The effects of aging on the total number and size of fibers, and the proportion and distribution of type 1 (slow twitch) and type 2 (fast twitch) fibers were studied in cross sections (15 mu thick) of autopsied whole m. vastus lateralis from two age groups. Each group consisted of six, previously physically healthy males (mean age 72 +/- 1 years and 30 +/- 6 years, respectively). The size of the muscles of the older individuals was 18% smaller (P less than 0.01) and the total number of fibers was 25% lower (P less than 0.01) than those of the young individuals (mean number 364,000 +/- 50,000 vs 478,000 +/- 56,000). There was, however, no significant difference in the mean fiber size (indirectly determined) or the proportion of the two fiber types, though a preferential reduction in type 2 fiber number in the aged individuals was seen. The relative occurrence of the fiber types at various depths in the aged muscles was found to be more even than in muscles from the young individuals. The results suggest that the aging atrophy in m. vastus lateralis, at least up to the age of 70, is primarily the result of a loss of fibers.

In order to determine the total number of fibres and the extent to which the relative occurrence of different fibre types varies within m. vastus lateralis, 15 micrometers thick cross-sections of whole muscles were prepared. The total number of type 1 and type 2 fibres was determined in every 48th square millimetre of the section, and the results thus obtained were analysed using a computer program allowing an assessment of bivariate data in the form of contour plots. The total number of fibres varied both in proximal to distal direction in the same muscle and between individuals. No obvious correlation existed between the mean fibre area and the muscle cross-sectional area. The proportion of type 1 fibres in the whole muscle varied between individuals (from 44% to 57%) with a mean value for all five of 52%. The distribution of different fibre types varied within the muscle, mainly as a function of depth, with a predominance to type 2 fibres at the surface and type 1 fibres in deeper regions of the muscle. Thus, the fibre type distribution in m. vastus lateralis is not random. This must be taken into consideration when data on fibre type composition are compared with functional variables.

The reduced maximal performance indicates a state of fatigue/overreaching and peripheral factors are suggested to limit performance even though HRmax and La(max) both were reduced. The reduced submaximal heart rates are probably a result of increased plasma volume. HRV in this group didn't seem to be affected by short-term overtraining.

The aim of this study was to investigate whether the mean power frequency of the electromyogram of the knee extensors was force and/or muscle fibre‐type dependent. Ten female subjects performed a gradually increasing static knee extension (5 seconds duration) using an isokinetic dynamometer. Electromyogram‐signals were obtained from the vastus lateralis, vastus medialis and the rectus femoris muscles. The torque signal and the three electromyogram signals were recorded on a tape recorder. From the electromyogram recordings the mean power frequency and the signal amplitude were determined. Muscle biopsies were later obtained from the right vastus lateralis and stained for alkaline and acid mATPase for the determination of fibre‐type proportion and areas. Both the mean power frequencies and the signal amplitudes of the three knee extensors were positively torque dependent. Furthermore it was found that the fibre type proportion and the regression coefficient of the torque (%)‐mean power frequency relationship were positively correlated. Also a negative correlation existed between the type‐1 (%) proportion and the intercept of the individual torque (%)‐mean power frequency relationships. In contrast to proposed models of the electromyogram signal no correlation was found between the mean power frequency and the fibre area.

The aim of this study was to examine the effect of high intensity physical group training in water and on land for patients with COPD with regard to physical capacity and health related quality of life (HRQoL). A controlled, semi-randomised study was conducted where 30 patients were randomised to training either in water or on land. Thirteen patients constituted a control group. Forty-three outpatients, with moderate to severe COPD (27w/16m), from two local hospitals in northern Sweden, were included in the study. High intensity physical group training in water (water group) or on land (land group) was performed for 12weeks, three times per week, 45min per session. The control group received no intervention. Pre- and post-intervention, all patients performed incremental and endurance shuttle walking tests (ISWT and ESWT), cycle ergometer tests and responded questionnaires about HRQoL (St. Georges Respiratory Questionnaire--SGRQ and SF-36). The patients trained with a mean heart rate of 80-90% of peak heart rate. Both training groups increased the distance walked, i.e. land group in ISWT (25m) and water group in ESWT (179m). The water group increased the distance in ESWT significantly more that both the land and the control groups. Both training groups increased the time cycled (40-85s) and work load (10-20W) in the cycle ergometer test. The control group deteriorated in HRQoL according to total score in SGRQ while the training groups remained constant. The water group improved their activity score in SGRQ and their physical health score in SF-36 and those improvements were significant as compared to the land and the control groups. In conclusion, high intensity physical group training in water is of benefit for patients with COPD. It was in some areas found to be even more effective regarding improvements in physical capacity and experienced physical health compared to the same kind of training on land.

Muscle performance and fibre type composition were investigated in women with fibromyalgia, work-related trapezius myalgia and healthy volunteers. Each subject performed 100 repetitive shoulder flexions using an isokinetic dynamometer during simultaneous registration of surface electromyography. A biopsy from the trapezius muscle was obtained. The groups differed neither in mechanical performance nor in fibre type proportions. An inability to relax between contractions was found in all registered muscles in patients with fibromyalgia. The patients with work-related myalgia displayed an inability to relax only in the myalgic trapezius muscle. An inability to relax during repetitive movements might play an important role both in initiating and upholding muscle pain.

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The results suggest that improved measures of both peripheral and central (aerobic) work capacities were associated with a reduction of low-frequency HRV in the tilted position. High-frequency and total HRV did not change in proportion with changes in muscle performance or aerobic capacity, but the ability to further improve VO(2max) with training in these already fit subjects seemed to depend on their average levels of these HRV measures, interpreted to reflect parasympathetic activity.