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.     

A cycle ergometer test of maximal aerobic power

Summary An indirect test of maximal aerobic power (IMAP) was evaluated in 31 healthy male subjects by comparing it with a direct treadmill measurement of maximal aerobic power ( O₂ max), with the prediction of O₂ max from heart rate during submaximal exercise on a cycle ergometer using åstrand's nomogram, with the British Army's Basic Fitness Test (BFT, a 2.4 km run performed in boots and trousers), and with a test of maximum anaerobic power. For the IMAP test, subjects pedalled on a cycle ergometer at 75 revs·min^–1. The workload was 37.5 watts for the first minute, and was increased by 37.5 watts every minute until the subject could not continue. Time to exhaustion was recorded. Predicted O₂ max and times for BFT and IMAP correlated significantly (p<0.001) with the direct O₂ max: r=0.70, r=0.67 and r=0.79 respectively. The correlation between direct O₂ max and the maximum anaerobic power test was significant (p<0.05) but lower, r=0.44. Although lactate levels after direct O₂ max determination were significantly higher than those after the IMAP test, maximum heart rates were not significantly different. Submaximal O₂ values measured during the IMAP test yielded a regression equation relating O₂ max and pedalling time. When individual values for direct and predicted O₂ max and times for BFT and IMAP were compared with equivalent standards, the percentages of subjects able to exceed the standard were 100, 65, 87, and 87 respectively. These data demonstrate that the IMAP test provides a valid estimate of O₂ max and indicate that it may be a practical test for establishing that an individual meets a minimum standard.     

Cardiac output in paraplegic subjects at high exercise intensities

Summary The purpose of this investigation was to compare cardiac output ( _c ) in paraplegic subjects (P) with wheelchair-confined control subjects (C) at high intensities of arm exercise. At low and moderate exercise intensity _c was the same at a given oxygen uptake ( O₂) in P and C. A group of 11 athletic male P with complete spinal-cord lesions between T6 and T12 and a group of 5 well-matched athletic male C performed maximal arm-cranking exercise and submaximal exercise at 50%, 70% and 80% of each individual's maximal power output (W_max) . Maximal O₂ ( O_2max) was significantly lower, O_2max per kilogram body mass was equal and maximal heart rate (f _c) was significantly higher in P compared to C. At O₂ of 1.3, 1.5 and 1.7 1-min^–1, and for P 65%–90% of the O_2max, _c was not significantly different between the groups, although, _c in P was achieved with a significantly lower stroke volume (SV) and a significantly higherf _c. Although the SV was lower in P, it followed the same pattern as SV in C during incremental exercise, i.e. an increase in SV until about 45%W _max and thereafter a stable SV. The similar _c at a given O₂ in both groups indicated that, even at high exercise intensities, circulation in P can be considered isokinetic with a complete compensation byf _c for a lower SV.     

A method for determining the maximal steady state of blood lactate concentration from two levels of submaximal exercise

The aim of this study was to estimate the characteristic exercise intensity _CL which produces the maximal steady state of blood lactate concentration (MLSS) from submaximal intensities of 20 min carried out on the same day and separated by 40 min. Ten fit male adults [maximal oxygen uptake _max 62 (SD 7) ml · min^–1 · kg^–1] exercisOed for two 30-min periods on a cycle ergometer at 67% (test 1.1) and 82% of _max (test 1.2) separated by 40 min. They exercised 4 days later for 30 min at 82% of _max without prior exercise (test 2). Blood lactate was collected for determination of lactic acid concentration every 5 min and heart rate and O₂ uptake were measured every 30 s. There were no significant differences at the 5th, 10th, 15th, 20th, 25th, or 30th min between , lactacidaemia, and heart rate during tests 1.2 and 2. Moreover, we compared the exercise intensities _CL which produced the MLSS obtained during tests 1.1 and 1.2 or during tests 1.1 and 2 calculated from differential values of lactic acid blood concentration ([1a^–]_b) between the 30th and the 5th min or between the 20th and the 5th min. There was no significant difference between the different values of _CL [68 (SD 9), 71 (SD 7), 73 (SD 6),71 (SD 11) % of _max (ANOVA test,P<0.05). Four subjects ran for 60 min at their _CL determined from periods performed on the same day (test 1.1 and 1.2) and the difference between the [la^–]_b at 5 min and at 20 min ( ([la^–]_b)) was computed. The [la^–]_b remained constant during exercise and ranged from 2.2 to 6.7 mmol · l^–1 [mean value equal to 3.9 (SD 1) mmol · l^–1]. These data suggest that the _CL protocol did not overestimate the exercise intensity corresponding to the maximal fractional utilization of _max at MLSS. For half of the subjects the _CL was very close to the higher stage (82% of _max where an accumulation of lactate in the blood with time was observed. It can be hypothesized that _CL was very close to the real MLSS considering the level of accuracy of [la^–]_b measurement. This study showed that exercise at only two intensities, performed at 65% and 80% of _max and separated by 40 min of complete rest, can be used to determine the intensity yielding a steady state of [la^–1]_b near the real MLSS workload value.     

