Metabolic profile of high intensity intermittent exercises

To evaluate the magnitude of the stress on the aerobic and the anaerobic energy release systems during high intensity bicycle training, two commonly used protocols (IE1 and IE2) were examined during bicycling. IE1 consisted of one set of 6-7 bouts of 20-s exercise at an intensity of approximately 170% of the subject's maximal oxygen uptake (VO2max) with a 10-s rest between each bout. IE2 involved one set of 4-5 bouts of 30-s exercise at an intensity of approximately 200% of the subject's VO2max and a 2-min rest between each bout. The accumulated oxygen deficit of IE1 (69 +/- 8 ml.kg-1, mean +/- SD) was significantly higher than that of IE2 (46 +/- 12 ml.kg-1, N = 9, p < 0.01). The accumulated oxygen deficit of IE1 was not significantly different from the maximal accumulated oxygen deficit (the anaerobic capacity) of the subjects (69 +/- 10 ml.kg-1), whereas the corresponding value for IE2 was less than the subjects' maximal accumulated oxygen deficit (P < 0.01). The peak oxygen uptake during the last 10 s of the IE1 (55 +/- 6 ml.kg-1.min-1) was not significantly less than the VO2max of the subjects (57 +/- 6 ml.kg-1.min-1). The peak oxygen uptake during the last 10 s of IE2 (47 +/- 8 ml.kg-1.min-1) was lower than the VO2max (P < 0.01). In conclusion, this study showed that intermittent exercise defined by the IE1 protocol may tax both the anaerobic and aerobic energy releasing systems almost maximally.     

Cardiovascular effects of nepicastat (RS-25560-197), a novel dopamine beta-hydroxylase inhibitor

PURPOSE: The aim of the present study was to develop a standard protocol for evaluating peak oxygen uptake and anaerobic threshold during upper body work by cross-country skiers. METHODS: All tests were performed on a specially developed ski ergometer and incorporated the double poling technique. In series I, continuous and discontinuous protocols for measuring VO2peak at different inclinations of the ski ergometer were performed. In series II, a protocol for evaluating anaerobic threshold during upper body work was established. Eleven well trained regional male cross-country skiers participated in the study. All tests in each series were carried out during a period of 14 d. RESULTS: VO2peak did not differ using continuous or discontinuous protocol while working on the ski ergometer. Inclination was found to influence VO2peak, which was reduced at 7 degrees compared with 3 degrees, 5 degrees, and 6 degrees. Th(an) working on the ski ergometer was reached at a power output, VO2, or fc, which gave on average a blood lactate concentration of 1.8 mmol.L-1 higher than those found after the warm-up period during a graded protocol. CONCLUSIONS: Testing only the traditional Th(an) and VO2max while running on a treadmill hides important determinants of endurance in cross-country skiing as shown by that no correlation was found between VO2max and VO2peak in the present study.     

Can the ventilatory equivalent for carbon dioxide predict the severity of functional impairment in patients with cardiac insufficiency?

OBJECTIVE: To evaluate whether the changes in the ventilatory equivalent for carbon dioxide (VE/VCO2), during the early stages of cardiopulmonary exercise testing, can predict maximal oxygen consumption (VO2max) in patients with chronic heart failure. METHODS: We studied 38 patients (30 males, mean age 56 +/- 11 years) with chronic heart failure. All patients performed maximal symptom limited, treadmill exercise test with breath-by-breath respiratory gas analysis. They were divided in two groups according to their maximal oxygen consumption (group I-VO2max above 14 ml/kg/min and group II-VO2max below 14 ml/kg/min). In both groups, we analysed VE/VCO2 at rest, at the anaerobic threshold (AT) and at peak exercise, and the percentage of VE/VCO2 reduction from rest to AT. RESULTS: Eleven patients had a VO2max below 14 ml/kg/min (group II). At rest VE/VCO2 = 53 +/- 13 in group II versus 47 +/- 10 in group I (p = 0.048), at the AT VE/VCO2 = 46 +/- 12 in group II versus 36 +/- 7 in group I (p = 0.001) and at peak exercise VE/VCO2 = 46.2 +/- 13 in group II versus 36.2 +/- 6 in group I (p = 0.0002). There was a 24% reduction in the VE/VCO2, from rest to AT in group I, compared to a 16% reduction in group II (p = 0.004). A reduction in the VE/VCO2 from rest to AT less than 16% predicted a VO2max below 14 ml/kg/min with a sensitivity of 60% and a specificity of 93%. CONCLUSIONS: Patients with severe functional impairment have higher values of VE/VCO2 in all exercise stages. A reduction of VE/VCO2 from rest to anaerobic threshold of less than 16% is a high specific predictor of a VO2max below 14 ml/kg/min.     

