Effects of Strength Training Associated With Whole-Body Vibration Training on Running Economy and Vertical Stiffness

Running economy (RE) is defined as the energy cost to maintain a submaximal running velocity and seems to be affected by individual's neuromuscular characteristics, such as stiffness level. Both resistance training (RT) and whole-body vibration training added to RT (WBV + RT) have been shown to influence those characteristics. Thus, it is conceivable that RT and WBV + RT could also affect RE. The objective of this study was to investigate if a 6-week training period of RT and WBV + RT influences RE and vertical stiffness (VS). Fifteen recreational runners were divided into RT or WBV + RT groups. Running economy, VS, and lower-limb maximum dynamic strength (1 repetition maximum [1RM] half-squat) were assessed before and after the 6-week training period. There was a main time effect for 1RM, but no other statistically significant difference was observed. Neither conventional RT nor RT performed on a WBV platform improved VS and RE in recreational long distance runners. It is possible that movement velocity was rather low, and utilization of stretch-shortening cycle might have been compromised, impairing any expected improvement in RE.

Changes in exercises are more effective than in loading schemes to improve muscle strength

This study investigated the effects of varying strength exercises and loading scheme on muscle cross-sectional area (CSA) and maximum strength after 4 strength training loading schemes: constant intensity and constant exercise (CICE), constant intensity and varied exercise (CIVE), varied intensity and constant exercise (VICE), varied intensity and varied exercise (VIVE). Forty-nine individuals were allocated into 5 groups: CICE, CIVE, VICE, VIVE, and control group (C). Experimental groups underwent twice a week training for 12 weeks. Squat 1 repetition maximum was assessed at baseline and after the training period. Whole quadriceps muscle and its heads CSA were also obtained pretraining and posttraining. The whole quadriceps CSA increased significantly (p ≤ 0.05) in all of the experimental groups from pretest to posttest in both the right and left legs: CICE: 11.6 and 12.0%; CIVE: 11.6 and 12.2%; VICE: 9.5 e 9.3%; and VIVE: 9.9 and 11.6%, respectively. The CIVE and VIVE groups presented hypertrophy in all of the quadriceps muscle heads (p ≤ 0.05), whereas the CICE and VICE groups did not present hypertrophy in the vastus medialis and rectus femoris (RF), and in the RF muscles, respectively (p > 0.05). The CIVE group had greater strength increments than the other training groups (effect size confidence limit of the difference [ESCLdiff] CICE: 1.41-1.56; VICE: 2.13-2.28; VIVE: 0.59-0.75). Our findings suggest: (a) CIVE is more efficient to produce strength gains for physically active individuals; (b) as long as the training intensity reaches an alleged threshold, muscle hypertrophy is similar regardless of the training intensity and exercise variation.

Determining the Optimum Power Load in Jump Squat Using the Mean Propulsive Velocity

The jump squat is one of the exercises most frequently used to improve lower body power production, which influences sports performance. However, the traditional determination of the specific workload at which power production is maximized (i.e., optimum power load) is time-consuming and requires one-repetition maximum tests. Therefore, the aim of this study was to verify whether elite athletes from different sports would produce maximum mean propulsive power values at a narrow range of mean propulsive velocities, resulting in similar jump heights. One hundred and nine elite athletes from several individual/team sport disciplines underwent repetitions at maximal velocity with progressive loads, starting at 40% of their body mass with increments of 10% to determine the individual optimum power zone. Results indicated that regardless of sport discipline, the athletes’ optimum mean propulsive power was achieved at a mean propulsive velocity close to 1.0 m.s⁻¹ (1.01 ± 0.07 m.s⁻¹) and at a jump height close to 20 cm (20.47 ± 1.42 cm). Data were narrowly scattered around these values. Therefore, jump squat optimum power load can be determined simply by means of mean propulsive velocity or jump height determination in training/testing settings, allowing it to be implemented quickly in strength/power training.

Effects of resistance training on neuromuscular characteristics and pacing during 10-km running time trial

PURPOSE

The purpose of this study was to analyze the impact of an 8-week strength training program on the neuromuscular characteristics and pacing adopted by runners during a self-paced endurance running.

METHODS

Eighteen endurance runners were allocated into either strength training group (STG, n = 9) or control group (CG, n = 9) and performed the following tests before and after the training period: (a) incremental test, (b) running speed-constant test, (c) 10-km running time trial, (d) drop jump test, (e) 30-s Wingate anaerobic test, (f) maximum dynamic strength test (1RM). During 1RM, the electromyographic activity was measured.

RESULTS

In the STG, the magnitude of improvement for 1RM (23.0 ± 4.2 %, P = 0.001), drop jump (12.7 ± 4.6 %, P = 0.039), and peak treadmill speed (2.9 ± 0.8 %, P = 0.013) was significantly higher compared to CG. This increase in the 1RM for STG was accompanied by a tendency to a higher electromyographic activity (P = 0.080). The magnitude of improvement for 10-km running performance was higher (2.5 %) for STG than for CG (-0.7 %, P = 0.039). Performance was improved mainly due to higher speeds during the last seven laps (last 2800 m) of the 10-km running trial. There were no significant differences between before and after training period for maximal oxygen uptake, respiratory compensation point, running economy, and anaerobic performance for both groups (P > 0.05).

