Maximal Dynamic Strength Research Articles

Assessing strength and power in resistance training

Maximal Dynamic Strength is usually assessed either by the one repetition maximum test (1-RM) or by a repetition maximum test with submaximal loads, which requires the application of a formula to estimate the value of 1-RM. This value is needed to establish the objective of resistance training: such as maximum strength, endurance strength, and/or explosive strength. However, both 1-RM and submaximal tests are unable to highlight the changes produced on power and velocity. This manuscript summarizes and reviews several common strength testing protocols and proposes a novel approach that may offer greater insight to hierarchical muscle functionality.

Comparison of Methods to Quantify Volume During Resistance Exercise

The purpose of this investigation was to compare 4 different methods of calculating volume when comparing resistance exercise protocols of varying intensities. Ten Appalachian State University students experienced in resistance exercise completed 3 different resistance exercise protocols on different days using a randomized, crossover design, with 1 week of rest between each protocol. The protocols included 1) hypertrophy: 4 sets of 10 repetitions in the squat at 75% of a 1-repetition maximum (1RM) (90-second rest periods); 2) strength: 11 sets of 3 repetitions at 90% 1RM (5-minute rest periods); and 3) power: 8 sets of 6 repetitions of jump squats at 0% 1RM (3-minute rest periods). The volume of resistance exercise completed during each protocol was determined with 4 different methods: 1) volume load (VL) (repetitions [no.] x external load [kg]); 2) maximum dynamic strength volume load (MDSVL) (repetitions [no.] x [body mass--shank mass (kg) + external load (kg)]); 3) time under tension (TUT) (eccentric time +milliseconds] + concentric time +milliseconds]); and 4) total work (TW) (force [N] x displacement [m]). The volumes differed significantly (p , 0.05) between hypertrophy and strength in comparison with the power protocol when VL and MDSVL were used to determine the volume of resistance exercise completed. Furthermore, significant differences in TUT existed between all 3 resistance exercise protocols. The TW calculated was not significantly different between the 3 protocols. These data imply that each method examined results in substantially different values when comparing various resistance exercise protocols involving different levels of intensity.

A regression model to determine load for maximum power output

The aims of this study were to create a regression model of the relationship between load and muscle power output and to determine an optimal load for maximum power output during a countermovement squat and a bench press. 55 males and 48 females performed power testing at 0, 10, 30, 50, 70, 90, and 100% of their individual one-repetition maximum (1-RM) in the countermovement squat and bench press exercises. Values for the maximum dynamic strength and load for each lift were used to develop a regression model in which the ratio of power was predicted from the ratio of the load for each type of lift. By optimizing the regression model, we predicted the optimal load for maximum muscle power. For the bench press and the countermovement squat, the mean optimal loads for maximum muscle output ranged from 50 to 70% of maximum dynamic strength. Optimal load in the acceleration phase of the upward movement of the two exercises appeared to be more important than over the full range of the movement. This model allows for specific determination of the optimal load for a pre-determined power output.

Resistance training induces qualitative changes in muscle morphology, muscle architecture, and muscle function in elderly postoperative patients

Although the negative effects of bed rest on muscle strength and muscle mass are well established, it still remains a challenge to identify effective methods to restore physical capacity of elderly patients recovering from hospitalization. The present study compared different training regimes with respect to muscle strength, muscle fiber size, muscle architecture, and stair walking power in elderly postoperative patients. Thirty-six patients (60-86 yr) scheduled for unilateral hip replacement surgery due to hip osteoarthritis were randomized to either 1) resistance training (RT: 3/wk x 12 wk), 2) electrical stimulation (ES: 1 h/day x 12 wk), or 3) standard rehabilitation (SR: 1 h/day x 12 wk). All measurements were performed at baseline, at 5 wk and 12 wk postsurgery. After 12 wk of resistance training, maximal dynamic muscle strength increased by 30% at 60 degrees /s (P < 0.05) and by 29% at 180 degrees /s (P < 0.05); muscle fiber area increased for type I (+17%, P < 0.05), type IIa (+37%, P < 0.05), and type IIx muscle fibers (+51%, P < 0.05); and muscle fiber pennation angle increased by 22% and muscle thickness increased by 15% (P < 0.05). Furthermore, stair walking power increased by 35% (P < 0.05) and was related to the increase in type II fiber area (r = 0.729, P < 0.05). In contrast, there was no increase in any measurement outcomes with electrical stimulation and standard rehabilitation. The present study is the first to demonstrate the effectiveness of resistance training to induce beneficial qualitative changes in muscle fiber morphology and muscle architecture in elderly postoperative patients. In contrast, rehabilitation regimes based on functional exercises and neuromuscular electrical stimulation had no effect. The present data emphasize the importance of resistance training in future rehabilitation programs for elderly individuals.

