CG, all exercise groups exhibited positive effects on back strength, sprint performance, 1RM, and core muscle biomechanics. Notably, the PSG showed superior enhancement in external oblique stiffness. However, no significant differences were observed among the exercise groups for rectus abdominis biomechanical properties.

Discussion

Structured resistance training effectively improved maximal strength, functional performance, and core muscle biomechanics. The pyramidal training modality conferred specific benefits for isokinetic muscle functions and external oblique stiffness, suggesting its efficacy in enhancing force production capabilities and core stability.

Effects of manual resistance versus weight resistance training on body composition and strength in young adults after a 14-week intervention

Manual Resistance Training (MRT) is an alternative training modality where the external resistance is provided by a spotter.

PURPOSE

The purpose of this study was to observe changes in body composition and muscular fitness after a 14-week MRT intervention compared to changes elicited by a Weight Resistance Training (WRT) intervention.

METHODS

Eighty-four young adults were randomly assigned to either the MRT (n = 53, height 170.1 ± 8.1 cm, body mass 73.9 ± 16.0 kg, and body fat 24.6 ± 8.7%) or WRT (n = 31, mean ± SD: height 169.6 ± 10.1 cm, body mass 75.0 ± 17.4 kg, and body fat 24.7 ± 8.5%) group. Body composition was assessed by Dual-energy X-ray Absorptiometry (DEXA), muscular strength and muscular endurance were tested before and after the intervention.

RESULTS

Findings indicated that trunk, arm, leg, and total lean mass increased in both groups after the intervention (p < 0.05). Moreover, total fat mass significantly decreased compared to baseline in both groups (p < 0.05). However, no statistically significant changes were observed in Bone Mineral Density and Bone Mineral Content in response to the intervention. Both MRT and WRT programs were successful at significantly increasing muscular strength and endurance (p < 0.05).

CONCLUSION

The changes in body composition after a 14-week MRT program were similar to those of the WRT intervention. Hence, an MRT program may be effectively used to increase lean mass and decrease fat mass.

Including the Eccentric Phase in Resistance Training to Counteract the Effects of Detraining in Women: A Randomized Controlled Trial

ABSTRACT

Coratella, G, Beato, M, Bertinato, L, Milanese, C, Venturelli, M, and Schena, F. Including the eccentric phase in resistance training to counteract the effects of detraining in women: a randomized controlled trial. J Strength Cond Res 36(11): 3023-3031, 2022-The current study compared the effects of concentric-based (CONC), eccentric-based (ECC), and traditional concentric-eccentric (TRAD) resistance training on muscle strength, mass, and architecture and the postdetraining retention of the training-induced effects in women. Sixty women were randomly assigned to unilateral volume-equated CONC, ECC, or TRAD knee extension training or control ( N = 15 per group). Before training, after an 8-week intervention period, and after an 8-week detraining period, isokinetic concentric, eccentric, and isometric torque were measured. In addition, thigh lean mass was assessed by dual X-ray absorptiometry and vastus lateralis thickness, pennation angle, and fascicle length by ultrasound. After training, concentric and isometric torque increased ( p < 0.05) similarly in all groups, whereas eccentric torque increased more in ECC than that in CONC (+13.1%, effect size (ES): 0.71 [0.04-1.38]) and TRAD (+12.6%, ES: 0.60 [0.12-1.08]). Thigh lean mass increased in ECC (+6.1%, ES: 0.47 [0.27-0.67]) and TRAD (+3.1%, ES: 0.33 [0.01-0.65]). Vastus lateralis thickness and pennation angle increased ( p < 0.05) similarly in all groups, whereas fascicle elongation was visible in ECC (+9.7%, ES: 0.92 [0.14-1.65]) and TRAD (+7.1%, ES: 0.64 [0.03-1.25]). After detraining, all groups retained ( p < 0.05) similar concentric torque. ECC and TRAD preserved eccentric torque ( p < 0.05), but ECC more than TRAD (+17.9%, ES: 0.61 [0.21-1.21]). All groups preserved isometric torque ( p < 0.05), but ECC more than CONC (+14.2%, ES: 0.71 [0.04-1.38]) and TRAD (+13.8%, ES: 0.65 [0.10-1.20]). Thigh lean mass and vastus lateralis fascicle length were retained only in ECC ( p < 0.05), pennation angle was preserved in all groups ( p < 0.05), and thickness was retained in CONC and ECC ( p < 0.05). Including the eccentric phase in resistance training is essential to preserve adaptations after detraining.

Effects of Cross-Education After 6 Weeks of Eccentric Single-Leg Decline Squats Performed With Different Execution Times: A Randomized Controlled Trial

BACKGROUND

Cross-education of strength refers to the strength gain that is transferred to the contralateral limb after a unilateral training program.

HYPOTHESIS

Unilateral eccentric training using different muscle contraction times would improve the structural and functional properties of the untrained contralateral limb.

STUDY DESIGN

Randomized controlled trial.

