Young-Hui Chang, Ph.D. Biological Sciences, Georgia Institute of Technology  

Committee Members:  

Boris Prilutsky, Ph.D.  

Biological Sciences, Georgia Institute of Technology  

Gregory Sawicki, Ph.D.  

ME, Georgia Institute of Technology  

Less Work After Spaceflight: 

Human Performance Biomechanics Following Adaptation to Simulated Hypogravity

In the next decade, humans are planning to return to the Moon and prepare for future explorations to Mars. Despite our intuitive knowledge of gravity, we still do not fully understand how our bodies develop, function, and navigate in hypogravity environments. This study aimed to evaluate the effect of hypogravity on the biomechanical adaptation of targeted countermovement jumping performance. Fifteen participants jumped in and out of simulated hypogravity using a reduced-gravity simulator that provided a constant upward force near the body’s COM, effectively simulating ~0.5g. The jump was divided into two main phases: (i) Lift (from countermovement initiation to take off) and (ii) Land (from touchdown until stabilization of ground reaction forces). Following hypogravity adaptation, there was a meaningful effect in the normalized work of the Lift and a significant decrease in the Land when compared to the baseline pre-adaptation jumps. Further investigation into the additional parts of the Lift and Land revealed meaningful effects in specifically the last part of the Lift and significant changes in the first part of the Land. Observations of normalized COM work revealed distinct control strategies for the Lift and Land phases. The work generated during the first parts of the Lift appears to be dominantly controlled through a reactive control strategy, as it showed no significant after-effects upon return to 1.0g. In contrast, the work generated during the late part of the Lift and absorbed during the early part of the Land was observed to be predominantly under a predictive control strategy, evidenced by the significant decrease in work upon returning to 1.0g. Thus, upon return to a higher gravity level, movements requiring the legs to quickly generate and absorb energy will be most affected by sensorimotor control prediction errors and should be taken into consideration during the post-adaptation re-acclimation process after prolonged exposure to hypogravity.