Effects of combined strength and sprint training on regulation of muscle contraction at the whole‐muscle and single‐fibre levels in elite master sprinters

This study aims at examining the effects of progressive strength and sprint training on regulation of muscle contraction at the whole-muscle and single-fibre levels in older sprint-trained athletes. Eleven men (52-78 years) were randomized to a training (EX, n = 7) or control (CTRL, n = 4) group. EX participated in a 20-week programme that combined sprint training with heavy and explosive strength exercises, while CTRL maintained their usual run-based training schedules. EX improved maximal isometric and dynamic leg strength, explosive jump performance and force production in running. Specific tension and maximum shortening velocity of single fibres from the vastus lateralis were not altered in EX or CTRL. Fibre type and myosin heavy chain isoform distributions remained unchanged in the two groups. There was a general increase in fibre areas in EX, but this was significant only in IIa fibres. The 10% increase in squat jump in EX was accompanied by a 9% increase in the integrated EMG (iEMG) of the leg extensors but the 21-40% increases in isometric and dynamic strength were not paralleled by changes in iEMG. Adding strength training stimulus to the training programme improved maximal, explosive and sport-specific force production in elite master sprinters. These improvements were primarily related to hypertrophic muscular adaptations.

Continuous Hemodynamic Response to Maximal Dynamic Strength Testing in Older Adults

de Vos NJ, Singh NA, Ross DA, Stavrinos TM, Orr R, Fiatarone Singh MA. Continuous hemodynamic response to maximal dynamic strength testing in older adults. Objective To quantify acute changes in blood pressure and heart rate during a maximal dynamic strength—single-repetition maximum lift (1-RM)—testing session in older adults with a low burden of chronic disease. Design Descriptive, cross-sectional study. Setting University rehabilitation center. Participants Volunteer sample of 43 community-dwelling, nonresistance-trained older adults aged 60 years and older (mean, 68±6y). Interventions Not applicable. Main Outcome Measures Systolic blood pressure (SBP), diastolic blood pressure (DBP), and heart rate was obtained by plethysmography at rest and during 1-RM strength testing on leg press, knee extension, and knee flexion resistance machines. Results Average resting SBP (132±28mmHg), DBP (54±15mmHg), and heart rate (65±11 beats/min) were independent of hypertensive diagnosis and overweight status. Maximal SBP, DBP, and heart rate increased significantly during the 1-RM in all exercises compared with rest ( P<.001). Highest values of SBP (236±51mmHg) and DBP (140±46mmHg) were measured during the leg press at 99.5%±6.7% of 1-RM. Lowest values of SBP (79±25mmHg) and DBP (38±15mmHg), and the highest (123±44 beats/min) and lowest heart rate (41±23 beats/min) were measured during the knee extension at 97.4%±8.1% of 1-RM. Absolute falls in SBP were greatest in treated hypertensive participants. No cardiovascular symptoms or events occurred in 129 1-RM tests. Conclusions Large, very transient, asymptomatic excursions in blood pressure and heart rate were measured during 1-RM testing. The most robust hemodynamic response occurred during the leg press. Thus the leg press may be the most important exercise to focus hemodynamic monitoring efforts upon during strength testing in clinical cohorts.

