The purpose of this study was to compare two contrasting training models, namely high-resistance training and prolonged submaximal training on the expression of Na+-K+ ATPase and changes in the potential of pathways involved in energy production in human vastus lateralis. The high-resistance training group (VO2peak = 45.3 +/- 1.9 mL kg(-1) min(-1), mean +/- SE, n = 9) performed three sets of six to eight repetitions maximal, each of squats, leg presses and leg extensions, three times per week for 12 weeks, while the prolonged submaximal training group (VO2peak = 44.4 +/- 6.6 mL kg(-1) min(-1), n = 7) cycled 5-6 times per week for 2 h day(-1) at 68% VO2peak for 11 weeks. In the HRT group, Na+-K+ ATPase (pmol g(-1) wet wt), measured with the 3H-ouabain binding technique, showed no change from 0 (289 +/- 22) to 4 weeks (283 +/- 15), increased (P < 0.05) by 16% at 7 weeks and remained stable until 12 weeks (319 +/- 19). For prolonged submaximal training, a 22% increase (P < 0.05) was observed from 0 (278 +/- 31) until 3 weeks (339 +/- 29) with no further changes observed at either 9 weeks (345 +/- 25) or 11 weeks (359 +/- 34). In contrast to high-resistance training, where a 15% increase (P < 0.05) was observed, only in the maximal activity of phosphorylase, prolonged submaximal training resulted in increases in malate dehydrogenase, beta-hydroxyl-CoA dehydrogenase, hexokinase and phosphofructokinase. In contrast to high-resistance training which failed to result in an increase in VO2peak, prolonged submaximal training increased VO2peak by approximately 15%. Only for prolonged exercise training was a relationship observed for VO2peak and Na+-K+-ATPase (r = 0.59; P < 0.05). Correlations between VO2peak and mitochondrial enzyme activities were not significant (P > 0.05) for either training programme. It is concluded that although both training programmes stimulate an up-regulation in Na+-K+ ATPase concentration, only the prolonged submaximal training programme enhances the potential for beta-oxidation, oxidative phosphorylation and glucose phosphorylation.

The effects of maturation on the interrelationship between skeletal muscle fiber area and capillarization was investigated in specific fiber types (I, IIa, IIb, IIc) of male Wistar rats at seven developmental periods ranging from 8 to 85 days postnatal. Fiber type specific developmental properties were compared in three different muscles, the diaphragm (DIA), extensor digitorum longus (EDL), and soleus (SOL), which are known to differ widely in function. All fiber types in each of the three muscles examined exhibited large increases in area (FA), the magnitude and time course of the increase being related to both the type of fiber and the muscle in which the fiber was located. For type I fibers, areas increased from 3- to 18-fold (SOL greater than EDL greater than DIA), whereas in type IIa fibers, area increased ranged between 5- to 11-fold (SOL greater than EDL greater than DIA). Growth rates in IIb fibers were more homogeneous between muscles ranging from 11- to 14-fold. Capillarization, as indicated by the capillary contacts per fiber (CC), increased in all fiber types regardless of muscle origin. These increases ranged between 1.7- and 2.2-fold for type I fibers, between 2.4- and 2.5-fold for type IIa fibers, and between 2.0- and 3.0-fold for type IIb fibers. In general, capillary density expressed as the ratio of the number of capillary contacts divided by the fiber area (CC/FA) progressively declined in all fiber types with age. The rate of the decline in CC/FA was mediated in large part by the changes in fiber area.(ABSTRACT TRUNCATED AT 250 WORDS)

To determine the effect of acute plasma volume (PV) expansion on substrate utilization, blood metabolites and catecholamines to prolonged, moderate intensity cycle exercise, eight untrained men mean maximal oxygen uptake VO2max 4.10 (SEM 0.32) 1.min-1 were infused (10 ml.kg-1) with a 6% dextran (DEX) solution. These responses were also compared to those elicited using a short-term training (TR) protocol involving cycling for 90 to 120 min.day-1 at 60% VO2max for 3 consecutive days. In general DEX, which resulted in a calculated expansion of PV by 23.9% was without effect in modifying exercise oxygen uptake or the reduction in the respiratory exchange ratio (R) observed during prolonged exercise. In addition, the concentrations of blood glucose, glycerol, alanine and serum free fatty acids, although altered (P < 0.05) by exercise, were not altered by DEX. Blood lactate concentration was only higher (P < 0.05) at 30 min of exercise during DEX compared to the control. With the exception of blood lactate concentration, which was reduced (P < 0.05), TR did not change R or the concentrations of other blood metabolites. The concentrations of nonadrenaline and adrenaline, were depressed (P < 0.05) by DEX and TR at 60 and 90 min of exercise. These results would suggest that mechanisms as yet undefined can compensate for the estimated 10% reduction in arterial oxygen content mediated by acute PV expansion and enable prolonged exercise to be performed without adjustments in substrate selection and substrate mobilization.

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