Investigation of factors affecting the rate of changes in endurance exercise performance by pre-cooling with ice slurry / 体力科学

To investigate the factors affecting the rate of improvement in endurance exercise performance following pre-cooling with ice slurry, we focused on individual physical characteristics and thermoregulatory capacity. Twenty-four healthy adults (12 males and 12 females) ingested 7.5g kg-1 of either ice slurry at -1°C (ICE) or control water at 20°C (CON) before cycling at 55% VO2max and continued cycling until the rectal temperature reached 38.5°C or untill exhaustion in a hot environment (controlled at 38°C, 40% relative humidity). The relationship between the rate of improvement in exercise performance and physical characteristics and thermoregulatory factors (changes in rectal temperature, the rate of rectal temperature increase, whole body sweat loss, mean metabolic heat production, and heat storage) was investigated. No correlation was noted between the rate of improvement in exercise performance and physical characteristics and heat storage. On the other hand, the rate of improvement in exercise performance showed significant correlations with changes in rectal temperature (r = -0.497), the rate of rectal temperature increases during exercise (r = -0.784), whole body sweat loss (r = 0.407), and mean metabolic heat production (r = -0.436). The rate of inhibition of sweating and the rate of increase in metabolic heat production by ice slurry ingestion during exercise have been suggested to be related to the rate of improvement in exercise performance. On the other hand, there was no relationship between body composition or VO2max and the rate of improvement in exercise performance.

Effects of hydrogen bathing on exercise-induced oxidative stress and delayed-onset muscle soreness / 体力科学

Several studies have reported that molecular hydrogen (H₂) acts as a therapeutic medical gas owing to scavenging reactive oxygen species (ROS). However, little is known about effects of H₂ on exercise-induced oxidative stress. The purpose of this study was to investigate the effects of weekly hydrogen bathing on exercise-induced oxidative stress and delayed-onset muscle soreness (DOMS). Nine healthy and active young men participated in this study, and each subject performed hydrogen bathing trial and placebo bathing trial in a crossover design. The subjects performed downhill running (8 % decline) at 75 % peak oxygen uptake (VO₂peak) for 30 min, and each subjects conducted hydrogen or placebo bathing for 20 min, respectively, 1-6 days after downhill running. Before and after exercise, we measured visual analogue scale (VAS) and collected blood samples (Pre- and 5 min, 60 min after the end of bathing, 1day, 2days, 3days, 7days after downhill running). Blood sample analyses include creatine kinase (CK), myoglobin (Mb), malondialdehyde (MDA), reactive oxygen metabolites (d-ROMs), biological antioxidant potential (BAP), myeloperoxidase (MPO), interleukin-6 (IL-6), interleukin-17a (IL-17a) and lactate concentrations. Weekly hydrogen bathing had no effects of exercise-induced oxidative stress and muscle damage. On the other hand, hydrogen bathing significantly reduced DOMS (VAS) 1 and 2days after downhill running (p=0.033). These findings suggest that hydrogen bath after downhill exercise can be effective for reduction of DOMS.

Age Differences in the Relation of Perceived Neighborhood Environment to Walking among Chinese adult women dwelling in urban area / 体力科学

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.

SOCIO-DEMOGRAPHIC CORRELATES OF MEETING THE PHYSICAL ACTIVITY RECOMMENDATION AMONG CHINESE ADULT INTERNET USERS / 体力科学

<b>Porpose:</b> 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.<b>Methods:</b> 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.<b>Results:</b> 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).<b>Conclusion:</b> 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.

EFFECTS OF CARBONATED AND NONCARBONATED BEVERAGE INTAKES IN RESPONSE TO PROLONGED CYCLE ERGOMETER EXERCISE / 体力科学

Athletes have been instructed to refrain from taking carbonated beverages in the sports world, but the mechanism has not been clear. The purpose of this study was to clarify how physiological and biochemical evaluation are affected by taking a 10% CHO carbonated beverage after cycle ergometer (60 min, 60% VO₂max). Seven subjects consumed a carbonated or noncarbonated (10% carbohydrate) beverage after exercise. No differences were observed in concentration of glucose, insulin, free fatty acids, K and Na in serum from carbonated beverage compared with noncarbonated beverage intakes after exercise.These results indicate that carbonated beverage did not affect the changes of physiological and biochemical parameter after prolonged exercise, and it could be more refreshing and stimulate taste rather than noncarbonated beverage, but seemed to be hard to drink immediately after exercise because it made subjects feel as if having drunk more than they did.

