Gas exchange kinetics during constant-load exercise were measured to investigate the possibility that excess CO₂ output during exercise might not be dependent on hyperventilation. Five healthy males performed twelve minutes of cycle exercise, including two minutes of 0 W pedaling, at 20, 40, 50, 60, 70, and 80% of their maximal work rate (WRmax) determined on the basis of preliminary ramp exercise of 30 W/min. Minute ventilation, O₂ uptake, and CO₂ output were measured breath-by-breath. Excess CO₂ output and CO₂ stores were calculated, assuming that the respiratory quotient (RQ) in tissue is constant during constant-load exercise and that the respiratory exchange ratio at the mouth level is equal to the RQ during the steady-state phase. Excess CO₂ output was observed at levels of WR greater than 40% WRmax after initial CO₂ storage, where VC_O2/V_E decreased gradually as though in parallel with the kinetics of CO₂ storage. VO₂/V_E, however, appeared to be constant after the initial peak. These data suggest that V_E is closely correlated with V_O2 rather than V_CO2 during constant-load exercise, indicating that excess CO₂ output to compensate lactate production is independent of hyperventilation.

A study was conducted to ascertain the relationship between oxygen uptake (Vo₂) and vertical velocity using a pedal-stepping stair simulator. Ten healthy volunteers performed fbur kinds of graded exercise using a stair simulator (SS), whose pitches were set at 80, 100, and 120 beat⋅min^-1, and also an electrically braked bicycle ergometer (BE) . Work rate on the SS was detemined on the basis of the vertical pedal velocity, in accord with the climbingvelocity for stairs. The incremental rate was set at 0.34 W⋅kg^-1 every 3 min. Heart rate and Vo₂ were measured during the final minute of every stage. Both heart rate and Vo₂ during SS were significantly lower than those on BE at the same level of work intensity. Regression equations between Vo₂ (ml⋅kg^-1⋅min^-1) and velocity (v: m⋅s^-1) were as follows;
pitch 80: Vo₂=1.00×v+0.06
pitch 100: Vo₂=0.88×v+1.58
pitch 120: Vo₂=0.84×v+2.13
These equations give a lower value of Vo₂ than the previous equation based on stair-climbingvelocity reported by the American College of Sports Medicine. Although the individual relationship between Vo₂ and heart rate was closely linear, there was a significant effect ofexercise mode and stepping pitch. These results indicate that the work intensity of pedalstepping exercise with a stair simulator is overestimated if it is calculated based on theprevious equation for stair-climbing.

A study was conducted to investigate the effect of exercise intensity on the recovery of autonomic nervous activity after exercise. Ten subjects performed four kinds of 10-min cycle exercise with target heart rates of 100, 120, 140, and 160 beats/min (THR 100, THR 120, THR 140 and THR 160, respectively) following 5 min of exercise to increase the heart rate to the target level. The beat-by-beat variability of the R-R interval was recorded throughout the experiment including the 5-min pre-exercise control period and the 30-min recovery period. Spectral analysis (fast Fourier transform) was applied to every 5-min R-R interval data set before, during ( 5-10 min) and after exercise at the target heart rate. The low- (0.05-0, 15 Hz : P₁) and high- (0, 15-1.0 Hz : P_h) frequency areas were calculated to evaluate sympathetic (SNS) and parasympathetic (PNS) nervous activities as P₁/P_hand P_h, respectively. During exercise, SNS of THR 160 was significantly higher, and PNS of THR 140 and THR 160 was significantly lower than the respective pre-exercise values (p<0.05) . Althouglt all indicators recovered to, or overshot the pre-exercise values at 20-30 min after THR 100 and THR 120, heart rate and SNS were still higher and PNS was still lower than the pre-exercise value after THR 160. These results suggest that the recovery of cardiac autonomic nervous activity is slower after high-intensity exercise than after low-intensity exercise, and that the recovery of autonomic nervous activity after acute exercise does not always corrrespond linearly on the exercise intensity.

The purpose of this study was to compare the thigh muscle oxygenation state of competitive road cyclists and non-cyclists during varied pedaling frequency cycling. Six male college road cyclists (CY group) and five male students (NC group) performed four sets of cycling bouts, consisting of 2 minutes of warm up (60 rpm, 50 watts) followed by 5 minutes of pedaling (150 watts) using an electro-magnetic braked cycle ergometer at 40, 60, 90, and 120 rpm. Oxygenated hemoglobin and/or myoglobin (Oxy-Hb/Mb) and deoxygenated Hb/Mb (Deoxy-Hb/Mb) concentrations in the vastus lateralis were measured by near infrared spatially resolved spectroscopy. The Oxy-Hb/Mb level was significantly higher in the CY group than the NC group. But there was no significant intraction effect of the group and pedaling rate on the Oxy-Hb/Mb level. These results suggest that the changes in muscle oxygenation state according to pedaling cadence do not differ between cyclists and non-cyclists. And though the whole body work efficiency decreased according to increasing pedaling cadence, Oxy-Hb/Mb and Deoxy-Hb/Mb levels in the vastus lateralis remained unchanged up to 90 rpm. However, at 120 rpm, the Oxy-Hb/Mb level decreased remarkably and the Deoxy-Hb/Mb level increased. These results suggest that deoxygenation in the vastus lateralis at 120 rpm was higher than that for lower frequencies. And, conversely, oxygen uptake in the vastus lateralis might have increased steeply at 120 rpm. It may be that the maximum pedaling cadence that would not reduce work efficiency in the vastus lateralis is around 90 rpm.

