Effects Of Short-term Simulated Weightlessness On Human Exercise Ability And Protection Of Transcutaneous Electrical

Research background: Aerospace weightlessness will adversely affect the physiological functions of the human body,such as decreased bone density,muscle atrophy,impaired vestibular function,and weakened cardiovascular function.Preliminary studies have shown that transcutaneous electrical acupoint stimulation can effectively protect against the decline of cardiovascular function caused by simulated weightlessness.Research purposes: To explore the effect of simulated weightlessness on human movement ability and the protective effect of transcutaneous electrical acupoint stimulation,and to provide new ideas and experimental basis for the screening of astronauts weightlessness protection scheme.Methods: Twenty-five male volunteers(age 28 ± 3 yrs,height 169.4 ± 3.8 cm,weight 64.3 ± 6.9 kg)were randomly assigned to a 15-day-6° head down bed rest(HDBR)short-term simulated weightlessness.The control group(n = 9)did not do any protection.During HDBR,the electrical stimulation group(n = 8)performed transcutaneous electrical stimulation of "Neiguan" and "Zusanli" for 30 minutes every day.The post-HDBR immediate electrical stimulation group(n = 8)was given 30 s of "Neiguan" transcutaneous electrical stimulation during or before the exercise test after HDBR.Before and after HDBR,aerobic capacity,30 s Wingate anaerobic work,vertical jump,balance and reaction time were tested respectively to analyze the effect of HDBR on human exercise physiology and the effect of acupoint electrical stimulation intervention.Result:Effects of simulated weightlessness on human exercise capacity before and after:(1)The absolute value of the human body’s anaerobic threshold decreased after 15-day simulated weightlessness,and the anaerobic threshold heart rate increased under the same load(P<0.05).(2)In the 30 s Wingate anaerobic cycling test,the peak power decreased significantly(P<0.05),while the average power of 30 s and the last 5s of anaerobic work decreased significantly(P<0.01).(3)In the balance test of standing on one foot,the time of standing on one foot after bed rest was significantly lower than that before bed rest(P<0.05).(4)In the vertical jump test,the vertical jump height after bed rest was significantly lower than that before bed rest(P<0.05).(5)There was no significant difference in the reaction time test before and after bed rest.(6)The calf muscle dimension decreased significantly after simulated weightless bed rest(P<0.05).Immediate electrical stimulation during and after the simulated weightlessness in the head-down position protects the human movement ability:(1)In the Wingate test,the 30-s average power and peak anaerobic work were not significantly changed by transcutaneous electrical acupoint stimulation compared with those before bed rest,but the average power in the last 5 s decreased and there was a significant difference(P<0.05).(2)During the 15-day simulated weightlessness period,the “Neiguan and Zusanli points” were subjected to 30-min transcutaneous electrical acupoint stimulation every day.There were no statistically significant changes in work and bed rest.(3)Whether it was 30 min electrical stimulation during bed rest or 30 s immediate electrical stimulation after bed rest,the vertical jump before bed rest,and the time of standing on one foot were significantly decreased(P<0.05),while the response time was statistically significant(P<0.05).There is no difference.Analysis of the data before and after shows that the simulated weightlessness of15 days greatly reduces the metabolic capacity of the human body,the skeletal muscle also atrophies,and the neuromuscular recruitment ability also declines.At the same time,the vestibular and other motor proprioceptive abilities were weakened after 15 days of simulated weightlessness,and the motor control ability became worse.Immediate electrical stimulation of "Neiguan Point" after bed rest can reduce exercise fatigue.Electrical stimulation of Neiguan and Zusanli points during bed rest can avoid muscle atrophy to a certain extent(there is no significant difference between calf dimensions and before bed rest),and at the same time,it can also avoid the decline of muscle anti-lactic acid ability.However,it has no protective effect on muscle nerve recruitment ability and motor perception system.