Effects of a 6-month incentive-based exercise program on adherence and work capacity.

The purpose of the study was to evaluate the effect of behavioral management techniques on exercise adherence linked to improvements in work capacity and maximal oxygen consumption (VO2max). One hundred thirty-seven participants in six different worksites on a university campus (five experimental and one comparison site) completed 6 months of a minimally supervised, incentive-based endurance exercise program. All participants in the experimental group contracted to engage in at least four bouts of 30 min of verified aerobic exercise within a prescribed target heart rate range each week for the duration of the program. Forty dollars deposited at the beginning of the program served as a response cost that could be lost as a result of failure to fulfill the weekly contracts. Individuals in the comparison group participated in a similar 6-month program but without the contracts and response cost strategies. Weekly adherence for both groups was strictly defined as verified fulfillment of all four bouts of exercise. Adherence for the experimental group was 97% by this definition, and adherence for the comparison group was 19% (P less than 0.01). VO2max increased 2.6% (P less than 0.01), and treadmill test time increased 16% (P less than 0.01) in the experimental group after the 6-month program, with no significant changes in the comparison group. Recovery heart rates at 2 and 4 min post-exercise were significantly lower at 6 months in the experimental group but not in the comparison group. These data provide evidence that adherence to a 6-month endurance exercise program can be improved significantly through the use of well conceived behavior management strategies.(ABSTRACT TRUNCATED AT 250 WORDS)

Caloric expenditure, life status, and disease in former male athletes and non-athletes.

This study examined the association between aerobic, caloric exercise expenditure and life status (living vs deceased) as well as the prevalence rates of hypertension (HBP) and cardiovascular disease (CVD) in former male athletes (ATH) and non-athletes (N-ATH). The initial survey for this study was done in 1952. Follow-up surveys of respondents were done in 1960, 1968, 1976, and 1984. The present study used all subjects who responded fully to activity and health questions in 1976 and who were reported as either dead or alive (not lost to follow-up) in 1984. A total of 348 subjects (185 ATH, 163 N-ATH) were assessed and caloric expenditure groups were established by kilocalories (kcal) of aerobic exercise per week; 0 kcal (group 1), 1-399 kcal (group 2), 400-899 kcal (group 3), 900-1499 kcal (group 4), 1500-2499 kcal (group 5), and 2500+ kcal (group 6). Only activity considered to be aerobic was used in the establishment of the aerobic categories. Death rate was highest in groups 1 and 2. Subjects in group 1 tended to be the oldest. Year of birth (age) (P less than 0.001) and CVD (P less than 0.05) as reported in 1976 were significantly related to mortality between 1976 and 1984. College athletic status and 1976 exercise level were not significantly related to mortality. Prevalence of CVD and HBP was highest in groups 1 and 6, suggesting a moderate amount of aerobic activity as optimal.

Somatotype and longevity of former university athletes and nonathletes.

A longitudinal study was conducted on 398 athletes and 369 nonathletes who were born before 1920 and attended Michigan State University. The subjects were compared to determine if intercollegiate athletic competition accounts for significant variation in longevity when considered with somatotype. Because some of the subjects were still alive at the time of the study, the BMDP Statistical Software was used to do a survival analysis with covariates. Preliminary comparisons considered the differences in somatotype between athletes and nonathletes. Two sample t-tests indicated that athletes were more mesomorphic and less ectomorphic (p less than .05) than nonathletes. When comparing the relationship between somatotype and longevity, the pooled data of athletes and nonathletes indicated that endomorphs were shorter lived than the other three comparison groups. When only the athletes were considered, similar results were found. However, the nonathlete group exhibited differences only between the mesomorphic and endomorphic groups. The endomorphs were shorter lived. Longevity was examined by using the Cox proportional hazards regression method with somatotype and athlete/nonathlete status as covariates. Somatotype, by itself, was found to be significantly related to longevity, (p less than .001). Athletic status was not significantly related to longevity, either by itself or when entered into the model with somatotype.

Postnatal muscle fibre histochemistry in the rat.