Anaerobic threshold and maximal aerobic power for three modes of exercise

Alterations in selected respiratory gas exchange parameters have been proposed as sensitive, noninvasive indices of the onset of metabolic acidosis (anaerobic threshold (AT) during incremental exercise. Our purposes were to investigate the validity and feasibility of AT detection using routine laboratory measures of gas exchange, i.e., nonlinear increases in VE and VCO2 and abrupt increases in FEO2. Additionally, we examined the comparability of the AT and VO2 max among three modes of exercise (arm cranking, leg cycling, and treadmill walk-running) with double determinations obtained from 30 college-age, male volunteer subjects. The AT's for arm cranking, leg cycling, and treadmill walk-running occurred at 46.5 +/- 8.9 (means +/- SD), 63.8 +/- 9.0, and 58.6 +/- 5.8% of VO2 max, respectively. No significant difference was found between the leg exercise modes (cycling and walk-running) for the AT while all pairwise arm versus leg comparisons were significantly different. Using nine additional subjects performing leg cycling tests, a significant correlation of r = 0.95 was found between gas exchange AT measurements (expressed as % VO2 max) and venous blood lactate AT measurements (% VO2 max). We conclude that the gas exchange AT is a valid and valuable indirect method for the detection of the development of lactic acidosis during incremental exercise.     

Correction of urinary calcium levels for urine osmotic pressure]

This study was performed to clarify the relationship between isocapnic buffering and maximal aerobic capacity (VO2max) in athletes. A group of 15 trained athletes aged 21.1 (SD 2.6) years was studied. Incremental treadmill exercise was performed using a modified version of Bruce's protocol for determination of the anaerobic threshold (AT) and the respiratory compensation point (RC). Ventilatory and gas exchange responses were measured with an aeromonitor and expressed per unit of body mass. Heart rate and ratings of perceived exertion were recorded continuously during exercise. The mean VO2max, oxygen uptake (VO2) at AT and RC were 58.2 (SD 5.8) ml x kg(-1) x min(-1), 28.0 (SD 3.3) ml x kg(-1) x min(-1) and 52.4 (SD 6.7) ml x kg(-1) x min(-1), respectively. The mean values of AT and RC, expressed as percentages of VO2max, were 48.3 (SD 4.2)% and 90.0 (SD 5.2)%, respectively. The mean range of isocapnic buffering defined as VO2 between AT and RC was 24.4 (SD 4.5) ml x kg(-1) x min(-1), and the mean range of hypocapnic hyperventilation (HHV) defined as VO2 between RC and the end of exercise was 5.8 (SD 3.0) ml x kg(-1) x min(-1). The VO2max per unit mass was significantly correlated with AT (r = 0.683, P < 0.01). In addition, VO2max/mass was closely correlated with both the range of isocapnic buffering (r = 0.803, P < 0.001) and RC (r = 0.878, P < 0.001). However, no correlation was found between VO2max per unit mass and the range of HHV (r = 0.011, NS.). These findings would suggest that the prominence of isocapnic buffering, in addition to the anaerobic threshold, may have been related to VO2max of the athletes. The precise mechanisms underlying this proposed relationship remain to be elucidated.     

