Aj. Wade et al., Influence of muscle temperature during fatiguing work with the first dorsal interosseous muscle in man: a P-31-NMR spectroscopy study, EUR J A PHY, 81(3), 2000, pp. 203-209
Citations number
32
Categorie Soggetti
Physiology
Journal title
EUROPEAN JOURNAL OF APPLIED PHYSIOLOGY AND OCCUPATIONAL PHYSIOLOGY
Six healthy subjects rapidly lifted and lowered a small (250 g) weight with
the first dorsal interosseous muscle (FDI) of one hand while the work perf
ormed was recorded continuously until fatigue (defined as losing the abilit
y to continue lifting). Work was recorded in units of chart recorder trace
displacement from baseline (centimetres) as an isotonic transducer followed
the movement of the weight. In all experiments, the temperature of the han
d was first adjusted by immersion in a controlled-temperature water bath. I
n the warmest condition, the skin surface temperature over the FDI was 30.5
(0.30)degrees C [mean (SE)]. After moderate cooling, this surface temperatu
re was 21.5(0.16)degrees C. Cooling significantly reduced the time taken to
reach fatigue and more than halved the work capacity. An intermediate degr
ee of cooling was also used in four subjects, showing that most of the effe
cts seen were changing incrementally. Before work, and at fatigue, intracel
lular metabolic conditions in the FDI were studied by phosphorus nuclear ma
gnetic resonance (P-31-NMR) spectroscopy? with occlusion of the blood flow
maintained during measurements. The mean intracellular pH of the FDI was al
so calculated. The changes observed were all consistent with the fact that
intense work requires energy which must be derived largely from intracellul
ar stores of phosphocreatine and glycogen. Less work made less demand upon
reserves, and created lower concentrations of waste products and by-product
s. The observations did not, however, allow us to explain why fatigue occur
red at a particular point or why work capacity was reduced by cooling.