RELATIONSHIP BETWEEN MUSCLE PROPORTION AND QUANTITY OF EXTREMITIES IN YOUNG JAPANESE WOMEN / 体力科学

Recently, a long-term health concern has been identified in young Japanese women. These women have a high percentage of body fat despite a normal shape index indicator such as BMI. This condition is called marked obesity, and shows relative low lean body mass. Using an analogous determination, we investigated low percentage of muscle quantity (LM) in the extremities of young Japanese women (n=156) . The cross-sectional areas of muscle, subcutaneous fat, and bone were measured in the upper arm and thigh using ultrasonography. Extremity shape index (CSA<SUB>t</SUB>/L) was defined as the total extremity cross-sectional area (CSA<SUB>t</SUB>) divided by the length of the limb (L), Percent muscle in each extremity (% MA) was calculated from the ratio of muscle CSA to whole limb CSA. LM was defined as the percentage of muscle in the upper arm or thigh less than 1 SD below average and the limb shape index less than 1 SD above average. Nine of 91 subjects displayed LM for the upper arm. A similar proportion of subjects showed LM for the thigh (15/156) . The muscle mass and strength in the upper arm or thigh were compared between the subjects with LM and non-LM subjects with a similar shape index of extremity. There was a tendency towards lower muscle mass and muscle strength in the subjects with LM. From the same comparison, the subjects with LM showed a greater load on extremity muscles to sustain the body weight (i.e., body weight per unit of upper arm or thigh muscle CSA) . To mitigate the deleterious health consequences of low percent muscle quantity it is recommended that young Japanese women who display such a condition should participate in a resistance-training program.

A cross-sectional study of the size and strength of the thigh muscles in sedentary 259 japanese adults / 体力科学

Thigh muscle cross-sectional area (CSA) and maximum voluntary isometric strength of knee extensor and flexor muscles were measured in 97 men (2065 years) and 162 women (2069 years) in sedentary Japanese adults. Each subject was assigned to one of five age groups (3<SUP>rd</SUP> 4<SUP>th</SUP> 5<SUP>th</SUP> 6<SUP>th</SUP> and 7<SUP>th</SUP> decade) . Thigh muscle CSA was estimated by our developmental measuring system using an ultrasonographic device, which was connected to a PC for graphical processing. Muscle CSA for the 7<SUP>th</SUP> decade in men was significantly smaller than that for the 3<SUP>rd</SUP> decade. For women, muscle CSA were no significant from the 3<SUP>rd</SUP> to the 7<SUP>th</SUP> decade. The isometric knee extensor strength showed a significant decline with age from the 7<SUP>th</SUP> decade in men, whereas there was no significant change with age in women. Isometric strength of knee flexors in men showed a gradual decline from the 5<SUB>th</SUB> decade. The aging-associated reduction of muscle strength per muscle CSA in the extensors and flexors started from the 6<SUB>th</SUB> decade in men. It was concluded that the size and strength of the thigh muscles begin to decrease simultaneously by approximately the 6<SUB>th</SUB> decade in men, whereas there are no change until the 7<SUP>th</SUP> decade in women.

Breath-by-breath differences between exercise gas exchange kinetics measured at the mouth and those estimated at the alveolar level / 体力科学

In order to study respiratory transients during exercise, we examined breath-by-breath differences between gas exchange kinetics measured at the mouth and those estimated at the alveolar level. The gas exchange data at the mouth were obtained by measurement of expired gases only (expiratory flow method) . Correction for breath-by-breath changes in lung gas stores was applied to the total gas exchange, which was obtained by subtracting expired from inspired gas volume (alveolar gas exchange method) . Constant work loads (150, 200, 250 W) and a ramp work load (30 W/min) preceded and followed by a 50 W load were generated by a computerized cycle ergometer. Best-fit first- or second-order model values for gas exchange kinetic parameters were found by the non-linear least-squares method.<BR>1. Regardless of work intensity and forcing function, the breath-by-breath variation in gas exchange measured at the mouth was larger than the gas exchange estimated at the alveolar level, in both a non-steady state and a steady state. The variation was caused by the invalidity of assuming zero N<SUB>2</SUB> exchange at the mouth, which was attributed to changes in lung volume.<BR>2. Vo<SUB>2</SUB> kinetics at the alveolar level were faster than those at the mouth, while the converse held for Vco<SUB>2</SUB> at the onset of constant load work, due to the effects of fluctuations in lung gas stores on the kinetics of gas exchange at the mouth. During ramp load work, Vo<SUB>2</SUB> and Vco<SUB>2</SUB> kinetics at the alveolar level were faster than those at the mouth.<BR>3. Steady state gas exchange values at the alveolar level and at the mouth were the same during constant load work, since the lung gas stores corrections added up to small fractions of the total gas exchange when summed over the long term.<BR>4. Consideration of both the proper end-expiratory lung volume and ventilationperfusion inhomogeneity was required in order to estimate the true alveolar gas exchange.