When Antagonist Muscles at the Ankle Interfere with Maximal Voluntary Contraction under Isometric and Anisometric Conditions

Purpose: While resultant maximal voluntary contraction (MVC) is commonly used to assess muscular performance, the simultaneous activation of antagonist muscles could dramatically underestimate the strength of the agonist muscles. While quantification of antagonist torque has been performed in plantar- (PF) and dorsi-flexion (DF) joint in isometric conditions, it has yet to be determined in anisometric (concentric and eccentric) conditions. Methods: The experiment was performed in 9 participants through 2 sessions (reliability). The MVCs in DF and PF were measured in isometric, concentric and eccentric conditions (10°.s-1). Electromyographic (EMG) activities from the soleus, gastrocnemius medialis and lateralis, and tibialis anterior muscles were simultaneously recorded. The EMG biofeedback method was used to quantify antagonist torque, where participants were asked to maintain a level of EMG activity, corresponding to antagonist EMG activity and related to the muscle contraction type, according to a visual EMG bio-feedback displayed on a screen. Results: Resultant torque significantly underestimated agonist torque in DF MVC (30-65%) and to a lesser extent in PF MVC (3%). Triceps surae antagonist torque was significantly modified with muscle contraction type, showing higher antagonist torque in isometric (29 Nm) than eccentric (23 Nm, p < 0.001) and concentric (14 Nm, p < 0.001) conditions and resulting in modification of the DF MVC torque-velocity shape. The difference between DF eccentric and concentric MVC was attenuated when considered agonist torque (12%) rather than resultant torque (45%). Conclusion: Estimation of the antagonist torque in isometric or anisometric condition brings new insights to assessment of muscular performance and could result in costly misinterpretation in strength training and/or rehabilitation programs.

Effects of Low-Level Laser Therapy on Muscular Performance and Soreness Recovery in Athletes: A Meta-analysis of Randomized Controlled Trials

Context: Athletes must maintain their peak state of strength. Previous studies have investigated the effect of low-level laser therapy (LLLT) on muscular performance. A previous systematic review and meta-analysis has investigated this issue in healthy participants but not in physically active athletes. Objective: To investigate whether LLLT can improve muscular performance and soreness recovery in athletes. Data Sources: PubMed, EMBASE, and Cochrane Library. Study Selection: Published randomized controlled trials and crossover studies till December 2020. Study Design: Systematic review and meta-analysis. Level of Evidence: Level 3. Data Extraction: Assessment of study quality was rated using the risk of bias assessment method for randomized trials (Cochrane Handbook for Systematic Reviews of Interventions). Results: A total of 24 studies were included. LLLT application before exercise significantly improved lower-limb muscle strength in 24-hour, 48-hour, 96-hour, and 8-week follow-up groups. Furthermore, decreased soreness index, serum creatine kinase concentrations, interleukin-6, and thiobarbituric acid reactive substance concentrations and a trend toward the improvement of contract repetition number and VO2 kinetic outcomes were observed. Conclusion: Although a definite therapeutic effect of LLLT is yet to be established, the current evidence supports that LLLT use improves muscular performance in physically active athletes. Additional trials with large sample sizes and robust design should be conducted before strong recommendations are made.

Predicting Adaptations to Resistance Training Plus Overfeeding Using Bayesian Regression: A Preliminary Investigation

Relatively few investigations have reported purposeful overfeeding in resistance-trained adults. This preliminary study examined potential predictors of resistance training (RT) adaptations during a period of purposeful overfeeding and RT. Resistance-trained males (n = 28; n = 21 completers) were assigned to 6 weeks of supervised RT and daily consumption of a high-calorie protein/carbohydrate supplement with a target body mass (BM) gain of ≥0.45 kg·wk−1. At baseline and post-intervention, body composition was evaluated via 4-component (4C) model and ultrasonography. Additional assessments of resting metabolism and muscular performance were performed. Accelerometry and automated dietary interviews estimated physical activity levels and nutrient intake before and during the intervention. Bayesian regression methods were employed to examine potential predictors of changes in body composition, muscular performance, and metabolism. A simplified regression model with only rate of BM gain as a predictor was also developed. Increases in 4C whole-body fat-free mass (FFM; (mean ± SD) 4.8 ± 2.6%), muscle thickness (4.5 ± 5.9% for elbow flexors; 7.4 ± 8.4% for knee extensors), and muscular performance were observed in nearly all individuals. However, changes in outcome variables could generally not be predicted with precision. Bayes R2 values for the models ranged from 0.18 to 0.40, and other metrics also indicated relatively poor predictive performance. On average, a BM gain of ~0.55%/week corresponded with a body composition score ((∆FFM/∆BM)*100) of 100, indicative of all BM gained as FFM. However, meaningful variability around this estimate was observed. This study offers insight regarding the complex interactions between the RT stimulus, overfeeding, and putative predictors of RT adaptations.

The effect of resistance training set configuration on strength and muscular performance adaptations in male powerlifters

The purpose of this study was to determine the effects of different set configurations on strength and muscular performance adaptations after an 8-week resistance training program. Twenty-four male powerlifters participated in this study and were randomly assigned to one of two resistance training groups: (1) cluster sets (CS: n = 8), (2), traditional sets (TS: n = 8), and a control group (CG: n = 8). All powerlifters were evaluated for thigh and arm circumference, upper and lower body impulsive activities, and 1 repetition maximum (1RM) in the back squat, bench press, and deadlift prior to and after the 8-week training intervention. After training, both the CS and TS groups increased arm and thigh circumferences and decreased body fat. The CS group resulted in greater increases in upper and lower body impulsive activities than the TS group, respectively. In addition, the CS and TS groups indicated similar changes in 1RM bench press, back squat, and deadlift following the 8 weeks training intervention. These results suggest that cluster sets induce adaptive changes that favor impulsive activities in powerlifters.