Contraction duration affects metabolic energy cost and fatigue in
skeletal muscle.
Hogan, Michael C., Erica Ingham, and S. Sadi Kurdak.
Division of Physiology, Department of Medicine, University of
California, San Diego, La Jolla, CA 92093-0623
APStracts 4:0257E, 1997.
It has been suggested that during a skeletal muscle contraction the
metabolic energy cost at the onset may be greater than the energy
cost related to holding steady state force. The purpose of the
present study was to investigate the effect of contraction duration
on the metabolic energy cost and fatigue process in fully perfused
contracting muscle in situ. Canine gastrocnemius muscle (n=6) was
isolated and 2 contractile periods (3 min of isometric, tetanic
contractions with 45 min rest between) were conducted by each muscle
in a balanced order design. The 2 contractile periods had stimulation
patterns that resulted in a 1:3 contraction-to-rest ratio, with the
difference in the 2 contractile periods being in the duration of each
contraction: short duration=0.25 sec stimulation/0.75 sec rest vs.
long duration=1 sec stimulation/3 sec rest. These stimulation
patterns resulted in the same total time of stimulation, number of
stimulation pulses, and total time in contraction for each 3-min
period. Muscle O2 uptake, the fall in developed force (fatigue), the
O2 cost of developed force, and the estimated total energy cost (ATP
utilization) of developed force were significantly greater (P<0.05)
with contractions of short duration. Lactate efflux from the working
muscle and muscle [lactate] were significantly greater with
contractions of short duration, such that the calculated energy
derived from glycolysis was three times greater in this condition.
These results demonstrate that contraction duration can significantly
affect both the aerobic and anaerobic metabolic energy cost and
fatigue in contracting muscle. In addition, it is likely that the
greater rate of fatigue with more rapid contractions was a result of
elevated glycolytic production of lactic acid.
Received 8 September 1997; accepted in final form 11 November
1997.
APS Manuscript Number E426-7.
Article publication pending Am. J. Physiol. (Endocrinol. Metab.).
ISSN 1080-4757 Copyright 1997 The American Physiological Society.
Published in APStracts on 12 December 1997