LEVEL OF EVIDENCE

Level 2.

METHODS

Thirty-six participants were randomized into a control group, experimental group 1 (EG6s; eccentric contraction runtime = 6 seconds) and experimental group 2 (EG3s; eccentric contraction runtime = 3 seconds). The thickness and elastographic index of the patellar tendon (PT), lean mass and fat percentage of the thigh, contractile properties of the vastus lateralis (VL), as well as isometric, concentric, and eccentric knee extensor peak torques, and eccentric single-leg decline squat (SLDS_e) 1 repetition maximum (1-RM) were measured after 6 weeks of SLDS_e training (3 times per week, 80% of 1-RM) and after 6 weeks of detraining in the untrained contralateral limb.

RESULTS

After training, there was an increase in lean thigh mass of the untrained limb in both groups: EG6s (0.17 ± 0.29 kg;P = 0.03; effect size [ES] = 0.15) and EG3s (0.15 ± 0.23 kg; P = 0.04; ES = 0.19). Likewise, both EG6s (62.30 ± 19.09 kg; P < 0.001; ES = 4.23) and EG3s (68.09 ± 27.49 kg; P < 0.001; ES = 3.40) increased their 1-RM, isometric (EG6s: 48.64 ± 44.82 N·m, P < 0.001, ES = 0.63; EG3s: 34.81 ± 47.30 N·m, P = 0.004, ES = 0.38), concentric at 60 deg/s and 180 deg/s and eccentric at 60 deg/s and 180 deg/s knee extensor peak torques (P < 0.05) in the untrained limb. However, no differences were found in the contractile properties of the VL or in the thickness of the PT after eccentric training in either of the 2 experimental groups.

CONCLUSION

Regardless of the runtime of the contraction, 6 weeks of SLSD_e was effective for inducing structural and strength adaptations in the contralateral untrained limb. However, most of these adaptations were lost after 6 weeks of detraining.

CLINICAL RELEVANCE

Our study suggests that cross-education training can be of great importance for clinical application and musculoskeletal and neuromuscular rehabilitative processes after unilateral injury.

Effects of Power-Oriented Resistance Training With Heavy vs. Light Loads on Muscle-Tendon Function in Older Adults: A Study Protocol for a Randomized Controlled Trial

Background

Power-oriented resistance training (PRT) is one of the most effective exercise programs to counteract neuromuscular and physical function age-related declines. However, the optimal load that maximizes these outcomes or the load-specific adaptations induced on muscle power determinants remain to be better understood. Furthermore, to investigate whether these adaptations are potentially transferred to an untrained limb (i.e., cross-education phenomenon) could be especially relevant during limb-immobilization frequently observed in older people (e.g., after hip fracture).

Methods

At least 30 well-functioning older participants (>65 years) will participate in a within-person randomized controlled trial. After an 8-week control period, the effects of two 12-week PRT programs using light vs. heavy loads will be compared using an unilateral exercise model through three study arms (light-load PRT vs. non-exercise; heavy-load PRT vs. non-exercise; and light- vs. heavy- load PRT). Muscle-tendon function, muscle excitation and morphology and physical function will be evaluated to analyze the load-specific effects of PRT in older people. Additionally, the effects of PRT will be examined on a non-exercised contralateral limb.

Discussion

Tailored exercise programs are largely demanded given their potentially greater efficiency preventing age-related negative consequences, especially during limb-immobilization. This trial will provide evidence supporting the use of light- or heavy-load PRT on older adults depending on individual needs, improving decision making and exercise program efficacy.

Clinical Trial Registration

NCT03724461 registration data: October 30, 2018.

Effects of Eccentric Single-Leg Decline Squat Exercise on the Morphological and Structural Properties of the Vastus Lateralis and Patellar Tendon

The purpose was to examine the effect of 6-week eccentric single-leg decline squat (SLDSe) training with two technical execution times (3 s or 6 s) on changes related to the structural properties of the vastus lateralis (VL) and patellar tendon (PT). Thirty-six physical active volunteers were randomly divided into three groups: control group (CG, n = 13, age = 20.8 ± 1.9 years, no intervention program), experimental group 1 (EG1, n = 11, age = 21.6 ± 2.5 years, execution time = 6 s) and experimental group 2 (EG2, n = 12, 21.1 ± 1.2 years, execution time = 3 s). Participants completed a 6-week SLDSe training program (80% of 1-RM) three days a week. The structural characteristics of the VL and the PT were measured with ultrasonography before and after 6-week SLDSe training and after 6 weeks of de-training. Our results indicate that EG1 increased ≈21.8% the thickness of the PT and EG2 increased ≈15.7% the thickness of the VL after the 6-week intervention program. EG1 and EG2 showed greater values (p < 0.05) of lean mass and lower values (p < 0.05) of fat percentage on the thigh after the intervention program. In conclusion, the SLDSe training carried out with the execution time of 6 s had greater effects on the structural and elastic properties of the PT, and the exercise with the execution time of 3 s caused greater structural adaptations in the VL musculature.