A COMPARISON OF CYCLISTS AND NON-CYCLISTS' THIGH MUSCLE OXYGENATION STATE DURING PEDALING / 体力科学

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.

Effects of Group-Versus Home-Based Walking Intervention on Lifestyle Activity / 体力科学

The purpose of this study was to examine the effect of class walking on lifestyle activity. The subjects were recruited from the community around the university, and volunteered to eight weeks intervention. The intervention groups were 2 different walking program groups that included a class-walking group (A : n=32) and a voluntary walking group (B : n=31) ; and the control was a blood-pressure monitor group (C : n=22) . Only A group participated in a walking class with group instruction. Physical activity was measured by pedometer counts before the start of the intervention, during the 8-week intervention and again as follow up four months afterwards. In A group, the number of pedometer counts, during the group walking activity of the 5 th and 6 th weeks, was measured in order to evaluate the number of voluntary steps on the class-walking day. Although there was no significant difference among the three groups in daily activity before the intervention, the activity of A group (12367±3290) and B group (9988±3461) was significantly increased during the intervention. Also, there were significant differences between A and B, A and C. As for A group, the number of steps due to group walking (9025±584 steps) enhanced the daily activity on the class-walking days (16191±3988 steps), but significantly attenuated the voluntary steps on the class-walking days (7166±3988 steps), which did not significantly differ from the baseline of the daily activity. The number of steps on the non-class walking days (i. e. steps other than those taken on the class-walking day ; 11719±3454 steps) was not significantly different than that of B. There was significant enhancement of daily activity 4 months after the intervention for A (11487±4057) and B (9564±2545 steps), but not for C (9070±3485 steps), compared to the baseline. There was not a significant difference between the daily activity of A and B after the intervention. These data suggest that the instruction given and the steps taken in class walking enhance daily activity during the intervention period, and that voluntary steps play a more important role in whether or not one remains active and adheres to regular exercise.

A Comparison between cyclists and noncyclists of joint torque of the lower extremities during pedaling / 体力科学

The purpose of this study was to compare the effect between cyclists and noncyclists of pedal rates on ankle, knee, and hip joint torque during pedaling exercises. Six male cyclists (CY) and seven male noncyclists (NC) pedaled at 40, 60, 90 and 120 rpm with a power output of 200 W. The lower limb was modeled as three rigid segment links constrained to plane motion. Based on the Newton-Euler method, the equation for each segment was constructed and solved on a computer using pedal force, pedal, crank, and lower limb position data to calculate torque at the ankle, knee, and hip joints. The average planter flexor torque decreased with increasing pedal rates in both groups. The average knee extensor torque for CY decreased up to 90 rpm, and then leveled off at 120 rpm. These results were similar to NC. The average knee flexor torque in both groups remained steady over all pedal rates. The average hip extensor torque for CY decreased significantly up to 90 rpm where it showed the lowest value, but increased at 120 rpm. For NC, the average hip extensor torque did not decrease at 90 rpm compared with 60 rpm, and was significantly higher than CY at 120 rpm (CY : 28.1 ± 9.0 Nm, NC : 38.6 ± 6.7 Nm, p<0.05) . The average hip flexsor torque for NC at 120 rpm increased significanly from 90 rpm, and was significantly higher than CY (CY : 11.6±2.9 Nm, NC : 22.6±11.8 Nm, p<0.05) . These results suggest that it would be better for cyclists to select a pedal rate of between 90 to 110 rpm to minimize joint torque, and, as a result, reduce peripheral muscle fatigue.

