Intermittent Short-Arm Centrifugation Is A Partially Effective Countermeasure Against Upright Balance Deterioration Following 60-Day Head-Down Tilt Bed Rest

This study investigated whether artificial gravity (AG), induced by short-radius centrifugation, mitigated deterioration in standing balance and anticipatory postural adjustments (APAs) of trunk muscles following 60-day head-down tilt bed rest. Twenty-four participants were allocated to one of three groups: control group (n = 8); 30-min continuous AG daily (n = 8); and intermittent 6 x 5 min AG daily (n = 8). Before and immediately after bed rest, standing balance was assessed in four conditions: eyes open and closed on both stable and foam surfaces. Measures including sway path, root mean square, and peak sway velocity, sway area, sway frequency power, and sway density curve were extracted from the center of pressure displacement. APAs were assessed during rapid arm movements using intramuscular or surface electromyography electrodes of the rectus abdominis; obliquus externus and internus abdominis; transversus abdominis; erector spinae at Ll, L2, L3, and L4 vertebral levels; and deep lumbar multifidus muscles. The relative latency between the EMG onset of the deltoid and each of the trunk muscles was calculated. All three groups had poorer balance performance in most of the parameters (all P < 0.05) and delayed APAs of the trunk muscles following bed rest (all P < 0.05). Sway path and sway velocity were deteriorated, and sway frequency power was less in those who received intermittent AG than in the control group (all P < 0.05), particularly in conditions with reduced proprioceptive feedback. These data highlight the potential of intermittent AG to mitigate deterioration of some aspects of postural control induced by gravitational unloading, but no protective effects on trunk muscle responses were observed.NEW & NOTEWORTHY This study presents novel insights into the effect of artificial gravity (AG) on the deterioration of standing balance and anticipatory postural adjustments (APAs) of trunk muscles induced by 60-day strict head-down bed rest. The results indicated severe balance dysfunction and delayed APAs during rapid arm movement. AG partially mitigated the deterioration in standing balance and may thus be considered as a potential countermeasure for future planetary surface explorations. Optimization of AG protocols might enhance effects.