Physiological correlates of 3-kilometer running performance in male children

The purpose of this study was to examine the influence of body fatness, aerobic and anaerobic ability on 3-km running performance in 19 physically active boys (mean +/- SD, age = 10.4 +/- 0.9 yrs). The sum of six skinfolds, VO2 at 8.04 and 9.65 km.hr-1, and VO2max were measured in the laboratory. Run time for 3 km was assessed twice on separate days on a 200-meter indoor track. Prior to each run, every child performed two 55-meter sprints and two vertical jumps. Mean +/- SD values for the sum of skinfolds, %VO2max at each running speed, VO2max and 3-km run time were: 33.9 +/- 14.9 mm; 70.6 +/- 6.6% and 81.0 +/- 7.9%; 54.6 +/- 5.0 ml.kg-1.min-1; 16.41 +/- 2.58 min, respectively. Significant (p < 0.05) correlations were observed between the following variables and run time: sum of skinfolds (r = 0.72); vertical jump (r = 0.67); sprint time (r = 0.59); VO2max (r = 0.61); and, %VO2max at each treadmill speed (r = 0.79 and r = 0.75, respectively). Stepwise multiple regression analysis indicated that the combination of the %VO2max at 8.04 km.hr-1 and vertical jump accounted for 83% (adjusted R2) of the variance in running time (SEE = 1.06 min, p < 0.05). This study suggests that 3-km run time in physically active boys is influenced by aerobic and anaerobic indices as well as body fatness, supporting the notion that children, compared to adults, are not metabolic specialists.     

Decline in maximal oxygen uptake on work performance in rats during the developmental phase

Development-related changes in maximal oxygen uptake (VO2max) and work performance were examined in young sedentary rats 4-11 weeks after birth during exercise. The running speed to elicit VO2max increased from 4 to 8 weeks of age, whereas the exercise VO2max declined progressively. Therefore, the work performance during the developmental phase, when rapid growth occurs, seems to be little related to the decline in the relative VO2 max.     

Effects of endurance training and heat acclimation on psychological strain in exercising men wearing protective clothing

Two experiments examined the influences of endurance training and heat acclimation on ratings of perceived exertion (RPE) and thermal discomfort (RTD) during exercise in the heat while wearing two types of clothing. In experiment 1, young men underwent 8 weeks of physical training [60-80% of maximal aerobic power (VO2max) for 30-45 min day-1, 3-4 days week-1 at 20-22 degrees C dry bulb (db) temperature] followed by 6 days of heat acclimation [45-55% VO2max for 60 min day-1 at 40 degrees C db, 30% relative humidity (rh)] (n = 7) or corresponding periods of control observation followed by heat acclimation (n = 9). In experiment 2, young men were heat-acclimated for 6 or 12 days (n = 8 each). Before and after each treatment, subjects completed bouts of treadmill exercise (1.34 m s-1, 2% grade in experiment 1 and 0% grade in experiment 2) in a climatic chamber (40 degrees C db, 30% rh), wearing in turn normal light clothing (continuous exercise at 37-45% VO2max for a tolerated exposure of 116-120 min in experiment 1 and at 31-34% VO2max for 146-150 min in experiment 2) or clothing protective against nuclear, biological, and chemical agents (continuous exercise at 42-51% VO2max for a tolerated exposure of 47-52 min in experiment 1 and intermittent exercise at 23% VO2max for 97-120 min in experiment 2). In experiment 1, when wearing normal clothing, endurance training and/or heat acclimation significantly decreased RPE and/or RTD at a fixed power output. There were concomitant reductions in relative work intensity (% VO2max) [an unchanged oxygen consumption (VO2) but an increased VO2max, or a reduced VO2 with no change of VO2max], rectal temperature (Tre), mean skin temperature (Tsk), and/or heart rate (HR). When wearing protective clothing, in contrast, there were no significant changes in RPE or RTD. Although training and/or acclimation reduced %VO2max or Tre, any added sweat that was secreted did not evaporate through the protective clothing, thus increasing discomfort after training or acclimation. Tolerance times were unchanged in either normal or protective clothing. In experiment 2, when wearing normal clothing, heat acclimation significantly decreased RPE and RTD at a fixed power output, with concomitant reductions in Tre, Tsk, and HR; the response was greater after 12 than after 6 days of acclimation, significantly so for RPE and HR. When wearing protective clothing, the subjects exercised at a lower intensity for a longer duration than in the moderate exercise trial. Given this tactic, either 6 or 12 days of heat acclimation induces significant reductions RPE and/or RTD, accompanied by reductions in Tre, Tsk, and/or HR. Tolerance times in protective clothing were also increased by 11-15% after acclimation, despite some increase of sweat accumulation in the protective clothing. The results suggest that (1) neither endurance training nor heat acclimation reduce psychological strain when protective clothing is worn during vigorous exercise, because increased sweat accumulation adds to discomfort, and (2) in contrast to the experience during more vigorous exercise, heat acclimation is beneficial to the subject wearing protective clothing if the intensity of effort is kept to a level that allows permeation of sweat through the clothing. This condition is likely to be met in most modern industrial applications.     

