A new approach to assessing maximal aerobic power in children: the Odense School Child Study

Summary In two experiments maximal aerobic power calculated from maximal mechanical power (W _max) was evaluated in 39 children aged 9–11 years. A maximal multi-stage cycle ergometer exercise test was used with an increase in work load every 3 min. In the first experiment oxygen consumption was measured in 18 children during each of the prescribed work loads and a correction factor was calculated to estimate using the equation . An appropriate increase in work rate based on height was determined for boys (0.16 W · cm^–1) and girls (0.15 W · cm^–1) respectively. In the second experiment 21 children performed a maximal cycle ergometer exercise test twice. In addition to the procedure in the first experiment a similar exercise test was performed, but without measurement of oxygen uptake. Calculated correlated significantly (p<0.01) with those values measured in both boys (r=0.90) and girls (r=0.95) respectively, and the standard error of estimation for (calculated) on (measured) wass less than 3.2%. Two expressions of relative work load (% and %W _max) were established and found to be closely correlated. The relative work load in % could be predicted from the relative work load in % W _max with an average standard error of 3.8%. The data demonstrate that calculated based on a maximal multi-stage exercise test provides an accurate and valid estimate of      

Factors which alter the relationship between ventilation and carbon dioxide production during exercise in normal subjects

The slope of the linear relationship between ventilation and carbon dioxide production has been thought to indicate that is one of the major stimuli to . A group of 15 normal subjects undertook different incremental treadmill exercise protocols to explore the relationship between and . An incremental protocol using 1 instead of 3-min stages of exercise resulted in an increase in the to ratio [26.84 (SEM 1.23) vs 31.08 (SEM 1.36) (P < 0.008) for the first stage, 25.24 (SEM 0.86) vs 27.83 (SEM 0.91) (P < 0.005) for the second stage and 23.90 (SEM 0.86) vs 26.34 (SEM 0.81) (P = 0.001) for the third stage]. Voluntary hyperventilation to double the control level of during exercise resulted in an increase in the to slope [from 21.3 (SEM 0.71) for the control run to 35.1 (SEM 1.2) for the hyperventilation run (P < 0.001)]. Prolonged hyperventilation (5 min) during exercise at stage 2 of the Bruce protocol resulted in a continuted elevation of and the slope. A steady state of and metabolic gas exchange can only be said to have been present after at least 3 min of exercise. Voluntary hyperventilation increased the slope of the relationship between and . End-tidal carbon dioxide fell, but remained within the normal range. These results would suggest that a non-carbon dioxide factor may have been responsible for the increase we found in during exercise, and that factors other than increased dead space ventilation can cause an increased ventilation to slope, such as that seen in some pathophysiological conditions, such as chronic heart failure.     

Effects of prolonged exercise at a similar percentage of maximal oxygen consumption in trained and untrained subjects

Summary Six trained male cyclists and six untrained but physically active men participated in this study to test the hypothesis that the use of percentage maximal oxygen consumption (% , as a normalising independent variable is valid despite significant differences in the absolute of trained and untrained subjects. The subjects underwent an exercise test to exhaustion on a cycle ergometer to determine and lactate threshold. The subjects were grouped as trained (T) if their exceeded 60 ml ·kg^–1 ·min^–1, and untrained (UT) if their was less than 50 ml · kg^–1 · min-^–1. The subjects were required to exercise on the ergometer for up to 40 min at power outputs that corresponded to approximately 50% and 70% The allocation of each exercise session (50% or 70% was random and each session was separated by at least 5 days. During these tests venous blood was taken 10 min before exercise (–10 min), just prior to the commencement of exercise (–10 min), after 20 min of exercise (20 min), at the end of exercise and 10 min postexercise (+ 10 min) and analysed for concentrations of cortisol, [Na⁺], [K⁺], [CI^–], glucose, free fatty acid, lactate [la-], [NH₃], haemoglobin [Hb] and for packed cell volume. The oxygen consumption ( ) and related variables were measured at two time intervals (14–15 and 34–35 min) during the prolonged exercise tests. Rectal temperature was measured throughout both exercise sessions. There was a significant interaction effect between the level of training and exercise time at 50% for heart rate ( _c:) and venous [la^–]. At 70% and ventilation ( ) for the T group and and carbon dioxide production for the UT group increased significantly with time and there was a significant interaction effect forf _c, ]Ia^–1], [Hb] and [NH₃]. The change in body mass at 50% and 70% was significantly greater in the T group. The present study found that when two groups of male subjects with different absolute exercised at a similar percentage of some effector responses were significantly different, questioning the validity of selecting % as a normalising independent variable.     

