Responses of neuromuscular properties to unloading and potential countermeasures during space exploration missions. (May 2022)

• Record Type: Journal Article
• Authors: Ohira, Takashi; Kawano, Fuminori; Goto, Katsumasa; Kaji, Hiroshi; Ohira, Yoshinobu
• Is Part Of: Neuroscience and biobehavioral reviews. Volume 136(2022)
• Publication Date: 2022-05
• Subjects: µ-G microgravity -- MHC myosin heavy chain -- HS hindlimb suspension -- EMG electromyogram -- ISS International Space Station -- CSA cross-sectional area -- MVC maximal voluntary contraction -- V0 maximal unloaded shortening velocity -- P0 maximal tension -- Fmax relative P0 per fiber CSA -- pCa50 free Ca2+ concentration required for half-maximal activation -- HT high treadmill group -- LT low treadmill group -- SDH succinate dehydrogenase -- L5 5th lumber spine -- CNS central nervous system; Weightlessness -- Weightlessness simulation -- Spaceflight -- Unloading-induced muscle atrophy -- Human bedrest -- Hindlimb suspension -- Slow-twitch muscles -- Electromyogram -- Neurogram; Psychophysiology -- Periodicals; Human behavior -- Periodicals; Animal behavior -- Periodicals; Neurology -- Periodicals; Behavior -- Periodicals; Ethology -- Periodicals; Neurology -- Periodicals; Psychophysiologie -- Périodiques; Comportement humain -- Périodiques; Animaux -- Mœurs et comportement -- Périodiques; Neurologie -- Périodiques; Animal behavior; Human behavior; Neurology; Psychophysiology; Periodicals; Electronic journals; 573.8
• DOI: 10.1016/j.neubiorev.2022.104617
• Languages: English
• ISSNs: 0149-7634

Abstract

Abstract: We reviewed the responses of the neuromuscular properties of mainly the soleus and possible mechanisms. Sensory nervous activity in response to passive shortening and/or active contraction, associated with plantar-flexion or dorsi-flexion of the ankle joints, may play an essential role in the regulation of muscle properties. Passive shortening of the muscle fibers and sarcomeres inhibits the development of tension, electromyogram (EMG), and afferent neurogram. Remodeling of the sarcomeres, which decreases the total sarcomere number in a single muscle fiber causing recovery of the length in each sarcomere, is induced in the soleus following chronic unloading. Although EMG activity and tension development in each sarcomere are increased, the total tension produced by the whole muscle is still less owing to the lower sarcomere number. Therefore, muscle atrophy continues to progress. Moreover, walking or slow running by rear-foot strike landing with the application of greater ground reaction force, which stimulates soleus mobilization, could be an effective countermeasure. Periodic, but not chronic, passive stretching of the soleus may also be effective. Graphical Abstract: ga1 Highlights: Responses of neuromuscular properties to gravitational unloading were reviewed. Neural activity and mechanical stress play a role in muscle response. Muscle afferent activity is important in the regulation of muscle properties. Soleus activity allows invasion of pathogenic T-cells into the CNS.