Physiological responses of human skeletal muscle to acute blood flow restricted exercise assessed by multimodal MRI

Important physiological quantities for investigating muscle hypertrophy include blood oxygenation, cell swelling, and changes in blood flow. The purpose of this study was to compare the acute changes of these parameters in human skeletal muscle induced by low-load (20% 1-RM) blood flow-restricted (BFR-20) knee extensor exercise compared with free-flow work-matched (FF-20_WM) and free-flow 50% 1-RM (FF-50) knee extensor exercise using multimodal magnetic resonance imaging (MRI). Subjects (n = 11) completed acute exercise sessions for each exercise mode in an MRI scanner, where interleaved measures of muscle R₂ (indicator of edema), [Formula: see text] (indicator of deoxyhemoglobin), macrovascular blood flow, and diffusion were performed before, between sets, and after the final set for each exercise protocol. BFR-20 exercise resulted in larger acute decreases in R₂ and greater increases in cross-sectional area than FF-20_WM and FF-50 (P < 0.01). Blood oxygenation decreased between sets during BFR-20, as indicated by a 13.6% increase in [Formula: see text] values (P < 0.01)), whereas they remained unchanged for FF-20_WM and decreased during FF-50 exercise. Quadriceps blood flow between sets was highest for the heavier load (FF-50), averaging 305 mL/min, and lowest for BFR-20 at 123 ± 73 mL/min until post-exercise cuff release, where blood flow rates in BFR-20 exceeded both FF protocols (P < 0.01). Acute changes in diffusion rates were similar for all exercise protocols. This study was able to differentiate the acute exercise response of selected physiological factors associated with skeletal muscle hypertrophy. Marked differences in these parameters were found to exist between BFR and FF exercise conditions, which contribute to explain the anabolic potential of low-load blood flow restricted muscle exercise.NEW & NOTEWORTHY Acute changes in blood flow, diffusion, blood oxygenation, cross-sectional area, and the "T₂ shift" are evaluated in human skeletal muscle in response to blood flow-restricted (BFR) and conventional free-flow knee extensor exercise performed in an MRI scanner. The acute physiological response to exercise was dependent on the magnitude of load and the application of BFR. Physiological variables changed markedly and established a steady state rapidly after the first of four exercise sets.

Mechanical Characteristics of Heavy vs. Light Load Ballistic Resistance Training in Older Adults

Rodriguez-Lopez, C, Alcazar, J, Sánchez-Martín, C, Ara, I, Csapo, R, and Alegre, LM. Mechanical characteristics in heavy vs. light load ballistic resistance training in older adults. J Strength Cond Res XX(X): 000-000, 2020-Although power-oriented resistance training (RT) is strongly recommended to counter age-related neuromuscular function declines, there is still controversy about which intensities of load should be used to elicit optimal training adaptations. Knowledge of the mechanical characteristics of power-oriented RT performed at different intensities might help to better understand the training stimulus that triggers load-dependent adaptations in older adults. Using a cross-over design, 15 well-functioning older volunteers (9 men and 6 women; 73.6 ± 3.8 years) completed 2 volume × load-matched ballistic RT sessions with heavy (HL: 6 × 6 × 80% 1-repetition maximum [1RM]) and light-load (LL: 6 × 12 × 40% 1RM) on a horizontal leg press exercise. Electromyographic (EMG) and mechanical variables (work, force, velocity, and power) as well as intraset neuromuscular fatigue (i.e., relative losses in force, velocity, and power) were analyzed. More concentric mechanical work was performed in the LL training session, compared with HL (36.2 ± 11.2%; p < 0.001). Despite the higher mean EMG activity of the quadriceps femoris muscle (13.2 ± 21.1%; p = 0.038) and greater concentric force (35.2 ± 7.6%; p < 0.001) during HL, higher concentric velocity (41.0 ± 12.7%, p < 0.001) and a trend toward higher concentric power (7.2 ± 18.9%, p = 0.075) were found for LL. Relative velocity losses were similar in both sessions (≈10%); however, relative force losses were only found in LL (7.4 ± 6.5%, p = 0.003). Considering the greater mechanical work performed and concentric power generated, ballistic RT using LL may, therefore, represent a stronger stimulus driving training adaptations as compared with volume × load-matched heavy-load training. Relative losses in force and power should be monitored in addition to velocity losses during ballistic RT.