CONCLUSIONS

These findings suggest that a strength training program offers a potent stimulus to counteract fatigue during the last parts of a 10-km running race, resulting in an improved overall running performance.

Effect of concurrent training with blood flow restriction in the elderly

The aim of this present study was to investigate on the effects of concurrent training with blood flow restriction (BFR-CT) and concurrent training (CT) on the aerobic fitness, muscle mass and muscle strength in a cohort of older individuals. 25 healthy older adults (64.7±4.1 years; 69.33±10.8 kg; 1.6±0.1 m) were randomly assigned to experimental groups: CT (n=8, endurance training (ET), 2 days/week for 30-40 min, 50-80% VO(2peak) and RT, 2 days/week, leg press with 4 sets of 10 reps at 70-80% of 1-RM with 60 s rest), BFR-CT (n=10, ET, similar to CT, but resistance training with blood flow restriction: 2 days/week, leg press with 1 set of 30 and 3 sets of 15 reps at 20-30% 1-RM with 60 s rest) or control group (n=7). Quadriceps cross-sectional area (CSAq), 1-RM and VO(2peak) were assessed pre- and post-examination (12 wk). The CT and BFR-CT showed similar increases in CSAq post-test (7.3%, P<0.001; 7.6%, P<0.0001, respectively), 1-RM (38.1%, P<0.001; 35.4%, P=0.001, respectively) and VO(2peak) (9.5%, P=0.04; 10.3%, P=0.02, respectively). The BFR-CT promotes similar neuromuscular and cardiorespiratory adaptations as CT.

Resistance training with instability in multiple system atrophy: a case report

This case report assessed quality of life, activities of daily living, motor symptoms, functional ability, neuromuscular parameters and mRNA expression of selected genes related to muscle protein synthesis and degradation in a patient with Multiple System Atrophy (MSA). The patient underwent resistance training with instability devices (i.e., bosu, dyna disk, balance disk, Swiss ball) for six months twice a week. After the six months training, the patient's left and right quadriceps muscle cross-sectional area and leg press one-repetition maximum increased 6.4%, 6.8%, and 40%, respectively; the patient's timed up and go, sit to stand, dynamic balance, and activities of daily living improved 33.3%, 28.6%, 42.3%, and 40.1%, respectively; the patient's severity of motor symptoms and risk of falls decreased 32% and 128.1%, respectively. Most of the subscales of quality of life demonstrated improvements as well, varying from 13.0% to 100.0%. mRNA expression of mechanogrowth factor and mammalian target of rapamycin increased 12.7-fold and 1.5-fold, respectively. This case report describes likely the first nonpharmacological therapeutic tool that might be able to decrease the severity of motor symptoms and risk of falls, and to improve functional ability, neuromuscular parameters, and quality of the life in a patient with MSA. Key pointsSix months of resistance training with instability alleviate the MSA-related effects and improve the quality of life in a patient with MSA.High complexity exercise intervention (i.e., resistance training with instability) may be very beneficial to individuals with impaired motor control and function as MSA patients.Caution should be exercised when interpreting our findings as they cannot be generalized to the entire MSA population and they do not allow establishing causal conclusions on the effects of this mode of exercise on MSA.

Early adaptations to six weeks of non-periodized and periodized strength training regimens in recreational males

This study compared quadriceps muscle cross-sectional area (CSA) and maximum strength (1RM) after three different short-term strength training (ST) regimens (i.e. non-periodized [NP], traditional-periodization [TP], and undulating-periodization [UP]) matched for volume load in previously untrained individuals. Thirty-one recreationally active males were randomly divided into four groups: NP: n = 9; TP: n = 9; UP: n = 8 and control group (C): n = 5. Experimental groups underwent a 6-week program consisting of two training sessions per week. Muscle strength was assessed at baseline and after the training period. Dominant leg quadriceps CSA was obtained through magnetic resonance imaging (MRI) at baseline and 48h after the last training session.

RESULTS

The 1RM increased from pre to post only in the NP and UP groups (NP = 17.0 %, p = 0.002; UP = 12.9 %, p = 0.03), respectively. There were no significant differences in 1RM for LP and C groups after 6 weeks (TP = 7.7 %, p = 0.58, C = 1.2 %, p = 1.00). The CSA increased from pre to post in all of the experimental groups (NP = 5.1 %, p = 0.0001; TP = 4.6 %, p = 0.001; UP = 5.2 %, p = 0.0001), with no changes observed in the C group (p = 0.93).

CONCLUSION

Our results suggest that different ST periodization regimens over a short-term (i.e. 6 weeks), volume load equated conditions seem to induce similar hypertrophic responses regardless of the loading scheme employed. In addition, for those recreational males who need to develop muscle strength in the short-term, the training regimen should be designed properly. Key pointsMuscle hypertrophy occurs within six weeks in recreationally active men regardless the ST training regimen employed.When the total volume is similar, training at greater intensities will demonstrate superior gains in the 1RM performance.Some caution should be exercised when interpreting our findings since long-term periodized regimens could produce different training-induced responses.