Effect of frutose ingestion before and during prolonged exercise on subsequent maximal exercise performance / 体力科学

The purpose of this study was to examine the effect of fructose ingestion on maximal exercise performance capacity following prolonged steady-state exercise compared with glucose or placebo ingestion, in 7 male college students (age 23.3±0.7 yr, height 171.3±1.9 cm, weight 68.4±1.4 kg, Vo2max 3.5±0.2 L/min, mean ± SEM) . The subjects cycled constantly on an ergometer at 59± 2 % Vo2max for 100 min divided in the middle by a 5-min rest, and then performed 10 min of all-out self-paced cycling. They ingested either 8 % fructose solution (F), 8 % glucose solution (G) or artifi-cially sweetened placebo (P) before and during exercise (at 20, 40, 65, 85 mm) . Before exercise and at 50 and 100 min of exercise and 5 min after the performance ride, blood samples were collected for determination of the concentrations of blood lactate, serum glucose and serum FFA. In the G trial, the serum FFA level was significantly lower than in the P and F trials at any of the time points dur-ing and after exercise (vs. P ; p<0.01, vs. F ; p<0.05) . However, glucose ingestion maintained serum glucose at a significantly higher level during and after exercise than placebo ingestion (p< 0.01) and improved the total work output in the 10-min performance ride (G vs. P ; 135± 8 KJ vs. 128± 8 KJ, p<0.05) . Although in the F trial, the serum FFA level was elevated during exercise compared to that in the G trial and the serum glucose level was significantly higher than in the P trial (vs. P ; p<0.01), the blood lactate level after exercise was lower than in the G trial and total work output was similar to that in the P trial (123± 8 KJ, vs. G ; p<0.01) . These results indicate that fructose ingestion before and during exercise cannot improve the ability to perform high-intensity exercise late in prolonged exercise despite maintaining the serum glucose level.

Metabolic and hormonal responses to prolonged intermittent exercise / 体力科学

The purpose of this study was to compare the influence of prolonged continuous (CON) and intermittent (INT) exercises on metabolic and hormonal responses in 8 male college students (age ; 23.0±0.5 yr, weight; 67.7±1.5 kg, VO<SUB>2</SUB>max ; 2.8±0.1 L/min, mean±SE) . Both trials consisted of two 40 min cycling bouts divided by a 5-min rest period. The intensity of INT was alternated every 4 min at low intensity (25% VO<SUB>2</SUB>max) and high intensity (75% VO<SUB>2</SUB>max), whereas the intensity of CON was maintained at 50% VO<SUB>2</SUB>max. Blood samples were collected before, and after 40 and 80 min of exercise, to determine blood lactate, serum glucose, FFA, insulin, plasma adrenaline and noradre-naline. Perceived exertion (RPE) was assessed at 40 and 80 min of exercise using the Borg scale. Although the changes in the concentration of plasma noradrenaline and serum insulin from basal values were similar in INT and CON, the degree of increase in plasma adrenaline during INT was significantly smaller than that during CON (90.5±16.6 vs. 152.8±27.0 pg/ml, p<0.05, after 80 min of exercise) . There was no difference in the change in the serum glucose level between the two trials. However, serum FFA in INT was significantly smaller than that in CON after 40 min (0.28±0.06 vs. 0.10±0.04 mEq/l, p<0.05) and 80 min (0.54±0.08 vs. 0.33±0.07 mEq/l, p<0.05) of exercise. RPE did not differ between the trials. These data indicate that even if performed total work and exercise duration are the same, metabolic and hormonal responses during prolonged intermittent exercise differ from those during continuous exercise.