Effects of concurrent exercise training on muscle dysfunction and systemic oxidative stress in older people with COPD

Oxidative stress is associated with disease severity and limb muscle dysfunction in COPD. Our main goal was to assess the effects of exercise training on systemic oxidative stress and limb muscle dysfunction in older people with COPD. Twenty-nine outpatients with COPD (66-90 years) were randomly assigned to a 12-week exercise training (ET; high-intensity interval training (HIIT) plus power training) or a control (CT; usual care) group. We evaluated mid-thigh muscle cross-sectional area (CSA; computed tomography); vastus lateralis (VL) muscle thickness, pennation angle, and fascicle length (ultrasonography); peak VO₂ uptake (VO_2peak ) and work rate (W_peak ) (incremental cardiopulmonary exercise test); rate of force development (RFD); maximal muscle power (P_max ; force-velocity testing); systemic oxidative stress (plasma protein carbonylation); and physical performance and quality of life. ET subjects experienced changes in mid-thigh muscle CSA (+4%), VL muscle thickness (+11%) and pennation angle (+19%), VO_2peak (+14%), W_peak (+37%), RFD (+32% to 65%), P_max (+38% to 51%), sit-to-stand time (-24%), and self-reported health status (+20%) (all P < 0.05). No changes were noted in the CT group (P > 0.05). Protein carbonylation decreased among ET subjects (-27%; P < 0.05), but not in the CT group (P > 0.05). Changes in protein carbonylation were associated with changes in muscle size and pennation angle (r = -0.44 to -0.57), exercise capacity (r = -0.46), muscle strength (r = -0.45), and sit-to-stand performance (r = 0.60) (all P < 0.05). The combination of HIIT and power training improved systemic oxidative stress and limb muscle dysfunction in older people with COPD. Changes in oxidative stress were associated with exercise-induced structural and functional adaptations.

Electrical stimulation increases hypertrophy and metabolic flux in tissue-engineered human skeletal muscle

In vitro models of contractile human skeletal muscle hold promise for use in disease modeling and drug development, but exhibit immature properties compared to native adult muscle. To address this limitation, 3D tissue-engineered human muscles (myobundles) were electrically stimulated using intermittent stimulation regimes at 1 Hz and 10 Hz. Dystrophin in myotubes exhibited mature membrane localization suggesting a relatively advanced starting developmental maturation. One-week stimulation significantly increased myobundle size, sarcomeric protein abundance, calcium transient amplitude (∼2-fold), and tetanic force (∼3-fold) resulting in the highest specific force generation (19.3mN/mm2) reported for engineered human muscles to date. Compared to 1 Hz electrical stimulation, the 10 Hz stimulation protocol resulted in greater myotube hypertrophy and upregulated mTORC1 and ERK1/2 activity. Electrically stimulated myobundles also showed a decrease in fatigue resistance compared to control myobundles without changes in glycolytic or mitochondrial protein levels. Greater glucose consumption and decreased abundance of acetylcarnitine in stimulated myobundles indicated increased glycolytic and fatty acid metabolic flux. Moreover, electrical stimulation of myobundles resulted in a metabolic shift towards longer-chain fatty acid oxidation as evident from increased abundances of medium- and long-chain acylcarnitines. Taken together, our study provides an advanced in vitro model of human skeletal muscle with improved structure, function, maturation, and metabolic flux.

Force-velocity profiling in older adults: An adequate tool for the management of functional trajectories with aging

INTRODUCTION

The actual mechanisms leading to a reduced muscle power and functional ability in older adults are poorly understood. We investigated the association between different force-velocity (F-V) profiles and impaired muscle power, physical and cognitive function, frailty, and health-related quality of life (HRQoL) in older people.

METHODS

Physical function (habitual gait speed, timed up-and-go test, sit-to-stand and stair-climbing ability), cognitive function, HRQoL and frailty were evaluated in 31 older subjects (70-85 years). The F-V relationship and maximal muscle power (P_max) were assessed in the leg press exercise. The skeletal muscle index (SMI) and fat index, moderate-to-vigorous physical activity (MVPA) and sedentary time were obtained from DXA scans and accelerometry, respectively.

RESULTS

While some subjects showed a force deficit (F_DEF), others presented a velocity deficit (V_DEF), both leading to an impaired muscle power [Effect size (ES) = 1.30-1.44], and to a likely-very likely moderate harmful effect in their physical and cognitive function, HRQoL and frailty levels (except the V_DEF group for cognitive function) [ES = 0.76-1.05]. Leg muscle mass and specific force were similarly associated with force at P_max, while MVPA but not sedentary time was related to fat index, force at P_max, and power values (all p < 0.05). A trend was found for the negative association between fat index and relative P_max (p = 0.075).

CONCLUSION

Older subjects exhibited different mechanisms (force vs. velocity deficits) leading to impaired muscle power. Both deficits were associated with a lower physical function and quality of life, and a higher frailty, whereas only a force deficit was associated with a lower cognitive function. Interventions aimed at reversing age- and/or disuse-related impairments of muscle power might evaluate the specific responsible mechanism and act accordingly.