Different loading schemes in power training during the preseason promote similar performance improvements in Brazilian elite soccer players

The present study investigated the effects of 2 different power training loading schemes in Brazilian elite soccer players. Thirty-two players participated in the study. Maximum dynamic strength (1RM) was evaluated before (B), at midpoint (i.e., after 3 weeks; T1), and after 6 weeks (T2) of a preseason strength/power training. Muscle power, jumping, and sprinting performance were evaluated at B and T2. Players were randomly allocated to 1 of 2 training groups: velocity-based (VEL: n = 16; age, 19.18 ± 0.72 years; height, 173 ± 6 cm; body mass, 72.7 ± 5.8 kg) or intensity-based (INT: n = 16; age, 19.11 ± 0.7 years; height, 172 ± 4.5 cm; body mass, 71.8 ± 4.6 kg). After the individual determination of the optimal power load, both groups completed a 3-week traditional strength training period. Afterward, the VEL group performed 3 weeks of power-oriented training with increasing velocity and decreasing intensity (from 60 to 30% 1RM) throughout the training period, whereas the INT group increased the training intensity (from 30 to 60% 1RM) and thus decreased movement velocity throughout the power-oriented training period. Both groups used loads within ±15% (ranging from 30 to 60% 1RM) of the measured optimal power load (i.e., 45.2 ± 3.0% 1RM). Similar 1RM gains were observed in both groups at T1 (VEL: 9.2%; INT: 11.0%) and T2 (VEL: 19.8%; INT: 22.1%). The 2 groups also presented significant improvements (within-group comparisons) in all of the variables. However, no between-group differences were detected. Mean power in the back squat (VEL: 18.5%; INT: 20.4%) and mean propulsive power in the jump squat (VEL: 29.1%; INT: 31.0%) were similarly improved at T2. The 10-m sprint (VEL: -4.3%; INT: -1.6%), jump squat (VEL: 7.1%; INT: 4.5%), and countermovement jump (VEL: 6.7%; INT: 6.9%) were also improved in both groups at T2. Curiously, the 30-m sprint time (VEL: -0.8%; INT: -0.1%) did not significantly improve for both groups. In summary, our data suggest that male professional soccer players can achieve improvements in strength- and power-related abilities as a result of 6 weeks of power-oriented training during the preseason. Furthermore, similar performance improvements are observed when training intensity manipulation occurs around only a small range within the optimal power training load.

The acute effects of strength, endurance and concurrent exercises on the Akt/mTOR/p70(S6K1) and AMPK signaling pathway responses in rat skeletal muscle

The activation of competing intracellular pathways has been proposed to explain the reduced training adaptations after concurrent strength and endurance exercises (CE). The present study investigated the acute effects of CE, strength exercises (SE), and endurance exercises (EE) on phosphorylated/total ratios of selected AMPK and Akt/mTOR/p70^S6K1 pathway proteins in rats. Six animals per exercise group were killed immediately (0 h) and 2 h after each exercise mode. In addition, 6 animals in a non-exercised condition (NE) were killed on the same day and under the same conditions. The levels of AMPK, phospho-Thr¹⁷²AMPK (p-AMPK), Akt, phospho-Ser⁴⁷³Akt (p-Akt), p70^S6K1, phospho-Thr³⁸⁹-p70^S6K1 (p-p70^S6K1), mTOR, phospho-Ser²⁴⁴⁸mTOR (p-mTOR), and phospho-Thr¹⁴⁶²-TSC2 (p-TSC2) expression were evaluated by immunoblotting in total plantaris muscle extracts. The only significant difference detected was an increase (i.e., 87%) in Akt phosphorylated/total ratio in the CE group 2 h after exercise compared to the NE group (P = 0.002). There were no changes in AMPK, TSC2, mTOR, or p70^S6K1 ratios when the exercise modes were compared to the NE condition (P ≥ 0.05). In conclusion, our data suggest that low-intensity and low-volume CE might not blunt the training-induced adaptations, since it did not activate competing intracellular pathways in an acute bout of strength and endurance exercises in rat skeletal muscle.

Training at the optimum power zone produces similar performance improvements to traditional strength training

The purpose of this study was to test if substituting a regular maximum strength-oriented training regimen by a power-oriented one at the optimal power load in the first phase of a traditional periodization produces similar performance improvements later on into the training period. Forty five soldiers of the Brazilian brigade of special operations with at least one year of army training experience were divided into a control group (CG - n = 15, 20.18 ± 0.72 yrs, 1.74 ± 0.06 m, 66.7 ± 9.8 kg, and 1RM/weight ratio = 1.14 ± 0.12), a traditional periodization group (TG - n = 15, 20.11 ± 0.7 yrs, 1.72 ± 0.045 m, 63.1 ± 3.6 kg, and 1RM/weight ratio = 1.21 ± 0.16); and a maximum-power group (MPG - n = 15, 20.5 ± 0.6 yrs, 1.73 ± 0.049m, 67.3 ± 9.8 kg, 1RM/weight ratio = 1.20 ± 0.14). Maximum strength (26.2% and 24.6%), CMJ height (30.8% and 39.1%) and sprint speed (11.6% and 14.5%) increased significantly (p < 0.05) and similarly for the MPG and TG, respectively, from pre- to post-assessments. Our data suggests that a power training regimen may be used in the initial phase of the training cycle without impairing performance later on into the training period. Key pointsTraining at the optimal power zone during two mesocycles of a traditional periodization did not hamper strength, speed and power performance improvements.Additional research is required in order to find out if longer periods of training at optimal power zone are capable of producing similar performance improvements to traditional strength training regimen.

