Diet, muscle glycogen and physical performance.
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Adult↗
Biomedical subjects
B Saltin
Publications and source records attributed to B Saltin.
Inhibition of nitric oxide synthesis by systemic N(G)-monomethyl-L-arginine administration in humans: effects on interstitial adenosine, prostacyclin and potassium concentrations in resting and contracting skeletal muscle.
We examined whether the formation or the release of the vasodilators adenosine, prostacyclin (PGI(2)) and potassium (K(+)) increase in skeletal muscle interstitium in response to nitric oxide synthase (NOS) inhibition. Five subjects performed one-legged knee extensor exercise at 30 W without (controls) and with prior N(G)-nitro-L-arginine methyl ester (L-NAME) infusion (4 mg/kg, intravenously). Samples from the interstitial fluid were obtained at rest, during exercise and after exercise with the microdialysis technique. Interstitial adenosine in controls increased (p<0.05) from 0.11+/-0.03 micromol/l at rest to 0.48 +/-0.06 micromol/l during exercise. Interstitial adenosine during exercise in L-NAME was similar (p>0.05) to controls. The 6-keto-prostaglandin F1alpha concentration in controls was 1.17+/-0.20 ng/ml at rest and increased (p<0.05) to 1.97+/-0.30 ng/ml during exercise and was further elevated (p<0.05) to 2.76+/-0.38 ng/ml after exercise and these concentrations were not different (p>0.05) in L-NAME. The interstitial K(+) concentration in controls increased (p< 0.05) from 4.1+/-0.1 mmol/l at rest to 9.5+/-0.5 mmol/l during exercise. The interstitial K(+) concentration during exercise (6.7+/- 0.4 mmol/l) was lower (p<0.05) in L-NAME than in controls. The present findings demonstrate that the muscle interstitial concentrations of adenosine, PGI(2) and K(+) during exercise are not increased with systemic NOS inhibition. Thus, the lack of effect of NOS inhibition on the rate of blood flow to contracting human skeletal muscle does not appear to be due to compensatory formation or release of adenosine, PGI(2) and K(+) in the muscle interstitium. The present study also supports a role for PGI(2) in the regulation of blood flow during exercise.
6-Ketoprostaglandin F1 alpha↗
Pulmonary flow-volume and pressure-volume relationship during submaximal and maximal exercise in young well-trained men.
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Adult↗
Adaptation of skeletal muscles to training.
Based on the myosin ATPase reaction, human skeletal muscles are composed of two main fibre types, named slow (ST) and fast (FT) twitch fibres, respectively. With few exceptions, ST and FT fibres are evenly represented in the muscles, however with a large interindividual variation. Endurance athletes tend to have a predominance of ST fibres while sprinters have a predominance of FT fibres. The ST fibres are surrounded by 3-4 capillaries, and they have the largest potential for terminal oxidation and the smallest for glycolysis. Of the FT fibres, two subtypes may be distinguished (a and b), of which no FTb fibres are seen in the endurance trained muscles of athletes. Training also results in an increase in the number of capillaries for all fibre types. FTa fibres have a metabolic potential which is intermediate to that of the ST and FTb fibres. With endurance training, the potential for terminal oxidation increases, resulting in a larger ability to use fat as a fuel during submaximal exercise and in a reduced production of lactate. Thus, training has a glycogen sparing effect and endurance increases. Human intercostal muscles appear to have approximately 60% ST fibres. In the external intercostal muscles, the number of capillaries and the occurrence of FTb fibres is similar to the findings in untrained muscles. In contrast, the internal intercostal muscles placed in the mid-axillary line have no FTb fibres and relatively many capillaries. Thus, these (expiratory) muscles appear to be extensively used.
Adenosine Triphosphatases↗