Chronic and acute inspiratory muscle loading augment the effect of a 6-week interval program on tolerance of high-intensity intermittent bouts of running.

This study examined the hypothesis that chronic (training) and acute (warm-up) loaded ventilatory activities applied to the inspiratory muscles (IM) in an integrated manner would augment the training volume of an interval running program. This in turn would result in additional improvement in the maximum performance of the Yo-Yo intermittent recovery test in comparison with interval training alone. Eighteen male nonprofessional athletes were allocated to either an inspiratory muscle loading (IML) group or control group. Both groups participated in a 6-week interval running program consisting of 3-4 workouts (1-3 sets of various repetitions of selected distance [100-2,400 m] per workout) per week. For the IML group, 4-week IM training (30 inspiratory efforts at 50% maximal static inspiratory pressure [P0] per set, 2 sets·d-1, 6 d·wk-1) was applied before the interval program. Specific IM warm-up (2 sets of 30 inspiratory efforts at 40% P0) was performed before each workout of the program. For the control group, neither IML was applied. In comparison with the control group, the interval training volume as indicated by the repeatability of running bouts at high intensity was approximately 27% greater in the IML group. Greater increase in the maximum performance of the Yo-Yo test (control: 16.9 ± 5.5%; IML: 30.7 ± 4.7% baseline value) was also observed after training. The enhanced exercise performance was partly attributable to the greater reductions in the sensation of breathlessness and whole-body metabolic stress during the Yo-Yo test. These findings show that the combination of chronic and acute IML into a high-intensity interval running program is a beneficial training strategy for enhancing the tolerance to high-intensity intermittent bouts of running.

Effects of 14-week Tai Ji Quan exercise on metabolic control in women with type 2 diabetes.

The present study investigated the effects of 14 weeks of practicing Tai Ji Quan (TJQ) on metabolic control and lipid metabolism in women with type 2 diabetes. Twenty Beijing female residents (57.4 +/- 6.2 years) were recruited and were randomly assigned to either the TJQ training or the control group. In the TJQ group, the exercise duration was 1 hour per day and 5 days a week for 14 weeks. FPG, GSP, FPI, TC, HDL-C, LDL-C, TG, resting blood pressures and heart rate were measured before and after the 14 weeks in the 2 groups. It was found that after 14 weeks, the TJQ group had significantly lower FPG, GSP, TG and higher FPI concentration, whereas there were no significant differences in TC, HDL-C and LDL-C. It was concluded that TJQ exercise could be used as an intervention tool to improve glycaemic control and serum TG level in the elderly people. Future research with TJQ of different styles and exercise of different intensities were recommended.

Effect of specific inspiratory muscle warm-up on intense intermittent run to exhaustion.

The effects of inspiratory muscle (IM) warm-up on the maximum dynamic IM function and the maximum repetitions of 20-m shuttle run (Ex) in the Yo-Yo intermittent recovery test were examined. Ten men were recruited to perform identical IM function test and exercise test in three different trials randomly. The control trial was without IM warm-up while the placebo and experimental trials were with IM warm-up by performing two sets of 30 breaths with inspiratory pressure-threshold load equivalent to 15% (IMW(P)) and 40% (IMW) maximum inspiratory mouth pressure, respectively. In IMW, maximum dynamic IM functions including the maximal inspiratory pressure at zero flow (P0) and maximal rate of P0 development (MRPD) were increased compared with control values (P < 0.05). The Ex was also augmented [mean (SD)] [19.5% (12.6)] while the slope of the linear relationship of the increase in rating of perceived breathlessness for every 4th exercise interval (RPB/4i) was reduced (P < 0.05). In IMW(P), although increase in Ex and reduction in RPB/4i were occurred concomitantly in some subjects, the differences in Ex, RPB/4i and dynamic IM functions between control and IMW(P) trials were not statistically significant. For the changes (Delta) in parameters in IMW and IMW(P) (n = 20), negative correlations were found between Delta RPB/4i and Delta Ex (r = -0.92), DeltaP0 and Delta RPB/4i (r = -0.48), and Delta MRPD and Delta RPB/4i (r = -0.54). Such findings suggested that the specific IM warm-up in IMW may entail reduction in breathlessness sensation, partly attributable to the enhancement of dynamic IM functions, in subsequent exhaustive intermittent run and, in turn, improve the exercise tolerance.

Reduced sensations of intensity of breathlessness enhances maintenance of intense intermittent exercise.

To identify the effect of normal breathlessness sensation elicited during intense intermittent exercise at exhaustion on limitation of exercise maintenance (Ex), the contribution of the flow-resistive unloading effect of normoxic helium-oxygen breathing on the breathlessness sensation to the change in the Ex was examined. Seven men repeatedly performed 12-s exercise at 160% maximal aerobic power output followed by passive recovery for 18-s under normal (CON) and unloaded (UL) breathing conditions until exhaustion. In UL, Ex was enhanced [mean (SD) 127.2 (11.8)% CON] concomitantly with reduction in averaged peak inhaled mouth pressure (PPmi) of recorded breathing cycles that reflected approximate true inspiratory muscle force output. At the iso-time point of CON exhaustion, the reduction in PPmi to [75.7(10.2)% CON] in UL was concomitant with the reductions in the rating of perceived breathlessness (RPB) [87.5 (13.1)% CON] and in the slope of time course for RPB (RPB/2-min period) [82.1 (17.2)% CON]. It was also concomitant with increases in ventilation and total oxygen consumption. However, the augmented oxygen consumption did not result in lowering of subjects' metabolic stress that was indicated by accumulations of blood lactate and plasma ammonia and uric acid. Nevertheless, the reductions in the RPB and RPB/2-min period, which reflected the breathlessness intensity, were correlated to the CON Ex enhancement in UL (RPB r=-0.57, RPB/2-min period r=-0.83; P<0.05). These findings implied that the normal noxious breathlessness sensation elicited during intense intermittent exercise at exhaustion might contribute to the limitation of subjects' exercise maintenance.