Cerebral blood flow distribution and systemic haemodynamic changes after repeated hyperbaric oxygen exposures in rats

The effects of acute and repeated exposures to 500 kPa O₂ on the distribution of cerebral blood flow and systemic haemodynamics were assessed in awake rats. After habituation, the control rats (group 1,n=7) were restrained for 1 h daily for 8 days in air at 101 kPa, while the test rats (group 2,n=8) were exposed to 500 kPa O₂ for 1 h daily for 8 consecutive days. During a final exposure, both groups were exposed to 500 kPa O₂. Systolic (BP_s) and mean arterial blood pressure (BP _a), and heart rate (f _c) were measured continuously from implanted arterial catheters; while cardiac output and regional were measured by the microsphere method in air before the O₂ exposure, and after both 5 min and 60 min at 500 kPa O₂ in all the animals. The baseline measurements in air of BP_s andBP _a were higher andf _c was lower in group 2, while the acid-base chemistries were similar in the two groups. Total was similar in both groups. However in group 2, blood flows and calculated O₂ supplies to colliculi, hippocampus, hypothalamus, and most cerebral cortical regions were higher, but lower to pons and medulla oblongata. During O₂ exposure andf _c decreased, andBP _a, BP_s, and peripheral vascular resistance increased in all the rats. Arterial partial pressure of CO₂ and [HCO₃ ^–] decreased in group 1, but remained at baseline levels in group 2. Total and decreased in both groups, and the distribution was altered. Calculated O₂ supplies to different brain regions varied according to the changes, so that most regions sustained baseline O₂ delivery, although O₂ delivery to some regions may have been reduced. The decline of also indicated reduced removal of waste from the brain, so that CO₂ tension and temperature could have been elevated, thereby potentiating the toxic effects of O₂ on brain cells. In conclusion, repeated O₂ exposures induced heterogeneous and persistent changes in , as well as a persistent increase in arterial pressure.     

Effects of training at and above the lactate threshold on the lactate threshold and maximal oxygen uptake

Summary Thirty-three college women (mean age=21.8 years) participated in a 5 d·wk^–1, 12 week training program. Subjects were randomly assigned to 3 groups, above lactate threshold (> LT) (N=11; trained at 69 watts above the workload associated with LT), =LT (N=12; trained at the work load associated with LT) and control (C) (N=10). Subjects were assessed for , LT, LT/ , before and after training, using a discontinuous 3 min incremental (starting at 0 watts increasing 34 watts each work load) protocol on a cycle ergometer (Monark). Respiratory gas exchange measures were determined using standard open circuit spirometry while LT was determined from blood samples taken immediately following each work load from an indwelling venous catheter located in the back of a heated hand. Body composition parameters were determined before and after training via hydrostatic weighing. Training work loads were equated so that each subject expended approximately 1465 kJ per training session (Monark cycle ergometer) regardless of training intensity. Pretraining, no significant differences existed between groups for any variable. Post training the > LT group had significantly higher (13%), (47%) and LT/ (33%) values as compared to C (p<.05). Within group comparisons revealed that none of the groups significantly changed as a result of training, only the > LT group showed a significant increase in (48%) (p<.05), while both the = LT and > LT group showed significant increases in LT/ (= LT 16%, > LT 42% (p<.05)). No differences were found between or within groups post training for body composition parameters. It was concluded that training above the LT results in an improvement in LT and that large improvements in may not be required for large improvements in .Data were collected at the Human Performance Laboratory, University of Colorado     

Relationship between record time and maximal oxygen consumption in middle-distance running

Summary The relationship between record time (t _r) and maximal oxygen uptake ( ) has been examined in 69 male physical education students who had taken part in 800-m and 1500-m footraces. It was found thatt _r and were inversely related. The relationshipst _r=f( ) have been fitted by two exponential equations:t _r(1500 m)=698e –0.0145 t _r(800 m) = 272e^–0.01 P<0.001. A mathematical formulation of the energy conservation principle in supramaximal running, based on the exponential increase of the oxygen uptake as a function of time with a rate constant of 0.025 s^–1 has been applied to thet _r calculation from . As calculatedt _r were highly correlated to measuredt _r (P<0.001), it was concluded that the relationshipst _r=f( ) can be interpreted on the basis of the model described in this study.     

