Alteração do limiar de variabilidade da freqüência cardíaca após treinamento aeróbio de curto prazo

During incremental tests, there is a consistent reduction in heart rate variability (VFC) until approximately 3 ms value, when calculated through the Poincaré Plotting (STDB). A stabilization of this index is observed in the subsequent intensities. This transition point, called VFC threshold (LiVFC) by Lima and Kiss (1999), can be considered as an indicator of aerobic capacity, because of its high correlation with the lactate and ventilatory thresholds. The aim of this study was to verify the effects of three weeks duration aerobic training program on LiVFC. A 25 non-athlete sample was divided in a Training Group (TR, n = 18) and a Control Group (C, n = 7), submitted to a pre- and post-training incremental test until exhaustion, with an initial power output of 0 W and increments of 14.5 W per minute. The R-R intervals were recorded using a Polar equipment, S810i model, and the VFC was calculated by means of the Polar Precision Performance software. TR underwent nine training sessions (3 times a week) of 30 min duration, with the intensity of approximately 50% of the peak power output (PPico) and that one associated to the LiVFC (PLiVFC) interval. The comparisons were made by a two way repeated measures ANOVA, followed by the Scheffé test (p < 0.05). During the pre-training test there was no significant difference in the VFC responses between the groups. In the post-training measure, the VFC of the TR was greater until the power output of 145.75 W, which caused the increase in PLiVFC. The TR experienced no significant improvement in the PPico and in maximal FC. The submaximal FC of TR in the post-training was lower until the power output of 189.5 W. It was concluded that LiVFC presents sensibility to the short-term aerobic training effects, suggesting its validity as an indicator of aerobic capacity.Em testes incrementais, há redução consistente da variabilidade da freqüência cardíaca (VFC) até aproximadamente o valor de 3 ms, quando calculada pela Plotagem de Poincaré (STDB), sendo observada estabilização desse indicador nas cargas seguintes. Este ponto, denominado limiar de VFC (LiVFC) por Lima e Kiss (1999), pode ser considerado um indicador da capacidade aeróbia, por sua alta relação com os limiares de lactato e ventilatório. O objetivo do estudo foi verificar os efeitos do treinamento aeróbio de três semanas sobre o LiVFC. A amostra de 25 indivíduos, não-atletas, foi dividida em Grupo Treinamento (TR, n = 18) e Grupo Controle, (C, n = 7), submetidos a teste incremental pré e pós-treinamento, com potência inicial de 0 W, e incrementos de 14,5 W por minuto, até a exaustão. Os intervalos R-R foram registrados pelo cardiofreqüencímetro Polar, modelo S810i, e a VFC foi calculada pelo programa Polar Precision Performance. O TR realizou nove sessões de treinamento (3 x semana) de 30 min, com intensidade aproximada de 50% do intervalo entre a potência associada ao LiVFC (PLiVFC) e a potência de pico (PPico). As comparações foram feitas por ANOVA two way para medidas repetidas, seguida do teste de Scheffé (p < 0,05). No teste pré–treinamento, não houve diferença significante no comportamento da VFC entre os grupos. No pós-treinamento, a VFC do TR foi maior até a potência de 145,75 W, o que provocou aumento da PLiVFC. O TR não experimentou melhora significante na PPico e na FC máxima. A FC submáxima de TR no pós-treinamento foi menor até a potência de 189,5 W. Conclui-se que o LiVFC é sensível aos efeitos do treinamento aeróbio de curto prazo, sugerindo sua validade como indicador de capacidade aeróbia

Effects of volume training on strength and endurance of back muscles: a randomized controlled trial