The cardiovascular health of residents in selected metropolitan cities in China.

BACKGROUND: To better understand the cardiovascular health and leisure-time physical activity of residents in major metropolitan cities in China, 2196 subjects (39.0 +/- 10.7 years) who lived in Beijing, Shanghai and Hong Kong were investigated. METHODS: During the months of January to June 2001, residents of the three cities who went through annual medical examinations at participating hospitals and exercise physiology laboratories were recruited as subjects, with a target of 800-900 subjects per city. Data on their behavior and health-related cardiovascular heart disease (CHD) risk factors were assessed. RESULTS AND CONCLUSIONS: It was found that over 80% of the subjects were sedentary (participating less than 90 min/week in leisure physical activity). The percentages of subjects having three or more cardiovascular heart disease risk factors were highest in Beijing (72.2%), followed by Shanghai (53.5%) and then Hong Kong (29.3%), suggesting that the cardiovascular health of Hong Kong residents was the best. It was noted that while all cities have similar health problems, there were significant differences in CHD risk factor due to geographical differences: Beijing residents smoked, drank, had high serum cholesterol and did not exercise; Shanghai residents had high blood pressure and drank; and Hong Kong residents were overweight and had lower HDL level. It was found that as subjects grew older, their cardiovascular health became worse. Gender differences were also observed-female subjects have generally fewer CHD risk factors and thus better health than male subjects. A model to examine the effects of age and behavior-related factors on health was developed for each city. Implications on planning strategies and primary prevention programs of CHD were discussed, in light of intervening identified risk factors.

Increased sensations of intensity of breathlessness impairs maintenance of intense intermittent exercise.

To identify the reserve of an individual's tolerance of the sensation of breathlessness and metabolic stress in maintaining intense intermittent exercise at exhaustion under conditions of normal breathing, the contribution of the effect of modest inspiratory load on these two responses to the change in the exercise sustainability (Ex(sus)) were examined. Seven men repeatedly performed 12 s exercise at 160% maximal aerobic power output followed by passive recovery for 18 s under normal and ventilatory muscle loaded (VML) breathing conditions until exhaustion. In the VML trial, ventilatory muscle work at exhaustion was double that of the normal control. The control Ex(sus) was reduced [mean (SEM)] [31.7 (6.6)%] while the slope of the time course for the rating of the perceived magnitude of breathing effort (RPMBE/Time), which reflected the intensity of breathlessness, was increased [164.8 (32.2)%] from control and the RPMBE at exhaustion was higher than corresponding control value [144.4 (21.8)%]. Moreover, increases in plasma ammonia and uric acid concentrations, which indicated metabolic stress, were increased [168.1 (28.0)% and 251.7 (57.4)%, respectively], with no change in total oxygen uptake from control when the control exercise was repeated with an identical duration of VML exercise. It was found that the reduction in Ex(sus) in the VML trial was correlated to the increase in their sensations of the intensity of breathlessness (RPMBE/Time: r=0.81; RPMBE at exhaustion: r=0.97, P<0.05). The reduction in Ex(sus), however, was not correlated to the increase in metabolite concentrations. These findings implied that there was no substantial reserve of tolerance of the sensation of breathlessness relative to that of metabolic stress in subjects maintaining intense intermittent exercise at exhaustion under normal conditions of breathing.

Physical development and lifestyle of Hong Kong secondary school students.

BACKGROUND: Objectives of the present investigation were to study the growth and development of adolescents in Hong Kong, to analyze the interrelationship between their development and lifestyle, and to provide some helpful suggestions for lifestyle modification. METHODS: A total of 404 secondary students ages 12-18 years served as subjects. Morphological measures, blood pressure, blood lipids, aerobic fitness, and body composition were tested. A self-report questionnaire was administered to assess physical activity and dietary habits. RESULTS AND CONCLUSIONS: Systolic blood pressure and diastolic blood pressure increased with age, and a gender difference was noted. Body height and body weight increased with age. Total cholesterol showed a lowering trend with age, and high-density lipoprotein had a slight rise. The percentage body fat for boys decreased with age but increased for girls. The higher percentage of overweight and obesity was closely associated with physical inactivity and inappropriate food selection such as eating snacks or food rich in fat or cholesterol. Tailor-made physical activity and nutritional education programs should be designed for adolescents, especially girls during puberty.

Acute changes in selected serum enzyme and metabolite concentrations in 12- to 14-yr.-old athletes after an all-out 100-m swimming sprint.

The purpose of this study was to investigate the acute effects of an all-out 100-m swimming sprint on changes in serum enzyme and calcium ion concentrations in young (12 to 14 years) male and female swimmers. Changes in serum enzyme concentrations of creatine kinase (CK), lactate dehydrogenase (LDH), glutamic pyruvate transaminase (GPT), glutamic oxaloacetate transaminase (GOT), serum glucose (GL), and calcium ion ((Ca2+) concentrations were measured in 23 elite swimmers (13 boys and 10 girls) before and after a 100-m freestyle all-out sprint. Analysis showed (1) there were significant sex differences in serum CK concentration at baseline (Pretest); (2) significant sex differences in serum CK and LDH concentrations after the 100-m spring; (3) no significant differences in Ca2+ concentration after the 100-m spring; and (4) significant increase in Serum GOT and blood glucose concentrations after the 100-m sprint, suggesting that these might both be useful indicators of anaerobic exercise stress in young swimmers.