The energetics of middle-distance running

Summary In order to assess the relative contribution of aerobic processes to running velocity (v), 27 male athletes were selected on the basis of their middle-distance performances over 800, 1500, 3000 or 5000 m, during the 1987 track season. To be selected for study, the average running velocity corresponding to their performances had to be superior to 90% of the best French of the season. Maximum O₂ consumption and energy cost of running (C) had been measured within the 2 months preceding the track season, which, together with oxygen consumption at rest allowed us to calculate the maximalv that could be sustained under aerobic conditions: . The treadmill runningv corresponding to a blood lactate of 4 mmol·^–1 (v _la4), was also calculated. In the whole group, C was significantly related to height (r=–0.43;P<0.03). Neither C nor (with, in this case, the exception of the 3000 m athletes) were correlated to . On the other hand,v _{a max} was significantly correlated to over distances longer than 800 m. These were also correlated tov _la4. Howeverv _la4 occurred at 87.5% SD 3.3% ofv _{a max}, this relationship was interpreted as being an expression of the correlation betweenv _{a max} and . Calculation ofv _{a max} provided a useful means of analysing the performances. At the level of achievement studied, sustained over 3000 m corresponded tov _{a max}. The shape of the relationship ofv/v _{a max} as a function of the duration of the event raised the question of a possible change in C as a function of v during middle-distance running competitions.     

The relationship between test protocol and the development of exercise-induced hypoxemia (EIH) in highly trained athletes

Healthy male endurance-trained cyclists [n = 11, age = 27.3 (3.9) years; mass = 73.0 (9.3) kg; height = 180.5 (6.9) cm; maximal oxygen consumption ( = 71.1 (5.8) ml · kg^–1 · min^–1, mean ± (SD)] were recruited to assess the relationship between test protocol and the development of desaturation of arterial hemoglobin with oxygen, during incremental exercise tests to maximal aerobic capacity . All subjects demonstrated resting pulmonary function within normal limits [forced vital capacity (FVC) = 6.0 (0.9); forced expiratory volume (FEV_1.0) = 4.9 (0.6); FEV_1.0/FVC = 0.8 (0.1)] and completed three ramped tests (Mijnhardt KEM-3 electronically braked cycle ergometer) beginning at 0 W with increments of either 20, 30 or 40 W · min^–1. All periods of testing were separated by a minimum of 72 h. , peak minute ventilation (Medical Graphics, CPX-D), peak heart rate (ƒ_cpeak)), peak power output , and minimum percentage arterial oxyhemoglobin saturation (%S _aO_2min) (Omeda Biox 3740 pulse oximeter) were determined. There were no significant differences (p > 0.05) in [191.5 (26.2), 196.0 (24.4), 194.3 (23.9) 1 · min^–1] ƒ_cpeak [191.4 (7.0), 190.3 (5.5), 187.8 (5.9) beats · min^–1], [5.0 (0.5), 5.1 (0.4), 5.1 (0.5) 1 · min^–1] or %S _aO_2min [89.5 (1.5), 89.6 (1.3), 90.0 (2.3)] between protocols. The 20-W protocol [417 (27) W] demonstrated significantly lower (P < 0.05) than the 30-W [434 (36) W] and 40-W [453 (38) W] protocols, indicating that peripheral fatigue may play an important factor in response to these tests. The results of this study demonstrate that arterial desaturation occurs as a result of intense exercise in highly trained athletes independent of the rate of attainment of .     

