Although physical activity is known to improve bone mineralization, it is unclear whether this occurs through altered absorption and/or excretion. The purpose of this study was to investigate the effects of a high-impact and resistance-training exercise program versus a period of restricted physical activity on urinary calcium excretion. Ten healthy, moderately active men (27.0 ± 5.8 yr) participated in a 3-wk randomized crossover study. Participants were assigned to complete either a period of daily participation in exercise including high-impact and resistance-training activities (EX) or a period of restriction in physical activity (NE) for 7 consecutive days. After a 1-wk washout period, participants completed the opposite trial. During both phases, participants consumed four 8-oz servings of low-fat (1%) milk daily and avoided other dietary and supplemental sources of calcium. Urine was collected throughout the final 72 hr of each study phase. Urinary calcium and sodium excretions were 14.7% ± 17.1% and 15.8% ± 9.9% lower (p < .05), respectively, during the EX phase than the NE phase. These results occurred despite participants consuming more (p < .05) sodium during the EX phase than the NE phase. These results suggest that healthy, moderately active men excrete significantly less urinary calcium concurrent with lower sodium excretion during a week of performing high-impact and resistancetraining exercises versus a week of restricted physical activity. The reduction in urinary loss of calcium might be at least partially responsible for improved bone mineralization that has been observed during periods of greater physical activity.
Tricia Nemoseck and Mark Kern
Katie J. Thralls, Jeanne F. Nichols, Michelle T. Barrack, Mark Kern and Mitchell J. Rauh
Early detection of the female athlete triad is essential for the long-term health of adolescent female athletes. The purpose of this study was to assess relationships between common anthropometric markers (ideal body weight [IBW] via the Hamwi formula, youth-percentile body mass index [BMI], adult BMI categories, and body fat percentage [BF%]) and triad components, (low energy availability [EA], measured by dietary restraint [DR], menstrual dysfunction [MD], low bone mineral density [BMD]). In the sample (n = 320) of adolescent female athletes (age 15.9± 1.2 y), Spearman’s rho correlations and multiple logistic regression analyses evaluated associations between anthropometric clinical cutoffs and triad components. All underweight categories for the anthropometric measures predicted greater likelihood of MD and low BMD. Athletes with an IBW ≤85% were nearly 4 times more likely to report MD (OR = 3.7, 95% CI [1.8, 7.9]) and had low BMD (OR = 4.1, 95% CI [1.2, 14.2]). Those in <5th percentile for their age-specific BMI were 9 times more likely to report MD (OR 9.1, 95% CI [1.8, 46.9]) and had low BMD than those in the 50th to 85th percentile. Athletes with a high BF% were almost 3 times more likely to report DR (OR = 2.8, 95% CI [1.4, 6.1]). Our study indicates that low age-adjusted BMI and low IBW may serve as evidence-based clinical indicators that may be practically evaluated in the field, predicting MD and low BMD in adolescents. These measures should be tested for their ability as tools to minimize the risk for the triad.