4 research outputs found

    Exploring differences in electromyography and force production between front and back squats before and after fatigue and how this differs between the sexes

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    Limited research has been conducted to explore sex differences in biomechanical and physiological demands of the front and back squat, especially in response to fatigue where technique may be altered. Therefore, this study investigated differences in electromyography and force production in performance of back and front squats before and after a fatigue protocol and how this differed between males and females. 35 participants (5 female, 30 male) performed a fatigue protocol for back and front squats with measures of maximal performance pre and post. Main findings were that mean and peak activation of the semitendinosus was greater in the back squat than the front squat suggesting that the back squat has greater hamstring activation possibly for hip stabilisation and knee flexion (p < 0.05). There were no differences in quadricep activation between back and front squats, disputing the notion that front squats have a greater quadricep focus, however, lending support to the hypothesis that quadricep activation equal to the back squat can be achieved with lighter absolute load in a front squat. There were no differences in electromyography as a result of fatigue however force production decreased for back squats following fatigue (p < 0.01). This decrease could result from decreased acceleration out of the bottom position and into the concentric phase. This study also presents preliminary findings of greater mean and peak rectus femoris activation in females compared to males in both front (p < 0.01) and back squats (p < 0.05). This was suggested to be in order to support the knee and in an attempt to prevent knee valgus and excess hip adduction. These findings have implications in programming for both high performance sport and for rehabilitation of lower limb injuries

    Weighted vests in CrossFit increase physiological stress during walking and running without changes in spatiotemporal gait parameters

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    This study quantified the physiological and biomechanical effects of the 20 lb (9.07 kg, males) and 14 lb (6.35 kg, females) weighted vest used in CrossFit, and whether they were predisposed to injury. Twenty subjects (10 males, 10 females) undertook walking (0%, 5% and 10% gradient) and running trials in two randomised study visits (weighted vest/no weighted vest). Physiological demand during walking was increased with the vest at 10% but not 5% or 0% with no change in gait variables. In the running trial, the weighted vest increased oxygen uptake (males; females) (+0.22L/min, p < 0.01; +0.07 L/min, p < 0.05), heart rate (+11bpm, p < 0.01; +11bpm, p < 0.05), carbohydrate oxidation (+0.6 g/min, p < 0.001; +0.2 g/min, p < 0.01), and energy expenditure (+3.8 kJ/min, p < 0.001; +1.5 kJ/min, p < 0.05) whilst blood lactate was increased only in males (+0.6 mmol/L, p < 0.05). There was no change in stride length or frequency. Weighted vest training increases physiological stress and carbohydrate oxidation without affecting measured gait parameters. Practitioner summary: We examined the effect of weighted vest training prescribed in CrossFit (20 lb/9.07 kg, males and 14 lb/6.35 kg, females) in a randomised controlled trial. We found that physiological stress is increased in both sexes, although three-fold greater in males, but with no change in biomechanical gait that predisposes to lower-limb injury

    EXPLORING DIFFERENCES IN ELECTROMYOGRAPHY AND GROUND REACTION FORCES BETWEEN FRONT AND BACK SQUATS BEFORE AND AFTER A FATIGUING PROTOCOL

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    Limited research has been conducted to explore differences in biomechanical and physiological demands of the front and back squat, especially in response to fatigue where technique may be altered. This study investigated differences in electromyography and ground reaction forces during a 3-repetition maximum back and front squat before and after a fatiguing protocol in 30 males. Mean and peak activation of the semitendinosus was greater in the back squat than the front squat (p < 0.05). There were no differences in quadricep activation between back and front squats. There were no differences in electromyography as a result of fatigue, however, force production decreased for back squats following fatigue (p < 0.01). This research disputed the notion that front squats have a greater quadricep focus, however lends support to the hypothesis that quadricep activation equal to the back squat can be achieved with lighter absolute load in a front squat. The finding that there were lower ground reaction forces for the back squat following the fatiguing protocol in addition to no differences in electromyography between front and back squats indicates greater effects of the fatiguing protocol on back squat performance
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