Maximal strength, number of repetitions, and total volume are differently affected by static-, ballistic-, and proprioceptive neuromuscular facilitation stretching

Stretching exercises have been traditionally incorporated into warm-up routines before training sessions and sport events. However, the effects of stretching on maximal strength and strength endurance performance seem to depend on the type of stretching employed. The objective of this study was to compare the effects of static stretching (SS), ballistic stretching (BS), and proprioceptive neuromuscular facilitation (PNF) stretching on maximal strength, number of repetitions at a submaximal load, and total volume (i.e., number of repetitions × external load) in a multiple-set resistance training bout. Twelve strength-trained men (20.4 ± 4.5 years, 67.9 ± 6.3 kg, 173.3 ± 8.5 cm) volunteered to participate in this study. All of the subjects completed 8 experimental sessions. Four experimental sessions were designed to test maximal strength in the leg press (i.e., 1 repetition maximum [1RM]) after each stretching condition (SS, BS, PNF, or no-stretching [NS]). During the other 4 sessions, the number of repetitions performed at 80% 1RM was assessed after each stretching condition. All of the stretching protocols significantly improved the range of motion in the sit-and-reach test when compared with NS. Further, PNF induced greater changes in the sit-and-reach test than BS did (4.7 ± 1.6, 2.9 ± 1.5, and 1.9 ± 1.4 cm for PNF, SS, and BS, respectively). Leg press 1RM values were decreased only after the PNF condition (5.5%, p < 0.001). All the stretching protocols significantly reduced the number of repetitions (SS: 20.8%, p < 0.001; BS: 17.8%, p = 0.01; PNF: 22.7%, p < 0.001) and total volume (SS: 20.4%, p < 0.001; BS: 17.9%, p = 0.01; PNF: 22.4%, p < 0.001) when compared with NS. The results from this study suggest that, to avoid a decrease in both the number of repetitions and total volume, stretching exercises should not be performed before a resistance training session. Additionally, strength-trained individuals may experience reduced maximal dynamic strength after PNF stretching.

Fit-climbing test: a field test for indoor rock climbing

The aim of this study was to develop an indoor rock-climbing test on an artificial wall (Fit-climbing test). Thirteen climbers (elite group [EG] = 6; recreational group [RG] = 7) performed the following tests: (a) familiarization in the Fit-climbing test, (b) the Fit-climbing test, and (c) a retest to evaluate the Fit-climbing test's reliability. Gas exchange, blood lactate concentration, handgrip strength, and heart rate were measured during the test. Oxygen uptake during the Fit-climbing test was not different between groups (EG = 8.4 ± 1.1 L; RG = 7.9 ± 1.5 L, p > 0.05). The EG performance (120 ± 7 movements) was statistically higher than the RG climbers' performance (78 ± 13 movements) during the Fit-climbing test. Consequently, the oxygen cost per movement during the Fit-climbing test of the EG was significantly lower than that of the RG (p < 0.05). Handgrip strength was higher in the EG when compared with that in the RG in both pre-Fit- and post-Fit-climbing test (p < 0.05). There were no significant differences in any other variables analyzed during the Fit-climbing test (p > 0.05). Furthermore, the performance in the Fit-climbing test presented high reliability (intraclass correlation coefficient = 0.97). Therefore, the performance during the Fit-climbing test may be an alternative to evaluate rock climbers because of its specificity and relation to oxygen cost per movement during climbing.

Molecular adaptations to concurrent training

This study investigated the chronic effects of concurrent training (CT) on morphological and molecular adaptations. 37 men (age=23.7±5.5 year) were divided into 4 groups: interval (IT), strength (ST) and concurrent (CT) training and a control group (C) and underwent 8 weeks of training. Maximum strength (1RM) and muscle cross-sectional area (CSA) were evaluated before and after training. Muscle samples were obtained before the training program and 48 h after the last training session. VO2max improved in 5±0.95% and 15±1.3% (pre- to post-test) in groups CT and IT, respectively, when compared to C. Time to exhaustion (TE) improved from pre- to post-test when compared to C (CT=6.1±0.58%; IT=8.3±0.88%; ST=3.2±0.66%). 1RM increased from pre-to post-test only in ST and CT groups (ST=18.5±3.16%; CT=17.6±3.01%). Similarly, ST and CT groups increased quadriceps CSA from pre-to post-test (6.2±1.4%; 7.8±1.66%). The p70S6K1 total protein content increased after CT. The ST group showed increased Akt phosphorylation at Ser473 (45.0±3.3%) whereas AMPK phosphorylation at Thr172 increased only in IT group, (100±17.6%). In summary, our data suggest that despite the differences in molecular adaptations between training regimens, CT did not blunt muscle strength and hypertrophy increments when compared with ST.

O treinamento de força com e sem o uso da plataforma vibratória é capaz de modular a variabilidade da frequência cardíaca em repouso?