Functional and Muscle-Size Effects of Flywheel Resistance Training with Eccentric-Overload in Professional Handball Players

The aim of the study was to analyse the effects of 6 week (15 sessions) flywheel resistance training with eccentric-overload (FRTEO) on different functional and anatomical variables in professional handball players. Twenty-nine athletes were recruited and randomly divided into two groups. The experimental group (EXP, n = 15) carried out 15 sessions of FRTEO in the leg-press exercise, with 4 sets of 7 repetitions at a maximum-concentric effort. The control group (CON, n = 14) performed the same number of training sessions including 4 sets of 7 maximum repetitions (7RM) using a weight-stack leg-press machine. The results which were measured included maximal dynamic strength (1RM), muscle power at different submaximal loads (PO), vertical jump height (CMJ and SJ), 20 m sprint time (20 m), T-test time (T-test), and Vastus-Lateralis muscle (VL) thickness. The results of the EXP group showed a substantially better improvement (p < 0.05-0.001) in PO, CMJ, 20 m, T-test and VL, compared to the CON group. Moreover, athletes from the EXP group showed significant improvements concerning all the variables measured: 1RM (ES = 0.72), PO (ES = 0.42 - 0.83), CMJ (ES = 0.61), SJ (ES = 0.54), 20 m (ES = 1.45), T-test (ES = 1.44), and VL (ES = 0.63 - 1.64). Since handball requires repeated short, explosive effort such as accelerations and decelerations during sprints with changes of direction, these results suggest that FRTEO affects functional and anatomical changes in a way which improves performance in well-trained professional handball players.

Gender, Success, and Drop-Out during a Resistance Exercise Program in Community Dwelling Old Adults

Background

Resistance exercise training can be effective against sarcopenia. We identified predictors of drop-out and compared physical outcomes between men and women after such training.

Methods

Subjects (N = 236, 73.7 ± 5.7 years) participated in a 12-week resistance exercise program. Outcome variables were measured at baseline and endpoint.

Results

Drop-out was 11.9% and not significantly different between genders. Drop-outs were significantly older and had poorer strength and physical function in comparison to completers. Anthropometrics, QoL, and cognitive function were not related to drop-out. According to multivariate analysis, gait speed and physical activity were the strongest predictors of drop-out. After the training, gains in lean mass or appendicular muscle were significantly higher in men than women; however relative gains in appendicular muscle as well as absolute improvements in strength and function were similar in men and women, respectively.

Conclusions

Participants who drop out are older, have poorer physical function, and are less physically active. Old women do not drop out more frequently than men and show meaningful improvements in relevant outcomes similar to men after such a training program. The trial is registered at the US National Library of Medicine (NCT01074879).

The effects of supramaximal versus submaximal intensity eccentric training when performed until volitional fatigue

PURPOSE

Our purpose was to compare supramaximal versus submaximal intensity eccentric training performed until volitional fatigue.

METHODS

Thirty-two young adults (19 males) were randomized into one of three groups: (1) ECC110 performed eccentric (ECC) only contractions at 110% of concentric (CON) 1-repetition maximum (1RM); (2) ECC80 performed ECC only contractions at 80% of CON 1RM; (3) a control group. Training progressed from 3 to 6 sets of unilateral ECC training of the elbow flexors over 8 weeks, with each set performed until volitional fatigue. Elbow flexors muscle thickness (via ultrasound) and 1RM were assessed pre- and post-training. Rating of perceived exertion (RPE) and muscle soreness was self-reported.

RESULTS

Both ECC110 (+0.25 cm) and ECC80 (+0.21 cm) showed a greater post-training increase in muscle thickness compared to control (-0.01 cm) (p < 0.05), with no differences between ECC110 and ECC80. ECC80 (+1.23 kg) showed a greater post-training increase in strength compared to control (p < 0.05), while ECC110 (+0.76 kg) had no significant difference post-training vs. control (-0.01 kg). ECC80 had significantly lower average RPE scores than ECC110 (p < 0.05).

CONCLUSIONS

Both supramaximal intensity eccentric training and submaximal intensity eccentric training are effective for increasing muscle size, but submaximal eccentric training is perceived to require less exertion than supramaximal training. These findings suggest that submaximal eccentric training may be an ideal strategy to increase muscle size and strength in individuals whose needs warrant training at a lower level of exertion.

Training load does not affect detraining's effect on muscle volume, muscle strength and functional capacity among older adults

Research underlines the potential of low-load resistance exercise in older adults. However, while the effects of detraining from high-load protocols have been established, it is not known whether gains from low-load training would be better/worse maintained. The current study evaluated the effects of 24weeks of detraining that followed 12weeks of high- and low-load resistance exercise in older adults. Fifty-six older adults (68.0±5.0years) were randomly assigned to leg press and leg extension training at either HIGH load (2×10-15 repetitions at 80% of one-repetition maximum (1-RM)), LOW load (1×80-100 repetitions at 20% of 1-RM), or LOW+ load (1×60 repetitions at 20% of 1-RM, immediately followed by 1×10-20 repetitions at 40% 1-RM). All protocols ended with volitional fatigue. The main outcome measures included mid-thigh muscle volume, leg press 1-RM, leg extension isometric and isokinetic strength, and functional performance. Tests were performed at baseline, post-intervention and after 24weeks of detraining. Results show no effect of load on preservation of muscle volume, which returned to baseline after detraining. Training-induced gains in functional capacity and isometric strength were maintained, independent of load. HIGH and LOW+ were more beneficial than LOW for long-lasting gains in training-specific 1-RM. To conclude, gains in muscle volume are reversed after 24weeks of detraining, independent of load. This emphasises the need for long-term resistance exercise adherence. The magnitude of detraining in neuromuscular and functional adaptations was similar between groups. These findings underline the value of low-load resistance exercise in older age. Clinical Trial Registration NCT01707017.

