RESUMEN
This study aimed to develop affective experience, attitude, and behavioral intention scales for exercise, and examine their associations with exercise behavior. A web-based questionnaire survey was conducted among 500 individuals aged 60 to 69 years at baseline. The survey measured respondents’ affective experiences, attitude, behavioral intention, exercise behavior, and demographic factors. The same survey was conducted 2 weeks (n = 345) and 1 year later (n = 338). Exploratory and confirmatory factor analyses showed that the factor structures of the affective experience (2 factors: 3 items each for positive experience and negative experience), attitude (2 factors: 3 items each for affective attitudes and instrumental attitudes), and behavioral intention scales (2 factors: 4 items each for intention to maintain behavior and intention to overcome barriers) were acceptable. For these scales, the Cronbach’s alpha coefficients ranged from 0.69 to 0.92, Pearson’s correlation coefficients for baseline and 2-week follow-up ranged from 0.51 to 0.81, and Cohen’s d values for the associations with exercise behavior ranged from 0.46 to 0.98. After adjusting for demographic factors and exercise behavior at baseline, structural equation modeling showed that an affective attitude toward exercise at baseline significantly predicted exercise behavior at 1-year follow-up (standardized coefficient = 0.27), and that the affective attitude was predominantly explained by the positive affective experience of exercise (standardized coefficient = 0.80). The results confirmed the validities and reliabilities of the scales. Positive affective experiences and affective attitudes may be important determinants of exercise behavior.
RESUMEN
Under the condition that entrainment between breathing rate and exercise rhythm was minimized. The limitation for deciding anaerobic threshold (AT) by respiratory frequency (f) was studied. Ten healthy subjects (5 male and 5 female) have volunteered to take part in two incremental cycle exercises (male : 30 watt/2 min, 50 rpm ; female : 20 watt/2 min, 50 rpm) . The subjects were either sedentary or active and performed tests under two different condi-tions. The different conditions are explained below.<BR>1) Condition M : Use a metronome to maintain pedalling frequency so entrainment would easily occur.<BR>2) Condition S : Use a tachometer to maintain pedalling frequency so entrainment would not easily occur.<BR>Oxygen uptake (VO<SUB>2</SUB>) at AT were determined by two different methods. The first method was to detect the point of non-linear increase in minute ventilation (VE) and carbon dioxide output (VCO<SUB>2</SUB>) and then to increase detection in the ventilatory equivalent for O<SUB>2</SUB> (VE/VO<SUB>2</SUB>) without increasing the ventilatory equivalent for CO<SUB>2</SUB> (VE/VCO<SUB>2</SUB>) (AT-V) . The second method was to detect inflection in f by multisegment linear regression (AT-CF) . There were no significant differences between AT-V (condition M : 26.0±6.2, condition S : 26.4±6.0 m<I>l</I>/kg/ min) and AT-CF (condition M : 31.6±10.2, condition S : 24.7±10.0 m<I>l</I>/kg/min) . A significant positive correlation between AT-V and AT-CF was observed in condition S (r=0.850, p< 0.05), but not in condition M (r=0.563, p>0.05) . The error between AT-V and AT-CF had individual variations. An error within±5% was observed in only 4 out of 10 subjects. These results suggested that even though the ability to detect AT using f is superior in condition S, f is an inadequate indicator for the AT, though the exercise entrained breathing is minimized.
RESUMEN
Circadian rhythms (diurnal variations) in many physiological parameters have been reported. However, there are no data on gas exchange kinetics at the onset of exercise. The purpose of this study was to establish whether there are circadian rhythms in gas exchange kinetics at the onset of exercise.<BR>Six male subjects performed 120W exercise on a cycle ergometer for 7 min in the morning (AM; 7: 30-8: 30) and evening (PM; 16: 30-17: 30) . Rectal temperature (Tr) and mean skin temperature (T<SUB>sk</SUB>) at rest were significantly higher PM than AM, the differences being 0.9±0.2°C and 0.7±0.2°C, respectively. Respiratory and circulatory parameters at rest and during exercise were not different between AM and PM. The time constants of oxygen uptake (Vo<SUB>2</SUB>), carbon dioxide output (Vco<SUB>2</SUB>), minute ventilation (V<SUB>E</SUB>), heart rate (HR), and oxygen pulse (Vo<SUB>2</SUB>/HR) showed the same results. There was no relationship between temperature parameters (Tr, T<SUB>sk</SUB>) and the time constants.<BR>It is suggested that circadian rhythms reflected by the change in body temperature do not have any effect on gas exchange kinetics at the onset of moderate bicycle exercise.
