記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：AMER PHYSIOLOGICAL SOC  

The knee extension exercise (KE) model engenders different muscle and fiber recruitment patterns, blood flow, and energetic responses compared with conventional cycle ergometry (CE). This investigation had two aims: 1) to test the hypothesis that upright two-leg KE and CE in the same subjects would yield fundamentally different pulmonary O-2 uptake (p(V)over dotO(2)) kinetics and 2) to characterize the muscle blood flow, muscle (V)over dotO(2) (m(V)over dotO(2)), and p(V)over dotO(2) kinetics during KE to investigate the rate-limiting factor(s) of p(V)over dotO(2) on kinetics and muscle energetics and their mechanistic bases after the onset of heavy exercise. Six subjects performed KE and CE transitions from unloaded to moderate [<ventilatory threshold (VT)] and heavy (>VT) exercise. In addition to p(V)over dotO(2) during CE and KE, simultaneous pulsed and echo Doppler methods, combined with blood sampling from the femoral vein, were used to quantify the precise temporal profiles of femoral artery blood flow (LBF) and m(V)over dotO(2) at the onset of KE. First, the gain (amplitude/work rate) of the primary component of p(V)over dotO(2) for both moderate and heavy exercise was higher during KE (similar to12 ml.W-1.min(-1)) compared with CE (similar to10), but the time constants for the primary component did not differ. Furthermore, the mean response time (MRT) and the contribution of the slow component to the overall response for heavy KE were significantly greater than for CE. Second, the time constant for the primary component of m(V)over dotO(2) during heavy KE [25.8+/-9.0 s (SD)] was not significantly different from that of the phase II p(V)over dotO(2). Moreover, the slow component of p(V)over dotO(2) evident for the heavy KE reflected the gradual increase in m(V)over dotO(2). The initial LBF kinetics after onset of KE were significantly faster than the phase II p(V)over dotO(2) kinetics (moderate: time constant LBF=8.0+/-3.5 s, p(V)over dotO(2)=32.7+/-5.6 s, P<0.05; heavy: LBF=9.7±2.0 s, p(V)over dotO(2)=29.9±7.9 s, P<0.05). The MRT of LBF was also significantly faster than that of p(V)O-2. These data demonstrate that the energetics (as gain) for KE are greater than for CE, but the kinetics of adjustment (as time constant for the primary component) are similar. Furthermore, the kinetics of muscle blood flow during KE are faster than those of p(V)over dotO(2), consistent with an intramuscular limitation to (V)over dotO(2) kinetics, i.e., a microvascular O-2 delivery-to-O-2 requirement mismatch or oxidative enzyme inertia.

DOI： 10.1152/ajpregu.00147.2004

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：PORTLAND PRESS  

The purpose of the present study was to define the influence of age and exercise training on the heart rate (HR) dynamic response (i.e. kinetics) to sinusoidal work. A total of 63 healthy subjects (31 men and 32 women; age range 19-69 years) underwent a three-step incremental work test, during which peak oxygen uptake (VO2peak) was estimated by the YMCA method. Sinusoidal work varying between 20% and 60% of HRreserve was employed for periods of I, 3, 6, 9 and 12 min. HR was monitored in a beat-by-beat manner with a cardiotachometer. The kinetics of the HR response were analysed by frequency analysis and estimated by a first-order transfer function with time constant (tau) and time delay (TD). Physical training status was estimated as stepping frequency, as measured with a pedometer during the daytime, and averaged over seven consecutive days. The mean response time of HR kinetics (HRMRT: tau pulse TD) tended to increase gradually with age (0.36 s(.)year(-1)), and linear regression analysis revealed that the correlation between HRMRT and age was significant (r = 0.31, P < 0.05), although not as highly significant as that between HRMRT and physical activity (r = -0.48, P < 0.0001). HRMRT was not related to the S. D. of HR variation (an indicator of parasympathetic mediation) at rest. In addition, VO2peak showed a significantly greater correlation with age (r = -0.60, P < 0.0001) than with physical activity (r = -0.14, not significant). In conclusion, these findings suggest that HR dynamics, which may depend on sympathetic nervous activity, are more sensitive to physical activity than to age, but that VO2Peak, as estimated by the age-associated decline in maximum HR, is unrelated to physical training status.