Use of oxygen uptake recovery curve to predict peak oxygen uptake in upper body exercise

A group of 18 well-trained white-water kayakers performed maximal upper body exercise in the laboratory and during.a field test. Laboratory direct peak oxygen uptake ( ) values were compared, firstly by a backward extrapolation estimation and secondly by an estimation calculated from measured during the first 20 s of exercise recovery. Direct peak correlated with backward extrapolation (r=0.89), but the results of this study showed that the backward extrapolation method tended to overestimate significantly peak by [0.57 (SD 0.31) 1·min^–1 in the laboratory, and 0.66 (SD 0.33) 1·min^–1 in the field,P<0.001]. The measured during the first 20 s of recovery, whether the exercise was performed in the laboratory or in the field, correlated well with the laboratory direct peak (r=0.92 andr=0.91, respectively). The use of the regression equation obtained from field data _2f20s, that is peak ₂=0.23+1.08 _2f20s, gave an estimated peak ₂, the mean difference of which compared with direct peak was 0.22 (SD 0.13) 1·min^–1. In conclusion, we propose the use of a regression equation to estimate peak from a single sample of the gas expired during the first 20 s of recovery after maximal exercise involving the upper part of the body.     

Relationship between muscle fatigue and oxygen uptake during cycle ergometer exercise with different ramp slope increments

Summary The surface electromyogram (EMG) from active muscle and oxygen uptake ( ) were studied simultaneously to examine changes of motor unit (MU) activity during exercise tests with different ramp increments. Six male subjects performed four exhausting cycle exercises with different ramp slopes of 10, 20, 30 and 40 W · min^–1 on different days. The EMG signals taken from the vastus lateralis muscle were stored on a digital data recorder and converted to obtain the integrated EMG (iEMG). The was measured, with 20-s intervals, by the mixing chamber method. A non-linear increase in iEMG against work load was observed for each exercise in all subjects. The break point of the linear relationship of iEMG was determined by the crossing point of the two regression lines (iEMG_bp). Significant differences were obtained in the exercise intensities corresponding to maximal oxygen uptake ( ) and the iEMG_bp between 10 and 30, and 10 and 40 W · min –1 ramp exercises (P < 0.05). However, no significant differences were obtained in and corresponding to the iEMG_bp during the four ramp exercises. With respect to the relationship between and exercise intensity during the ramp increments, the -exercise intensity slope showed significant differences only for the upper half (i.e. above iEMG_bp). These results demonstrated that the and at which a nonlinear increase in iEMG was observed were not varied by the change of ramp slopes but by the exercise intensity corresponding to and the iEMG_bp was varied by the change of ramp slopes. In addition, the significant differences in the exercise intensity slopes for the upper half of the tests would suggest that the recruitment patterns of MU and/or muscle metabolic state might be considerably altered depending upon the ramp slope increments.     

The influence of weekly training distance on fractional utilization of maximum aerobic capacity in marathon and ultramarathon runners

Summary This study was designed to examine the interrelationships between performance in endurance running events from 10 to 90 km, training volume 3–5 weeks prior to competition, and the fractional utilization of maximal aerobic capacity (% ) during each of the events. Thirty male subjects underwent horizontal treadmill testing to determine their , and steady-state at specific speeds to allow for calculation of % sustained during competition. Runners were divided into groups of ten according to their weekly training distance (group A trained less than 60 km · week^–1, group B 60 to 100 km · week^–1, and group C more than 100 km · week^–1). Runners training more than 100 km · week^–1 had significantly faster running times (average 19.2%) in all events than did those training less than 100 km · week^–1. or % sustained during competition was not different between groups. The faster running speed of the more trained runners, running at the same % during competition, was due to their superior running economy (19.9%). Thus all of the group differences in running performance could be explained on the basis of their differences in running economy. These findings suggest either that the main effect of training more than 100 km · week^–1 may be to increase running economy, or that runners who train more than 100 km · week^–1 may have inherited superior running economy. The finding that the maximal horizontal running speed reached during the progressive maximal treadmill test was a better predictor (r=0.72) of running performance at all distances than was the (r=0.54) suggests that peak treadmill running speed can predict performance in endurance running events.     

