Diet restriction and age alters skeletal muscle capillarity in B6C3F1 mice.

The effects of 40% diet restriction on skeletal muscle fiber area, capillary density (CD) and capillary to fiber ratio (C/F) were compared in 12, 24 and 30-month-old female B6C3F1 female hybrid mice. We hypothesized that diet restriction (DR) would retard the aging effects observed in skeletal muscle, in particular DR would pose opposite effects on skeletal muscle capillarity and fiber area. Samples were prepared for light microscopic examination by standard methods and for morphometric analysis using NIH-image software. There was a significant effect of age on muscle fiber area (p<0.05). The age-associated decrease in fiber area between 12 and 30 months of age was greater (p<0.05) in the ad libitum (AL) (37.7%) animals as compared to the diet restricted (DR) mice (29.2%). Diet had a significant effect on CD (p<0.05) and C/F (p<0.05). This finding suggests that the lower capillarity in the older DR mice may have been due to their larger muscle fibers. The results of this study support the contention that diet restriction delays the progression of age-associated muscle atrophy.

Exercise and dietary cholesterol alter rat myocardial capillary ultrastructure.

The effects of a cholesterol-rich diet and exercise training on the myocardial capillary network and capillary ultrastructure were examined using Sprague-Dawley rats subjected to a 7-week exhaustive swimming scheme. A total of 16 animals were randomly divided into four groups consisting of normal dietinactive, normal dietexercise, cholesterol dietinactive, and cholesterol dietexercise. Following the experimental regimen the largest heart-mass-to-body-mass ratios were measured for the exercised rats fed a normal diet and the smallest ratios were found for the cholesterol-fed inactive rats. The capillary-to-fiber ratios and the capillary densities of the exercise-trained animals fed normal and cholesterol-containing diets were higher than those of either of the inactive groups. Diet and exercise had significant and opposing effects on the number of capillary pinocytotic vesicles and no significant effect on vesicle size. The capillary endothelium of the exercise-trained animal groups occupied a smaller proportion of the capillary area when compared to diet-matched inactive groups. The results of this study imply that exercise training and a cholesterol-containing diet have opposite effects on the heart-mass-to-body-mass ratio and capillary pinocytotic vesicle number. Furthermore, exercise increases the capillary network of the myocardium and may facilitate receptor-mediated transport in heart capillaries.

A comparison of exercise performance on bicycle and rowing ergometers in female master recreational rowers.

Limited information exists on the response to maximal exercise testing in female masters level recreational rowers. This study examined cardiorespiratory and physiologic responses to progressive, incremental exercise using a variable resistance rowing ergometer and a cycle ergometer in six experienced female masters level rowers. Maximal oxygen uptake (VO2 max:33.8 +/- 7.3, 33.5 +/- 6.6 ml.kg-1.min-1) and minute ventilation (VEmax: 86.1 +/- 9.6 l.min-1, 88.7 +/- 13.8 l.min-1) were similar during both tests (rower vs cycle). Maximal heart rates were significantly higher on the cycle ergometer (177 +/- 9 beats/min-1) compared to the rowing ergometer (173 +/- 11 beats/min-1), while peak power on the rowing ergometer (175 +/- 22 watts) was lower than the cycle ergometer (187 +/- 41 watts). Blood lactate levels taken 1 minute following exercise were similar on the rowing ergometer (10.5 +/- 1.7 mM/l) and cycle ergometer (11.8 +/- 1.5 mM/l) and indicated maximal effort was achieved in all subjects. Ventilatory threshold levels were significantly different on the rower (2.0 +/- 0.16) versus the cycle ergometer (1.9 +/- 0.18) (p = 0.38). These data suggest that the cycle and rowing ergometers yield relatively similar results when testing maximal exercise performance in this population.

Prescribing water-based exercise from treadmill and arm ergometry in cardiac patients.

