Resistance training is a fundamental component of athletic preparation due to the potential to develop high levels of strength and power. The nature and magnitude of adaptation is enhanced by the appropriate overload and specificity of the program design. Of particular importance is the mechanical specificity of the selected exercise. Bilateral exercises such as the weightlifting, squats and deadlifts are common throughout the literature for two primary reasons. First, these exercises share similar mechanical specificity to athletic movements such as jumping and sprinting. Second, they permit substantial external resistance to be used, resulting in very high levels of neuromuscular overload. This overload facilitates the development of favourable neuromuscular adaptations such as the recruitment of high-threshold motor units. The combination of overload and high mechanical specificity has been demonstrated to transfer to improved jumping and sprinting ability. However, in the sporting arena, jumping and sprinting are rarely performed as bilateral actions, but rather unilateral actions predominate. For this reason, the mechanical specificity of unilateral training has long been recognised as more specific to athletic development. However, unilateral exercises have typically remained confined to rehabilitation or junior development programs and as such, there is a distinct lack of research on the mechanistic factors contributing to performance enhancement from overloaded unilateral resistance training.
Therefore, the primary purpose of this research is to compare the mechanical specificity and the transfer of training to performance between bilateral and unilateral resistance training exercises.
The first study will involve a cross-sectional investigation of the kinetics and kinematics of the squat (bilateral exercise) and the step-up (unilateral exercise) by a cohort of 20 very experienced, resistance trained athletes. A thorough analysis of muscle activation (electromyography), force application (ground reaction forces via force plates) and three dimensional movement (motion analysis) patterns will be conducted on the performance of the squat and step-up at matched intensities. The second cross-sectional study will use similar biomechanical analyses to determine the specificity of bilateral and unilateral resistance training exercises to common athletic movements (jumping, sprinting and changing direction). Muscle activation, force development and movement characteristics will be analysed in a group of 20 highly trained athletes. The third study will compare the efficacy of bilateral and unilateral resistance training on maximal strength development and examine if training with bilateral or unilateral movements has a superior transfer of training effect. This 16-week longitudinal study will involve 30 athletes with substantial resistance training history, randomly assigned to either a bilateral or unilateral training group, and 15 participants allocated into a control group. Outcome measures include maximal strength and jump, sprint and change of direction performance.
This research will provide much needed insight into the role of unilateral resistance training in improving athletic performance.
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