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.

Effects of spontaneous wheel running on the rate of fatty acid synthesis in viva was studied. Adult female rats were housed in a sedentary condition or free access to a running wheel for 50 days.
The weight gain of the exercising rats was slower than that of the sedentary rats. At the end of 50 days free access to the running wheel, the body weight of sedentary rats was 285±8g and that of the exercising rats was 263±5g. This difference in body weight between sedentary and exercising rats was mainly due to the difference in an amount of body fat (47±5g vs. 31±3g) . The weight of the parametrial adipose tissue of the sedentary rats was 6.1±1.0 g and that of the exercising rats was 2.8± 0.6 g. The diameter of adipocytes of the exercising rats was smaller than that of the sedentary rats (118±9 μm v.s. 150±7 μm) on the other hand there was no significant difference in adipocyte number between the both groups.
At the end of 50 days free access to a running wheel, the rats were injected intraperitoneally ³H₂O to determine the total rate of fatty acid synthesis. The rats were killed 60 minutes after the injection and the amount of ³H incorporated from ³H₂O into fatty acid in a parametrial adipose tissue and liver was determined. The amount of fatty acid synthesized was calculated from the amount of ³H incorporated into fatty acid and the specific radioactivity of water in serum. Because it is known that the rate of fatty acid synthesis fluctuates within a day, we measured the rate of fatty acid synthesis during the light and dark period. The rate of fatty acid synthesis in adipose tissue of the exercising rats was higher than that of the sedentary rats in both light and dark period (light period : 21.8±5.2 v.s. 6.6±1.7, dark period: 53.5±10.3 vs. 18.2±5.2μ mol C-2 units/tissue/h) . The rate of fatty acid synthesis in liver of the exercising rate was higher than that of the sedentary rats during dark period (480± 79 v.s. 283 ±50 μ mol C-2 units/tissue/h) . During the light period, there was a same tendency in fatty acid synthesis in the liver (230±30 v.s. 197±44) .

A whole body indirect calorimeter provides accurate measurement of energy expenditure and the respiration quotient over long periods of time, but has limitations to assess dynamic changes in energy metabolism due to the small amplitude of the signal in relation to the size of the room. The present study aimed to improve algorithm for the whole body indirect calorimetry by adopting a deconvolution with a regularization parameter. Performance of the new algorithm was compared with trends identification (Med. & Biol. Eng. & Comput 34 : 212, 1996) against four validation tests. In a simulated problem, in which metabolic rate cycled with a period of 20 min, mean square errors (MSEs) computed at every 1 min by the deconvolution (0.0036 for O₂ consumption and 0.0017 for CO₂ production) were smaller than those for trends identification algorithms (0.0198 and 0.0142). Deconvolution algorithm clearly separated individual CO₂ infusion of 8 min intervals, while trends identification could no longer separate them. During the validation by ethanol combustion, which produced a near-steady state condition, the deconvolution (MSEs were 0.0022 for O₂ consumption and 0.0010 for CO₂ production) performed better than trends identification algorithms (MSEs were 0.0086 and 0.0041). When validated against direct measurement of gas production rate during non-steady state condition, produced by a human subject intermittently exercising in the calorimeter, deconvolution (MSEs were 0.0032 for O₂ consumption and 0.0038 for CO₂ production) performed better than trends identification algorithms (0.0182 and 0.0167). The new algorithm significantly improved transient response of the whole body indirect calorimeter.

[Objective] This study examined the effects of resting metabolic rate (RMR), sleeping metabolic rate (SMR), and diet-induced thermogenesis (DIT) during acute weight loss in elite male wrestlers.[Methods] Subjects were elite male wrestlers (n=6), who were instructed to reduce the body weight in seven days. RMR, SMR, and DIT were measured by indirect calorimetry in normal training phase and after rapid weight loss. Body composition and energy intake were also measured.[Results] Energy intake significantly decreased in rapid weight loss phase (P<0.05). After the rapid weight reduction, percent reduction of body weight (-4.4%), fat mass (-17.5%), and total body water (-3.2%) significant compare with that of normal training phase (P<0.05). RMR(-15.2%), and SMR (-11.8%) significantly decreased during acute weight loss (P<0.05). DIT(-89.4%) tended to be decrease during acute weight loss.[Conclusion] The present study suggests that rapid weight loss in elite male wrestlers causes decreases in RMR and SMR.