Evidence from Western countries suggests that built environmental attributes can influence the physical activity participation in adults, but whether or not this is the case for Chinese is unknown. Also, the strength of the relationship of environment to physical activity may differ by age group. The present study examined age-related differences in associations between perceived neighborhood environment and walking in Chinese women dwelling in Beijing. Cross-sectional data were collected through an internet-based survey. Total of 737 women aged 30 to 59 years responded. All of them were then divided into three groups based on the age: aged from 30-39, from 40-49 and from 50-59. In addition to socio demographic information, the perceived neighborhood environment was measured by Neighborhood Environment Walkability Scale Questionnaire, and their walking time per week was collected through International Physical Activity Questionnaire. To measure relationship between perceived neighborhood environment and walking time, partial correlations were computed, adjusting for socio demographics. Walking time was significantly related to residential density in aged 40-49 years, and land use mix-access, walking/cycling facilities, traffic safety variables in aged 50-59 years. The present study indicates that there would be differences in associations between neighborhood attributes by age-groups. Future, public health promotion of walking activity and the design of interventions need to consider the contribution of neighborhood level built environment influences.

Porpose: Physical inactivity is a modifiable risk factor for many chronic diseases. In China, inactive lifestyle is increasing yearly on Chinese adults by rapid economic development which produces their lifestyle changes. Thus, we investigated the prevalence and socio-demographic correlates of meeting the physical activity recommendation among Chinese adult internet users.Methods: Data were analyzed for 1394 Chinese adults who responded an internet based cross-sectional survey. The International Physical Activity Questionnaire Chinese version was used to determine whether the individuals met the physical activity recommendation (150minutes/week) on the ACSM/AHA guideline. Demographic data (gender, age, marital status, employment status, educational level, annual income level, and body mass index) were also obtained. A multivariate logistic regression analysis was utilized.Results: Overall, 87.3% of respondents met the physical activity recommendation. Age and annual income were significantly associated with meeting the physical activity recommendation. Women aged 40-49 years were more likely to meet the physical activity recommendation than those aged 30-39 years (OR = 2.12). Women with annual incomes of 40000∼50000 Yuan were more likely to meet the physical activity recommendation than those with annual incomes of 30000 Yuan or less (OR = 2.40).Conclusion: The high prevalence rate and different socio-demographic correlates of meeting physical activity recommendation were observed among Chinese adults compared with these in developed countries. Specific strategies accounting for such socio-demographic correlates may be needed for effectively promoting physical activity among Chinese adults.

A study was conducted to investigate the determinants of exercise intensity using a rowing ergometer from the viewpoint of effects on oxygen uptake. Eight healthy males performed incremental exercises for three minutes at each intensity on a rowing ergometer and a bicycle ergometer, which were controlled to exert a constant preset power. Rowing pitches were set at 17, 20 and 25 strokes/min. Mechanical power for the rowing ergometer, heart rate, and oxygen uptake were measured during the final minute of each respective stage at the set load. The mechanical power which was actually exerted on the rowing ergometer increased with the rowing pitch, even though it was controlled at a constant level for each respective set load. Oxygen uptake increased with rowing pitch as well as the set load. Multiple regression analysis revealed that the rowing pitch had a greater effect on oxygen uptake than the set load. Gross efficiency varied widely with the set load, from 3.6% to 18.7%, which was a lower range than that for a bicycle ergometer. The relationship between individual heart rate and oxygen uptake for rowing exercise was similar to that for cycling exercise, indicating that heart rate is preferable for the precise prescription of exercise intensity on a rowing ergometer if the HR-VO₂ relationship is previously determined.

Spectral analysis was applied to investigate whether the system for control of heart rate (HR) is influenced by exercise intensity. Five healthy males performed incremental exercise on an electrically braked cycle ergometer until exhaustion. The work rate was increased at 12 W/min following 2 min of exercise at a constant load of 20 W. HR was measured every second from R-R intervals. The power spectrum was calculated every 10 s using the FFT method for 64 consecutive data points. Power spectra during 20 W exercise showed a similar pattern to those in previous reports on resting HR perturbations, Although interindividual differences were observed for the spectrum patterns related to exercise intensity, there was a characteristic pattern revealing dissipation of the spectral power above a frequency of 0.2 Hz for all subjects. This pattern was not maintained for more than 1 min in any of the subjects, and was followed by a semirandom pattern whose magnitude varied among the subjects. These results support the hypothesis that the cardiac pacemaker is influenced by exercise intensity, presumably due to sympatho-vagal interaction with the respiratory control system.