RESUMEN
Amplitude and phase response of ventilation (V<SUB>E</SUB>), carbon dioxide output (VCO<SUB>2</SUB>) and oxygen uptake (VO<SUB>2</SUB>) during sinusoidally varying work load for periods (T) of 1-16 min were studied in six healthy men. The relationships between these parameters and aerobic capacity (VO<SUB>2</SUB>max, ATVO<SUB>2</SUB>) were also examined. The results and conclusions obtained were as follows:<BR>(1) The relationship between the period (T) of exercise and amplitude response of VO<SUB>2</SUB>, VCO<SUB>2</SUB> and V<SUB>E</SUB> was well described by first-order exponential models. However, the relationship between the period of exercise and the phase shift (phase responses of VO<SUB>2</SUB>, VCO<SUB>2</SUB>, and V<SUB>E</SUB>) was better described by complex models comprising a first-order exponential function and a linear equation. This can be explained by Karpman's threshold theory.<BR>(2) High negative correlations were observed between the steady-state amplitude (A) of phase response or the time constants (r) of amplitude response and VO<SUB>2</SUB>max, and ATVO<SUB>2</SUB>. Significantly high negative correlations for all gas exchange parameters may be more rapid in individuals with greater aerobic capacity.<BR>(3) A close relationship between the response of VCO<SUB>2</SUB> and V<SUB>E</SUB> was demonstrated by a higher correlation coefficient than that between VO<SUB>2</SUB> and VCO<SUB>2</SUB> or between VO<SUB>2</SUB> and V<SUB>E</SUB>. This can be partly, but not completely, explained by the cardiodynamic theory.
RESUMEN
In order to evaluate the effect of muscle pump on blood circulation at the start and end of exercise, cardiac responses to pedaling exercise at 75 watt in the supine position were investigated under lower body negative pressure (LBNP) of -60mmHg. Six healthy male college students volunteered for subjects. Cardiac output (Q), stroke volume (SV), thoracic impedance (ZO) and heart rate (HR) were determined by using ensemble-averaged impedance cardiogram and ECG.<BR>The results obtained were as follows.<BR>1) By the initiation of exercise under LBNP, SV and Q promptly and more markedly increased and ZO decreased than the control experiment which were done under normal pressure. These changes were suggested to be caused by mobilization of previously pooled blood in the legs by muscle pump. Effects of muscle pump arrived to a plateau within about 30 sec after the start of exercise. And these effects were immediately disappeard by the cessation of exercise.<BR>2) By the release of LBNP during resting condition, the same changes were observed in SV, Q and ZO as in the start of exercise under LBNP. However HR decreased in the case while it increased in the case of exercise in LBNP. This difference in HR might be the result of the chronotropic effects by the exercise.<BR>3) In the very early phase of exercise in the control exercise, SV decreased and ZO increased. These changes were probably caused by superiority of chronotropic action by the exercise to increase in venous return in this position.<BR>These results led us to a conclusion that the effect of muscle pump appeares immediately by the start of the exercise and it arrives at plateau within about 30 sec. This effect is immediately disappeared by the cessation of exercise.
RESUMEN
The purpose of this study was to investigate the possible individual difference in temperature regulating ability during identical relative exercise load under various temperature environments.<BR>Seven healthy males, aged 21 to 26 years, performed bicycle ergometer exercise of 60% VO<SUB>2</SUB>max for 60 minutes. All exercises were carried out in a climatic chamber under the conditions of 15°C (RH=70%), 25°C (RH=55%) or 35°C (RH=45%) . Herat rate, O<SUB>2</SUB> consumption, pulmonary ventilation, rectal temperature, mean skin temperature, local sweat rate at the lower part of scapula and total sweat rate were determined intermittently through the experiments. Moreover, heat loss by evaporation, radiation, convection and effective sweat rate was calculated using the heat valance equations.<BR>The results obtained are as follows :<BR>1. The increase in rectal temperature at the end of exercise was almost identical in 15°C and 25°C but significantly higher in 35°C.<BR>2. A significant positive correlation was observed between mean skin temperature (ΔTsk) at the end of exercise and effective sweat rate (r=0.468, p<0.05) during exercise.<BR>3. Inspite of the equality of relative exercise intensity (60%VO<SUB>2</SUB>max), marked individual variations were observed in rectal temperature during exercise.<BR>4. The subjects who showed marked increase in rectal temperature during exercise showed less marked increase in mean skin temperature in 15°C and 25°C and less marked increase in local sweat rate in 35°C than other subjects.<BR>It would be concluded that the main cause of individual variation in rectal temperature during exercise depends on difference in evaporative heat loss in hot environment and difference in skin temperature in mild or cold environment.