Changes in muscle morphology in dialysis patients after 6 months of aerobic exercise training.

BACKGROUND: In the present study we investigated the effect of a 6-month aerobic exercise programme on the morphology of the gastrocnemius muscle of end-stage renal disease (ESRD) patients. METHODS: Twenty-four ESRD patients volunteered to participate in the training programme and underwent muscle biopsy before training. Eighteen patients completed the training programme of whom nine agreed to a post-training biopsy (one woman and eight men, mean age 56 +/- 15 years). Data are presented for the nine subjects who were biopsied before (PRE) and after training (POST) and separately for the 15 subjects for whom we only have a biopsy before training (cross-sectional group). RESULTS: There were no significant differences (P > 0.05) in fibre type distribution or myosin heavy chain (MyHC) expression between the cross-sectional and PRE/POST groups. The mean cross-section fibre area after training (POST) increased by 46% compared with the PRE training status (P < 0.01). The proportion of atrophic fibres decreased significantly after training in type I, IIa and IIx fibre populations (from 51 to 15%, 58 to 21% and 62 to 32%, respectively). Significant differences were also found in capillary contact per fibre (CC/F), with the muscle having 24% (P < 0.05) more CC/F compared with the PRE training status. No significant differences in cytochrome c oxidase concentration were found between the groups. CONCLUSIONS: In conclusion, exercise appeared to be beneficial in renal rehabilitation by correcting the fibre atrophy, increasing the cross-section fibre area and improving the capillarization in the skeletal muscle of renal failure patients.     

High proportion of type I fibres in thigh muscle of young dancers

A previous study showed that adult female dancers have a high percentage of type I fibres in vastus lateralis. similar to that of endurance-trained female runners ar female cross-country skiers. It is not known if dancers already at an early age are characterized by a high percentage of type I fibres or develop a high percentage of type I fibres as a consequence of dance training. Furthermore. the muscle fibre composition of male dancers has not previously been studied. Therefore the aim of the study was to analyse skeletal muscle fibre characteristics in 10-year-old and 20-year-old dancers of both sexes. Age-matched boys and girls whose physical activity was average for their age groups served as controls. Muscle biopsies for histochemical analysis were obtained from vastus lateralis using the percutaneous needle technique. The major finding of the present study was that the vastus lateralis of young dancers of both sexes had a higher percentage of type I fibres than that of controls. Moreover. the higher type I percentage was seen not only in 20 year aids. but also in 10 year aids. who had begun their dance training at a professional level only a few weeks earlier. No significant difference in this respect was found between female and male dancers. In conclusion. the muscle fibre type composition in young dancers of both sexes differs from that of the average individual of the same age and is characterized by a high percentage of type I fibres.     

Mechanisms of tolerance during treatment with nitroglycerin patches for 24 h

Objective: We examined the relationship between tolerance development, counterregulatory responses and arterial vasodilating effects evaluated by digital pulse plethysmography. Methods: Twenty patients with stable angina pectoris were exercise tested before, after 2 and after 24 h of open nitrate patch treatment. Results: The effects observed after 2 h of treatment on exercise duration, ST-segment depression, blood pressure and heart rate were lost in most individuals after 24 h. In contrast, the effects on the arterial pulse curves persisted after 24 h, with a mean change from baseline of 29%, compared to 33% at 2 h. After 24 h, a significant decrease in haematocrit and an increase in body weight were observed. The haematocrit changes correlated with the loss of clinical efficacy (r =0.57 for ST-segment depression, and r =0.54 for exercise duration). Conclusion: Clinical nitrate tolerance may be observed despite maintenance of the arterial vasodilating effects, and tolerance is more related to plasma volume expansion as a counterregulatory mechanism. Received: 28 February 1996/Accepted in revised form: 5 July 1996     

Comparison of the treadmill exercise score and single-photon emission computed tomographic thallium imaging in risk assessment

Background  

This study compared the prognostic value of exercise single-photon emission computed tomographic (SPECT) thallium imaging with that of treadmill exercise score in medically treated patients with coronary artery disease (CAD)     

Effect of prior exercise in Pi/PC ratio and intracellular pH during a standardized exercise. A study on human muscle using [31P]NMR

Seven subjects underwent a standard localized exercise of calf muscles in order to investigate whether the metabolic exercise-induced steady-state, as revealed by the evaluation of inorganic phosphate/phosphocreatine ratio, depends on the conditioning of the muscle just prior to the exercise. The experimental protocols consisted of two separate experiments using first [³¹P]nuclear magnetic resonance spectroscopy and second (on 3 subjects) infrared oxyphotometry to respectively follow variation of energy metabolism and tissular deoxygenation. The exercise consisted of 240 successive plantar flexions (0.5 Hz frequency) against a high load equivalent to SO% of the maximal voluntary contraction. This exercise was accomplished before cold exercise and after warm exercise, a warming-up period bringing to approximately 50% of Vo_2max. The results showed that: (1) steady-state level of phosphate/phosphocreatine and intracellular acidosis was significantly lowered by warming-up; (2) cold and warm exercise steady-state of calculated adenosine diphosphate values were not significantly different; (3) cold exercise rapidly induced a high tissular deoxygenation that is not observed during warm exercise; and (4) time-constant of phosphocreatine resynthesis is lowered after warm exercise but the initial slope of time-evolution is not modified. Parallel experiments also showed that phosphate/phosphocreatine steady-state was not modified in comparison with warm exercise when the same power of exercise was reached by stepwise incrementation of the charge. From these results we postulate that a better tissue oxygenation due to a global or localized warming-up allows to reach the same mechanical performance with a lower decrease of PCr content, owing to a faster adjustment of oxidative metabolism during the transitional period. However the aerobic pathway flux during the steady-state is probably the same before and after the warming-up despite different values of phosphate/phosphocreatine. As a consequence it can be assumed that this ratio is not a good indicator of the rate of muscle oxidative metabolism during the steady-state phase of the exercise.     