Effect of high-speed resistance training on muscle cross-sectional area and speed of movement / 体力科学

A conducted to determine 1) the effect of high-velocity movement in resistance training with a constant load on the velocity of movement after training and 2) the differences in the effect on muscle hypertrophy according to training velocity. Fourteen of the total subjects (male; n=10, female ; n=7) were placed in the experimental group and agreed to participate in 8 weeks of training sessions (4 times a week) . Five of the 17 subjects were in control a group before the training session. Subjects performed elbow extension and flexion exercise using 50% of one repetition maximum (% 1 RM) load. The exercise session consisted of 6 sets of 10 repetitions and 30s of rest was taken between the sets. The subjects in the experimental group trained their arms using two different protocols ; one was high-velocity movement performed as rapidly as possible (Type R), the other was low-velocity movement performed at a constant and slow velocity (Type S) . Isokinetic torque in elbow flexion was measured at angular velocities of 60, 180, 300 deg/s, respectively, during elbow flexion performed under different constant loads of 0, 30, 50% 1 RM, and the muscle cross-sectional area (CSA) of the elbow flexor was determined before and after training. It was found that Type R did not increased isokinetic torque at 300 deg/s significantly after training. However, the increase in angular velocity of elbow flexion in Type R exercise tended to be higher than in Type S exercise. The increase in CSA [Type S; 11.2%, Type R ; 14.2%] was significantly higher in Type R exercise (p<0.05) . These results suggest that high-velocity movement with a constant load in resistance training might increase the angular velocity of movement in the same mode, but might not produce a change in isokinetic strength, which involves a different mode of muscle contraction. Muscle hypertrophy would be induced to a greater extent by high-velocity movement than by low-velocity movement in resistance training with a constant load.

Effect of exercise intensity on autonomic nervous system activity during and after acute exercises / 体力科学

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 : P<SUB>1</SUB>) and high- (0, 15-1.0 Hz : P<SUB>h</SUB>) frequency areas were calculated to evaluate sympathetic (SNS) and parasympathetic (PNS) nervous activities as P<SUB>1</SUB>/P<SUB>h</SUB>and P<SUB>h</SUB>, 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.

Work intensity during pedal-stepping exercise determined using a stair simulator based on vertical velocity / 体力科学

A study was conducted to ascertain the relationship between oxygen uptake (Vo<SUB>2</SUB>) 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<SUP>-1</SUP>, 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<SUP>-1</SUP> every 3 min. Heart rate and Vo<SUB>2</SUB> were measured during the final minute of every stage. Both heart rate and Vo<SUB>2</SUB> during SS were significantly lower than those on BE at the same level of work intensity. Regression equations between Vo<SUB>2</SUB> (m<I>l</I>⋅kg<SUP>-1</SUP>⋅min<SUP>-1</SUP>) and velocity (<I>v</I>: m⋅s<SUP>-1</SUP>) were as follows;<BR>pitch 80: Vo<SUB>2</SUB>=1.00×<I>v</I>+0.06<BR>pitch 100: Vo<SUB>2</SUB>=0.88×<I>v</I>+1.58<BR>pitch 120: Vo<SUB>2</SUB>=0.84×<I>v</I>+2.13<BR>These equations give a lower value of Vo<SUB>2</SUB> than the previous equation based on stair-climbingvelocity reported by the American College of Sports Medicine. Although the individual relationship between Vo<SUB>2</SUB> 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.

Excess CO2 output independent of hyperventilation during constant-load exercise / 体力科学

Gas exchange kinetics during constant-load exercise were measured to investigate the possibility that excess CO<SUB>2</SUB> 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, O<SUB>2</SUB> uptake, and CO<SUB>2</SUB> output were measured breath-by-breath. Excess CO<SUB>2</SUB> output and CO<SUB>2</SUB> 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 CO<SUB>2</SUB> output was observed at levels of WR greater than 40% WRmax after initial CO<SUB>2</SUB> storage, where VC<SUB>O2</SUB>/V<SUB>E</SUB> decreased gradually as though in parallel with the kinetics of CO<SUB>2</SUB> storage. VO<SUB>2</SUB>/V<SUB>E</SUB>, however, appeared to be constant after the initial peak. These data suggest that V<SUB>E</SUB> is closely correlated with V<SUB>O2</SUB> rather than V<SUB>CO2</SUB> during constant-load exercise, indicating that excess CO<SUB>2</SUB> output to compensate lactate production is independent of hyperventilation.

Power spectrum of heart rate fluctuations during incremental cycle exercise / 体力科学

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.

Determinants of exercise intensity using a rowing ergometer / 体力科学

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-VO<SUB>2</SUB> relationship is previously determined.