There are various complexities with performing in-flight investigations. In order to maximize the potential for the most relevant data to be collected with minimal impact on crew time, we propose a two-phase program. Biomechanical analyses need to occur during actual exercise in microgravity to ensure optimal application of the results. However, since crew time is limited, ground-based evaluations should occur prior to in-flight data collection to ensure that the analyses performed on International Space Station (ISS) are completed as efficiently as possible. We propose to complete the analysis in three phases. Phase 1, which is detailed in this study, involved a detailed data collection on ground while subjects performed variations of squat and deadlift exercises on the ARED. Variations of each exercise included placement of the feet, speed of the lift, and range of motion and were examined. A computational model was used to compute joint loads and torques during each exercise. Six subjects (3 M/3 F) of small, medium, and large body types as described by NASA anthropometric standards were tested. The purpose of this investigation was to quantify the joint loading that occurred during typical resistance exercise on the ARED. The goal was to better understand the kinematic and kinetic similarities between exercise variations and to determine a subset of exercises that will be included in a future proposal that will include a biomechanical analysis of exercise on the ISS using the subset of exercises determined during phase 2.

Each exercise can be modified by increasing or decreasing stance width, movement velocity, and/or range of motion. Although the fundamental movement remains the same, these variations or combinations thereof may result in differences in long-term training effects. In order for practitioners to better understand and utilize these variations in creating optimal exercise programs, the joint motions and loads need to be quantified. This research, because it was performed in normal gravity, is beneficial to strength coaches, rehabilitation personnel, and scientists who use squat and deadlift exercise as a part of their exercise programs. In addition, this is the first study to quantify the hip joint motions in the frontal and transverse planes, which is important in differentiating between exercise variations and better understanding why slight variations load the musculoskeletal system differently.

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.

There are various complexities with performing in-flight investigations. In order to maximize the potential for the most relevant data to be collected with minimal impact on crew time, we propose a two-phase program. Biomechanical analyses need to occur during actual exercise in microgravity to ensure optimal application of the results. However, since crew time is limited, ground-based evaluations should occur prior to in-flight data collection to ensure that the analyses performed on ISS are completed as efficiently as possible. We propose to complete the analysis in three phases. Phase 1, which is detailed in this proposal, will involved a detailed data collection on ground while subjects perform squat and deadlift exercise on the ARED. Variations of each exercise, including resistance level and placement of the feet, hands, and range of motion will be examined to quantify the specific condition that optimizes joints loads. A computational model will be used to analyze joint loads and torques during each exercise. Six subjects (3 M/3 F) of small, medium, and large body types as described by NASA anthropometric standards will be used as subjects. The purpose of this investigation is 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 using the subset of exercises determined during phase 2.

[Ed. note: project added to Task Book in February 2010 when information received from JSC]