A comprehensive understanding of the kinematics and kinetics of resistance exercise performance in microgravity is necessary to optimize exercise prescription by including the exercise variations that have the greatest potential health benefits. However, to date, there have been no biomechanical investigations of resistance exercise performance on the International Space Station (ISS), and none of Advanced Resistive Exercise Device (ARED) exercise in microgravity. Collecting biomechanical data during actual exercise sessions on the ISS is expensive and complex, but is required for program optimization. The investigators proposed this initial ground-based evaluation that would increase the probability of success for a future experiment to be performed on the ISS. The purpose of this investigation was to quantify the joint loading that occurs during typical resistance exercise on the ARED. The goal is to determine a subset of exercises that show the greatest potential for maximizing health benefits to inform a future proposal that will include a biomechanical analysis of exercise on the ISS.
Specific Aim 1: To quantify the joint loading that occurs during resistance exercise using the ARED.
The goal of this aim was to determine joint kinematics, torque, power, and work during typical resistance exercise on the ARED. The objective was to identify the exercises that will optimize exercise effectiveness for bone and muscle health, and to determine if kinetic responses depend upon exercise type.
Specific Aim 2.: To create a list of exercises that will be used during a future in-flight analysis of resistance exercise on the ARED.
The goal of this aim was to determine which form variations of the squat and deadlift exercise would be most beneficial to study during an in-flight study of resistance exercise. The objective was to determine the exercises that either maximize joint loading or are sufficiently different from other form variations to be considered unique.
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Six subjects participated in this study. This study was approved by the NASA Johnson Space Center Committee for Protection of Human Subjects. The subjects all received Air Force Class III physicals and provided informed consent. All subjects were active and had participated in squat and deadlift exercise sessions prior to inclusion in the study. Subjects participated in three exercise sessions: a familiarization session, a 10-repetition maximum (10 RM) evaluation session, and the biomechanical data collection session. During familiarization and 10 RM sessions, subjects wore comfortable exercise clothing of their choice, but were not instrumented in any way. During the biomechanical data collection session, the subjects were provided with a Spandex tank top, Spandex shorts, and running shoes (Nike, model) and were outfitted with instrumentation (motion capture retroreflective markers).
This study utilized the ARED trainer that is located in the Johnson Space Center Astronaut Rehabilitation Facility. This trainer device is very similar to the on-orbit ARED on the ISS that provides astronauts with their primary mode of resistive exercise during their space flight. The device is capable of providing up to 600 lbs of resistance, incorporates a vacuum cylinder and flywheel resistance system to provide constant and inertial resistance, and allows for the performance of many typical resistive exercises performed in the gymnasium. All subject preparation, familiarization, and data collection sessions were completed at the Astronaut Rehabilitation Center.
The six subjects successfully completed all of the trials for each lift in the study. During data analysis it became apparent that while gross motions were similar between subjects for each lift, there were some between subject differences that may be due to technique differences between subjects. Ground reaction force (GRF) data indicated that peak loads were dependent upon exercise type and that the peak GRF did not always occur at the same time during a repetition depending upon the exercise. Bilateral joint kinematics were generally symmetrical; however, hip adduction and rotation displayed increased bilateral asymmetry. Joint kinetics differed between exercise types although there were no specific trends across all variables. In general, during the downward motion, work was performed on the hip and knee extensors for all exercises, and work was performed by the hip and knee extensors during the upward motion. Positive and negative work for hip adduction/abduction, hip internal/external rotation, and ankle flexion varied across exercises. Bilateral joint kinetics were asymmetrical, which may reflect a property of ARED that needs further study.
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