CONTEXT: Strength/resistance training volume has historically been supported in the American College of Sports Medicine recommendations. However, for the back muscles, exercise prescription related to the number of sets, such as single vs. multiple, is not well established in the literature. OBJECTIVE: The purpose of this study was to compare the effects of two training volumes on strength and endurance of back extensor muscles in untrained young participants, with regard to a repeated measures design. DESIGN: Randomized controlled trial. SETTING: Laboratory of functional evaluation and human motor performance. PARTICIPANTS: Forty-four untrained young participants (mean age = 21 yrs) were randomized into three groups: single set (SSG, n = 14), multiple sets (MSG, n = 15), and untrained control (CG, n = 15). INTERVENTION: The SSG and MSG underwent a 10-wk progressive resistance training program (2 days·week-1) using a 45° Roman chair. MAIN OUTCOME MEASURES: Back maximal strength (dynamometer) and isometric and dynamic endurance (time-limit, trunk extension-flexion cycles, and electromyography muscle fatigue estimates). RESULTS: The results showed differences between the MSG and control group for isometric endurance time (mean 19.8 seconds, 95% CI 44.1 to 4.8), but without time intervention significance. Significant improvement after training (P 0.05) difference in either strength or electromyography estimates after training. CONCLUSIONS: Both multiple and single volume training were efficient in promoting better back endurance during dynamic performance based on mechanical variables (time and number of repetitions)

Branched-chain amino acids do not improve muscle recovery from resistance exercise in untrained young adults.

The purpose of this study was to investigate the effects of BCAA supplementation on muscle recovery from resistance exercise (RE) in untrained young adults. Twenty-four young adults (24.0 ± 4.3 years old) were assigned to 1 of 2 groups (n = 12 per group): a placebo-supplement group or a BCAA-supplement group. The groups were supplemented for a period of 5 days. On day 1 and 3, both groups underwent a RE session involving two lower body exercises (hack squat and leg press) and then were evaluated for muscle recovery on the 3 subsequent moments after the RE session [30 min (day 3), 24 h (day 4), and 48 h (day 5)]. The following indicators of muscle recovery were assessed: number of repetitions, rating of perceived exertion in the last RE session, muscle soreness and countermovement jump (CMJ) during recovery period (30 min, 24 h, and 48 h after RE session). Number of repetitions remained unchanged over time (time, P > 0.05), while the rating of perceived exertion increased (time, P  0.05). Muscle soreness increased (time, P  0.05). The results indicate that BCAA supplementation does not improve muscle recovery from RE in untrained young adults

Lumbar stabilisation exercises versus back endurance-resistance exercise training in athletes with chronic low back pain: Protocol of a randomised controlled trial

Background: Chronic low back pain (CLBP) is an important disorder in athletes that may negatively affect their performance in competitions. The literature usually recommends physiotherapy based on exercises for back pain management in athletes. Recent evidence suggests that interventions based on lumbar muscle stabilisation exercises (LMSE) and back endurance-resistance exercises (BERE) may improve back pain and function performance. However, it is still unclear which type of exercise is more effective for the treatment of CLBP in athletes. Objective: To compare the efficacy of LMSE versus BERE in athletes with CLBP. Design: The study is a 2-arm, prospectively registered, randomised controlled trial. Setting: The physical therapy clinical and biomechanics laboratory of the UNOPAR University. Participants: 32 male athletes with CLBP, age between 18 and 40 years old, recruited from the local community. Intervention: An 8-week intervention programme will be carried out with LMSE s versus BERE. Measurements Trunk neuromuscular patterns during balance tasks (unipodal and over a ball) using electromyography and force platform parameters, pain, disability, fear and avoidance will be assessed by a blinded assessor at baseline and at follow-up after 8 weeks of intervention period. Limitations: The absence of blinding intervention and the exclusion of female athletes, seated sports and swimmers will affect the internal and external validity of the study. Conclusions: The results of this study will elucidate which of these two interventions promote better results in trunk neuromuscular pattern, back pain and function in male athletes with CLBP

Impact of lifting of two types of barrels on postural control, trunk muscle recruitment, and kinematic measures in manual workers

The aim of this study was to evaluate the impact of 2 types of beer barrels on postural control, trunk activation, and kinematic measures in adult workers. Twelve (12) males randomly performed 4 tasks on a force platform for 20 s: (1) hold an empty recyclable barrel, (2) hold a full recyclable barrel (30 L), (3) hold an empty steel barrel, and (4) hold a full steel barrel (30 L). Trunk muscular activation, force platform and kinematic measures at the trunk, hip, and knee joints were computed. The full steel barrel produced greater postural oscillation than other conditions. Higher trunk activity was also reported during the full steel barrel task. Significant kinematic changes only in the trunk were observed between the empty steel barrel and the full recyclable barrel tasks. In conclusion, the full steel barrel produced a negative impact on postural control, increasing trunk activity and changing trunk flexion angle in adult workers

