Recently, bioelectrical impedance analysis systems (BIA) have become available for determination of human body composition. The validity of BIA has been found to be sufficiently in the American population. However, more work is needed to assess the validity and applicability of BIA to the Japanese population. The purposes of this study were (1) to test the validity of body composition measured by BIA in comparison with the underwater weighing criterion method, and (2) to develop a convenient equation that would reliably predict body composition using BIA and anthropometric measurements in Japanese females. The subjects were 226 Japanese women and girls aged 11 to 55 years (23.9±8.3) . Body impedance was measured using a tetrapolar electrode method, with a localized 800-μA and 50-kHz current injection (Selco SIF-881) . The percentage of body fat (%fat) estimated by BIA was significantly correlated with densitometrically determined %fat (r=0.793, Lukaski et al, method ; and r=0.800, Segal et al, method) . The magnitude of these correlations was substantially higher when compared with r=0.615 found between the skinfold thickness method and the criterion method. Absolute %fat values estimated by BIA were, however, significantly lower than those determined by the criterion method, thereby indicating the need for a more accurate method of assessing Japanese body composition. For this, we propose the use of D=1.1303-0.0726 (Wt×R/Ht2), where D=body density in g/ml, Wt=body weight in kg, R= (R2+Xc2) 0.5 in ohms, and Ht=body height in cm. Lean body mass (LBM) and %fat predicted from this equation were correlated significantly (r=0.924 and r=0.799, respectively) with values determined by densitometry. The standard error of estimates of LBM and %fat resulted in figures of 1.9 kg and 3.7%, respectively. Thus we suggest that BIA is valid, convenient, and inexpensive, and that the prediction equation proposed in this study is useful for assessment of body composition in Japanese adult females.
The effects of exercise training on bone development in growing rats were studied using the photon-absorption method and histomorophological analyses. Thirty-seven male Wistar strain rats at 4 wks of age were divided into five groups : sedentary control (C; N=7), 15 min/day training (T 15 ; N=6), 30 min/day training (T 30 ; N=8), 60 min/day training (T 60 ; N=8) and 120 min/day training (T 120 ; N=8) . All rats in these training groups were subjected to a treadmill running at a speed of 30 m/min, 5 days/wk for 11 wks. The results of our study were summarized as follows : 1) Fat-free dry weight of the tibia was significantly heavier in T 30, T 60 and T 120 than C and T 15, respectively. 2) Bone mineral content (mg/cm) of tibial midshaft in all T groups was significantly higher than that in C group, respectively, while no differences were found between any of the training groups. 3) On histological parameters of cross-sectional samples from tibia, such as cortical area, total area and appositional growth rate on periosteum, higher values were observed in T groups compared with C group. These results suggest that physical training induce markedly facilitative girth growth associated with elevated bone formation of periosteum in the tibia, and moreover, the daily exercise duration does not change the degree of bone hypertrophy.
The effect of swimming training on creatine ki nase (CK) isoenzyme compositions (cytoplasmic CK : CK-MM, -MB, -BB ; mitochondrial CK : m-CK) of coleus (SOL), extensor digitorum longus (EDL) and heart muscles were studied. Wistar strain male rats were trained by swimming at a water temperature of 38±2°C, loaded with a weight equal to 5% of their body weight attached to their tails, and made to swim 4-days per week from the age of 4 weeks old for 4, 6 and 8 weeks. CK isoenzyme compositions of SOL, EDL and heart were different from those of other muscles. The activities of CK-MB and m-CK of SOL, EDL and heart increased following exercise training. CK isoenzyme composition of skeletal muscle (SOL and EDL) tended to qualitatively resemble the heart with training. These results suggest that the training-induced metabolic change in skeletal muscle causes similar CK isoenzyme composition to the heart muscle, and ensure energy production for the continuous muscle contraction during endurance exercise. The possibility that the source of the increased serum CK-MB activity after exercise is from the skeletal muscle should be examined thoroughly when the high serum CK-MB activity is interpreted.