Relationships between Stretch-shortening Cycle Performance and Maximum Muscle Strength

This study aimed to examine the relationships between muscle power output using the stretch-shortening cycle (SSC) and maximum strength, as measured by the 1 RM (1 repetition maximum) test and the isokinetic dynamometer under elbow flexion. Sixteen trained, young adult males pulled a constant load of 40% MVC (maximum voluntary elbow flexion contraction) by ballistic elbow flexion under the following two preliminary conditions: 1) the static relaxed muscle state (SR condition) and 2) using the SSC (SSC condition). Muscle power was determined from the product of the pulling velocity and load mass by a power measurement instrument with a rotary encoder. The 1 RM bench press (1RM BP) and isokinetic maximum strength under elbow flexion with the Cybex-325 were measured as indicators of dynamic maximum strength. 1) The early power output exerted under the SSC condition showed a significant and high correlation with the 1 RM BP (r = 0.83), but only moderate correlation with the isokinetic muscle strength (r = 0.50-0.67). 2) The contribution of the 1 RM BP to the early muscle contraction velocity exerted under the SSC condition was large. These results suggested that muscle power exerted using the SSC shows a stronger relationship with maximum muscle strength measured by a 1 RM test rather than isokinetic maximum strength.

Relationship Between Throwing Velocity, Muscle Power, and Bar Velocity During Bench Press in Elite Handball Players

The purpose of this study was to examine the relationship between ball-throwing velocity during a 3-step running throw and dynamic strength, power, and bar velocity during a concentric-only bench-press exercise in team-handball players. Fourteen elite senior male team-handball players volunteered to participate. Each volunteer had power and bar velocity measured during a concentric-only bench-press test with 26, 36, and 46 kg, as well as having 1-repetition-maximum (1-RMBP) strength determined. Ball-throwing velocity was evaluated with a standard 3-step running throw using a radar gun. Ball-throwing velocity was related to the absolute load lifted during the 1-RMBP (r = .637, P = .014), peak power using 36 kg (r = .586, P = .028) and 46 kg (r = .582, P = .029), and peak bar velocity using 26 kg (r = .563, P = .036) and 36 kg (r = .625, P = .017). The results indicate that throwing velocity of elite team-handball players is related to maximal dynamic strength, peak power, and peak bar velocity. Thus, a training regimen designed to improve ball-throwing velocity in elite male team-handball players should include exercises that are aimed at increasing both strength and power in the upper body.

Suplementação de creatina e treinamento de força: alterações na resultante de força máxima dinâmica e variáveis antropométricas em universitários submetidos a oito semanas de treinamento de força (hipertrofia)

OBJETIVO: Verificar as alterações promovidas pela suplementação de creatina nas variáveis antropométricas e da resultante de força máxima dinâmica (RFMD) em universitários submetidos a oito semanas de treinamento de força. METODOLOGIA: Participaram deste estudo, 18 universitários do sexo masculino, com idade entre 19 e 25 anos. Antes do treinamento foram determinadas a estatura (cm), a massa corporal (kg) e testes de ação muscular voluntária máxima dinâmica (1AMVMD), os sujeitos foram assinalados a um dos dois grupos, A (creatina) e B (placebo), foi adotado o protocolo duplo-cego. Após oito semanas de treinamento de força, repetiu-se a bateria de testes do pré-treinamento. RESULTADOS: Após oito semanas, verificou-se que tanto no grupo A como no B houve alterações estatisticamente significantes (ES) na RFMD em todos os exercícios (p = 0,007 a 0,008). A análise da melhora percentual e do delta da RFMD, nos exercícios de agachamento, desenvolvimento e supino fechado, mostrou que o grupo A teve alterações positivas ES superiores ao grupo B (p = 0,008 a 0,038). A massa magra aumentou ES somente no grupo A (p = 0,038). Contudo, o percentual de gordura corporal não mostrou alterações em nenhum dos grupos. A relação entre a melhora percentual (MP) das circunferências (C) do braço e antebraço e a MP na RFMD do exercício de desenvolvimento foi ES (r = 0,481 e 0,546, respectivamente), bem como entre a MP na C da coxa e na MP da RFMD do exercício de agachamento (r = 0,619). CONCLUSÃO: Independente do suplemento ingerido o treinamento de força foi capaz de induzir ajustes positivos na RFMD; contudo, a suplementação de creatina mostrou-se mais eficiente que o placebo, induzindo a maior aumento percentual e de delta na força.

