Sensorimotor control is vital for successful execution of mission-critical tasks in microgravity, and on planetary and lunar surfaces. However, exposure to microgravity results in disruptions in sensorimotor, cardiovascular, and neuromuscular systems that can present as balance and gait disturbances, cardiovascular deconditioning, and loss of muscle mass, muscle coordination, and strength. Astronauts regularly participate in strength and conditioning programs to mitigate cardiovascular and strength decrements associated with space flight; however, recent research suggests sensorimotor-based countermeasures may be necessary to maintain functional performance following spaceflight. Neuromuscular control enables dynamic interactions with the environment via fast subcortical responses.
Through this study, the researchers seek to examine the patented Leg Dexterity System (the leg version of the Valero Dexterity Test™ from Neuromuscular Dynamics, LLC) to enhance neuromuscular control and complement and amplify the efficacy of exercise as a countermeasure to neuromuscular performance decrements during and after space flight.
This experiment will address two hypotheses:
(1) Supplementing an eight-week strength and conditioning regimen with the Leg Dexterity System increases dynamic stabilization and neuromuscular control abilities.
(2) Despite the sex differences in dexterity levels reported in past research, there will be no sex difference in the amount of improvement in dynamic stabilization and neuromuscular control abilities.
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This study will recruit 30 subjects (15 males, 15 females) between 40-60 years of age to complete eight consecutive weeks of small group circuit training classes (three one-hour duration classes per week for 24 total sessions). Participants will be randomly assigned to one of two cohorts: with Leg Dexterity System training and without Leg Dexterity System training. Subjects enrolled in the study will participate in small group circuit training classes using high-intensity aerobics to target strength building and muscular and cardiovascular endurance.
Participants undergoing Leg Dexterity System training will apply compression force to a platform affixed to a spring on a single-axis force sensor while partially seated on a bicycle saddle and holding on to handlebars. While in this position, participants will be instructed to support their weight equally using the bicycle saddle and nontest limb in order to unload the test leg. A tablet will provide real-time visual feedback of the compression force to encourage a steady maximal sustained compression for 10 seconds. Support for the hypotheses of this study will be quantified by improvements in dynamic and static stability via pre- and post-training outcome measures, including a single limb balance test, single limb hop and balance test, and phase portrait analysis.
The results of this ground experiment will inform the utility of the simple and compact Leg Dexterity System to mitigate neuromuscular control decrements and justify space flight analog studies to further refine the development of this sensorimotor-based countermeasure.