Esse trabalho comparou a variabilidade da frequência cardíaca (VFC) de repouso antes e após 10 semanas de treinamento de força de grupos que usaram e não usaram a plataforma vibratória. Dezessete homens saudáveis foram divididos nos grupos treinamento de força convencional (TF) ou treinamento de força sobre a plataforma vibratória a frequência de 30 Hz (TF+V30). As mensurações do desempenho de força dinâmica máxima (1-RM) no exercício meio agachamento e da VFC de repouso foram feitas antes e após o programa de treinamento. Ambos os grupos tiveram aumento significante da força no período pós (de 15,1% no grupo TF e de 16,4% no grupo TF+V30), no entanto esse aumento se alterou na mesma magnitude para os dois grupos, não havendo diferença entre eles no desempenho de 1-RM nos períodos pré e pós-treinamento. Não foi observada diferença nas comparações entre os grupos e nas situações pré e pós-treinamento nas análises da VFC de repouso, no entanto a magnitude do effect size foi moderada (ES = 0,50-0,80) para algumas variáveis (intervalo R-R, desvio-padrão da média de todos os intervalos R-R - SDNN, raiz quadrada da média dos quadrados das diferenças entre os intervalos R-R sucessivos - RMSSD, componente de baixa frequência ajustada por meio de logarítmico - InLF e componente de alta frequência ajustada por meio de logarítmico - InHF) no grupo TF+V30 após o período de treinamento. Conclui-se que 10 semanas de treinamento de força com e sem a presença da vibração proporcionou aumento semelhante no desempenho de 1-RM em ambos os grupos e, embora o estímulo adicional da vibração tenha dado indícios de maior atividade vagal analisado por meio do ES, nenhum dos grupos apresentou alteração significante da VFC.

Efeito agudo dos exercícios de flexibilidade no desempenho de força máxima e resistência de força de membros inferiores e superiores

Este estudo verificou o efeito agudo dos exercícios de flexibilidade estática (EFlex) no desempenho de força máxima (FM) e de resistência de força (RF) em membros inferiores e superiores. Treze voluntários participaram do estudo e foram submetidos a testes de FM e RF (70% 1RM) nos exercícios supino e agachamento precedidos ou não de EFlex. O teste T pareado foi utilizado para comparação das médias nas duas condições. Os EFlex diminuíram a FM no agachamento (141,2±34,2 vs 132±34,9kg; p=0,007) e no supino (77,5±21,7 vs 71,7±17,7kg p=0,04). A RF no agachamento não sofreu efeito dos EFlex (16,2±5,7 vs 16,3±6,8 repetições p=0,48), porém, no supino a RF apresentou diminuição significante (11,7±4,8 vs 9,9±5,1 repetições; p=0,008). Portanto, os EFlex reduziram a FM nos membros inferiores e superiores e a RF somente nos membros superiores. Essa diferença na RF estaria relacionada ao volume de exercícios de flexibilidade pelo tamanho do grupo muscular.

Influence of different resistance exercise loading schemes on mechanical power output in work to rest ratio - equated and - nonequated conditions

It is well known that most sports are characterized by the performance of intermittent high-intensity actions, requiring high muscle power production within different intervals. In fact, the manipulation of the exercise to rest ratio in muscle power training programs may constitute an interesting strategy when considering the specific performance demand of a given sport modality. Thus, the aim of this study was to evaluate the influence of different schemes of rest intervals and number of repetitions per set on muscle power production in the squat exercise between exercise to rest ratio-equated and -nonequated conditions. Nineteen young males (age: 25.7 ± 4.4 years; weight: 81.3 ± 13.7 kg; height: 178.1 ± 5.5 cm) were randomly submitted to 3 different resistance exercise loading schemes, as follows: short-set short-interval condition (SSSI; 12 sets of 3 repetitions with a 27.3-second interval between sets); short-set long-interval condition (SSLI; 12 sets of 3 repetitions with a 60-second interval between sets); long-set long-interval (LSLI; 6 sets of 6 repetitions with a 60-second rest interval between sets). The main finding of the present study is that the lower exercise to rest ratio protocol (SSLI) resulted in greater average power production (601.88 ± 142.48 W) when compared with both SSSI and LSLI (581.86 ± 113.18 W; 578 ± 138.78 W, respectively). Additionally, both the exercise to rest ratio-equated conditions presented similar performance and metabolic results. In summary, these findings suggest that shorter rest intervals may fully restore the individual's ability to produce muscle power if a smaller exercise volume per set is performed and that lower exercise to rest ratio protocols result in greater average power production when compared with higher ratio ones.

Effects of strength and power training on neuromuscular adaptations and jumping movement pattern and performance

This study aimed at comparing the effects of strength and power training (ST and PT) regimens on neuromuscular adaptations and changes on vertical jump performance, kinetics, and kinematics parameters. Forty physically active men (178.2 ± 7.0 cm; 75.1 ± 8.6 kg; 23.6 ± 3.5 years) with at least 2 years of ST experience were assigned to an ST (n = 14), a PT (n = 14), or a control group (C; n = 12). The training programs were performed during 8 weeks, 3 times per week. Dynamic and isometric maximum strength, cross-sectional area, and muscle activation were assessed before and after the experimental period. Squat jump (SJ) and countermovement jump (CMJ) performance, kinetics, and kinematics parameters were also assessed. Dynamic maximum strength increased similarly (p < 0.05) for the ST (22.8%) and PT (16.6%) groups. The maximum voluntary isometric contraction increased for the ST and PT groups (p < 0.05) in the posttraining assessments. There was a main time effect for muscle fiber cross-sectional area (p < 0.05), but there were no changes in muscle activation. The SJ height increased, after ST and PT, because of a faster concentric phase and a higher rate of force development (p < 0.05). The CMJ height increased only after PT (p < 0.05), but there were no significant changes in its kinetics and kinematics parameters. In conclusion, neuromuscular adaptations were similar between the training groups. The PT seemed more effective than the ST in increasing jumping performance, but neither the ST nor the PT was able to affect the SJ and the CMJ movement pattern (e.g., timing and sequencing of joint extension initiation).

