title: Constant relationships between force, phosphate concentration, and pH in muscles with differential fatigability.
abstract: We examined the relationships between muscle force and both phosphate and hydrogen ion concentrations in muscles with differential fatigability and in different types of exercise. We measured force and 31phosphorus nuclear magnetic resonance spectra from the tibialis anterior (a slow-contracting, fatigue resistant, postural leg muscle) during a sustained maximum contraction (anaerobic exercise) and during intermittent contractions (aerobic exercise). We observed similar relationships between the decline in muscle force during fatigue and changes in both phosphate and hydrogen ion concentrations during both aerobic and anaerobic exercise in tibialis anterior. Furthermore, these relationships were similar to those previously observed in the adductor pollicis. The demonstration of constant relationships between muscle contraction force and metabolism under different exercise conditions and in muscles of different function supports the view that both phosphate and hydrogen ions are important regulatory factors in the fatigue of human muscle.
authors: Magnetic Resonance Unit, Veterans Administration Medical Center, San Francisco.
authors: M W
authors: MW
authors: Weiner
authors: R S
authors: RS
authors: Moussavi
authors: A J
authors: AJ
authors: Baker
authors: M D
authors: MD
authors: Boska
authors: R G
authors: RG
authors: Miller
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D006801:Humans; D006863:Hydrogen-Ion Concentration; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D009132:Muscles / Q000502:physiology*; D009928:Organ Specificity; D010710:Phosphates / Q000378:metabolism*; D010725:Phosphocreatine / Q000378:metabolism; D005082:Physical Exertion; D012016:Reference Values
chemical_list: D010710:Phosphates; D010725:Phosphocreatine; D000255:Adenosine Triphosphate