Inessa B. Kozlovskaya

Adaptation of neuromuscular activation patterns during treadmill walking after long-duration space flight

The precise neuromuscular control needed for optimal locomotion, particularly around heel strike and toe off, is known to he compromised after short duration (8- to 15-day) space flight. We hypothesized here that longer exposure to weightlessness would result in maladaptive neuromuscular activation during postflight treadmill walking. We also hypothesized that space flight would affect the ability of the sensory-motor control system to generate adaptive neuromuscular activation patterns in response to changes in visual target distance during postflight treadmill walking. Seven crewmembers, who completed 3- to 6-month missions, walked on a motorized treadmill while visually fixating on a target placed 30 cm (NEAR) or 2 m (FAR) from the subjects eyes. Electronic foot switch data and surface electromyography were collected from selected muscles of the right lower limb. Results indicate that the phasic features of neuromuscular activation were moderately affected and the relative amplitude of activity in the tibialis anterior and rectus femoris around toe off changed after space flight. Changes also were evident after space flight in how these muscles adapted to the shift in visual target distance.

The use of in-flight foot pressure as a countermeasure to neuromuscular degradation.

The purpose of this study was to determine whether applying foot pressure to unrestrained subjects during space flight could enhance the neuromuscular activation associated with rapid arm movements. Four men performed unilateral arm raises while wearing--or not wearing--specially designed boots during a 81- or 115-day space flight. Arm acceleration and surface EMG were obtained from selected lower limb and trunk muscles. Pearson r coefficients were used to evaluate similarity in phasic patterns between the two in-flight conditions. In-flight data also were magnitude normalized to the mean voltage value of the muscle activation waveforms obtained during the no-foot-pressure condition to facilitate comparison of activation amplitude between the two in-flight conditions. Foot pressure enhanced neuromuscular activation and somewhat modified the phasic features of the neuromuscular activation during the arm raises.

Using foot pressure to maintain neuromuscular function during long-duration spaceflight

It is proposed that the application of foot pressure can result in enhanced lower limb neuromuscular activation over the course of a long-duration spaceflight. If confirmed, a device that generates increased foot sensory input can be developed for use on the International Space Station as a countermeasure to neuromuscular degradation. In the present experiment, surface EMG was collected from six subjects during freefloating arm raises performed with or without foot pressure. Two subjects performed the experiment multiple times during their flight. The results indicate that foot pressure results in significantly increased magnitudes of lower limb neuromuscular activation when compared to movements performed without foot pressure. Furthermore, repeated application of pressure throughout a flight continues to produce enhanced neuromuscular activation without significant modification of the phasic activation features. These findings suggest that the development of a countermeasure utilizing foot pressure meri...