Efeito da familiarização na estabilização dos valores de 1RM para homens e mulheres

O objetivo deste estudo foi verificar o número de sessões de familiarização necessárias para estabilização da carga do teste de uma repetição máxima (1RM) no exercício agachamento em homens e mulheres. Oito homens (25 ± 4 anos) e oito mulheres (20 ± 1anos) foram submetidos a cinco sessões experimentais. ANOVA e plotagem de Bland-Altman foram utilizadas para comparar a carga de 1RM entre as sessões (p<0,05). A estabilização da carga ocorreu na quarta sessão para os homens e na terceira para as mulheres, com aumentos significantes da força absoluta e relativa da primeira à quarta (17kg e 19%) e da primeira à terceira (9kg e 14%) sessões, respectivamente. Porém, não houve diferença significante na força relativa entre os gêneros. De acordo com nossos resultados, indivíduos inexperientes em treinamento de força atingem alta reprodutibilidade ao teste de 1RM no exercício agachamento, após realizar três a quatro sessões de familiarização.

Efeito do número e intensidade das ações excêntricas nos indicadores de dano muscular

A realização de uma sessão de treinamento de força, especialmente de ações excêntricas, provoca danos à estrutura muscular. Algumas características da realização das ações excêntricas parecem agravar a ocorrência do dano. O número de contrações realizadas e o grau de tensão desenvolvida em cada uma delas parecem afetar a magnitude o dano. Dessa maneira, o objetivo deste estudo foi investigar se o número e a intensidade das ações excêntricas contribuem para o aumento do dano muscular, avaliado através das alterações de marcadores indiretos. Vinte e quatro jovens adultos do sexo masculino foram divididos aleatoriamente em três grupos. Um dos grupos realizou 30 ações excêntricas para os flexores do cotovelo com 70% de 1RM (EXC30-70, n = 8). Outro grupo realizou o mesmo número de repetições, porém com 110% de 1RM (EXC30110, n = 8). Um terceiro grupo realizou um número maior de repetições (60) com 70% de 1RM (EXC60-70, n = 8). A amplitude de movimento, a circunferência do braço, a força máxima (1RM) e a dor muscular tardia foram avaliadas antes, imediatamente, 48 e 96 horas após o exercício. Os resultados foram analisados através de análise de variância com dois fatores e revelaram que as alterações foram maiores no grupo EXC30-110 comparadas com EXC30-70 e EXC60-70. Esses dados sugerem que a intensidade das ações excêntricas afeta mais a ocorrência de dano do que o número de contrações.

Bioenergetics and neuromuscular determinants of the time to exhaustion at velocity corresponding to VO2max in recreational long-distance runners

The purpose of this study was to investigate the main bioenergetics and neuromuscular determinants of the time to exhaustion (T(lim)) at the velocity corresponding to maximal oxygen uptake in recreational long-distance runners. Twenty runners performed the following tests on 5 different days: (a) maximal incremental treadmill test, (b) 2 submaximal tests to determine running economy and vertical stiffness, (c) exhaustive test to measured the T(lim), (d) maximum dynamic strength test, and (e) muscle power production test. Aerobic and anaerobic energy contributions during the T(lim) test were also estimated. The stepwise multiple regression method selected 3 independent variables to explain T(lim) variance. Total energy production explained 84.1% of the shared variance (p = 0.001), whereas peak oxygen uptake (V(O2)peak) measured during T(lim)and lower limb muscle power ability accounted for the additional 10% of the shared variance (p = 0.014). These data suggest that the total energy production, V(O2)peak, and lower limb muscle power ability are the main physiological and neuromuscular determinants of T(lim)in recreational long-distance runners.

The acute effects of varying strength exercises bouts on 5Km running

This study investigated if there were acute interference effects of strength exercises on subsequent continuous and intermittent 5Km aerobic exercises. Eleven physically active males (23.1 ± 3.1 yrs, 1.75 ± 0.07 m, 70.5 ± 8.8 kg, and 58.2 ± 8.3 VO2max) performed the following experimental sessions: A) 5 sets of 5 RM on the leg press followed by a 5km run performed continuously (average velocity of the first and second ventilatory thresholds, vΔ50), B) 5 sets of 5 RM on the leg press followed by a 5km run performed intermittently (1 min run at the vVO2max : 1 min of rest); C) 2 sets of 15 RM on the leg press followed by a 5km continuous run; and D) 2 sets of 15 RM on the leg press followed by a 5km intermittent run. Heart rate, blood lactate concentration, rate of perceived exertion, and VO2 at the first and the fifth km were considered for statistical purposes. There were no significant effects of both strength bouts on any of the variables associated with endurance performance (p > 0.05). It seems that both maximum and strength endurance bouts do not acutely impair aerobic performance. Key pointsResidual acute peripheral fatigue does not seem to be the only cause in the interference effect observed during concurrent training regimens.Peripheral fatigue mechanisms of running such as lactate concentration are not altered by prior lower volume strength exercises.Strength and strength endurance exercises performed before a running bout do not seem to impair the performance in the latter.