The effects of one- and two-legged exercise on the lactate and ventilatory threshold

Summary The purpose of this investigation was to compare differences between one- and two-legged exercise on the lactate (LT) and ventilation (VT) threshold. On four separate occasions, eight male volunteer subjects (1-leg =3.36 l · min^–1; 2-leg =4.27 l · min^–1) performed 1- and 2-legged submaximal and maximal exercise. Submaximal threshold tests for 1- and 2-legs, began with a warm-up at 50 W and then increased every 3 minutes by 16 W and 50 W, respectively. Similar increments occurred every minute for the maximal tests. Venous blood samples were collected during the last 30 s of each work load, whereas noninvasive gas measures were calculated every 30 s. No differences in (l · min^–1) were found between 1- and 2-legs at LT or VT, but significant differences (p<0.05) were recorded at a given power output. Lactate concentration ([LA]) was different (p<0.05) between 1-and 2-legs (2.52 vs. 1.97 mmol · l^–1) at LT. This suggests it is rather than muscle mass which affects LT and VT. for 1-leg exercise was 79% of the 2-leg value. This implies the central circulation rather than the peripheral muscle is limiting to .Supported by NSERC A7555     

Times to exhaustion at 100% of velocity at\dot V{\text{O}}_{\text{2}} max and modelling of the time-limit / velocity relationship in elite long-distance runners

The aim of this study was to measure running times to exhaustion (Tlim) on a treadmill at 100% of the minimum velocity which elicits _{max max} in 38 elite male long - distance runners _max = 71.4 ± 5.5 ml.kg^–1.min^–1 and _max = 21.8 ± 1.2 km.h^–1). The lactate threshold (LT) was defined as a starting point of accelerated lactate accumulation around 4 mM and was expressed in _max. Tlim value was negatively correlated with _max (r = -0.362, p< 0.05) and _max (r = –0.347, p< 0.05) but positively with LT (%v _max) (r = 0.378, p < 0.05). These data demonstrate that running time to exhaustion at _max in a homogeneous group of elite male long-distance runners was inversely related to _max and experimentally illustrates the model of Monod and Scherrer regarding the time limit-velocity relationship adapted from local exercise for running by Hughson et al. (1984) .     

The effects of dietary manipulation upon the respiratory exchange ratio as a predictor of maximum oxygen uptake during fixed term maximal incremental exercise in man

Summary This study examined the effects of dietary manipulation upon the respiratory exchange ratio ( ) as a predictor of maximum oxygen uptake ( ). Seven healthy males performed fixed term maximal incremental treadmill exercise after an overnight fast on three separate occasions. The first test took place after the subjects had consumed their normal mixed diet (45±5% carbohydrate (CHO)) for a period of three days. This test protocol was then repeated after three days of a low CHO diet (3±2% CHO), and again after three days of a high CHO diet (61±5% CHO). Respiratory gases were continuously monitored during each test using an online system. No significant changes in mean exercise oxygen uptake ( ), or maximum functional heart rate (FHR_max) were found between tests. Mean exercise carbon dioxide output ( ) and R were significantly lower than normal after the low CHO diet (bothp<0.001) and significantly higher than normal after the high CHO diet (bothp<0.05). Moreover, compared with the normal CHO diet, the R-time relationship during exercise was at all times significantly (p<0.001) shifted to the right after the low CHO diet, and shifted to the left, being significantly so (p<0.05) over the final 5 min of exercise, after the high CHO diet. As a result, predictions of based on the R-time relationship were similar to recorded after the normal CHO dietary condition (-1.5±1.9%), but higher after the low CHO diet (+14.8±3.9%,p<0.001) and lower after the high CHO diet (–7.0±4.5%,p<0.01). These results indicate that dietary manipulation can significantly affect respiratory gas exchanges during fixed term maximal incremental exercise, and by doing so can significantly influence predictions of based on R.     