Submaximal working capacity,heart size and body size in boys 8–18 years

Heart diameters, heart volume (HV), PWC ₁₃₀, O₂ at 130 heart rate, and cardiorespiratory reactions during work at 3 kgm·s^–1 were obtained in 237 boys ranging in age from 8–18 years. Results indicate that heart size, PWC ₁₃₀, O₁₃₀, and exercise HR, O₂/HR, and SBP change significantly with age. On the other hand, HV·kg^–1 and work O₂, _E and _E/ O₂ remain rather stable throughout the growth period.Correlation analysis indicates that about 85% of the observed variation in the size of the heart during growth can be accounted for by body weight, while about 70% of the variation in light submaximal working capacity ( O₁₃₀) can be explained by HV alone. Holding age, height and body weight constant by partial correlation procedures yields significant relationships between HV and O₁₃₀ (r = 0.461), and between HV·kg^–1 and O₁₃₀ (r = 0.414). Age, height, weight and size of the heart correlated simultaneously against O₁₃₀ account for 75% of the variance in the dependent variable.It would seem important to suggest the need for study of the interactions between age, size and maturity, in addition to indicators of size and efficiency of the oxygen delivery system, and indices of muscle oxygen utilization efficiency. Such an approach will permit a more definite partitioning of the variance in submaximal aerobic capacity during growth, and would probably yield a more conservative estimate of the relationship between the size of the heart and submaximal working capacity during growth.Abbreviations used HV heart volume - HV·kg^–1 heart volume per kg of body weight - PWC ₁₃₀ physical working capacity in kgm·s^–1 of work at a heart rate of 130·min^–1 - O₁₃₀ oxygen consumption per min at a heart rate of 130·min^–1 - O₂, , _E, _E/ O₂, HR, O₂/HR, SBP oxygen consumption, breathing frequency, expiratory volume, respiratory equivalent, heart rate, oxygen pulse, systolic blood pressure in the third minute of work at 3 kgm·s^–1 - CA chronological age Partially supported by grants from the Kuratorium für die Sportmedizinische Forschung, Federal Republic of Germany and Laval University, Quebec, Canada     

The influence of inspired oxygen on the oxygen uptake response to ramp exercise

The relation between and work rate (WR) was examined in seven male subjects who performed ramp (1 W·3 s^–1) two-legged cycle ergometry to exhaustion while inspiring either hypoxic (12% O₂), normoxic (21% O₂), or hyperoxic (40% O₂) air. The anaerobic threshold was estimated from respiratory gas exchange data and is thus referred to as the respiratory gas exchange threshold (RGET). Prior to the RGET, the was greater under normoxic [mean (SD); 10. 19(1.04) ml O₂·min^–1·W^–1] and hyperoxic [10.44 (0.72)] conditions compared with hypoxia [9.34 (0.89)]. Above the RGET, the for hypoxia [8.91 (0.63)], normoxia [10.40 (0.77)], and hyperoxia [11.08 (0.48)] were all significantly different from each other. These data indicated that for two-legged, cycle, ramp ergometry in normoxia below the RGET, both the and response time was constant. Above the RGET, the normoxic response was the net result of a declining and a longer response time to the unsteady state character of a ramp exercise protocol.     