Effects of 4 weeks of low-load unilateral resistance training, with and without blood flow restriction, on strength, thickness, V wave, and H reflex of the soleus muscle in men

PURPOSE

To test the effects of 4 weeks of unilateral low-load resistance training (LLRT), with and without blood flow restriction (BFR), on maximal voluntary contraction (MVC), muscle thickness, volitional wave (V wave), and Hoffmann reflex (H reflex) of the soleus muscle.

METHODS

Twenty-two males were randomly distributed into three groups: a control group (CTR; n = 8); a low-load blood flow restriction resistance training group (BFR-LLRT; n = 7), who were an inflatable cuff to occlude blood flow; and a low-load resistance training group without blood flow restriction (LLRT; n = 7). The training consisted of four sets of unilateral isometric LLRT (25% of MVC) three times a week over 4 weeks.

RESULTS

MVC increased 33% (P < 0.001) and 22% (P < 0.01) in the trained leg of both BFR-LLRT and LLRT groups, respectively. The soleus thickness increased 9.5% (P < 0.001) and 6.5% (P < 0.01) in the trained leg of both BFR-LLRT and LLRT groups, respectively. However, neither MVC nor thickness changed in either of the legs tested in the CTR group (MVC -1 and -5%, and muscle thickness 1.9 and 1.2%, for the control and trained leg, respectively). Moreover, V wave and H reflex did not change significantly in all the groups studied (V_wave/M _wave ratio -7.9 and -2.6%, and H _max/M _max ratio -3.8 and -4%, for the control and trained leg, respectively).

CONCLUSIONS

Collectively, the present data suggest that in spite of the changes occurring in soleus strength and thickness, 4 weeks of low-load resistance training, with or without BFR, does not cause any change in neural drive or motoneuronal excitability.

Intramuscular Anabolic Signaling and Endocrine Response Following Resistance Exercise: Implications for Muscle Hypertrophy

Maintaining skeletal muscle mass and function is critical for disease prevention, mobility and quality of life, and whole-body metabolism. Resistance exercise is known to be a major regulator for promoting muscle protein synthesis and muscle mass accretion. Manipulation of exercise intensity, volume, and rest elicit specific muscular adaptations that can maximize the magnitude of muscle growth. The stimulus of muscle contraction that occurs during differing intensities of resistance exercise results in varying biochemical responses regulating the rate of protein synthesis, known as mechanotransduction. At the cellular level, skeletal muscle adaptation appears to be the result of the cumulative effects of transient changes in gene expression following acute bouts of exercise. Thus, maximizing the resistance exercise-induced anabolic response produces the greatest potential for hypertrophic adaptation with training. The mechanisms involved in converting mechanical signals into the molecular events that control muscle growth are not completely understood; however, skeletal muscle protein synthesis appears to be regulated by the multi-protein phosphorylation cascade, mTORC1 (mammalian/mechanistic target of rapamycin complex 1). The purpose of this review is to examine the physiological response to resistance exercise, with particular emphasis on the endocrine response and intramuscular anabolic signaling through mTORC1. It appears that resistance exercise protocols that maximize muscle fiber recruitment, time-under-tension, and metabolic stress will contribute to maximizing intramuscular anabolic signaling; however, the resistance exercise parameters for maximizing the anabolic response remain unclear.

Neither load nor systemic hormones determine resistance training-mediated hypertrophy or strength gains in resistance-trained young men

We reported, using a unilateral resistance training (RT) model, that training with high or low loads (mass per repetition) resulted in similar muscle hypertrophy and strength improvements in RT-naïve subjects. Here we aimed to determine whether the same was true in men with previous RT experience using a whole-body RT program and whether postexercise systemic hormone concentrations were related to changes in hypertrophy and strength. Forty-nine resistance-trained men (23 ± 1 yr, mean ± SE) performed 12 wk of whole-body RT. Subjects were randomly allocated into a higher-repetition (HR) group who lifted loads of ∼30-50% of their maximal strength (1RM) for 20-25 repetitions/set (n = 24) or a lower-repetition (LR) group (∼75-90% 1RM, 8-12 repetitions/set, n = 25), with all sets being performed to volitional failure. Skeletal muscle biopsies, strength testing, dual-energy X-ray absorptiometry scans, and acute changes in systemic hormone concentrations were examined pretraining and posttraining. In response to RT, 1RM strength increased for all exercises in both groups (P < 0.01), with only the change in bench press being significantly different between groups (HR, 9 ± 1, vs. LR, 14 ± 1 kg, P = 0.012). Fat- and bone-free (lean) body mass and type I and type II muscle fiber cross-sectional area increased following training (P < 0.01) with no significant differences between groups. No significant correlations between the acute postexercise rise in any purported anabolic hormone and the change in strength or hypertrophy were found. In congruence with our previous work, acute postexercise systemic hormonal rises are not related to or in any way indicative of RT-mediated gains in muscle mass or strength. Our data show that in resistance-trained individuals, load, when exercises are performed to volitional failure, does not dictate hypertrophy or, for the most part, strength gains.