Perceived exertion associated with breathing hyperoxic mixtures during submaximal work

The effect of an enriched inspired oxygen concentration on perceived exertion (RPE) was investigated while running at two submaximal treadmill loads. Twelve males (VO2 max = 49.3 ml/kg-min) worked at 50% and 80% VO2 max, breathing either air or 80% O2-20% N2 in random order using a single blind technique. Subjects were evaluated while running for 10 min and during a 20 min recovery. Heart rate (HR), ventilation (VE), respiration rate (RR), tidal volume (VT) and RPE were measured before, during and after work. Blood lactate was measured 1 min after work. Oxygen concentration did not statistically affect HR, VE, RR or VT during exercise or recovery. At both loads, RPE at the end of exercise was significantly reduced breathing the hyperoxic mixture. At 50% VO2 max, mean RPE decreased from 11.2 breathing room air to 9.6 breathing 80% O2 and, 80% VO2 max, from 13.8 to 11.7 (P less than 0.01). Blood lactates were significantly reduced breathing 80% O2; from 23.4 mg to 13.3 at 50% VO2 max and from 55.5 to 36.5 at 80% VO2 max (P less than 0.01). The RPE correlated with lactate (r=0.64) at the end of work. Results indicate that during moderate and heavy work RPE is significantly affected by the inspired O2 concentration and there is a significant relationship between RPE and blood lactate.     

Effect of voluntary exercise on maximal oxygen uptake in young female Fischer 344 rats

The effect of voluntary exercise on maximal oxygen uptake (VO2 max) was studied in young female Fischer 344 rats. After 10 weeks of wheel-running training, the absolute VO2 max and VO2 max relative to body mass increased without a decline in body mass. The running speed eliciting VO2 max, heart and soleus muscle mass, and succinate dehydrogenase (SDH) activity in the soleus muscle also increased. These results suggest that voluntary exercise is an effective means of increasing the aerobic exercise capacity of young female Fischer 344 rats.     

Muscle performance and enzymatic adaptations to sprint interval training

Our purpose was to examine the effects of sprint interval training on muscle glycolytic and oxidative enzyme activity and exercise performance. Twelve healthy men (22 +/- 2 yr of age) underwent intense interval training on a cycle ergometer for 7 wk. Training consisted of 30-s maximum sprint efforts (Wingate protocol) interspersed by 2-4 min of recovery, performed three times per week. The program began with four intervals with 4 min of recovery per session in week 1 and progressed to 10 intervals with 2.5 min of recovery per session by week 7. Peak power output and total work over repeated maximal 30-s efforts and maximal oxygen consumption (VO2 max) were measured before and after the training program. Needle biopsies were taken from vastus lateralis of nine subjects before and after the program and assayed for the maximal activity of hexokinase, total glycogen phosphorylase, phosphofructokinase, lactate dehydrogenase, citrate synthase, succinate dehydrogenase, malate dehydrogenase, and 3-hydroxyacyl-CoA dehydrogenase. The training program resulted in significant increases in peak power output, total work over 30 s, and VO2 max. Maximal enzyme activity of hexokinase, phosphofructokinase, citrate synthase, succinate dehydrogenase, and malate dehydrogenase was also significantly (P < 0.05) higher after training. It was concluded that relatively brief but intense sprint training can result in an increase in both glycolytic and oxidative enzyme activity, maximum short-term power output, and VO2 max.     