EFFECTS OF A DRINK CONTAINING CREATINE,AMINO ACIDS, AND PROTEIN COMBINED WITH TEN WEEKS OF RESISTANCE TRAINING ON BODY COMPOSITION, STRENGTH, AND ANAEROBIC PERFORMANCE

The purpose of this study was to examine the effects of a drink containing creatine, amino acids, and protein vs. a carbohydrate placebo on body composition, strength, muscular endurance, and anaerobic performance before and after 10 weeks of resistance training. Fifty-one men (mean ± SD; age: 21.8 ± 2.9 years) were randomly assigned to either the test drink (TEST; n = 23) or the placebo (PLAC; n = 28) and performed two 30-second Win-gate Anaerobic Tests for determination of peak power (PP) and mean power (MP), were weighed underwater for percent body fat (%fat) and fat-free mass (FFM), and were tested for 1 repetition maximum (1RM) dynamic constant external resistance strength and muscular endurance (END; number of repetitions performed with 80% of 1RM) on the bilateral leg extension (LE) and free-weight bench press (BP) exercises. The testing was conducted before (PRE) and after (POST) 10 weeks of resistance training (3 sets of 10 repetitions with 80% of the subject's 1RM performed 3 times per week) on the LE and BP exercises. Body weight, FFM, LE 1RM, LE END, BP 1RM, and BP END increased (p < 0.05), whereas %fat decreased (p < 0.05) from PRE to POST for both the TEST and PLAC groups. Peak power and MP, however, increased for the TEST group, but not for the PLAC group. These results suggested that the creatine-, amino acid–, and protein-containing drink provided no additional benefits when compared with carbohydrates alone for eliciting changes in body composition, strength, and muscular endurance after a 10-week resistance training period. The TEST drink was, however, more effective than carbohydrates alone for improving anaerobic power production.

Poster 18: Effects of a Periodized Aquatic Program for Strength Training on the Maximum Dynamic Strength

Objective: To determine if an aquatic program for strength training (APST) can improve the strength of movements carried out on dry land. Design: Nonrandomized controlled trial. Setting: Hydrotherapy pool. Participants: Fit, healthy men. Exercise group: n=7; age, 21±1 years old. Control group: n=5; age, 21.4±1.34 years old. Intervention: With gloves that increased frontal and drag resistance in water, an APST of 8 weeks with 8 to 12 repetitions (9–10 on the OMNI perceived exertion scale for resistance exercise), while adapting the speed of movements by using a metronome. Main Outcome Measures: One repetition maximum with a pre-post submaximal test (<6 repetitions) of the following exercises: plane bench press with barbell, vertical rowing with barbell, horizontal rowing on bench with barbell, and dumbbell lateral raise. Results: APST improved the maximum dynamic strength of the exercise group versus the control group, respectively: bench press, +3.187kg (P=.003) versus −2.118kg (P=.209); vertical rowing, +4.880kg (P=.018) versus +1.440kg (P=.235); horizontal rowing, +4.460kg (P=.033) versus +0.948kg (P=.541); and dumbbell lateral raise, +2.303kg (P=.044) versus –0.006kg (P=.686). Conclusions: An APST combining monitoring of the speed of movements, perceived exertion, and progressive increase in volume and intensity is effective in improving maximum dynamic strength.

Influence de l'expertise sur l'évolution de la cadence de pédalage au cours d'un test progressif maximal

Aim The purpose of this work is the study of the evolution of the freely chosen cadence (FCC) during a pedalling test, applied to various populations with different physical and physiological capacities. Materials and methods Three groups of 8 subjects (less-trained non-cyclists, OCC – trained cyclists, CYC – trained runners, COU) participated in this experimentation. During a same session of evaluation, each subject realized a test of determination of the maximal dynamic strength of the lower limbs. This test was followed 1 hour later by a progressive, maximal and continuous test for determination of maximal oxygen uptake ( V . O 2max) on an electromagnetic brake-cycle ergometer. Results Our results show that trained cyclists adopt a constant FCC, while non-cyclists (i.e. OCC and COU) significantly increase their FCC between the beginning and the end of the test. Besides, although the FCC of the cyclists is significantly higher than the FCC of the non-cyclists at the beginning of the exercise, one does not see any persisting difference between the FCC of the three populations, later on. Conclusion The stability of cyclists' FCC can be explained through expertise, that is, throw the fact that the subjects develop specific skills inferred by a learning process.