DOI： 10.1042/CS20010059

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：AMER PHYSIOLOGICAL SOC  

The dependence of O-2 uptake ((V) over dot o(2)) kinetics on the muscle mass recruited under conditions when fiber and muscle recruitment patterns are similar following the onset of exercise has not been determined. We developed a motorized cycle ergometer that facilitated one-leg (1L) cycling in which the electromyographic (EMG) profile of the active muscles was not discernibly altered from that during two-leg (2L) cycling. Six subjects performed 1L and 2L exercise transitions from unloaded cycling to moderate [<ventilatory threshold (VT)] and heavy (>VT) exercise. The 1L condition yielded kinetics that was unchanged from the 2L condition [the phase 2 time constants (tau (1), in s) for <VT were as follows: 1L = 16.8 +/- 8.4 (SD), 2L = 18.4 +/- 8.1, P > 0.05; for >VT: 1L = 26.8 +/- 12.0; 2L = 27.8 +/- 16.1, P > 0.05]. The overall (V) over dot o(2) kinetics (mean response time) was not significantly different for the two exercise conditions. However, the gain of the fast component (the amplitude/work rate) during the 1L exercise was significantly higher than that for the 2L exercise for both moderate and heavy work rates. The slow-component responses evident for heavy exercise were temporally and quantitatively unaffected by the 1L condition. These data demonstrate that, when leg muscle recruitment patterns are unchanged as assessed by EMC analysis, on-transient ire, kinetics for both moderate and heavy exercise are not dependent on the muscle mass recruited.

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記述言語：日本語   掲載種別：研究論文（学術雑誌）  

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出版者・発行元：1  

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記述言語：英語   出版者・発行元：Taylor and Francis  

DOI： 10.4324/9780203613771

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記述言語：英語   出版者・発行元：AMER PHYSIOLOGICAL SOC  

Chin LM, Kowalchuk JM, Barstow TJ, Kondo N, Amano T, Shiojiri T, Koga S. The relationship between muscle deoxygenation and activation in different muscles of the quadriceps during cycle ramp exercise. J Appl Physiol 111: 1259-1265, 2011. First published July 28, 2011; doi:10.1152/japplphysiol.01216.2010.-The relationship between muscle deoxygenation and activation was examined in three different muscles of the quadriceps during cycling ramp exercise. Seven young male adults (24 +/- 3 yr; mean +/- SD) pedaled at 60 rpm to exhaustion, with a work rate (WR) increase of 20 W/min. Pulmonary oxygen uptake was measured breath-by-breath, while muscle deoxygenation (HHb) and activity were measured by time-resolved near-infrared spectroscopy (NIRS) and surface electromyography (EMG), respectively, at the vastus lateralis (VL), rectus femoris (RF), and vastus medialis (VM). Muscle deoxygenation was corrected for adipose tissue thickness and normalized to the amplitude of the HHb response, while EMG signals were integrated (iEMG) and normalized to the maximum iEMG determined from maximal voluntary contractions. Muscle deoxygenation and activation were then plotted as a percentage of maximal work rate (%WR(max)). The HHb response for all three muscle groups was fitted by a sigmoid function, which was determined as the best fitting model. The c/d parameter for the sigmoid fit (representing the %WR(max) at 50% of the total amplitude of the HHb response) was similar between VL (47 +/- 12% WR(max)) and VM (43 +/- 11% WR(max)), yet greater (P < 0.05) for RF (65 +/- 13% WR(max)), demonstrating a "right shift" of the HHb response compared with VL and VM. The iEMG also showed that muscle activation of the RF muscle was lower (P < 0.05) compared with VL and VM throughout the majority of the ramp exercise, which may explain the different HHb response in RF. Therefore, these data suggest that the sigmoid function can be used to model the HHb response in different muscles of the quadriceps; however, simultaneous measures of muscle activation are also needed for the HHb response to be properly interpreted during cycle ramp exercise.

DOI： 10.1152/japplphysiol.01216.2010

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記述言語：日本語   出版者・発行元：日本体力医学会  

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記述言語：英語   掲載種別：研究発表ペーパー・要旨（国際会議）   出版者・発行元：FEDERATION AMER SOC EXP BIOL  

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