Changes in maximum oxygen uptake during prolonged training, overtraining, and detraining in horses

Thirteen standardbred horses were trained as follows: phase 1 (endurance training, 7 wk), phase 2 (high-intensity training, 9 wk), phase 3 (overload training, 18 wk), and phase 4 (detraining, 12 wk). In phase 3, the horses were divided into two groups: overload training (OLT) and control (C). The OLT group exercised at greater intensities, frequencies, and durations than group C. Overtraining occurred after 31 wk of training and was defined as a significant decrease in treadmill run time in response to a standardized exercise test. In the OLT group, there was a significant decrease in body weight (P < 0.05). From pretraining values of 117 +/- 2 (SE) ml.kg-1.min-1, maximal O2 uptake (VO2max) increased by 15% at the end of phase 1, and when signs of overtraining were first seen in the OLT group, VO2max was 29% higher (151 +/- 2 ml.kg-1.min-1 in both C and OLT groups) than pretraining values. There was no significant reduction in VO2max until after 6 wk detraining when VO2max was 137 +/- 2 ml.kg-1.min-1. By 12 wk detraining, mean VO2max was 134 +/- 2 ml.kg-1.min-1, still 15% above pretraining values. When overtraining developed, VO2max was not different between C and OLT groups, but maximal values for CO2 production (147 vs. 159 ml.kg-1.min-1) and respiratory exchange ratio (1.04 vs. 1.11) were lower in the OLT group. Overtraining was not associated with a decrease in VO2max and, after prolonged training, decreases in VO2max occurred slowly during detraining.     

Effect of age and menopausal status on cardiorespiratory fitness in masters women runners

Forty-nine trained masters women endurance runners (mean = 42 km.wk-1) between the ages of 35 and 70 yr (mean = 46.4 +/- 8.3) were tested on a treadmill to examine cardiorespiratory fitness (VO2max and VO2 submax) in relation to age, training, and menopausal status. Although VO2max was lower with increasing age, no age group differences occurred in VO2 submax at 5.4 km.h-1, 8% treadmill grade. The younger runners (35-39 and 40-44 yr) had significantly higher VO2max than the other 5-yr competitive age groups (45-49, 50-55, 55-70 yr) (P < 0.01). HR max did not differ across age, but HR submax was higher with increasing age. Premenopausal, transitional, and post-menopausal women were not significantly different on any exercise variable when age and/or training differences among the groups were statistically controlled. A decrease in VO2max of 0.58 ml.kg-1 x min-1 x yr-1 was determined (r = -0.62). It was concluded that 1) these highly trained women runners had higher cardiorespiratory fitness than previously reported for women of comparable age, 2) menopausal status did not effect cardiorespiratory fitness when age and training were accounted for, and 3) regular physical training seems to prevent age-related changes in HR max in women, but not age-related changes in maximal oxygen uptake.     

Anaerobic and aerobic responses of males and females to rope skipping

Six male and six female subjects performed maximal bicycle ergometer work and skipped rope at selected rates. Measures included oxygen uptake (VO2), oxygen debt (VO2 debt), blood lactate, and heart rate (HR). Mean values for males for the maximum test and while skipping at 120, 140, and 160 turns . min-1 were, respectively: VO2-50.2, 38.3, 39.7, and 44.3 ml . kg-1 . min-1; HR-185, 166, 168, and 178 beats . min-1; VO2 debt--5.70, 3.65, 3.50, and 4.04 liter; and lactate--12.7, 7.4, 7.6, and 9.2 mM . 1(-1). For females: VO2--42.8, 39.8, 39.4, and 39.4 ml . kg-1 . min-1; HR--185, 181, 181, and 181 beats . min-1; VO2 debt--4.71, 4.27, 4.22, and 4.15 liter; and lactate--11.5, 11.5, 12.2, and 11.9 mM . l-1. No significant differences were found between treatments for females for any measure. Rope skipping placed high demands on both aerobic (females, 92% VO2max, males, 76-88%) and anaerobic capacities (females, 100-106% lactate values after maximum bicycle exercise; males, 58-72%). In males, who did not reach VO2max during rope skipping, it was verified that the VO2 requirement does not increase with skipping rate over a relatively wide range, but that extremely high rates do require more energy from both aerobic and anaerobic sources. Differences in tolerance of males and females to rope skipping were attributed to the lower aerobic power and higher body fat of females.     

