Search

Context: With a long duration return mission to Mars on the horizon, we must learn as much about the environment and its influence on the musculoskeletal system as possible to develop countermeasures and mitigate deleterious health effects and maladaptation.Aims: To determine the influence of simulated Mars gravity on the activity of four locomotor muscles while walking, in comparison to 1 G, using lower body positive pressure (LBPP).Material and Methods: A total of 14 male subjects (mean age: 20.6 ± 2.4 years) performed bouts of walking in both simulated Mars gravity (0.38 G) and Earth gravity (1 G) using an LBPP device. The dependent variables were the muscle activity evoked in the tibialis anterior, vastus lateralis, gluteus maximus and lateral portion of the gastrocnemius, measured using electromyography and expressed as percentages of maximum voluntary isometric contractions, and heart rate (HR). For statistical analysis, a paired t-test was performed. Statistical significance was defined as P < 0.05.Results: No significant differences in muscle activity were found across conditions for any of the investigated muscles. A significant mean difference in the HR was identified between Earth (105.15 ± 8.1 bpm) and Mars (98.15 ± 10.44 bpm) conditions (P = 0.027), wherein the HR was lower during the Mars trial.Conclusions: The Mars environment may not result in any deteriorative implications for the musculoskeletal system. However, if future research should report that stride frequency and thus activation frequency is decreased in the simulated Mars gravity, negative implications may be posed for muscle retention and reconditioning efforts on the Red Planet. [ABSTRACT FROM AUTHOR]

Introduction: Squats recruit a large proportion of the body's muscular system and provide a foundation for strength training programs for athletes. However, our understanding of electromyographical activity in variations of the high-bar back-squat, notably the split squat, is limited. Therefore, this study aims to investigate surface electromyography (EMG) in the free, Smith and split types of squat. Method: A randomised sample of 10 healthy strength-trained males (mean ± SD age, 20.3 ± 0.5 years; height, 1.7 ± 0.6 m; mass, 78.1 ± 9.5 kg; strength training, 2.5 ± 0.5 years) performed 3 repetitions of each type of squat at 75% of their one repetition maximum. A Noraxon EMG - Raxon system was used to collect peak EMG, root-mean-square EMG (RMS EMG), and integrated EMG (iEMG) data for the eccentric and concentric phases of the squat. EMG data from the free and split squats were normalised to the Smith squat. Two-way ANOVAs were used for the analysis of type-of-squat and phase-of-squat (p ≤ 0.01). Results: Statistically significant effects for type-of-squat were found for peak EMG and iEMG of the bicep femoris (BF), lateral gastrocnemius (LG) and tibialis anterior (0.001 ≤ p ≤ 0.003), and for RMS EMG of the BF (p = 0.002) and LG (p = 0.001). Significant differences in phase-of-squat were found for peak EMG and RMS EMG of BF(p = 0.001). Discussion: The split squat elicited higher BF and LG muscle activity compared to the free and Smith squats. The findings suggest that the split squat effectively stimulates the BF and LG muscles and should consequently form an integral part of strength programs for athletes. [ABSTRACT FROM AUTHOR]

Introduction: Inconclusive previous research on squat depth and the evoked electromyography (EMG) activity muddles our understanding of muscle recruitment in the back squat. This study determined EMG activity as a function of squat depth in four superficial muscles of the lower limb using relative loading. Method: Eight resistance trained males (mean ± SD age: 21 ± 1 years) performed back squats to partial, parallel and full depth using depth-relative 5-repetition-maximum loads. Muscle activity in the vastus medialis oblique (VMO), vastus lateralis (VL), gluteus maximus (GM), and biceps femoris (BF) during the concentric and eccentric phases of the squat was determined using surface electromyography. Peak (Peak EMG), mean (Mean EMG), and integrated (iEMG) EMG normalised to their respective maximum voluntary isometric contraction (MVIC) for each muscle were evaluated. Results: Three-way Anovas and Sidak post-hoc analysis revealed significant effects for squat type (p = 0.021 - 0.001), squat phase (p = 0.001), and muscle (p = 0.001). The significant differences were between the partial and the parallel squat (p = 0.016 - 0.001); for iEMG significant effects were also found between the partial and full squat (p = 0.001). The VMO elicited the highest EMG activity (e.g., Peak EMG 93.4 ± 36.9% MVIC; parallel squat, concentric) and the BF the lowest (e.g., Peak EMG 49.9 ± 14.7%). Greater GM activity occurred in parallel squats compared to full squats (mean difference in Peak EMG = 9.1% MVIC). Conclusion: The findings suggest that squatting to the parallel position or lower induces optimal contractile stimulation of the quadriceps. Squatting to parallel depth maximises EMG activation of the GM, possibly due to a more advantageous external moment arm or a reduction in neural drive. [ABSTRACT FROM AUTHOR]