The present study was conducted to obtain basic information about blood glucose fluctuation and relation with race performance during 100 km marathon. Subcutaneous glucose of one well-trained runner was measured by continuous glucose monitoring system (CGMS) at 5 min interval and blood samples for biochemical analysis were drawn at pre, middle and post of the race. Energy balance during one week prior to the 100 km race was recorded, and the whole energy and fluid intake during the race was analyzed. Blood glucose fluctuated reflecting duration of exercise and energy supply during the race. During the latter part of the race (65–70 km), abrupt declines in blood glucose level, which reflected insufficient carbohydrate intake before the race (119 g), were accompanied by decrease in running speed. The present report suggests that continuous glucose monitoring supplemented with standard nutritional and physiological measurement provides precise and valuable information on runner’s energy state during the ultra-endurance race, and that athletes need to reassess their preparation for the race and planning of energy intake during the race.

The present study was conducted to examine whether gene expression of the insulin signaling pathway is activated in response to a single bout of exercise. Adult male rats underwent a single bout of treadmill exercise for 90 min at 22 m/min on a 6°C incline. The animals were sacrificed immediately after exercise or after a predetermined post-exercise recovery period of up to 48 h, and the level of mRNA in the gastrocnemius muscle was measured by the RT-PCR method. Immediately after exercise, mRNA levels of insulin signal transduction intermediates in the gastrocnemius muscle were lower in the exercise group than in the controls. Following this tendency reduction, mRNA levels of insulin receptor, IRS-1, PI 3-kinase, SH-PTP2 and Nck were higher in the exercise group than in the controls. The levels of PI 3-kinase mRNA was significantly higher in the exercise group than in the controls within 6 h after exercise, while levels of mRNA for insulin receptor, IRS-1, SH-PTP2 and Nck were significantly higher in the the exercise group than in the controls at 48 h after exercise. Gene expression of oncogenes was also affected by a single bout of exercise. Levels of c-fos and c-myc mRNA were significantly higher than in the controls immediately after exercise, while the level of c-jun mRNA was lower in the exercise group at 3 h after exercise. Thus, a single bout of exercise affects the gene expression of insulin signal transduction pathway intermediates and oncogenes in rat gastrocnemius muscle. The present findings suggest that an exercise-induced adaptive increase of skeletal muscle insulin sensitivity is a cumulative effect of a single bout of exercise on the gene expression of insulin signal transduction pathway intermediates.

The present study was conducted to obtain basic information about blood glucose fluctuation and relation with race performance during 100 km marathon. Subcutaneous glucose of one well-trained runner was measured by continuous glucose monitoring system (CGMS) at 5 min interval and blood samples for biochemical analysis were drawn at pre, middle and post of the race. Energy balance during one week prior to the 100 km race was recorded, and the whole energy and fluid intake during the race was analyzed. Blood glucose fluctuated reflecting duration of exercise and energy supply during the race. During the latter part of the race (65–70 km), abrupt declines in blood glucose level, which reflected insufficient carbohydrate intake before the race (119 g), were accompanied by decrease in running speed. The present report suggests that continuous glucose monitoring supplemented with standard nutritional and physiological measurement provides precise and valuable information on runner’s energy state during the ultra-endurance race, and that athletes need to reassess their preparation for the race and planning of energy intake during the race.

Side to side difference in tennis players' mid-radius and cross-sectional study on mid-tibia of jumpers and sedentary controls suggest that the improvement of mechanical properties of cortical bone in response to long-term exercise is related to geometric adaptation and not to volumetric bone mineral density. In the present study, geometric and mechanical properties of right tibia were estimated along 64 directions centering center of gravity of the bone on cross-sectional peripheral quantitative computed tomography (pQCT) images. The tibias of 17 jumpers (7 females, 10 males) and 15 controls (8 females, 7males), aged 18-23, were scanned at mid site using pQCT. Periosteal and endocortical radius were larger, cortical thickness was thicker, and mechanical properties (moment of inertia of area and strength strain index) were greater in jumpers compared to those of controls. The differences in cortical thickness between the two groups were dependent on direction of measurement. Defined a direction from tibia's center of gravity to fibula's as 0°, difference in the cortical thickness between jumpers and controls was the greatest at around 240°. Along this direction, differences in mechanical properties were also the most significant, suggesting that the site-specific adaptation of bone to long-term exercise is due to geographical relation of bone to muscle.