The amplitude of force variability is correlated in the knee extensor and elbow flexor muscles

The purpose of this study was to determine motor output variability for different muscles in the same individuals. Ten young (21.7 +/- 3.4 years) and ten elderly (72.1 +/- 3.9 years) men underwent assessment of maximal isometric (MVC) and dynamic (1-RM) strength, and performed constant-force (2-50% MVC), constant-load (5-50% 1-RM load), and unloaded postural contractions as steadily as possible with the first dorsal interosseus (FDI), elbow flexors (EF), and knee extensors (KE). The coefficient of variation (CV) of force for isometric contractions and the standard deviation (SD) of acceleration for concentric, eccentric, and postural contractions were calculated. The 1-RM load, the CV of force for four of five isometric target forces, and the SD of acceleration during postural contractions were correlated between the EF and KE muscles. MVC force, 1-RM load, and SD of acceleration during postural contractions were not correlated between the FDI/EF or FDI/KE. The CV of force was correlated between the FDI/EF and FDI/KE for two of five isometric target forces. The SD of acceleration during concentric and eccentric contractions was not correlated between muscles. The normalized fluctuations during isometric contractions were greater for the FDI compared with the EF and KE. Elderly adults displayed greater fluctuations only for the FDI during low-force isometric and postural contractions. The dominant frequency of fluctuations was similar for the EF and KE muscles. The correlated fluctuations for the EF and KE muscles, within subjects, suggests that the two motor neuron pools transform the various neural inputs similarly.

Association between Fitness and Performance of Instrumental Activities of Daily Living in Elderly Women

PURPOSE: to examine the association between fitness variables and the performance on Instrumental Activities of Daily Living (IADL) in elderly women. METHODS: A total of 928 elderly women (mean age = 69.2 ± 6.1 years, ranging from 60 to 88 years) were studied. Subjects were non-institutionalized and currently enrolled in leisure programs for the elderly. IADL was denned by the Instrumental Activities of Daily Living questionnaire proposed by Lawton and Brody (1969). Fitness variables were obtained using the following tests: 6 min walk test (6MW), Arm Curl test (AC), 30 sec chair stand (30SCS), chair sit-and-reach (CSR) and 8 Foot Up and Go (8FUG) proposed by Rikli e Jones (1999); Berg balance scale (BBS), proposed by Berg et al, (1992), isometric strength using handgrip dynamometry, and maximal dynamic strength using 1-RM on bench press. Fitness variables were categorized into quartiles to obtain Odds Ratios (OR). Performance on IADL was categorized was independent (score of 17) or partially independent (score < 17). Logistic regression analysis was used to predict performance on IADL from the fitness predictors, adjusting for age. RESULTS: Balance, handgrip strength, maximal dynamic strength and age were significant predictors of performance on IADL. The highest-versus-lowest quartile comparisons for the BBS obtained an OR = 1.717 (95% CI= 1.112 – 2.650); for handgrip strength, OR = 1.676 (95% CI = 1.051 – 2.673), p < 0.05. The comparison between the highest-versus-lowest quartile for Maximal dynamic strength obtained OR = 1.944 (95% CI = 1.239 – 3.050), and highest-versus-second lowest quartile, OR = 1.816 (95% CI = 1.140 – 2.891), p < 0.05. CONCLUSION: Balance, handgrip strength, maximal dynamic strength, independent of age, were predictors of performance in IADL in this population of elderly women.

