Retraction: PREDICTION MODELS OF SARCOPENIA IN JAPANESE ADULT MEN AND WOMEN / 体力科学

The purpose of this study was to develop prediction models of sarcopenia in 1,894 Japanese men and women aged 18-85 years. Reference values for sarcopenia (skeletal muscle index, SMI; appendicular muscle mass/height2, kg/m2) in each sex were defined as values two standard deviations (2SD) below the gender-specific means of this study reference data for young adults aged 18-40 years. Reference values for predisposition to sarcopenia (PSa) in each gender were also defined as values one standard deviations (1SD) below. The subjects aged 41 years or older were randomly separated into 2 groups, a model development group and a validation group. Appendicular muscle mass was measured by DXA. The reference values of sarcopenia were 6.87 kg/m2 and 5.46 kg/m2, and those of PSa were 7.77 kg/m2 and 6.12 kg/m2. The subjects with sarcopenia and PSa aged 41 years or older were 1.7% and 28.8% in men and 2.7% and 20.7% in women. The whole body bone mineral density of PSa was significantly lower than in normal subjects. The handgrip strength of PSa was significantly lower than in normal subjects. Stepwise regression analysis indicated that the body mass index (BMI), waist circumference and age were independently associated with SMI in men; and BMI, handgrip strength and waist circumference were independently associated with SMI in women. The SMI prediction equations were applied to the validation group, and strong correlations were also observed between the DXA-measured and predicted SMI in men and women. This study proposed the reference values of sarcopenia in Japanese men and women. The prediction models of SMI using anthropometric measurement are valid for alternative DXA-measured SMI in Japanese adults.

PREDICTION MODELS OF SARCOPENIA IN JAPANESE ADULT MEN AND WOMEN / 体力科学

The purpose of this study was to develop prediction models of sarcopenia in 1,894 Japanese men and women aged 18-85 years. Reference values for sarcopenia (skeletal muscle index, SMI; appendicular muscle mass/height², kg/m²) in each sex were defined as values two standard deviations (2SD) below the gender-specific means of this study reference data for young adults aged 18-40 years. Reference values for predisposition to sarcopenia (PSa) in each gender were also defined as values one standard deviations (1SD) below. The subjects aged 41 years or older were randomly separated into 2 groups, a model development group and a validation group. Appendicular muscle mass was measured by DXA. The reference values of sarcopenia were 6.87 kg/m² and 5.46 kg/m², and those of PSa were 7.77 kg/m² and 6.12 kg/m². The subjects with sarcopenia and PSa aged 41 years or older were 1.7% and 28.8% in men and 2.7% and 20.7% in women. The whole body bone mineral density of PSa was significantly lower than in normal subjects. The handgrip strength of PSa was significantly lower than in normal subjects. Stepwise regression analysis indicated that the body mass index (BMI), waist circumference and age were independently associated with SMI in men; and BMI, handgrip strength and waist circumference were independently associated with SMI in women. The SMI prediction equations were applied to the validation group, and strong correlations were also observed between the DXA-measured and predicted SMI in men and women. This study proposed the reference values of sarcopenia in Japanese men and women. The prediction models of SMI using anthropometric measurement are valid for alternative DXA-measured SMI in Japanese adults.

Effects of Water Immersion on Systemic Cardiovascular Responses During Recovery Period Following Steady State Land Exercise / 体力科学