Plasma lactate accumulation and distance running performance. 1979

Laboratory and field assessments were made on eighteen male distance runners. Performance data were obtained for distances of 3.2, 9.7, 15, 19.3 km (n = 18) and the marathon (n = 13). Muscle fiber composition expressed as percent of slow twitch fibers (%ST), maximal oxygen consumption (VO2max), running economy (VO2 for a treadmill velocity of 268 m/min), and the VO2 and treadmill velocity corresponding to the onset of plasma lactate accumulation (OPLA) were determined for each subject. %ST (R > or equal to .47), VO2max (r > or equal to .83), running economy (r > or equal to .49), VO2 in ml/kg min corresponding to the OPLA (r > or equal to .91) and the treadmill velocity corresponding to OPLA (r > or equal to .91) were significantly (p < .05) related to performance at all distances. Multiple regression analysis showed that the treadmill velocity corresponding to the OPLA was most closely related to performance and the addition of other factors did not significantly raise the multiple R values suggesting that these other variables may interact with the purpose of keeping plasma lactates low during distance races. The slowest and fastest marathoners ran their marathons 7 and 3 m/min faster than their treadmill velocities corresponding to their OPLA which indicates that this relationship is independent of the competitive level of the runner. Runners appear to set a race pace which allows the utilization of the largest possible VO2 which just avoids the exponential rise in plasma lactate.     

Polydipsic and home-cage fluid choices: the effects of sweetening

MAO inhibitors of diverse chemical structures were found to inhibit the uptake of 3H-NE into chopped rat cerebral cortex in vitro. The following molar (M) IC50 values to inhibit 3H-NE uptake were obtained: iproniazid, 7.9 X 10(-4)M; pargyline, 3.1 X 10(-4)M; pheniprazine, 6.3 X 10(-6)M; phenelzine, 3.9 X 10(-6)M; tranylcypromine, 2.5 X 10(-6)M; amphetamine, 2.5 X10(-7)M. In addition to decreasing deaminative catabolism, 5 X 10(-5)M amphetamine, tranylcypromine and pheniprazine plus 10(-3)M phenelzine produced a release of 3H-NE from tissue stores into incubation media. Similar concentrations of pargyline and iproniazid were ineffective to release 3H-NE from brain tissue.     

Hypnosis in a dental patient with allergies

The purpose of the study was to mathematically model the regression of percent of maximal oxygen consumption (% VO2 max) on relative (% of max) heart rate (HR). The 26 subjects (Ss) were classified based on activity levels into high, medium, and low-fitness. Each S performed a series of treadmill walks and runs ranging from 30 to 100% of max VO2. Percent of VO2 max and relative HR were determined during each exercise bout. The data were subjected to a trend analysis utilizing multiple regression techniques. The associated Rs were: linear 0.966, quadratic 0.971, cubic 0.971, and quartic 0.977. The second and fourth order terms statistically accounted for more of the variability than their predecessors, but these differences were not of practical significance. There were no statistically significant differences among the fitness subgroup regression slopes or intercepts for any of the sets of regression equations. The bivariate equation was Y = 1.369-X-40.99 (Y = % VO2 max and X=relative HR) with a standard error of the estimate of 5.67 % VO2 max.     

