Significant muscle size and architectural adaptations can occur in concurrently training athletes in response to a 5-wk training program. These adaptations were possibly associated with the force and velocity characteristics of the training exercises but not the movement patterns. Factors other than, or in addition to, muscle architecture must mediate changes in strength, sprint, and jump performance.

The purpose of this study was to investigate the effects of a progressive resistance training program on myosin heavy chain isoform expression, fiber type, and capillarization in patients with symptomatic peripheral arterial disease. Patients were randomized to either a training group (n = 11, mean +/- SD, 70 +/- 6 years, 4 men, 7 women) or a control group (n = 9, 66 +/- 6 years, 5 men, 4 women). The training sessions were completed 3 times/week, using 2 sets of various exercises, each performed for 8-15 repetitions. Muscle biopsies were obtained before and after 24 weeks from the medial gastrocnemius. Following the 24-week training program, the training group had significantly decreased the percentage of myosin heavy chain type IIB. The proportion of type IIB/AB fibers as measured by using myosin adenosine triphosphatase histochemistry decreased significantly in the training group. There were significant increases in type I and type II fiber areas, and capillary density also increased significantly in the training group. There were significant increases in 10 repetition maximum leg press and calf press strengths in the trained subjects. There were no significant changes in any of the measurements in the control group. It is concluded that progressive resistance training results in significant increases in muscle strength and alters skeletal muscle composition of subjects with peripheral arterial disease.

This study showed a significant modification in the expression of MHC isoforms and muscle fiber type in the gastrocnemius in patients with symptomatic PAD. These results suggest that muscle ischemia resulting from PAD is an important factor in causing the adaptations in the contractile apparatus of the muscle.

Integrated electromyography (iEMG) of the m. vastus lateralis was analysed during cycle ergometry in male subjects (n = 8). Two work trials were conducted, one under normoxia (N), the other under environmental normobaric hypoxia (EH in which the oxygen fraction in inspired gas = 0.116), each trial lasting 10 min. The absolute power output (180 W) was the same for both trials and was equivalent to 77 (4)% of maximum heart rate in trial N. Maximal voluntary isometric contractions were performed after each trial to assess changes in force, muscle fibre conduction velocity (MFCV), electromechanical delay (EMD), median frequency of EMG (MF) and maximal iEMG (iEMGmax). Biopsy samples of muscle were obtained from the m. vastus medialis before testing. Myosin heavy chain (MHC) differences were determined through sodium dodecyl-polyacrylamide gel electrophoresis followed by densitometric analysis. No differences in submaximal iEMG were observed between EH and N trials during the first minute of work. At the end of both work trials iEMG was significantly elevated compared with starting values, however the iEMG recorded in EH exceeded N values by 15%. At the end of the EH trials the following were observed: a decrease in isometric force, MFCV and MF with an increase in EMD and the iEMGmax/force ratio. The iEMGmax was unchanged. No differences in any of these variables were observed after the N trial. Mean (SD) lactate concentrations following EH and N trials were 9.2 (4.4) mmol x 1(-1) and 3.5 (1.1) mmol x 1(-1), respectively. Results indicate that an increased motor unit recruitment and rate coding was needed in EH to maintain the required power output. The increased motor unit recruitment and rate coding were associated with myoelectric evidence of "peripheral" muscle fatigue. Subjects with higher compositions of type II MHC accumulated more lactate and displayed greater reductions in MF and MFCV during fatigue.

Eleven women (TRW; 64 +/- 4 yrs) and ten men (TRM; 65 +/- 5 yrs) participated in the strength/power training twice a week for 24 weeks. Basal concentrations of serum total and free testosterone, growth hormone (GH), dehydroepiandrosterone sulfate (DHEAS), cortisol and sex hormone binding globulin (SHBG) as well as acute responses of serum total and free testosterone, growth hormone (GH) were measured. Maximal 1RM strength in the squat, chair rise time and muscle fibre distribution and areas of type I and IIa and IIb of the vastus lateralis were also examined. 1RM squat increased in TRW by 26 (SD10)% (p < .001), and in TRM by 35 (7)% (p < .001) and chair rise time improved in both groups (p < .001). Fibre areas increased in type I, (p < .01), IIa (p < .01) and IIb (p < .01) in TRM and type I (p < .05) and IIa (p < .05) in TRW. The proportion of type IIa increased from 31% to 43% (p < .05) in TRW and that of type IIb decreased from 27% to 17% (p < .05) in TRW and from 25% to 17% (p < .05) in TRM. Individual concentrations of testosterone/cortisol ratios correlated (r = 0.63; p < .05) with the individual increases in 1RM strength in TRW. The exercise sessions resulted in acute increases in serum GH in both groups (p < .05) with a further increase (p < .01) up to 10 minutes post-loading in TRM at post-training.

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It was concluded that short-term high intensity resistance training provides an effective means for increasing muscular strength in women between 45 and 65 yr. The training effects on lumbar BMD were not apparent in the present study.

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