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Effect of Malnutrition on Aerobic and Anaerobic Performance of Fast‐ and Slow‐Twitch Muscles of Rats
Author(s) -
Nishio Mary L.,
Jeejeebhoy Khursheed N.
Publication year - 1992
Publication title -
journal of parenteral and enteral nutrition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.935
H-Index - 98
eISSN - 1941-2444
pISSN - 0148-6071
DOI - 10.1177/0148607192016003219
Subject(s) - anaerobic exercise , endocrinology , medicine , stimulation , chemistry , tetanic stimulation , soleus muscle , muscle relaxation , skeletal muscle , physiology , inhibitory postsynaptic potential , excitatory postsynaptic potential
The effect of malnutrition on the functional properties of fast‐ and slow‐twitch muscles from rats was studied using aerobic and anaerobic preparations. A 2‐day fast and hypocaloric feeding to a weight loss of 25% were used as models of malnutrition. Soleus (slow‐twitch) and extensor digitorum longus (EDL) (fast‐twitch) muscles were studied using an in situ preparation with the blood supply intact and an in uitro preparation to which cyanide had been added to render the muscles anaerobic. We found that a 2‐day fast had little effect on the function of muscles stimulated in situ, whereas anaerobic stimulation produced a decrease in force per gram of muscle weight in the soleus, but not in the EDL, compared with control values. Hypocaloric feeding resulted in a slowed relaxation rate, an increased F s /F max ratio, and an upward shift of the force‐frequency curve relative to controls when studied in situ. Under anaerobic conditions, soleus muscles from hypocaloric rats continued to show a slow relaxation rate and demonstrated a loss of force per gram of muscle weight compared with controls, particularly at low stimulation frequencies. EDL muscles from hypocaloric rats had an increased relaxation rate and were able to maintain force with anaerobic stimulation. Soleus and EDL muscles from the fasted and hypocaloric groups had lower activities of phosphofructokinase. We conclude that slow‐twitch muscles from malnourished rats are at a disadvantage when required to function under anaerobic conditions. These findings suggest that muscle performance may be impaired in malnourished patients subjected to hypoxia. (Journal of Parenteral and Enteral Nutrition 16:219–225, 1992)