Norepinephrine response to exercise at the same relative intensity before and after endurance exercise training

It is well documented that endurance exercise training results in a blunted norepinephrine (NE) response to exercise of a given absolute exercise intensity. However, it is not clear what effect training has on the catecholamine response to exercise of the same relative intensity because previous studies have provided conflicting results. The purpose of the present study was, therefore, to determine the catecholamine response to exercise of the same relative exercise intensity before and after endurance exercise training. Six women and three men [age 28 +/- 8 (SD) yr] performed 10 wk of training. Maximal O2 uptake (VO2 max) was determined during treadmill exercise. Fifteen-minute treadmill exercise bouts were performed at 60, 65, 70, 75, 80, and 85% of VO2 max before and after training. VO2 max was increased by 20% (from 39.2 +/- 7.7 to 46.9 +/- 8.1 ml. kg-1. min-1; P < 0.05) in response to training. Plasma NE concentrations were higher (P < 0.05) during exercise at the same relative intensity after, compared with before, training at 65-85% of VO2 max. Differences between heart rates and plasma epinephrine concentrations after, compared with before, training were not statistically significant. These results provide evidence that the NE response to exercise is dependent on the absolute as well as the relative intensity of the exercise.     

Is peak VO2 a maximal index of children's aerobic fitness?

A levelling of oxygen uptake (VO2 plateau) at high exercise intensities is conventionally used as the criterion for establishing VO2max during progressive, incremental exercise testing. Only a minority of children, however, demonstrate a VO2 plateau during exercise to voluntary exhaustion. This study was therefore designed to investigate whether a VO2 plateau is required before peak VO2 can be considered a maximal index of children's aerobic fitness. Eighteen girls and 17 boys (age 9.9 +/- 0.4 yrs) carried out three treadmill tests to exhaustion one week apart. The first test comprised a discontinuous, incremental protocol to voluntary exhaustion. In test two each child warmed up and then ran to exhaustion at the same belt speed but on a gradient 2.5% greater than that which had produced an exhaustive effort on the first test. The third test was conducted similarly but the treadmill gradient was raised to 5% greater than that which had produced an exhaustive effort on the first test. Seven girls and 6 boys demonstrated a VO2 plateau (< or = 2 ml.kg-1.min-7) on the first test but no significant differences in either anthropometrical or peak physiological data were detected between those who demonstrated a plateau and those who did not. Mean peak VO2 values during tests two and three (supramaximal tests) did not increase significantly above that achieved on test one although indicators of an increased anaerobic contribution were significantly higher in both supramaximal tests. These findings indicate that peak VO2 in test one was a maximal value despite the absence of a VO2 plateau. The requirement of a VO2 plateau before peak VO2 can be regarded as a maximal index of young children's aerobic fitness is therefore untenable.     

Relationship between 800-m running performance and accumulated oxygen deficit in middle-distance runners

PURPOSE: To determine whether there is a significant relationship between accumulated oxygen deficit (AOD) and 800-m running performance in a group of runners of homogeneous ability. METHODS: Nine well-trained male middle and long distance runners (age = 24.7 +/- 4.5 yr, body mass = 69.4 +/- 8.5 kg, VO2max = 64.8 +/- 4.5 mL.kg-1.min-1) underwent treadmill testing to determine maximum oxygen uptake (VO2max), running economy (RE) at 1% and 10.5% treadmill gradient, and AOD at 1% and 10.5% treadmill gradient; 800-m running performance was determined by time trials on an outdoor 440-yd track, for which the average time was 132 +/- 4 s. For the AOD test, subjects were required to run on the treadmill at supramaximal speeds until volitional exhaustion. The AOD value was calculated using linear (LIN) and curvilinear (CUR) extrapolation procedures. RESULTS: Mean AOD values using LIN and CUR were 45.0 +/- 6.9 and 59.3 +/- 10.1 mL.kg-1 at a 1% treadmill gradient and 63.2 +/- 10.6 and 93.6 +/- 19.7 mL.kg-1 at a 10.5% gradient, respectively. No significant relationship was found between 800-m run time and AOD at 1% gradient or 10.5% gradient or when AOD was estimated from a linear or curvilinear fit of the VO2 data. Other variables measured in this study (e.g., VO2max and running economy) were not found to be predictive of 800-m run time. CONCLUSION: Among a homogeneous group of well-trained male middle- and long-distance runners, AOD measured at a 1% and 10.5% treadmill gradient is not significantly related to 800-m running performance.