The aim of this studv was to clarify the effects of water immersion on the cardiovascular recovery process following submaximal steady state exercise on land. Seven male subjects (23 yrs old) underwent experiments under four separate conditions on separate days (15 minutes of cycling exercise at 50% and 80% maximal oxygen consumption followed by 16 minutes of recovery in a sitting position in water and out of water) . Concerning conditions in water, mean water temperature was 29.4 degrees, and the immersion level was set at xiphoid. Mean room temperature in out of water conditions, and during all conditions of exercise, was 24.4 degrees. Oxygen consumption (VO<SUB>2</SUB>), heart rate (HR) and blood pressure (systolic: SBP, diastolic: DBP) were measured under each condi tion. Mean blood pressure was calculated from SBP and DBP (MBP=1/3× ( SBP-DBP) +DBP) . Stroke volume (SV) was measured by Doppler echocardiography, and then cardiac output (CO=SV×HR), total peripheral resistance (TPR=NIBP/CO) and arteriaVmixed venous oxygen difference (a-v O<SUB>2</SUB>diff=VO<SUB>2</SUB>/CO) were calculated. In comparison with the same exercise intensity condition, there were no significant differences between recovery processes of VO<SUB>2</SUB>, HR, SBP, DBP and MBP in and out of water. SV and CO were significantly higher (p<0.05) during the recovery process in water than out of water (SV: at 50 and 80% maximal oxygen consumption conditions, CO: at 80% condition) . The TPR and a-v O<SUB>2</SUB>diff were significantly lower (p<0.05) during the recovery process in water than out of water at 80% oxygen consumption condition. These results indicate that water immersion facilitates circulating blood volume during the recovery process without increasing blood pressure, especially during recovery after high intensity exercise. Therefore, we suggest that increased left ventricular preload with immersion would be an important factor in cardiovascular regulation not only at rest but also during recovery after exercise.

Effect of Different frequencies of Skipping Rope on Elastic Components of Muscle and Tendon in Human Triceps Surae / 体力科学

The purpose of this study was to clarify the effects of different frequencies of skipping rope on the elastic components of muscle and tendon in human triceps surae. Six male subjects performed ten rounds of skipping rope. Skipping tempos were with in a range of 100-170 skips per minute (SPM) . The vertical ground reaction force and the surface EMG of triceps surae muscles were recorded during each skipping round. Elastic components of muscle and tendon were estimated by Residual Time (RT : lag time difference between the vanishing point of muscle discharge and disappearance of EMG, and the end of the ground reaction force wave) and RTintegrate (integration of ground reaction force while RT still appears) . RT and RTintegrate at 100 SPM were the smallest values for all jump frequencies. On the other hand, integrated EMG (iEMG) at 100 SPM was the largest value for all jump frequencies. Although RT and RT<SUB>integrate</SUB>progressively increased as SPM was increased, iEMG correspondingly decreased. Rate in utilization of elastic components of muscle and tendon assessed by RT<SUB>integrate</SUB>at 170 SPM corresponds to 150% at 100 SPM. These results suggest that the rate in utilization of the elastic components of muscle and tendon while skipping rope, depend on jump frequency.

The relationship between resting bradycardia with endurance training and autonomic nervous system modulation / 体力科学

We investigated whether the autonomic nervous system (ANS) modulation contribute to the bradycardia induced by endurance training. First, the meta-analysis approach was used to collect group mean values of maximal oxygen consumption (Vo<SUB>2</SUB>max) and heart rate variability (HRV) from 14 studies involving 30 groups and 485 subjects. Subsequently, we performed a cross-sectional (n=116) and intervention (n=training group : 10 and control group : 6) studies. In both studies, ANS modulation was estimated by spectral analysis of HRV. In the meta-analysis and cross-sectional study, HR and natural logarithmic high frequency power (In HF power) were correlated with Vo<SUB>2</SUB>max or peak oxygen uptake (peak Vo<SUB>2</SUB>) . The significant negative correlations were found between HR and In HF power (meta-analysis and the cross-sectional study ; r<SUP>2</SUP> = 0.42 and 0.44, respectively) . Endurance training in the intervention study increased peak Vo<SUB>2</SUB> and resting In HF power, and decreased resting HR. These results strongly suggest that endurance training induces an increase in resting ANS modulation especially parasympathetic modulation. Furthermore, about half of the variability of resting HR can be accounted for by difference in parasympathetic modulation.