THE RELATIONSHIP BETWEEN CARDIAC MUSCLE, SKELETAL MUSCLE MASS, AND VESSEL STRUCTURE IN ELDERLY WOMEN / 体力科学

The purpose of this study was to clarify the relationship between left ventricular muscle mass, skeletal muscle volume and vessel structures in elderly women (n=15, 76.0±5.4 years). We measured the thigh muscle thickness, and brachial and common carotid arterial diameter using B-mode ultrasound method. Posterior wall thickness, interventricular septal thickness, left ventricular end-diastolic internal diameter, and aorta artery were measured by B-mode echocardiography. No significant relationship was obtained between brachial and common carotid arterial diameters, and aortic diameter. On the other hand, significant correlation coefficients were obtained between cardiac muscle thickness and thigh muscle thickness (r=0.674, p<0.01). A significant correlation coefficient was also obtained between the estimated skeletal muscle volume and left ventricular mass [LVmass](r=0.542, p<0.05). The slope of regression equation between estimated thigh muscle volume and LVmass in elderly women in this study was (y=0.11x+75.65) steeper than in children (y=0.06x+14.02) reported previously. These results indicate that the ventricular muscle (LVmass) is closely related to the skeletal muscle volume in ordinary elderly women and skeletal muscle mass at a given LVmass is smaller in elderly women than children.

CHANGES IN BRACHIAL AND FEMORAL ARTERY VASCULAR CONDUCTANCE IN NON-EXERCISING LIMBS DURING HANDGRIP EXERCISE / 体力科学

The purpose of this study was to determine the difference in vascular conductance changes in brachial and femoral artery (BVC, FVC) of non-exercising limbs during handgrip exercise at different intensities. Six subjects performed rhythmic handgrip exercise, which consisted of 2-second contraction and 2-second relaxation at the intensities of 15%, 30%, and 45% of maximal voluntary contraction (MVC). Brachial and femoral artery blood flow (Doppler ultrasound method) of non-exercising limbs, blood pressure, and heart rate were measured. The BVC during exercise at lower intensities (15% and 30%MVC) and FVC during exercise at any of three intensities did not change significantly. However, BVC significantly decreased at 45%MVC when the exercise was continued to longer than 60% of maximal endurance time (P<0.05). These results suggest that FVC of the non-exercising limb dose not change during handgrip exercise at the intensity lower than 45%MVC, but BVC of the non-exercising limb change during handgrip exercise depending on the exercise intensity and duration.

BLOOD FLOW AFTER CONTRACTION OF SHORT DURATION REACHES ITS PEAK BY 3^rd CARDIAC CYCLE / 体力科学

The purpose of this study was to elucidate how long it takes to reach peak blood flow after muscle contractions in consideration of the cardiac cycle. Seven healthy female subjects performed two successive dynamic plantar flexions of 1-s duration at 30, 50 and 70% of maximal voluntary contraction (MVC). Based upon the blood flow response after a single contraction, we set up intervals during two successive contractions each corresponding to 10% (10 I), 30% (30 I) and 50% (50 I) of the time required to reach peak blood flow. Upon cessation of contraction, the popliteal artery blood flow (Qpa) increased progressive, beat-by-beat increase and peaked by the 5^th cardiac cycle, for all conditions. The highest peak blood flow among the cardiac cycle was at 3^rd cycle in overall data. Peak Qpa values reached after exercise did not differ among intervals, whereas peak Qpa value attained after exercise was significantly greater in 50 and 70%MVC than 30%MVC (p<0.05). The result indicates that the augmentation of the Qpa after exercise with short duration differed with the exercise intensity but the timing for reaching peak post-exercise value did not differ in terms of the number of cardiac cycles.

Cardiac output and active limb blood flow responses to unilateral and bilateral dynamic handgrip exercise / 体力科学

The purposes of this study were 1) to determine cardiac output and active limb blood flow responses to unilateral and bilateral dynamic handgrip exercises and 2) to investigate the effects of exercise intensity and a change in active muscle mass on the relationship between limb blood flow and cardiac output. Five physically active women performed dynamic handgrip exercises with the right hand (right handgrip exercise ; RHG), with the left hand (left handgrip exercise ; LHG), and bilaterally (bilateral handgrip exercise ; BHG) . Exercise intensities were 10%, 30% and 50% of the subjects' maximum voluntary contraction (MVC) and the exercise frequency was 60 contractions per minute. The 10%MVC exercise duration was 10 min, while the 30% and 50%MVC exercise conditions were performed to exhaustion. During exercise, stroke volume (SV) and heart rate (HR) were measured using Doppler ultrasound and electrocardiogram (ECG), respectively. Cardiac output (Q<SUB>sys</SUB>) was calculated as the product of SV and HR. Blood flow to the forearm (Q<SUB>foream</SUB>, ) was measured by venous occlusion plethysmography. Q<SUB>sys</SUB>, did not differ significantly between RHG, LHG and BHG. However, SV was lower in BHG than in RHG and LHG. Reciprocally, HR was higher during BHG than RHG and LHG. The increase in the Q<SUB>forearm</SUB>, was significantly lower during BHG than RHG and LHG exercise (p<0.05) .<BR>These results suggest that Q<SUB>sys</SUB>, does not differ between unilateral and bilateral handgrip exercise, despite the increase in active muscle mass. The unchanged Q<SUB>sys</SUB> could be explained by the Q<SUB>forearm</SUB> reduction during BHG. The Q<SUB>forearm</SUB> was lower during BHG than during the unilateral handgrip exercises, possibly due to vasoconstriction induced by BHG exercise.