A comparison of volume-equated knee extensions to failure, or not to failure, upon rating of perceived exertion and strength adaptations

The present study aimed to compare the effects of repetition duration-, volume-, and load-matched resistance training to muscular failure (MMF) or not to muscular failure (NMF) on maximal voluntary isometric knee extensor strength. This design also allowed testing of the efficacy of “5×5” training. Nine recreationally active males (age, 21.4 ± 1.2 years; height, 1.79 ± 0.07 m; weight, 78.4 ± 7.1 kg) performed unilateral resistance training at 80% of maximal torque at 2×/week for 6 weeks. Using their nondominant leg, participants performed 5 sets of 5 repetitions (NMF). Using their dominant leg, participants performed 25 repetitions in as few sets as possible (MMF). All repetitions were performed at a pace of 2 s concentric, 1 s isometric pause, and 2 s eccentric with a 2-min rest interval between sets. Analyses identified significant pre- to post-intervention strength increases for both MMF and NMF, with effect sizes (ESs) of 2.01 and 1.65, respectively, with no significant differences between conditions (p > 0.05). Peak and mean ratings of perceived exertion (RPEs) were significantly higher for MMF compared with NMF conditions (p < 0.0001), and a tendency for significantly higher RPE values reported for later sets for the NMF condition. Total training time per session was significantly longer for NMF compared with MMF (p < 0.001). The present study suggests that in untrained participants, resistance training NMF produces equivocally the same strength increases as training to MMF when volume-matched. However, resistance training to MMF appears to be a more time-efficient protocol and may produce greater strength gains as indicated by a larger ES.

Inter-repetition rest training and traditional set configuration produce similar strength gains without cortical adaptations

This study compared the functional and neural effects of two strength training programmes differing in set configuration. Thirteen participants performed 10 sessions, over a period of 5 weeks, of unilateral leg extensions with different set configurations but with identical work-to-rest ratios for each limb: a traditional configuration (4 sets of 8 repetitions, 10RM load, 3-min pause between sets) and an inter-repetition rest configuration (32 repetitions, 10RM load, 17.4 s of rest between each repetition). Mean propulsive velocity of the traditional sessions was lower than for inter-repetition rest sessions (0.48 ± 0.06 vs. 0.54 ± 0.06 m · s(-1); P < 0.001), while perceived exertion was higher (8.3 ± 0.9 and 6.56 ± 1.6 for traditional training and IRT; P = 0.002). One repetition maximum (RM), work with 10RM load, maximum mean propulsive power, maximum voluntary contraction and time to failure with 50% of maximum isometric force improved similarly in both legs (time effect, P < 0.001; effect size range, 0.451-1.190). Time and set configuration did not show significant main effects or interactions for cortical adaptations (motor-evoked potentials, short-interval intracortical inhibition, intracortical facilitation). There were no significant correlations between changes in cortical and peripheral neural adaptations and strength improvement. In conclusion, inter-repetition rest configuration was as effective as traditional training in improving muscle performance.

Dose-Response Relationships of Resistance Training in Healthy Old Adults: A Systematic Review and Meta-Analysis

BACKGROUND

Resistance training (RT) is an intervention frequently used to improve muscle strength and morphology in old age. However, evidence-based, dose-response relationships regarding specific RT variables (e.g., training period, frequency, intensity, volume) are unclear in healthy old adults.

OBJECTIVES

The aims of this systematic review and meta-analysis were to determine the general effects of RT on measures of muscle strength and morphology and to provide dose-response relationships of RT variables through an analysis of randomized controlled trials (RCTs) that could improve muscle strength and morphology in healthy old adults.

DATA SOURCES

A computerized, systematic literature search was performed in the electronic databases PubMed, Web of Science, and The Cochrane Library from January 1984 up to June 2015 to identify all RCTs related to RT in healthy old adults.

STUDY ELIGIBILITY CRITERIA

The initial search identified 506 studies, with a final yield of 25 studies. Only RCTs that examined the effects of RT in adults with a mean age of 65 and older were included. The 25 studies quantified at least one measure of muscle strength or morphology and sufficiently described training variables (e.g., training period, frequency, volume, intensity).