Pulmonary gas exchange and ventilatory responses to brief intense intermittent exercise in young trained and untrained adults

To investigate pulmonary gas exchange and ventilatory responses to brief intense intermittent exercise and to study the effects of physical fitness on thes responses, nine trained and nine untrained healthy male subjects aged 18–33 years performed the force-velocity (F-) exercise test. This test consisted of 6-s sprints against increasing braking forces (F) separated by 5-min recovery periods. Oxygen uptake ( ), carbon dioxide output ( CO₂), and ventilation _E) were continuously measured during the test and the magnitudes of their responses to the sprints were then calculated.For all subjects CO₂ increased rapidly after beginning the sprints, and the peaks of the responses (F = 13.4;P < 0.001), end of recovery values (F = 6.5;P < 0.01), and O₂ magnitudes of response (F = 12.4;P < 0.001) rose significantly with the repetition of the sprints. The O₂ magnitudes of response correlated with the corresponding sprint power outputs (r = 0.55;P < 0.001) and with the sprint repetitions (r = 0.51,P < 0.001). The CO₂ (F = 7.1;P < 0.01) and {ie442-8} (F = 5.0;P < 0.01) peaks of response increased with the initial load incrementation, then stabilized when the subjects attained peak power output. End of recovery CO₂ (F = 18.0;P < 0.001) and _E (F = 14.1;P < 0.001) values rose with increasingF. TheF- peak O₂, CO₂, _E, tidal volume and respiratory frequency responses attained 53%, 40%, 44%, 66%, and 82% of the peak values measured at exhaustion of maximal graded exercise, respectively.Trained and untrained subjects had the same first sprint power output and braking, force. Nevertheless, the trained subjects had higher O₂ peaks (F = 35.2;P < 0.001) and CO₂ magnitudes of response (F = 30.0;P < 0.001) than the untrained subjects for all sprints. The higher peak O₂ values represented similar percentages of maximal oxygen uptake in the trained and untrained subjects. In summary, the present study showed that in brief intense intermittent exercise, i.e. theF- test, the O₂, CO₂, and ventilatory responses in young subjects were submaximal with respect to the peak values attained at exhaustion of maximal graded exercise. The CO₂ magnitude of response increase was related to the power output rise in the corresponding sprints and to the repetition of sprints. Moreover, the trained subjects presented higher CO₂ peaks and magnitudes of response to the sprints than the untrained subjects.     

Respiratory responses of elite oarsmen,former oarsmen,and highly trained non-rowers during rowing,cycling and running

The position of the body and use of the respiratory muscles in the act of rowing may limit ventilation and thereby reduce maximal aerobic power relative to that achieved in cycling or running, in spite of the greater muscle mass involved in rowing. This hypothesis was investigated for three groups of male subjects: nine elite senior oarsmen, eight former senior oarsmen and eight highly trained athletes unskilled in rowing. The subjects performed graded exercise to maximal effort on a rowing ergometer, cycle ergometer and treadmill while respiratory minute volume and oxygen consumption were monitored continuously. The VE at a given during intense submaximal exercise (greater than 75% of maximal ) was not significantly lower in rowing compared with that in cycling and treadmill running for any group, which would suggest that submaximal rowing does not restrict ventilation. At maximal effort, and for rowing were less than those for the other types of exercise in all the groups, although the differences were not statistically significant in the elite oarsmen. These data are consistent with a ventilatory limitation to maximal performance in rowing that may have been partly overcome by training in the elite oarsmen. Alternatively, a lower maximal VE in rowing might have been an effect rather than a cause of a lower maximal if maximal was limited by the lower rate of muscle activation in rowing.     

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.     

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.     