Effect of eccentric exercise velocity on akt/mtor/p70(s6k) signaling in human skeletal muscle

It has been suggested that muscle tension plays a major role in the activation of intracellular pathways for skeletal muscle hypertrophy via an increase in mechano growth factor (MGF) and other downstream targets. Eccentric exercise (EE) imposes a greater amount of tension on the active muscle. In particular, high-speed EE seems to exert an additional effect on muscle tension and, thus, on muscle hypertrophy. However, little is known about the effect of EE velocity on hypertrophy signaling. This study investigated the effect of acute EE-velocity manipulation on the Akt/mTORCI/p70(S6K) hypertrophy pathway. Twenty subjects were assigned to either a slow (20°·s(-1); ES) or fast EE (210°·s(-1); EF) group. Biopsies were taken from vastus lateralis at baseline (B), immediately after (T1), and 2 h after (T2) the completion of 5 sets of 8 repetitions of eccentric knee extensions. Akt, mTOR, and p70(S6K) total protein were similar between groups, and did not change postintervention. Further, Akt and p70(S6K) protein phosphorylation were higher at T2 than at B for ES and EF. MGF messenger RNA was similar between groups, and only significantly higher at T2 than at B in ES. The acute manipulation of EE velocity does not seem to differently influence intracellular hypertrophy signaling through the Akt/mTORCI/p70S6K pathway.

Do whole-body vibration exercise and resistance exercise modify concentrations of salivary cortisol and immunoglobulin A?

A single bout of resistance exercise (RE) induces hormonal and immune responses, playing an important role in a long-term adaptive process. Whole-body vibration (WBV) has also been shown to affect hormonal responses. Evidence suggests that combining WBV with RE may amplify hormonal and immune responses due to the increased neuromuscular load. Therefore, the aim of this study was to evaluate salivary cortisol (Scortisol) and salivary IgA (SIgA) concentrations following a RE session combined or not with WBV. Nine university students (22.9 ± 5.1 years, 175.8 ± 5.2 cm, and 69.2 ± 7.3 kg) performed five sets of squat exercise (70% one-repetition-maximum) combined (R+V30) or not (R) with WBV at 30 Hz. Saliva samples were obtained before and after exercise. Subjects also rated their effort according to the Borg CR-10 scale (RPE). Data were analyzed by a mixed model. RPE was higher after R+V30 (8.3 ± 0.7) compared to R (6.2 ± 0.7). However, Scortisol (pre: 10.6 ± 7.6 and 11.7 ± 7.6, post: 8.3 ± 6.3 and 10.2 ± 7.2 ng/mL for R and R+V30, respectively) and SIgA concentrations (pre: 98.3 ± 22.6 and 116.1 ± 51.2, post: 116.6 ± 64.7 and 143.6 ± 80.5 µg/mL for R and R+V30, respectively) were unaffected. No significant correlations were observed between Scortisol and RPE (r = 0.45, P = 0.22; r = 0.30, P = 0.42, for R and R+V30, respectively). On the basis of these data, neither protocol modified salivary cortisol or IgA, although RPE was higher after R+V30 than R.

Incidence of adverse events associated with percutaneous muscular biopsy among healthy and diseased subjects

The development of the percutaneous muscle biopsy technique is recognized as one of the most important scientific contributions in advancing our understanding of skeletal muscle physiology. However, a concern that this procedure may be associated with adverse events still exists. We reported the incidence of adverse outcomes associated with percutaneous muscle biopsy in healthy and diseased subjects. Medical records of 274 volunteers (496 muscle biopsies) were reviewed. This included 168 healthy subjects (330 muscle biopsies) as well as 106 chronically ill patients (166 muscle biopsies). This latter group encompassed patients with type II diabetes (n=28), osteoarthritis (n=39), inclusion body myositis (n=4), polymyositis (n=4), and chronic heart failure (n=31). The most common occurrences were pain (1.27%), erythema (1.27%), and ecchymosis (1.27%). Panic episode, bleeding, and edema were also reported (0.21%, 0.42%, and 0.84%, respectively), while infection, hematoma, inflammation, denervation, numbness, atrophy, and abnormal scarring were not verified. The percent of incidents did not differ between healthy and ill individuals. In conclusion, the incidence of complications associated with percutaneous muscle biopsy is scarce and of minor clinical relevance. Additionally, the rate of adverse events is comparable between healthy and chronically ill subjects.