Cardiorespiratory and metabolic adaptations to hyperoxic training

This study examined the effects of hyperoxic training on specific cardiorespiratory and metabolic responses. A group of 19 male subjects trained for 5 weeks on a cycle ergometer at 70% of hyperoxic or normoxic maximal heart rate, the hyperoxic group (HG) breathing 70% O₂, the normoxic group (NG) breathing 21% O₂. The subjects were tested pre- and post-training under both hyperoxia and normoxia. Measurements included cardiac output , stroke volume (SV), heart rate (HR), pulmonary ventilation , oxygen consumption , partial pressure of oxygen (PO₂), partial pressure of inspired carbon dioxide (PCO₂), blood lactate concentration [L], and fiber type composition. The was significantly lower at submaximal work rates (P < 0.05) and maximal increased after training in both groups for both test conditions; hyperoxic was lower than normoxic (P < 0.05). The maximal increased significantly (P < 0.05) in both groups for both tests and was 11%–12% higher during hyperoxia. Post-training maximal heart rate (HR_max) was significantly decreased (P < 0.05) at the same absolute work rate regardless of the training group or test type. The SV was increased at each work rate and was unchanged. The maximal increased significantly (P < 0.05) for both groups and types of test: for normoxia: NG 27.3–30.4 l · min^–1 and HG 30.3–32.31 · min^–1 and for hyperoxia: NG 24.7–25.6 and HG 27.9–31.2 l · min^–1. Although working at the same intensity relative to HR_max, HG showed significantly lower [L] following a single training session, yet maximal values were unchanged after training. Both groups showed a significant increase in the percentage of type IIA fibers post-training but HG retained a larger percentage of HB fibers. Mitochondrial enzymes; citrate kinase, 3-hydroxyacyl CoA dehydrogenase, and cytochrome c-oxidase were increased in the normoxic trained subjects (P < 0.05). In summary, training induced adaptive responses in maximal aerobic power, HR, SV, , [L], and muscle fiber type composition, independent of inspired PO₂. Intramuscular data suggested there may be some differences between hyperoxic and normoxic training and these were substantiated by mitochondrial enzyme and lactate findings. Our data would suggest that transport mechanisms may limit the ability to increase aerobic power.     

Body composition,work capacity,and work efficiency of active and inactive young men

On 46 healthy young men, of whom 18 took part in strenuous sport at least once a week, height, weight, total body fat (as % of body mass) and lean body mass (LBM) were determined. The subjects performed submaximal exercise on a bicycle ergometer and climbing on an upwardly inclined treadmill at work loads of 60, 110, and 140 watts. Oxygen consumption ( ), respiratory quotient (RQ), energy expenditure (), and heart rate (f _H) were measured at rest and at each work load, and maximum oxygen intake ( max) and physical work capacity (PWC₁₅₀, PWC₁₇₀) were calculated.Anthropometric parameters did not differ significantly between sportsmen and sedentary subjects. max, PWC₁₅₀, and PWC₁₇₀ had higher correlations with LBM than with the other anthropometric parameters. max expressed in terms of LBM (ml/kg LBM/min) was the parameter which showed the clearest distinction between sportsmen and sedentary individuals. The sportsmen had higher max on the treadmill test than on the bicycle ergometer. PWC₁₅₀ and PWC₁₇₀ were higher on the bicycle than on the treadmill and had high correlations with max. Work efficiency was of the same order in both groups and showed negative correlation with the degree of obesity on the bicycle ergometer and positive correlation on the treadmill.     

Maximal cardiorespiratory responses to one- and two-legged cycling during acute and long-term exposure to 4300 meters altitude

Summary During exposure to altitudes greater than about 2200 m, maximal oxygen uptake ( ) is immediately diminished in proportion to the reduction in the partial pressure of oxygen in the inspired air. If the exposure lasts longer than a couple of days, an increase in arterial oxygen content (CaO₂), due to a hemoconcentration and an increase in arterial oxygen saturation, occurs. However, there is also a reduction in maximal cardiac output ( ) at altitude which offsets the increase in CaO₂ and, therefore, does not improve. The purpose of this investigation was to study the contribution of the increase in CaO₂ to the working muscles without the potentially confounding problem of a reduced . The approach used was to have seven male subjects (aged 17 to 24 years) perform one- and two-legged tests on a cycle ergometer at sea level (SL, PIO₂ = 159 Torr), after 1 h at 4300 m simulated altitude (SA, PIO₂ = 94 Torr) and during two weeks of residence on the summit of Pikes Peak, CO. (pP, 4300 m, PIO₂ = 94 Torr). Cardiac output limits maximal performance during two-legged cycling but does not limit performance during one-legged cycling. During the study, CaO₂ changed from 189±3 (mean ±SE) at SL to 161±4 ml·L^–1 during SA (SL vs. SA,p<0.01) and to 200±6 ml·L^–1 at PP (SL vs. PP,p<0.05; SA vs. PP,p<0.01). Two-legged decreased from 3.64±0.26 L·min^–1 at SL to 2.70±0.14 L·min^–1 during SA (p<0.01) to 2.86±0.16 L·min^–1 at PP (p<0.01). One-legged decreased from 2.95±0.22 at SL to 2.25±0.17 L·min^–1 during SA (SL vs. SA,p<0.01) but improved to 2.66±0.18 L·min^–1 at PP (SA vs. PP,p<0.05). Since only one-legged increased as more oxygen was made available to the working muscles, the altitude-induced reduction in can be implicated as being responsible for the reduction in during two-legged cycling.     