Histochemical techniques were used to study the postnatal muscle fibre differentiation patterns in the plantaris and soleus muscles of male Sprague-Dawley rats. Nine groups of animals (n = 6/group) were killed at 1, 6, 11, 16, 21, 26, 31, 36, and 140 days of age. Serial transverse sections of the two muscles were stained with H & E, NADH-D, and myofibrillar ATPase with acid (pH 4.35) or alkali (pH 10.4) preincubation. In each of the age groups, all available fibres across the muscle sections were classified. Obtained data show that fibre types are basically undifferentiated at birth in both muscles. In the plantaris muscle there are about 99% type IIA and less than 1% type I fibres at 6 days of age. Type IIB fibres can be identified at 11 days of age. There are increases in the percentages of type I fibres (from 0.7% to 3.5%) and type IIB fibres (from 1.1% to 6.5%) between 6 and 11 days and between 16 and 21 days respectively. By 36 days of age the relative numbers of type IIA, IIB, and type I fibres in the plantaris are approximately 80%, 14%, and 6%, respectively. A gradual change in fibre-type composition continues until it becomes 47% for type IIA, 43% for type IIB, and 10% for type I at 140 days of age. In the soleus muscle there are approximately 73% type IIA and 26% type I fibres at both 6 and 11 days of age. However, type IIA fibres decrease to 44% and type I fibres increase to 56% at 16 days of age. This rapid shift in fibre composition continues up to 31 days of age when the distribution becomes 25% for type IIA and 74% for type I fibres. Thereafter, the differentiation rate is much slower. At 140 days of age, there are 17% type IIA and 83% type I fibres in the soleus muscle. The results of this study show that the fibre populations in the plantaris and soleus muscles of the rat undergo a postnatal differentiation process. In both muscles the adult fibre population is established by 140 days of age. Although relatively rapid increases of type I and type IIB fibres occur in the plantaris during the second and third weeks of life, differentiation in that muscle appears to be an essentially continuous process. There is a notable shift in the fibre composition of the soleus muscle during the second postnatal week. Differences between the patterns of differentiation in the two muscles are apparent.

Differential effects of running and weight-lifting on the rat coronary arterial tree.

Twenty-four postpubertal male albino rats were assigned randomly to sedentary-control (C), endurance-running (ER), and weight-lifting (WL) groups to study the effects of different chronic-exercise regimens on precapillary vascularity in the heart. The exercise routines were administered 5 d/wk. At the end of either 8 or 16 wk of treatments, half of the animals in each group were anesthetized. A 12% vinyl acetate solution was injected into the coronary arteries of each anesthetized animal at a pressure of 300-350 mmHg, through the ascending aorta. The injected hearts were removed and weighed. A 10% potassium hydroxide solution was used to digest tissues from the vinyl cast of each coronary arterial tree. No differences in absolute or relative heart weights were observed between the control and trained groups. When compared to the control group, the ER animals had heavier left and total coronary cast weights and higher total cast weight-to-heart weight ratios (P less than 0.05). Although an overall increase in precapillary vascularity of the heart was evident in the endurance-trained ER animals, none was found in the strength-trained WL group. However, the WL animals had significantly increased right coronary cast weights, and their ratios of right coronary cast weight to total cast weight also were higher than those of the control animals (P less than 0.05).

Skeletal muscle fiber splitting with weight-lifting exercise in rats.

Adult male albino rats were assigned randomly to control (CON) and weight-lifting (WL) groups. The WL rats were subjected to a progressive weight-lifting program against high resistance for 8 weeks. During the last 2 weeks, each WL rat lifted a load equal to 130% of its body weight. The mean weight of the adductor longus muscle was significantly increased in the WL group ( p < 0.05). This increased muscle weight was shown to be due to an increase in the number of fibers per unit cross-sectional area ( p < 0.05), and the mean sizes of both fast-twitch oxidative glycolytic and slow-twitch oxidative fibers were significantly smaller in the WL rats than in the CON rats (p < 0.05). Light and electron microscopic examination showed that five out of eight WL rats exhibited longitudinally split muscle fibers, while only one CON rat had a few centrally placed nuclei. The splitting process appeared as either a "pinching-off" of a small segment from the parent fiber or an invagination of the sarcolemma deep into the muscle fiber in a plane parallel to the sarcomeres. There were preliminary indications that this work-induced fiber-splitting process may be a physiological adaptation of muscle to the stress of exercise.

The Longevity and Morbidity of College Athletes.

This well-designed study does not prove that athletic participation affects longevity and morbidity. Perhaps the same study of highly trained athletes would produce different results.

Effects of an anabolic steroid and sprint training on selected histochemical and morphological observations in rat skeletal muscle types.