Influência do nível de força máxima na produção e manutenção da potência muscular

Indivíduos mais fortes (com nível mais elevado de força máxima, Fmax) demonstram menor resistência de força que indivíduos mais fracos (com nível mais baixo de Fmax) em uma mesma intensidade relativa. Como o nível de Fmax influencia a produção de potência, espera-se que sujeitos mais fortes também apresentem uma menor resistência de potência. O objetivo deste estudo foi avaliar a influência do nível de Fmax na produção e na resistência de potência durante repetições e séries múltiplas do exercício meio-agachamento. Quarenta e dois sujeitos foram classificados de acordo com o resultado no teste de força dinâmica máxima (1RM) e destes os 10 mais fortes e os 10 mais fracos foram selecionados para participar no estudo. Para avaliar a resistência de potência os dois grupos realizaram 10 séries de seis repetições a 40% e a 60% 1RM na maior velocidade possível. A potência absoluta (PA) e a potência relativa ao peso corporal (PR) desenvolvidas na fase concêntrica do exercício foram medidas. A análise de variância (ANOVA two-way) revelou que os sujeitos mais fortes diminuíram a PA a 60% 1RM a partir da quarta repetição e a PR a partir da quinta repetição. Já os sujeitos mais fracos diminuíram a PA apenas na sexta repetição e mantiveram o rendimento na PR ao longo das 10 séries. Não houve efeito significante na intensidade de 40% 1RM. Isso sugere que sujeitos mais fortes fadigam antes em maiores intensidades de carga. Essa fadiga precoce nos sujeitos mais fortes poderia estar ligada a diferentes fatores associados ao controle da homeostase orgânica como o comportamento da pressão arterial, da atividade eletromiográfica e a proporção de fibras musculares dos tipos I e II.

Is acute static stretching able to reduce the time to exhaustion at power output corresponding to maximal oxygen uptake?

This study analyzed the effect of an acute static stretching bout on the time to exhaustion (Tlim) at power output corresponding to VO2max. Eleven physically active male subjects (age 22.3+/-2.8 years, VO2max 2.7+/-0.5 L.min) completed an incremental cycle ergometer test, 2 muscle strength tests, and 2 maximal tests to exhaustion at power output corresponding to VO2max with and without a previous static stretching bout. The Tlim was not significantly affected by the static stretching (164+/-28 vs. 150+/-26 seconds with and without stretching, respectively, p=0.09), but the time to reach VO2max (118+/-22 vs. 102+/-25 seconds), blood-lactate accumulation immediately after exercise (10.7+/-2.9 vs. 8.0+/-1.7 mmol.L), and oxygen deficit (2.4+/-0.9 vs. 2.1+/-0.7 L) were significantly reduced (p<or=0.02). Thus, an acute static stretching bout did not reduce Tlim at power output corresponding to VO2max possibly by accelerating aerobic metabolism activation at the beginning of exercise. These results suggest that coaches and practitioners involved with aerobic dependent activities may use static stretching as part of their warm-up routines without fear of diminishing high-intensity aerobic exercise performance.

Effect of eccentric contraction velocity on muscle damage in repeated bouts of elbow flexor exercise

Eccentric exercise induces muscle damage, but controversy exists concerning the effect of contraction velocity on the magnitude of muscle damage, and little is known about the effect of contraction velocity on the repeated-bout effect. This study examined slow (60°·s–1) and fast (180°·s–1) velocity eccentric exercises for changes in indirect markers of muscle damage following 3 exercise bouts that were performed every 2 weeks. Fifteen young men were divided into 2 groups based on the velocity of eccentric exercise: 7 in the Ecc60 (60°·s–1) group, and 8 in the Ecc180 (180°·s–1) group. The exercise consisted of 30 maximal eccentric contractions of the elbow flexors at each velocity, in which the elbow joint was forcibly extended from 60° to 180° (full extension) on an isokinetic dynamometer. Changes in maximal voluntary isometric contraction strength, range of motion, muscle soreness, and plasma creatine kinase activity before and for 4 days after the exercise were compared in the 2 groups using a mixed-model analysis (group × bout × time). No significant differences between groups were evident for changes in any variables following exercise bouts; however, the changes were significantly smaller (p < 0.05) after the second and third bouts than after the first bout. These results indicate that the contraction velocity does not influence muscle damage or the repeated-bout effect.

Efeitos da suplementação de creatina sobre força e hipertrofia muscular: atualizações

A suplementação de creatina vem sendo utilizada amplamente na tentativa de aumentar força e massa magra em sujeitos saudáveis e atletas. Além disso, diversos estudos têm sido conduzidos no intuito de desvendar os mecanismos responsáveis pelas eventuais adaptações a esse suplemento. Diante disso, essa revisão teve como objetivos: 1) discutir os principais estudos que investigaram os efeitos da suplementação de creatina na força e hipertrofia; e 2) reunir as evidências acerca dos possíveis mecanismos responsáveis pelo aumento de força e massa magra como consequência desse suplemento, enfatizando os mais recentes achados e as perspectivas sobre o tema. De fato, existem fortes evidências demonstrando que a suplementação de creatina é capaz de promover aumentos de força e hipertrofia. Os efeitos desse suplemento sobre a retenção hídrica, o balanço proteico, a expressão de genes/proteínas associados à hipertrofia e ativação de células satélites, podem explicar as adaptações musculoesqueléticas observadas. Diante desses achados, os potenciais efeitos terapêuticos desse suplemento emergem como um futuro e promissor campo de estudo.