Neuromuscular Adaptations Following 90 Days Bed Rest With or Without Resistance Exercise
2016 (English)In: AEROSPACE MEDICINE AND HUMAN PERFORMANCE, ISSN 2375-6314, Vol. 87, no 7, 610-617 p.Article in journal (Refereed) PublishedText
INTRODUCTION: This study examined the effects of long-term bed rest with or without a concurrent resistance exercise protocol on different muscle function indices of the knee extensors and their influence on previously shown atrophy, neural impairment, and slow-to-fast phenotype shift. METHODS: Nine men underwent 90 d of bed rest only (BR), while eight men in addition performed maximal supine squats every third day (BRE). Before and at day 1 and 5 following bed rest, surface quadriceps electromyographic (EMG) activity was measured during a sustained (60-s) submaximal isometric action and rate of force development (RFD) was assessed during a maximal isometric action, both in the supine squat position. Maximal torque was measured during isokinetic knee extensions at different angular velocities before and after (day 2 and 11) bed rest. RESULTS: EMG amplitude at a fixed submaximal load increased in BR, but not in BRE. The increase in amplitude during the sustained action was elevated in BR but not in BRE. RFD decreased in BR; this effect was attenuated day 1 and normalized day 5 in BRE. RFD expressed relative to maximal force was maintained in both groups. Angle-specific torque decreased equally for all velocities in BR. The decrease in isokinetic strength was attenuated day 2 in BRE. DISCUSSION: Phenotype changes were not reflected in muscle function measurements, probably because they were overridden by the effects of atrophy and neural adaptation. The protective effect of resistance exercise was more pronounced in tasks similar to the training action, inferring great impact of neural mechanisms.
Place, publisher, year, edition, pages
AEROSPACE MEDICAL ASSOC , 2016. Vol. 87, no 7, 610-617 p.
electromyography; fatigue; force-velocity; rate of force development; spaceflight
Environmental Health and Occupational Health
IdentifiersURN: urn:nbn:se:liu:diva-130265DOI: 10.3357/AMHP.4383.2016ISI: 000378466300004PubMedID: 27503040OAI: oai:DiVA.org:liu-130265DiVA: diva2:950651
Funding Agencies|Swedish National Space Board (SNSB); European Space Agency (ESA); National Space Development Agency of Japan (NASDA); Centre dEtudes Spatiales (CNES); Swedish National Centre for Research in Sports (CIF); Futurum - the Academy for Healthcare, Region Jonkoping County, Sweden2016-08-012016-07-282016-08-15Bibliographically approved