This study investigated the appropriateness of prescribing upright water-based exercise from treadmill and arm ergometry in uncomplicated, trained patients with cardiovascular disease (CVD) who were accustomed to water-based activities. Ten male patients with established CVD (mean age 59.4 +/- 8.7 yr) underwent maximal treadmill and arm ergometry in randomized counterbalanced order (half of the patients completed the treadmill test first and the other half completed the arm ergometer test first). Electrocardiographic (ECG), rating of perceived exertion (RPE), and oxygen uptake (VO2) measurements were made during both tests. Patients performed upright water-based exercise at 60, 70, and 80% of their maximal treadmill heart rate for 6 min at each intensity in a heated pool with a water temperature of 28-30 degrees C. They also performed an easy tethered swim, defined as performing at a comfortable exercise intensity, eliciting a heart rate of 86% of the treadmill maximum. VO2 and RPE were collected for all water-based exercise. To compare the RPE and VO2 between water-based, treadmill, and arm ergometry exercise, individual regression equations were constructed between heart rate, VO2, and RPE for both treadmill and arm ergometry tests. VO2 and RPE were then compared at the same heart rates between the three exercise modes. At 60% intensity, treadmill exercise exhibited a higher VO2 than water-based and arm ergometry exercise (P less than 0.05) but similar RPE. At 70%, treadmill exercise still yielded higher VO2, but also lower RPE than (P less than 0.05) and arm ergometry exercise (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Plasma creatine kinase activity and exercise-induced muscle damage in older men.

Plasma creatine kinase (CK) activity has often been used as a marker of exercise-induced skeletal muscle damage. While the pattern of muscle damage following eccentric exercise has been established in young adults, there is little data available on eccentric exercise-induced muscle damage in older individuals. The purpose of this study was to compare ultrastructural changes in skeletal muscle following high intensity eccentric exercise of young and older men and to determine whether CK activity is a reliable predictor of muscle damage. Five young (20-30 yr) and five older untrained men (59-63 yr) performed three 15-min bouts of eccentric exercise at 90, 80, and 70% of maximal concentric power output. There was a prolonged increase in CK up to 10 d following exercise that was not significantly different between groups. Light and electron microscopic examination of needle biopsies obtained from the vastus lateralis showed evidence of focal damage in greater than 90% of the post-exercise fibers examined in the older subjects, compared with values ranging from 5 to 50% reported previously in young subjects. Quantitative analysis using light microscopy showed greater damage in the older subjects than reported previously in young subjects. These data suggest that older adults experience greater muscle damage following eccentric exercise than young subjects, which may be due in part to the smaller muscle mass and lower VO2max seen in older men. In addition, there was no relationship between CK activity and the corresponding amount of muscle damage observed in each subject, suggesting that CK activity may be a poor predictor of exercise-induced muscle damage.

Influence of exercise and cholesterol feeding on lipids and lipoproteins in rats.

The purpose of the study was to investigate the separate influence of exercise and dietary intervention and their interaction on body weight, heart weight, total cholesterol, and high density lipoprotein cholesterol (HDL-C) in rats. Thirty-two male rats were randomly placed into 4 groups: normal diet-inactive (NI), normal diet-exercise (NE), cholesterol diet-inactive (CI), and cholesterol diet-exercise (CE). The exercise protocol consisted of swimming to exhaustion with a 5% gram tail weight, 5 days x wk-1 for seven weeks. Both diet and exercise had a significant effect on heart weight/body weight ratios, primarily due to changes in body weight. Neither exercise nor diet intervention produced a significant change in heart weight. The high cholesterol diet produced greater total cholesterol levels (p less than 0.05), but significantly lower HDL-C levels (p less than 0.05) than the normal diet. Exercise exhibited no independent effect on cholesterol or HDL-C concentrations, although there was a trend in a favorable direction. The data suggest that exercise cannot offset the effects of a high cholesterol diet, and that dietary treatment may play a greater role than exercise on altering serum cholesterol and HDL-C. These data imply that aggressive diet therapy should accompany exercise in the treatment of high serum cholesterol.