The effects on selected histochemical and morphological parameters of anabolic steroid administration and of high-intensity sprint running, separately, and in combination, were studied in young adult male rats. Dianabol (methandrostenolone) 1 mg/day for 8 weeks had no significant effects on phosphorylase or glycogen staining intensities and on fiber area in skeletal muscles of either trained or sedentary animals. The program of sprint training resulted in significantly decreased intensities of phosphorylase in all ten regions of the gastrocnemius, plantaris, and soleus muscles that were studied. Glycogen localization was significantly increased with training in five regions of the gastrocnemius and plantaris muscles which contained predominantly fast-switch fibers. No changes in fiber area occurred with the training program. We conclude from these results that (a) normal androgen levels in young, healthy male animals are sufficiently high so that the intake of large doses of anabolic steroid does not result in the stimulation of glycogen metabolism or hypertrophy of skeletal muscle; (b) the changes induced by high-intensity, short-duration sprint training suggest that the existing glycolytic capacity of muscle is adequate to supply the muscles energy needs even during the stress of very strenous exercise, and that more fast-twitch fibers were recruited by the exercise regimen than slow-twitch fibers.

Skeletal muscle enzyme alterations after sprint and endurance training.

Specifically designed programs of sprint and endurance running were used to determine how different types of training affect enzyme activities in selected energy metabolism pathways. Three types of rat skeletal muscle were studied. After 8 wk of training, small but significant decreases in lactate dehydrogenase activity (15%) were found in the soleus and white vastus lateralis muscles of the sprint animals. Decreased levels of phosphoglucomutase and lactate dehydrogenase (approx. 20%) of the white vastus lateralis muscles of the endurance group were observed at the same time. By 16 wk of training, fumarase activity increased approximately twofold in the white vastus muscles and 45% in the soleus and plantaris muscles of the endurance group. Similarly, increased fumarase activity (42%) was seen in the soleus muscles of the sprint group. In all muscles, phosphoglucomutase and lactate dehydrogenase activities generally were lower in the endurance animals than in the control animals. No significant differences were found between the sprint and endurance groups at either or sixteen weeks of training. These results suggest that similar enzyme adaptations occur over time with both types of training.

Effects of dianabol and high-intensity sprint training on body composition of rats.

The effects on body composition and organ weights of anabolic steroid administration and of high-intensity sprint running, separately and in combination, were studied in young adult male rats. Dianabol (methandrostenolone) 1 mg/day for 8 weeks had no significant effects on muscle weight or lean body mass in either the trained or the sedentary animals. The program of sprint training resulted in a lower body weight, a lesser percentage of body fat (Runners, 8.5%, vs. sedentary, 13.5% P less than 0.01) and a greater relative lean body mass (runners, 91.5% vs. sedentry, 86.5%, P less than 0.01). We conclude from these results that (a) normal androgen levels in young, healthy male animals are sufficiently high so that the addition of a large dose of anabolic steroid does not result in stimulation of additional muscle growth, and (b) the changes in body composition induced by high-intensity, short-duration sprint training are qualitatively similar to those seen with endurance exercise training.

Skeletal muscle function and structure after depletion of creatine.

Experiments were conducted to determine if normal skeletal muscle function and structure are dependent upon their ability to store large quantities of metabolic energy in the form of N-phosphorylcreatine. Muscle levels of creatine and N-phosphorylcreatine were reduced by feeding young male rats diets containing 1 per cent beta-guanidinopropionic acid (beta-GPA). Muscle function was evaluated by monitoring performance during a 4-week, short duration, high intensity exercise program in a control running wheel. Structural effects were determined by histochemistry, morphometric analysis, and routine histologic procedures using light microscopy. Evidence of abnormal creatine metabolism of rats fed beta-GPA included: excessive creatinuria, reduction in urine creatinine, reduced levels of muscle and brain creatine, and a reduced activity of muscle creatine kinase. In separate experiments, beta-GPA inhibited the reaction of creatine with creatine kinase in vitro. When muscle function was evaluated by running, the percentage of expected revolutions for the group of rats fed beta-GPA was below the expected normal values. The white (type II) fibers from the gastrocnemius of exercised rats fed beta-GPA were smaller than fibers from the same muscle areas of rats fed normal diets. The histochemical characteristics of red (type I) and white fibers of all rats tested were within normal limits. It is concluded that feeding beta-GPA will result in structural and functional changes in skeletal muscles of exercised young male rats. These changes are believed to result from the ability of beta-GPA to block creatine entry into muscle and thereby prevent muscle from accumulating and maintaining its normal complement of creatine and N-phosphorylcreatine.