The Influence of the Type of Continuous Exercise Stress Applied during Growth Periods on Bone Metabolism and Osteogenesis

BACKGROUND: In this study, we examined the influence of exercise loading characteristics on bone metabolic responses and bone morphology in the growth phase and adulthood. METHODS: Running exercise (RUN) and jumping exercise (JUM) were used for the exercise loading in 28-day-old male Wistar rats. Bone metabolism was measured by blood osteocalcin (OC) and tartrate-resistant acid phosphatase (TRACP) levels. For bone morphology, the maximum bone length, bone weight, and bone strength of the femur and tibia were measured. RESULTS: A pre- and post-exercise loading comparison in the growth phase showed significantly increased OC levels in the RUN and JUM groups and significantly decreased TRACP levels in the JUM group. On the other hand, a pre- and post-exercise loading comparison in adulthood showed significantly decreased TRACP levels in the RUN and JUM groups. Femur lengths were significantly shorter in the RUN and JUM groups than in the control (CON) group, while bone weight was significantly greater in the JUM group than in the CON group. CONCLUSIONS: Exercise loading activates OC levels in the growth phase and suppresses TRACP levels in adulthood. On the other hand, these results suggest that excessive exercise loading may suppress bone length.

INFLUENCE OF PERCENT BODY FAT WITH AND WITHOUT WATER IN BIOELECTRICAL IMPEDANCE ANALYSIS / 体力科学

Measuring the bioelectrical impedance (BI) is a simple and non-invasive method for estimating body fat or muscle mass. However, body impedance is affected by variations in the distribution of body fluid without reference to actual body fat or muscle mass. Twenty healthy college students (10 males, 10 females; mean age 21.0±2.3 years) participated in the study. Their mean body mass index was 20.7±2.6 kg/m². Bipolar electrodes were place on all extremities, and InBody 3.0^TM (Biospace Co., Ltd., Seoul, Korea) was used to measure bioelectrical impedance. Each subject remained in a supine position on a comfortable bed between 07:00 and 12:00 except for excretion and measurement of BI. BI was measured hourly using frequencies ranging from 5 to 500 kHz. The subjects refrained from eating, drinking and exercising between 07:00 and 12:00 during the first week of measurements, and drank 6.7 ml/kg of water at 07:00 after the first measurement of BI during a subsequent week of measurements. Bioelectrical impedance was higher in female subjects in all body segments and conditions (<i>p</i><0.01). BI in the right arm was lower than that in the left in all participants (<i>p</i><0.001). The difference between the highest and lowest BI among six measurements was largest in the upper extremities, followed by the lower extremities. Differences in the coefficient of variation CV values of the right arm of both females and males at 50, 250, and 500 kHz during fasting were significantly smaller than after drinking water. Hydration had no effect on the differences in the CV values of the body trunk and lower extremity BI or BI at lower frequencies. BI indicates the possibility of remarkable decrease in variation in the upper extremity BI at higher frequencies by taking 6.7 ml/kg of water at get up and enables minimizing the estimate error of body fat percentage.