Exercise has been proposed as one strategy for improving or maintaining the structural competence of bone. In contrast with previous densitometric analysis using dual energy x-ray absorptiometry (DXA) which reported that areal bone mineral density (aBMD ; bone mineral content per projected area) increased with exercise, the studies using peripheral quantitative computed tomography (pQCT) revealed that an improvement in the mechanical properties of adult bone in response to exercise is related to negative changes in volumetric BMD (vBMD ; bone mineral content in a unit volume). Therefore, if exercise does not increase vBMD, what does it change? The pQCT studies showed that periosteal area and cortical area were significantly greater in trained bone, together with an increase in cortical thickness. Furthermore, by assessing geometric bone adaptation to mechanical loading, cortical thickness and the mechanical properties of trained and sedentary bone were compared along 64 directions centering the center of gravity of the bone on cross-sectional pQCT images. The differences in these parameters for both groups depended on the direction of measurement, suggesting that site-specific adaptation of bone to exercise is related to the geographical relation of bone to muscle. Thus, the improvement in the mechanical properties of bone in response to long-term physical exercise is related to geometric adaptation and not vBMD.
The purpose of this study was to examine the relation between body composition and athletic performance of long distance relay runners in a four week weight reduction program. Six male collegiate runners, aged 19.0 ± 0.9 years, participated in this study. Body water content and fat free mass (FFM) were measured by bioelectrical impedance spectroscopy. The weight loss by 4.1% of the initial body weight consisted of decreases in FFM and fat mass (54% and 46% respectively). Percentage of body fat did not change significantly by the end of the fourth week. The total body water (TBW) loss comprised of intracellular water (ICW) and extracellular water (ECW) at the end of the fourth week, and TBW loss and FFM loss were nearly the same values. Isokinetic muscular strength of right thigh, maximal oxygen intake (VO2max) and total treadmill running time (maximal workout time) measured did not show any significant change. These results indicate (1) half of the weight loss consisted of decrease in FFM, (2) TBW loss was due to the reduction of ICW and ECW, (3) the content of FFM loss was considered to be body water, and (4) there was no impact on muscular strength of right thigh, VO2max or maximal workout time.
This study was conducted to examine the prevalence of undernourished elderly in community-dwelling elderly people, and to analyze the correlation between under-nutritional status and health status and physical fitness of the elderly. The subjects comprised 1758 residents (757 men and 1001 women) aged 70 or over living in Itabashi-ku, Tokyo, who took part in an interview and biochemical blood examination as part of the “OTASHA-KENSHIN”. In this study, we set the ‘under-nutrition group’ as serum albumin level ≤ 3.8 g/dL (normal group serum albumin level ≥ 3.9 g/dL). Based on this standard, 124 subjects (72 men and 52 women) were found to be undernourished. Physical fitness was measured by handgrip strength, knee extension power, and walking capability (usual and maximal walking speed). The prevalence of undernourished elderly was significantly higher in men than in women, and in those living alone or with a spouse compared with those living with children. It became clear that the lifestyle and health status of the under-nutrition group was generally poor compared with those of the normal group. Handgrip strength and knee extension power were significantly lower in the under-nutrition group than in the normal group of men. Although usual and maximal walking speed tended to be lower in the under-nutrition group, there was no significant difference. In women, a significant difference in handgrip strength, knee extension power, and walking capability was not seen between the two groups. These results suggest that an intervention program for the undernourished elderly living in the community should target an improvement not only of nutrition but also of physical fitness.
It is well known that extreme repetitive stress on the apophysis without considering the physical characteristics of children induces a growth disorder of the growing skeleton. However, only a few studies have evaluated the indexes of the muscle-tendon complex as a risk factor of apophysitis. The purpose of this study was to investigate the relationship between the elastic properties of the Achilles tendon, physical characteristics, muscle tightness (MT) and general joint laxity score (GLP), and tenderness from typical apophysitis (calcaneal tubercle, tibial tuberosity and iliac spine) in kindergarten and elementary school students. Body and lower leg size, and MT of the calf muscle increased ; while GLP decreased significantly with age. The Elastic index of the Achilles tendon and its standard deviations were greater among 5th and 6th graders than among 3rd and 4th graders. Point tenderness was more frequent in older age groups (4th-6th graders) than in younger age groups (kindergartren-3rd graders) and was greatest in 4th graders. When subjects were categorized into groups with and without point tenderness, no significant differences were found between GLP, muscle tightness of gastrocnemius, quadriceps and iliopsoas. However subjects who showed point tenderness had a higher Elastic index (p=0.07). Considering the pathomechanics of apophysitis, repetitive traction of the apophysis by a stiffer muscle-tendon unit lead to injury of the apophysis and growth plate. Tendon properties appear to be more sensitive to the pathomechanics of apophysitis.