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Electromyographic study of the contractile and electrical properties of the human triceps surae muscle in a simulated microgravity environment
Author(s) -
Koryak Yuri
Publication year - 1998
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1111/j.1469-7793.1998.287bz.x
Subject(s) - isometric exercise , triceps surae muscle , contraction (grammar) , immersion (mathematics) , chemistry , muscle contraction , force transducer , electromyography , anatomy , muscle fatigue , medicine , physical medicine and rehabilitation , mathematics , physics , acoustics , pure mathematics
1 The effects of 7 days of simulated space flight, achieved with the technique of ‘dry’ water immersion, on human triceps surae muscle function have been investigated. 2 The maximal voluntary contraction (MVC) was reduced by 33.8 % ( P < 0.01 ) while the electrically evoked maximal tetanic contraction force ( P o ) decreased by 8.2 % ( P > 0.05 ). This suggests that most of the force loss is due to a reduction in motor drive. 3 The decrease in P o was associated with a small increase in maximal rates of tension development (7.2 %). The twitch tension ( P t ) was not significantly changed and the P t : P o ratio was decreased by 8.7 % after immersion. 4 A standard fatigue test, consisting of sixty 1 s intermittent isometric contractions (50 impulses s −1 ) separated by 1 s rest decreased tetanic force to approximately 60 % of initial values, but force reduction was not significantly different before and after immersion: the fatigue index was 36.2 ± 5.4 % before and 38.6 ± 2.8 % after immersion ( P > 0.05 ). Whilst there were similar changes in mechanical output between control and disused muscles, there were differences in the pattern of electrical activity.