Photobiomodulation Therapy at 808 nm Does Not Improve Biceps Brachii Performance to Exhaustion and Delayed-Onset Muscle Soreness in Young Adult Women: A Randomized, Controlled, Crossover Trial

ObjectiveThis study aims to investigate the effects of laser photobiomodulation (PBM) at 808 nm on biceps brachii performance to exhaustion, rating of perceived exertion (RPE), and delayed onset muscle soreness (DOMS) in untrained young women.MethodsThirteen young women (20.1 ± 2.9 years) participated in a crossover study in which they received, in a counterbalanced manner, active and placebo laser PBM on two occasions (T1 and T2), separated by a 7-day washout period. During T1 and T2, participants received active (100 mW output power, irradiance of 35.7 W cm–2, and total energy of 28 J/arm) or placebo laser irradiation on the biceps brachii muscle at 20 min before the repetitions-to-failure test [six sets at 60% of one-repetition maximum (1RM) until failure] for elbow flexion exercise. The number of repetitions performed and RPE over the six sets, as well as DOMS from basal up to 72 h after the repetitions-to-failure test, were recorded.ResultsThere was a significant (time, p &lt; 0.05) reduction in the number of repetitions performed and an increase in RPE over six sets, with no statistical differences between placebo and active laser conditions (treatment × time, p &gt; 0.05). DOMS increased at 24 h postexercise and progressively returned to baseline after 72 h in both conditions (time, p &lt; 0.05; treatment × time, p &gt; 0.05).ConclusionOur results indicate that acute laser PBM at 808 nm does not improve biceps brachii performance to exhaustion, RPE, and DOMS in untrained women

Adaptações morfofuncionais e respostas moleculares do músculo esquelético de ratos submetidos ao treinamento resistido

Embora fortes evidências demonstrem que os fatores de regulação miogênica (MRFs) e o fator de crescimento semelhante à insulina (IGF-I) apresentem um importante papel na resposta hipertrófica após treinamento resistido (TR) agudo, permanece desconhecido se a resposta dos MRFs e IGF-I também ocorre durante a adaptação ao TR a longo-prazo. Portanto, o objetivo deste estudo foi testar a hipótese de que a resposta hipertrófica e modulação das fibras do músculo esquelético após TR a longo-prazo poderia estar associada ao aumento na expressão gênica dos MRFs e IGF-I. Ratos Wistar (80 dias de idade, 250-300 g) foram divididos em quatro grupos: Controle 8 semana (C8, n = 8), Treinado 8 semanas (T8, n = 8), Controle 12 semanas (C12, n = 8) e Treinado 12 semanas (T12, n = 8). Os grupos T8 e T12 foram submetidos a um programa de TR progressivo (3 dias/semana) durante 8 e 12 semanas, respectivamente. O protocolo de treinamento consistiu de quatro séries de 10-12 repetições, com um período de descanso de 40 segundos entre cada série, realizado a 65-75% de uma repetição máxima (1RM). Ao término do experimento, os animais foram sacrificados e o músculo plantar coletado para as análises morfológica e molecular. O TR durante 8 e 12 semanas não promoveu qualquer alteração (p > 0,05) significante no ganho de peso corporal e consumo alimentar dos grupos T8 e T12 em relação aos grupos C8 e C12, respectivamente. Após 8 e 12 semanas de TR, a força absoluta (T8: 69,7% and T12: 126,0%, p 0,05) entre os grupos T8 e T12, comparados aos grupos C8 e C12, respectivamente...Although strong evidence show that the myogenic regulatory factors (MRFs) and insulin-like growth factor (IGF-I) have important roles in the hypertrophy response after acute resistance training, it is still unclear if response of MRFs and IGF-I also occurs during the adaptation to prolonged periods of resistance training (RT). Therefore, the purpose of this study was to test the hypothesis that fiber-types transition and hypertrophy during long-term RT could be associated with increased MRFs and IGF-I mRNA expression in the skeletal muscle. Male Wistar rats (80 days old, 250-300 g) were divided into four groups: 8 weeks control (C8, n = 8), 8-weeks trained (T8, n = 8), 12-weeks control (C12, n = 8), 12-weeks trained (T12, n = 8). T8 and T12 groups were submitted to a progressive RT program (3 day/week) for 8 and 12 weeks, respectively. The training protocol consisted of four sets of 10–12 repetitions, with a 40 s rest period between each set, performed at 65–75% of one repetition maximum (1RM). At the end of the experiment, animals were sacrificed and the plantaris muscle collected for morphological and molecular analysis. The RT did not change (p > 0.05) in body weight gain and food intake in the T8 and T12 compared to the C8 and C12 groups, respectively. After 8 and 12 weeks of RT, the absolute (T8: 69.7% vs. T12: 126.0%; p 0.05), MyoD (T8: 22.9% vs. T12: 22.3%; p > 0.05) and muscle fiber crosssectional area (CSA) (T8: 29% vs. T12: 35%; p > 0.05) in the T8 and T12, compared to C8 and C12 groups, respectively. After 8 weeks of RT, IGF-I increased in 30.1% in the T8 compared to C8 group, but returned to baseline after 12 weeks... (Complete abstract click electronic access below)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP

A Meta-Analysis of Randomized Controlled Trials on the Effects of Photobiomodulation Therapy on Running Performance

International Journal of Exercise Science 17(4): 327-342, 2024. Objective: To conduct a meta-analysis to investigate the effects of Photobiomodulation (PBM) therapy on running performance. Introduction: PBM has recently been advocated as a valuable non-pharmacological ergogenic strategy, however, the efficacy of PBM on running performance remains unproven. Methods: A computerized literature search was conducted until June 2023. The databases searched were PubMed/Medline, Embase, Scopus, SPORTDiscus, and Web of Science. Inclusion/exclusion criteria were determined through the PICO process. The running variables analyzed were time-trial or time-to-exhaustion. Results were combined with the standardized mean differences (SMD) and the 95% confidence intervals. Results: Twelve studies fulfilled the inclusion criteria. No significant effects in favor of PBM were found (SMD = 0.13; p = 0.11). There was no effect considering the presence (SMD = 0.16; p = 0.38) and absence (SMD = 0.11; p = 0.25) of training, and there was no dose-response effect (p = 0.82). Conclusion: Our findings indicate that PBM alone or combined with a training program does not improve running performance in terms of time-trial and time-to-exhaustion testing. More studies involving PBM plus training and doses higher than 1000 J are needed to determine if PBM is effective in improving running performance

Citrulline malate does not improve muscle recovery after resistance exercise in untrained young adult men

he effects of citrulline malate (CM) on muscle recovery from resistance exercise remains unknown. We aimed to determine if citrulline malate supplementation improves muscle recovery after a single session of high-intensity resistance exercise (RE) in untrained young adult men. Nine young adult men (24.0 ± 3.3 years) participated in a double-blind crossover study in which they received 6 g of CM and placebo (PL) on two occasions, separated by a seven-day washout period. Each occasion consisted of a single session of high-intensity RE (0 h) and three subsequent fatigue tests sessions (at 24, 48, and 72 h) to assess the time course of muscle recovery. During the tests sessions, we assessed the following variables: number of maximum repetitions, electromyographic signal (i.e., root mean square (RMS) and median frequency (MF)), muscle soreness and perceived exertion, as well as blood levels of creatine kinase (CK), lactate, insulin, and testosterone:cortisol ratio. CK levels increased at 24 h post-exercise and remained elevate at 48 and 72 h, with no difference between CM and PL conditions. Muscle soreness increased at 24 h post-exercise, which progressively returned to baseline at 72 h in both conditions. Lactate levels increased immediately post-exercise and remained elevated at 24, 48, and 72 h in both conditions. No significant treatment × time interaction was found for all dependents variables (maximum repetitions, perceived exertion, CK, lactate, RMS, MF, and testosterone:cortisol ratio) during the recovery period. In conclusion, our data indicate that CM supplementation (single 6 g dose pre-workout) does not improve the muscle recovery process following a high-intensity RE session in untrained young adult men