Effects of dynamic resistance training on fascicle lengthand isometric strength

The aims of this study were to assess changes in muscle architecture, isometric and dynamic strength of the leg extensor muscles, resulting from dynamic resistance training, and the relationships between strength and muscle architecture variables. The participants (n = 30) were randomly assigned to one of two groups. The training group (n = 16; age 21.8 ± 2.3 years, body mass 74.8 ± 9.2 kg, height 1.75 ± 0.08 m) performed dynamic resistance training for 13 weeks. The control group (n = 14; age 19.9 ± 1.5 years, body mass 74.0 ± 8.5 kg, height 1.76 ± 0.05 m) did not perform any resistance training. Maximal dynamic and isometric strength were tested in both groups, before and after the training period. The members of the training group used the free-weight squat lift (90°) as their training exercise. The concentric phase of the squat was performed explosively. Skeletal muscle architecture of the vastus lateralis was visualized using ultrasonography. At the end of the study, significant increases in vastus lateralis muscle thickness (+6.9%, P < 0.001), fascicle length (+10.3%, P < 0.05), one-repetition maximum (+8.2%, P < 0.05), rate of force development (+23.8%, P < 0.05) and average force produced in the first 500 ms (+11.7%, P < 0.05) were seen only in the training group. Adaptations to the muscle architecture in the training group limited the loss of fibre force, and improved the capacity for developing higher velocities of contraction. The architectural changes in the training group were similar to those seen in studies where high-speed training was performed. In conclusion, dynamic resistance training with light loads leads to increases in muscle thickness and fascicle length, which might be related to a more efficient transmission of fibre force to the tendon.

Peak Force and Rate of Force Development During Isometric and Dynamic Mid-Thigh Clean Pulls Performed at Various Intensities

Eight male collegiate weightlifters (age: 21.2 +/- 0.9 years; height: 177.6 +/- 2.3 cm; and body mass: 85.1 +/- 3.3 kg) participated in this study to compare isometric to dynamic force-time dependent variables. Subjects performed the isometric and dynamic mid-thigh clean pulls at 30-120% of their one repetition maximum (1RM) power clean (118.4 +/- 5.5 kg) on a 61 x 121.9-cm AMTI forceplate. Variables such as peak force (PF) and peak rate of force development (PRFD) were calculated and were compared between isometric and dynamic conditions. The relationships between force-time dependent variables and vertical jump performances also were examined. The data indicate that the isometric PF had no significant correlations with the dynamic PF against light loads. On the one hand, there was a general trend toward stronger relationships between the isometric and dynamic PF as the external load increased for dynamic muscle actions. On the other hand, the isometric and dynamic PRFD had no significant correlations regardless of the external load used for dynamic testing. In addition, the isometric PF and dynamic PRFD were shown to be strongly correlated with vertical jump performances, whereas the isometric PRFD and dynamic PF had no significant correlations with vertical jump performances. In conclusion, it appears that the isometric and dynamic measures of force-time curve characteristics represent relatively specific qualities, especially when dynamic testing involves small external loads. Additionally, the results suggest that athletes who possess greater isometric maximum strength and dynamic explosive strength tend to be able to jump higher.

Short-Term Plyometric Training Improves Running Economy in Highly Trained Middle and Long Distance Runners

Fifteen highly trained distance runners VO(2)max 71.1 +/- 6.0 ml.min(-1).kg(-1), mean +/- SD) were randomly assigned to a plyometric training (PLY; n = 7) or control (CON; n = 8) group. In addition to their normal training, the PLY group undertook 3 x 30 minutes PLY sessions per week for 9 weeks. Running economy (RE) was assessed during 3 x 4 minute treadmill runs (14, 16, and 18 km.h(-1)), followed by an incremental test to measure VO(2)max. Muscle power characteristics were assessed on a portable, unidirectional ground reaction force plate. Compared with CON, PLY improved RE at 18 km.h(-1) (4.1%, p = 0.02), but not at 14 or 16 km.h(-1). This was accompanied by trends for increased average power during a 5-jump plyometric test (15%, p = 0.11), a shorter time to reach maximal dynamic strength during a strength quality assessment test (14%, p = 0.09), and a lower VO(2)-speed slope (14%, p = 0.12) after 9 weeks of PLY. There were no significant differences in cardiorespiratory measures or VO(2)max as a result of PLY. In a group of highly-trained distance runners, 9 weeks of PLY improved RE, with likely mechanisms residing in the muscle, or alternatively by improving running mechanics.