A New Acceleration Driven Pacemaker: Rate Modulation Versus Normal Sinus Rhythm—Comparison During Treadmill Exercise

The pocing rate response of a new acceleration driven pulse generator (SWING 100, SORIN BIOMEDICA) was compared with simultaneous normal sinus rhythm (NSR) during two different treadmill exercises. This pacemaker has a gravitational acceleration sensor able to discriminate between physical activities and vibrations. Six healthy volunteers (three male, three female; aged 21.7 ± 4,3 years), with the pacemaker strapped to their right infraclavicular area, performed each test three times with different rise response curve (RRC) each time: fast, normal, and slow. The fall response curve used was the same as the rising one during each test. Pacing rates were recorded using the VEGA analyzer (SORIN BIOMEDICA) and compared with simultaneous NSR recorded by a 7-channel ECG recorder (MINGOGRAF 7, SIEMENS), During all tests immediate (within seconds) rapid increase in pacemaker rate was seen up to about 60 seconds, then a slower increase followed thereafter. The mean correlation between pacing rates and NSR during the Bruce tests were 0.7941 ± 0.10, 0.8562 ± 0.14, and 0.8292 ± 0.07; during the discontinous tests 0.7292 ± 0.16, 0.7233 ± 0.10, and 0.7480 ± 0.11 for fast, normal, and slow RRC, respectively. Each 30 seconds, nonsignificant differences were present between pacing rate and NSR during all the discontinuous tests; similar responses were observed only during the first two stages of Bruce tests after which NSR was significantly higher than pacemaker rates. The speed of rise to upper rate was the main difference between the different programs (fast, normal, and slow). The discontinuous tests showed that the pacemaker responds more to speed than to grade. In conclusion, the Swing pacemaker is easy to use and program, fast, reliable, and is able to mimic the normal sinus behavior especially during discontinuous activities.     

Differential effect of oestrogen on post‐exercise cardiac muscle myeloperoxidase and calpain activities in female rats

The effects of oestrogen administration on 1 h post‐exercise cardiac muscle myeloperoxidase (MPO) and calpain activities were determined in female rats. Rats were ovariectomized and implanted for 2 weeks with either oestrogen (25 mg 17‐oestradiol) or placebo pellets or left with ovaries intact. Rats were then run for 1 h at 21 m min^–1, 12% grade, killed 1 h post‐exercise and cardiac muscle and blood samples were removed. Control animals from each group were killed without prior exercise. Serum oestrogen levels in the order of the highest to lowest were; ovariectomized oestrogen replaced rats > intact ovaries rats > ovariectomized placebo rats. Oestrogen induced significant (P < 0.05) elevations in cardiac MPO activity at rest and at 1 h post‐exercise in ovariectomized rats. No significant elevations in cardiac MPO activity were evident in placebo ovariectomized or normal ovary rats at rest or post‐exercise. Cardiac calpain activities were similar in all unexercised groups. Ovariectomized placebo and intact ovary rats had significantly (P < 0.05) elevated cardiac calpain activities 1 h post‐exercise while calpain activity was not significantly elevated in hearts from ovariectomized oestrogen rats. These results demonstrate that oestrogen supplementation in ovariectomized rats induces elevations in cardiac muscle MPO activities at rest and at 1 h post‐exercise. This is opposite to the effect of oestrogen in post‐exercise skeletal muscle and implies a greater neutrophil infiltration into cardiac muscle caused by oestrogen. This effect cannot be explained by changes in 1 h post‐exercise cardiac muscle calpain activity, the elevation of which was suppressed by oestrogen administration. Oestrogen influences cardiac calpain activity similarly to its effect in skeletal muscle. Thus, oestrogen administration to ovariectomized rats induces elevations in cardiac MPO activity while suppressing cardiac calpain activity.     

Fibromyalgia syndrome: the beneficial effects of exercise.

This article highlights positive outcomes for a convenience sample of six women (49-64 years of age) with fibromyalgia syndrome (FMS) who participated in an exercise program over 5 years. This group showed improvement with various FMS symptoms,fitness, and psychosocial factors early in the program, then showed further improvement as a result of adding new exercises to the protocol during the fourth and fifth years. Data suggest that certain people with FMS can improve their functional capacity with exercise over time, and move to even higher levels of physical function while aging and coping with FMS. Practical advice is provided for rehabilitation nurses regarding exercise and FMS.