The effects of 24 weeks of moderate- or high-intensity exercise on insulin resistance.

This study was designed to investigate the effect of exercise intensity on insulin resistance by comparing moderate- and high-intensity interventions of equal energy cost. Maximum oxygen consumption (VO(2max)), insulin, glucose and triglycerides were measured in 64 sedentary men before random allocation to a non-exercise control group, a moderate-intensity exercise group (three 400-kcal sessions per week at 60% of VO(2max)) or a high-intensity exercise group (three 400-kcal sessions per week at 80% of VO(2max)). An insulin sensitivity score was derived from fasting concentrations of insulin and triglycerides, and insulin resistance was assessed using the homeostasis model assessment of insulin resistance (HOMA-IR). Data were available for 36 men who finished the study. After 24 weeks, insulin concentration decreased by 2.54+/-4.09 and 2.37+/-3.35 mU l(-1), insulin sensitivity score increased by 0.91+/-1.52 and 0.79+/-1.37, and HOMA-IR decreased by -0.6+/-0.8 and -0.5+/-0.8 in the moderate- and high-intensity exercise groups, respectively. When data from the exercise groups were combined, one-way analysis of variance with one-tailed post hoc comparisons indicated that these changes were significantly greater than those observed in the control group (all P<0.05). Twenty-four week changes in insulin concentration, insulin sensitivity score and HOMA-IR were not significantly different between the exercise groups. These data suggest that exercise training is accompanied by a significant reduction in insulin resistance, as indicated by well-validated surrogate measures. These data also suggest that moderate-intensity exercise is as effective as high-intensity exercise when 400 kcal are expended per session.

Age-related changes in maximal power and maximal heart rate recorded during a ramped test in 114 cyclists age 15-73 years.

This study assessed age-related changes in power and heart rate in 114 competitive male cyclists age 15-73 years. Participants completed a maximal Kingcycle ergometer test with maximal ramped minute power (RMPmax, W) recorded as the highest average power during any 60 s and maximal heart rate (HRmax, beats/min) as the highest value during the test. From age 15 to 29 (n = 38) RMPmax increased by 7.2 W/year (r = .53, SE 49 W, p < .05). From age 30 to 73 (n = 78) RMPmax declined by 2.4 W/year (r = - .49, SE 49 W, p < .05). Heart rate decreased across the full age range by 0.66 beats . min( -1 ) . year( -1 ) (r = -.75, SE 9 beats/min, p < .05). Age accounted for only 25% of the variance in RMPmax but 56% in HRmax. RMPmax was shown to peak at age 30, then decline with age, whereas HRmax declined across the full age range.

Changes in cardiorespiratory fitness and coronary heart disease risk factors following 24 wk of moderate- or high-intensity exercise of equal energy cost.

This study was designed to investigate the effect of exercise intensity on cardiorespiratory fitness and coronary heart disease risk factors. Maximum oxygen consumption (Vo(2 max)), lipid, lipoprotein, and fibrinogen concentrations were measured in 64 previously sedentary men before random allocation to a nonexercise control group, a moderate-intensity exercise group (three 400-kcal sessions per week at 60% of Vo(2 max)), or a high-intensity exercise group (three 400-kcal sessions per week at 80% of Vo(2 max)). Subjects were instructed to maintain their normal dietary habits, and training heart rates were represcribed after monthly fitness tests. Forty-two men finished the study. After 24 wk, Vo(2 max) increased by 0.38 +/- 0.14 l/min in the moderate-intensity group and by 0.55 +/- 0.27 l/min in the high-intensity group. Repeated-measures analysis of variance identified a significant interaction between monthly Vo(2 max) score and exercise group (F = 3.37, P < 0.05), indicating that Vo(2 max) responded differently to moderate- and high-intensity exercise. Trend analysis showed that total cholesterol, low-density lipoprotein cholesterol, non-high-density lipoprotein cholesterol, and fibrinogen concentrations changed favorably across control, moderate-intensity, and high-intensity groups. However, significant changes in total cholesterol (-0.55 +/- 0.81 mmol/l), low-density lipoprotein cholesterol (-0.52 +/- 0.80 mmol/l), and non-high-density lipoprotein cholesterol (-0.54 +/- 0.86 mmol/l) were only observed in the high-intensity group (all P < 0.05 vs. controls). These data suggest that high-intensity training is more effective in improving cardiorespiratory fitness than moderate-intensity training of equal energy cost. These data also suggest that changes in coronary heart disease risk factors are influenced by exercise intensity.

Right and left ventricular diastolic function of male endurance athletes.

BACKGROUND: Echocardiography of endurance athletes has demonstrated a substantial increase in left ventricular mass with no disturbance of diastolic function as assessed by the e:a ratio. Few studies have examined the right ventricle of athletes. The present study evaluated diastolic function of both right and left ventricles of endurance athletes through use of measurements of the motion of the atrioventricular (AV) plane. METHODS: Endurance athletes (runners) and sedentary subjects were studied. All subjects were male, aged 30-45 years and were free of cardiovascular disease. There were 21 runners and 40 sedentary subjects. The diastolic motion of the AV plane was assessed by measurement of total displacement and peak early velocity. RESULTS: The runners had a greater peak oxygen consumption (ml kg(-1) min(-1)) (59.5 vs. 33.5, P<10(-3)) and left ventricular mass (g) (281 vs. 202, P<10(-3)). The e:a ratio for both groups was similar (1.41 vs. 1.45, P=0.8). Both total displacement and peak early velocity for both ventricles were similar between groups, P>0.3. No correlation with age was found for total displacement or peak early velocity for either group in either ventricle, with the exception of peak early velocity for the right ventricle in the runners, where a highly significant correlation was found: peak early velocity=24.0-0.4 age, r(2)=0.75, P=10(-5). CONCLUSION: Chronic endurance training is associated with a greater LV mass than in comparable sedentary subjects. Despite this, no effect on AV plane motion was found. A decline in right ventricular peak early velocity of the AV plane with increasing age was identified in the runners. This was an unexpected finding and requires further study.

Method of lactate elevation does not affect the determination of the lactate minimum.

PURPOSE: The aim of the study was to examine the effects of different lactate elevation protocols on the determination of the lactate minimum (Lac(min)) point. METHODS: Eight highly trained racing cyclists each completed four continuous ramp lactate minimum tests using the following blood lactate elevation protocols: 1) continuous ramp maximal aerobic power (RMP(max)) assessment, 2) 30-s maximal sprint, 3) 40-s maximal sprint, and 4) two 20-s maximal sprints separated by a 1-min recovery. Each blood lactate elevation protocol was followed by a 5-min active recovery leading into a continuous ramp test commencing at a power of 60% of RMP(max), using a 6 W x min ramp rate, lasting 15 min. RESULTS: Peak [La](b) values were significantly higher (P > 0.05) after the RMP(max) compared with all other protocols and higher in the 40-s versus 30-s sprint. However, by the start of Lac(min) ramp, [La](b) after the RMP(max) was no longer higher than the 40-s sprint, but Lac(min) [La](b) was similar for all protocols. This resulted in no differences in the total decline of [La](b) measured as a percentage from the highest to the lowest value. At Lac(min) point, there were no significant differences in power (P > 0.05), but heart rate was higher in the RMP versus 2 x 20 s and VO(2) was significantly higher after the 40 s compared with the 2 x 20 s protocol. CONCLUSION: This study demonstrated that the determination of lactate minimum power in cycling is not dependent upon the lactate elevation protocol.