Changes in force and intracellular metabolites during fatigue of human skeletal muscle.
- 1 November 1989
- journal article
- Published by Wiley in The Journal of Physiology
- Vol. 418 (1), 311-325
- https://doi.org/10.1113/jphysiol.1989.sp017842
Abstract
1. The relationship between intracellular metabolites and the generation of force during fatigue has been examined in the first dorsal interosseous muscle of the hand. With the arm made ischaemic, the muscle was fatigued by three bouts of maximal voluntary contraction, leaving approximately three minutes ischaemic rest between contractions. During one series of experiments intracellular phosphorus metabolites were measured by nuclear magnetic resonance during the intervals between the fatiguing contractions: in the second series contractile properties were tested with brief electrical stimulation during the rest intervals. 2. The relationships between loss of force and change in metabolite concentrations obtained with four normal subjects were compared with those from one subject with myophosphorylase deficiency (MPD) who could not utilize muscle glycogen and therefore produced no hydrogen ion from glycolysis during exercise. 3. For both the MPD and normal subjects the relationship between relative force loss and inorganic phosphate (Pi) concentration was curvilinear, force changing little in the early stages of the contraction when the intracellular Pi was accumulating rapidly but falling faster when the Pi was above 25 mM and increasing relatively slowly. 4. In the normal subjects intracellular pH fell from a mean of 7.03 +/- 0.01 (mean +/- S.E. of mean, n = 19) in the fresh muscle to 6.51 +/- 0.02 at the end of the fatiguing exercise; force, as a percentage of the initial value, fell in proportion to the increase in H+ concentration. In the MPD subject pH did not change and force loss was therefore independent of H+ accumulation. In the normal subjects the force of the fatiguing muscle showed an approximately linear relationship with the concentration of the monobasic form of inorganic phosphate. However, the MPD subject showed a quite different relationship, with force loss being much greater for a given concentration of monobasic phosphate. This result indicates that monobasic phosphate is not a unique determinant of force loss in fatigued muscle. 5. During the first 60 s of recovery in the normal subjects, pH remained low while force recovered, indicating a mechanism of force loss that was independent of H+ accumulation. However, the recovery of force was not complete, so that for comparable phosphocreatine contents the recovering, more acid, muscle generated less force than the muscle that was being fatigued. It was estimated that H(+)-dependent and independent mechanisms contributed roughly equally to the observed force loss. The relationship between force and the concentration of monobasic phosphate differed in fatiguing and recovering muscle.Keywords
This publication has 21 references indexed in Scilit:
- The metabolic causes of slow relaxation in fatigued human skeletal muscle.The Journal of Physiology, 1989
- Maximum tension and force‐velocity properties of fatigued, single Xenopus muscle fibres studied by caffeine and high K+.The Journal of Physiology, 1989
- 31P nuclear magnetic resonance studies of high energy phosphates and pH in human muscle fatigue. Comparison of aerobic and anaerobic exercise.JCI Insight, 1988
- The inhibition of rabbit skeletal muscle contraction by hydrogen ions and phosphate.The Journal of Physiology, 1988
- It Is Diprotonated Inorganic Phosphate That Depresses Force in Skinned Skeletal Muscle FibersScience, 1987
- Excitation frequency and muscle fatigue: Mechanical responses during voluntary and stimulated contractionsExperimental Neurology, 1979
- Muscular fatigue investigated by phosphorus nuclear magnetic resonanceNature, 1978
- Contraction and recovery of living muscles studied by 31p nuclear magnetic resonanceThe Journal of Physiology, 1977
- Metabolic changes associated with the slowing of relaxation in fatigued mouse muscle.The Journal of Physiology, 1975
- Chemical basis of fatigue in isolated mouse soleus muscleAmerican Journal of Physiology-Legacy Content, 1970