1. The effects of altered tissue temperature on muscle metabolism during successive isometric contractions, sustained to fatigue, have been studied in the quadriceps muscle of @entity1 by combining biochemical analyses of metabolites in needle biopsy samples with measurements of endurance time with a force of 2/3 maximum voluntary contraction. Fatigue and recovery were observed repeatedly in a series of seven contractions at intervals of 20 sec, following immersion of the test leg in water at 12, 26 or 44 degrees C for 45 min. Muscle temperatures corresponding to these water temperatures were 22.5, 32.6 and 38.6 degrees C respectively.2. Increased levels of several glycolytic intermediates at rest in the heated muscle suggested an increased rate of glycolysis. @entity855 and @entity1734 were lower at the end of the first contraction and the calculated rate of @entity855 utilization (including the contribution from anaerobic glycolysis) was highest in the heated nuscle.3. Significantly shorter endurance times were found for the heated muscle. These could not be attributed to depletion of local energy resources in muscle. Fatigue may be due to a reduction in the rate of regeneration of @entity855 from anaerobic glycolysis below that needed to maintain the contraction force. Lower values for the ratio of @entity4567 : @entity16117 at the end of contractions, particularly at the highest temperature, are compatible with the hypothesis that there is partial inhibition of the rate controlling enzyme phosphofructokinase, possibly due to the accumulation of @entity3884 ions in muscle.

Effect of temperature on muscle energy metabolism and endurance during successive isometric contractions, sustained to fatigue, of the quadriceps muscle in XXXX .

@entity1 :: ('9606', 'Species') :: ['man'] @entity1734 :: ('CHEBI:17287', 'Chemical') :: ['phosphoryl creatine'] @entity3884 :: ('MESH:D006859', 'Chemical') :: ['hydrogen'] @entity16117 :: ('MESH:C027618', 'Chemical') :: ['fructose 6-phosphate'] @entity4567 :: ('MESH:C029063', 'Chemical') :: ['fructose 1,6-diphosphate'] @entity855 :: ('MESH:D000255', 'Chemical') :: ['ATP']
@entity1 :: (9606,Species) :: ['man']