STUDY APPRAISAL AND SYNTHESIS METHODS

We quantified the overall effects of RT on measures of muscle strength and morphology by computing weighted between-subject standardized mean differences (SMDbs) between intervention and control groups. We analyzed the data for the main outcomes of one-repetition maximum (1RM), maximum voluntary contraction under isometric conditions (MVC), and muscle morphology (i.e., cross-sectional area or volume or thickness of muscles) and assessed the methodological study quality by Physiotherapy Evidence Database (PEDro) scale. Heterogeneity between studies was assessed using I2 and χ2 statistics. A random effects meta-regression was calculated to explain the influence of key training variables on the effectiveness of RT in terms of muscle strength and morphology. For meta-regression, training variables were divided into the following subcategories: volume, intensity, and rest. In addition to meta-regression, dose-response relationships were calculated independently for single training variables (e.g., training frequency).

RESULTS

RT improved muscle strength substantially (mean SMDbs = 1.57; 25 studies), but had small effects on measures of muscle morphology (mean SMDbs = 0.42; nine studies). Specifically, RT produced large effects in both 1RM of upper (mean SMDbs = 1.61; 11 studies) and lower (mean SMDbs = 1.76; 19 studies) extremities and a medium effect in MVC of lower (mean SMDbs = 0.76; four studies) extremities. Results of the meta-regression revealed that the variables "training period" (p = 0.04) and "intensity" (p < 0.01) as well as "total time under tension" (p < 0.01) had significant effects on muscle strength, with the largest effect sizes for the longest training periods (mean SMDbs = 2.34; 50-53 weeks), intensities of 70-79% of the 1RM (mean SMDbs = 1.89), and total time under tension of 6.0 s (mean SMDbs = 3.61). A tendency towards significance was found for rest in between sets (p = 0.06), with 60 s showing the largest effect on muscle strength (mean SMDbs = 4.68; two studies). We also determined the independent effects of the remaining training variables on muscle strength. The following independently computed training variables are most effective in improving measures of muscle strength: a training frequency of two sessions per week (mean SMDbs = 2.13), a training volume of two to three sets per exercise (mean SMDbs = 2.99), seven to nine repetitions per set (mean SMDbs = 1.98), and a rest of 4.0 s between repetitions (SMDbs = 3.72). With regard to measures of muscle morphology, the small number of identified studies allowed us to calculate meta-regression for the subcategory training volume only. No single training volume variable significantly predicted RT effects on measures of muscle morphology. Additional training variables were independently computed to detect the largest effect for the single training variable. A training period of 50-53 weeks, a training frequency of three sessions per week, a training volume of two to three sets per exercise, seven to nine repetitions per set, a training intensity from 51 to 69% of the 1RM, a total time under tension of 6.0 s, a rest of 120 s between sets, and a rest of 2.5 s between repetitions turned out to be most effective.

LIMITATIONS

The current results must be interpreted with caution because of the poor overall methodological study quality (mean PEDro score 4.6 points) and the considerable large heterogeneity (I2) = 80%, χ2 = 163.1, df = 32, p < 0.01) for muscle strength. In terms of muscle morphology, our search identified nine studies only, which is why we consider our findings preliminary. While we were able to determine a dose-response relationship based on specific individual training variables with respect to muscle strength and morphology, it was not possible to ascertain any potential interactions between these variables. We recognize the limitation that the results may not represent one general dose-response relationship.

CONCLUSIONS

This systematic literature review and meta-analysis confirmed the effectiveness of RT on specific measures of upper and lower extremity muscle strength and muscle morphology in healthy old adults. In addition, we were able to extract dose-response relationships for key training variables (i.e., volume, intensity, rest), informing clinicians and practitioners to design effective RTs for muscle strength and morphology. Training period, intensity, time under tension, and rest in between sets play an important role in improving muscle strength and morphology and should be implemented in exercise training programs targeting healthy old adults. Still, further research is needed to reveal optimal dose-response relationships following RT in healthy as well as mobility limited and/or frail old adults.

Effects of resistance training with moderate vs heavy loads on muscle mass and strength in the elderly: A meta-analysis

The purpose of the present study was to perform a meta-analysis to compare the efficacy of heavy (∼80% of one repetition maximum, 1RM) vs light-moderate load (∼45% 1RM) resistance training (RT) programs in inducing strength gains and skeletal muscle hypertrophy in elderly people. To assess the role of training volumes, studies in which training protocols were matched for mechanical work were independently analyzed. In all 15 studies included (448 subjects, age 67.8 years), when comparing heavy with light-moderate loads, strength gains tended to be larger following RT with higher intensities of load, with the resulting total population effect being μ = 0.430 (P = 0.060). Effect sizes were substantially smaller in "work-matched" studies (μ = 0.297, P = 0.003). Training with higher loads also provoked marginally larger gains in muscle size, although the degree of training-induced muscle hypertrophy was generally small (0.056 < μ < 0.136). To conclude, provided a sufficient number of repetitions is performed, RT at lower than traditionally recommended intensities of load may suffice to induce substantial gains in muscle strength in elderly cohorts.