Plasma sulpho-conjugated catecholamine dynamics up to 8 h after 60-min exercise at 50% and 70% maximal oxygen uptakes

The prolonged effects of steady-state exercise and meals on plasma sulpho-conjugated catecholamines (CA) after exercise were examined. Seven male subjects exercised on 2 separate days for 60 min at 50% and 70% of maximal oxygen uptake ( ) on a cycle ergometer and then rested, for 8 h sitting in an armchair. A control trial without any exercise was also performed. At 2 h after the end of exercise the subjects were given a meal. The plasma free and sulphated CA, oxygen uptake ( ) and heart rate (HR) were all measured before exercise, during exercise and hourly during the 8-h recovery period. The sulphated noradrenaline (NA-S) and adrenaline (A-S) concentrations increased after exercise, and, furthermore, only the NA-S concentrations remained elevated for 6 h after exercise at 50% and for 8 h at 70% trial, compared with the control trial. There were no changes in either the plasma NA-S or A-S concentrations after consuming a meal, whereas the dopamine sulphate concentration demonstrated a dynamic change. A significantly higher excess postexercise was observed at 2 h postexercise at 50% and at 6 h postexercise at 70% trials. The mean HR was still elevated at 6 and 8 h after exercise, which closely correlated with the duration of the elevated NA-S concentrations. These results suggest that sulphated CA, especially NA-S, could represent an additional index of sympathetic nerve activity after exercise, and that a meal containing small amounts of the amines would seem to have no effect on plasma NA-S and A-S concentrations.     

Use of the force-velocity test to determine the optimal braking force for a sprint exercise on a friction-loaded cycle ergometer

A group of 15 untrained male subjects pedalled on a friction-loaded cycle ergometer as fast as possible for 5–7 s to reach the maximal velocity (V{immax}) against different braking forces (F _B). Power was averaged during a complete crank rotation by adding the power dissipated againstF _B to the power necessary to accelerate the flywheel. For each sprint, determinations were made of peak power output ( ) power output attained atV _max ( ) calculated as the product ofV _max andF _B and the work performed to reachV _max expressed in mean power output ( ). The relationships between these parameters andF _B were examined. A biopsy taken from the vastus lateralis muscle and tomodensitometric radiographs of both thighs were taken at rest to identify muscle metabolic and morphometric properties. The value was similar for allF _B. Therefore, the average of values was defined as corrected maximal power ( ). This value was 11 higher than the maximal power output uncorrected for the acceleration. Whereas the determination did not require high loads, the highest value ( ) was produced when loading was heavy, as evidenced by the -F _B parabolic relationship. For each subject, the braking force ( ) giving was defined as optimal. The , equal to 0.844 (SD 0.108) N · kg⁻¹ bodymass, was related to thigh muscle area (r = 0.78,P < 0.05). The maximal velocity ( ) reached against this force seemed to be related more to intrinsic fibre properties (% fast twitch b fibre area and adenylate kinase activity). Thus, from the determination, it is suggested that it should be possible to predict the conditions for optimal exercise on a cycle ergometer.     

Effect of coupling the breathing- and cycling rhythms on oxygen uptake during bicycle ergometry

Summary The influence of the degree of coupling between the breathing and cycling rhythms (K) on oxygen uptake was examined in 30 volunteers. They cycled on an ergometer with a load equal to 50% of their work capacity 170 in two experimental runs with spontaneous breathing rhythm, and in a further two runs with acoustically triggered breathing. K was continuously ascertained. and other respiratory parameters were measured by an automatic breath-by-breath analysis system.In 16 subjects, -differences between runs were correlated with the differences in K. In the majority of these subjects (12), decreased significantly with increasing K. In 14 subjects, -and K-variations within individual runs were analyzed. Phases with higher K were regularly accompanied by a decrease in .It is concluded that coupling the breathing and cycling rhythms reduces for a given moderate work load, although the magnitude of the -reduction varies considerably between individuals.