Influence of postexercise glucose ingestion upon serum potassium levels and ECG function.

Thirteen trained runners were studied to determine whether postexercise glucose ingestion contributes to electrocardiogram (ECG) alterations by enhancing decreases in serum potassium (K+) concentrations. For the two randomly ordered trials, subjects ingested a 100 g (25% w/v glucose polymer) drink, either alone or with the addition of 3 g of potassium chloride (KCl), within 15 min following a 90-min run. ECG parameters, serum K+, and glucose concentrations were measured preexercise (Time 0), 2-3 min post-exercise (Time 1), and 25 (Time 2) and 60 (Time 3) min postexercise. The data suggest that postexercise glucose ingestion may cause ECG changes that are not directly related to the return of K+ to muscle, and that these changes, although characteristic of hypokalemia, may be related to serum glucose excursions rather than to absolute levels of serum K+. The addition of KCl may have prevented these changes by delaying gastric emptying of glucose.

Bone mineral content and menstrual regularity in female runners.

The relationship between bone mineral content and menstrual regularity in 10 amenorrheic runners (0-3 menses during the past year), 12 runners with regular menstrual cycles (10-12 menses during the past year), and 15 non-athletic women with regular menstrual cycles was investigated. Comparisons of the two groups of runners indicated no significant differences in body fatness, average weekly running distance, or average daily intake of calcium (Ca), phosphorus (P), and Ca/P ratios. Mean bone mineral content for the three groups, measured by photon absorptiometry, was 0.508, 0.529, and 0.544 g X cm-2, respectively, at 3 cm distal radius, and 0.707, 0.700, and 0.707 g X cm-2, respectively, at one-third distal radius, indicating no significant differences among the groups (P less than 0.05). However, a significant relationship (r = 0.77) was noted between bone mineral content and body fatness only in the amenorrheic runners. Within the amenorrheic population, the five thinnest runners had significantly lower mean bone mineral content values at 3 cm distal radius (0.457 g X cm-2) than the five runners with higher relative body fatness (0.559 g X cm-2). We conclude, therefore, that amenorrhea, independent of body composition, was not related to reduced bone mineral content in female runners. However, the combination of excessive thinness and amenorrhea may, in fact, predispose female athletes to reduced bone mass.

Physical activity and osteoporosis in post-menopausal women.

Osteoporosis is an accepted fact of the female's aging process. This decrease in bone mass is most often linked to a lack of estrogen; however, prolonged inactivity is also known to cause atrophy in both muscle and bone. The purpose of this study was to investigate the relationship between the degree of osteoporosis and the physical activity levels of a group of post-menopausal women. Forty women between the ages of 60-69 yr were selected at random from a group of volunteers. The possible existence of a correlation between cortical diameter and activity level was investigated by using linear-model analysis. The width of the cortex may be related to many factors in addition to activity level. Some of the more important factors also considered were height, weight, ponderal index, age, years since taking estrogen, and total metacarpal diameter. The inclusion of these terms in the linear-model analysis allowed for an accounting of variability as associated with variables that could not be held constant. The variables showing the most significant relationships with the cortical diameter were the activity level and the use of estrogen. The relationships investigated through the linear-model analysis do not need to be independent. It is possible that combinations of these variables act to retard or enhance osteoporosis. Therefore, because the primary concern of the investigators was the relationship between physical activity and osteoporosis, a t-test was performed comparing the 10 most active women with the 10 most sedentary.(ABSTRACT TRUNCATED AT 250 WORDS)