Muscle size and strength are increased following walk training with restricted venous blood flow from the leg muscle, Kaatsu-walk training

Previous studies have shown that low-intensity resistance training with restricted muscular venous blood flow (Kaatsu) causes muscle hypertrophy and strength gain. To investigate the effects of daily physical activity combined with Kaatsu, we examined the acute and chronic effects of walk training with and without Kaatsu on MRI-measured muscle size and maximum dynamic (one repetition maximum) and isometric strength, along with blood hormonal parameters. Nine men performed Kaatsu-walk training, and nine men performed walk training alone (control-walk). Training was conducted two times a day, 6 days/wk, for 3 wk using five sets of 2-min bouts (treadmill speed at 50 m/min), with a 1-min rest between bouts. Mean oxygen uptake during Kaatsu-walk and control-walk exercise was 19.5 (SD 3.6) and 17.2 % (SD 3.1) of treadmill-determined maximum oxygen uptake, respectively. Serum growth hormone was elevated (P < 0.01) after acute Kaatsu-walk exercise but not in control-walk exercise. MRI-measured thigh muscle cross-sectional area and muscle volume increased by 4-7%, and one repetition maximum and maximum isometric strength increased by 8-10% in the Kaatsu-walk group. There was no change in muscle size and dynamic and isometric strength in the control-walk group. Indicators of muscle damage (creatine kinase and myoglobin) and resting anabolic hormones did not change in both groups. The results suggest that the combination of leg muscle blood flow restriction with slow-walk training induces muscle hypertrophy and strength gain, despite the minimal level of exercise intensity. Kaatsu-walk training may be a potentially useful method for promoting muscle hypertrophy, covering a wide range of the population, including the frail and elderly.

Effect of Loading on Unintentional Lifting Velocity Declines During Single Sets of Repetitions to Failure During Upper and Lower Extremity Muscle Actions

The purpose of this study was to examine the effect of different loads on repetition speed during single sets of repetitions to failure in bench press and parallel squat. Thirty-six physical active men performed 1-repetition maximum in a bench press (1 RM (BP)) and half squat position (1 RM (HS)), and performed maximal power-output continuous repetition sets randomly every 10 days until failure with a submaximal load (60 %, 65 %, 70 %, and 75 % of 1RM, respectively) during bench press and parallel squat. Average velocity of each repetition was recorded by linking a rotary encoder to the end part of the bar. The values of 1 RM (BP) and 1 RM (HS) were 91 +/- 17 and 200 +/- 20 kg, respectively. The number of repetitions performed for a given percentage of 1RM was significantly higher (p < 0.001) in half squat than in bench press performance. Average repetition velocity decreased at a greater rate in bench press than in parallel squat. The significant reductions observed in the average repetition velocity (expressed as a percentage of the average velocity achieved during the initial repetition) were observed at higher percentage of the total number of repetitions performed in parallel squat (48 - 69 %) than in bench press (34 - 40 %) actions. The major finding in this study was that, for a given muscle action (bench press or parallel squat), the pattern of reduction in the relative average velocity achieved during each repetition and the relative number of repetitions performed was the same for all percentages of 1RM tested. However, relative average velocity decreased at a greater rate in bench press than in parallel squat performance. This would indicate that in bench press the significant reductions observed in the average repetition velocity occurred when the number of repetitions was over one third (34 %) of the total number of repetitions performed, whereas in parallel squat it was nearly one half (48 %). Conceptually, this would indicate that for a given exercise (bench press or squat) and percentage of maximal dynamic strength (1RM), the pattern of velocity decrease can be predicted over a set of repetitions, so that a minimum repetition threshold to ensure maximal speed performance is determined.

Efeitos da acupuntura na performance de atletas velocistas de alto rendimento do Rio de Janeiro

Objective: To verify the effects of acupuncture on dynamic maximum strength, power, anaerobic resistance and speed on high level athletes from Celio de Barro...