This investigation was completed in 2010, and a final report was submitted to NASA.
The purpose of this investigation was to quantify the joint kinematics and kinetics that occur during squat and deadlift exercise on the ARED to inform a future proposal that will include a biomechanical analysis of exercise on the ISS. Six subjects (3m/3f) were tested while performing single legged squats, normal squats, increased range of motion squats, wide stance squats, fast squats, reduced range of motion squats, normal deadlift, and sumo deadlift. Ground reaction force (GRF) and motion capture data were collected as each subject performed a single repetition using a load that approximated their 10 repetition maximum. Testing loads were determined during an earlier training session. Three dimensional joint kinematics and kinetics were computed using a standard inverse dynamics approach. 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.
Based on our results, we suggest that the exercises included in a future flight study include, along with the justification:
1) Normal Squat: A baseline measure
2) Single Legged Squat: Increased net hip torque and only exercise inducing hip adduction
3) Wide Normal Squat: Hip adduction and rotation kinematics suggest femoral head loading differences
4) Normal Deadlift: Baseline measure, but with different kinematics than the squat
Furthermore, we suggest the following:
1) Increasing the subject size of the current study to allow for standard statistical analyses
2) Retest of current subjects bilateral symmetry using a free weight condition
3) Further study of the FS condition relative to free weights to better understand joint kinetic differences
Although IR (increased range of motion) squats had larger kinetic values than others, variation was also increased because of between subject differences. We did not recommend this lift because of the larger subject variation, but this lift should also be considered in a future study.