Changes in skeletal muscle oxygenation during incremental exercise measured with near infrared spectroscopy

To determine the change in muscle oxygenation in response to progressively increasing work rate exercise, muscle oxyhemoglobin + oxymyoglobin saturation was measured transcutaneously with near infrared spectroscopy in the vastus lateralis muscle during cycle ergometry. Studies were done in 11 subjects while gas exchange was measured breath-by-breath. As work rate was increased, tissue oxygenation initially either remained constant near resting levels or, more usually, decreased. Near the work rate and metabolic rate where significant lactic acidosis was detected by excess CO₂ production (lactic acidosis threshold, LAT), muscle oxygenation decreased more steeply. As maximum oxygen uptake ( ) was approached, the rate of desaturation slowed. In 8 of the 11 subjects, tissue O₂ saturation reached a minimum which was sustained for 1–3 min before was reached. The LAT correlated with both the (r = 0.95,P < 0.0001) and the work rate (r = 0.94,P < 0.0001) at which the rate of tissue O₂ desaturation accelerated. These results describe a consistent pattern in the rate of decrease in muscle oxygenation, slowly decreasing over the lower work rate range, decreasing more rapidly in the work rate range of the LAT and then slowing at about 80% of , approaching or reaching a minimum saturation at .     

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.     

Relationships of the anaerobic threshold with the 5 km, 10 km,and 10 mile races

Summary The purpose of present study was to assess the relationship between anaerobic threshold (AT) and performances in three different distance races (i.e., 5 km, 10 km, and 10 mile). AT, O₂ max, and related parameters for 17 young endurance runners aged 16–18 years tested on a treadmill with a discontinuous method. The determination of AT was based upon both gas exchange and blood lactate methods. Performances in the distance races were measured within nearly the same month as the time of experiment. Mean AT- O₂ was 51.0 ml·kg^–1·min^–1 (2.837 l·min^–1), while O₂ max averaged 64.1 ml·kg^–1·min^–1 (3.568 l·min^–1). AT-HR and %AT (AT- O₂/ O₂ max) were 174.7 beats·min^–1 and 79.6%, respectively. The correlations between O₂ max (ml·kg^–1·min^–1) and performances in the three distance races were not high (r=–0.645, r=–0.674, r=–0.574), while those between AT- O₂ and performances was r=–0.945, r=–0.839, and r=–0.835, respectively. The latter results indicate that AT- O₂ alone would account for 83.9%, 70.4%, and 69.7% of the variance in the 5 km, 10 km, and 10 mile performances, respectively. Since r=–0.945 (5 km versus AT- O₂) is significantly different from r=–0.645 (5 km versus O₂ max), the 5 km performance appears to be more related to AT- O₂ than VO₂ max. It is concluded that individual variance in the middle and long distance races (particularly the 5 km race) is better accounted for by the variance in AT- O₂ expressed as milliliters of oxygen per kilogram of body weight than by differences in O₂ max.     

Oxygen uptake during swimming in a hypobaric hypoxic environment

Summary The purpose of this study was to determine oxygen uptake O₂) at various water flow rates and maximal oxygen uptake ( O_2max) during swimming in a hypobaric hypoxic environment. Seven trained swimmers swam in normal [N; 751 mmHg (100.1 kPa)] and hypobaric hypoxic [H; 601 mmHg (80.27 kPa)] environments in a chamber where atmospheric pressure could be regulated. Water flow rate started at 0.80 m · s^–1 and was increased by 0.05 m· s^–1 every 2 min up to 1.00 m · s^–1 and then by 0.05 m · s^–1 every minute until exhaustion. At submaximal water flow rates, carbon dioxide production ( CO₂), pulmonary ventilation ( _E) and tidal volume (V _T) were significantly greater in H than in N. There were no significant differences in the response of submaximal O₂, heart rate (f _c) or respiratory frequency (f _R) between N and H. Maximal _E,f _R,V _T,f _c blood lactate concentration and water flow rate were not significantly different between N and H. However, VO_2max under H [3.65 (SD 0.11) l · min^–1] was significantly lower by 12.0% (SD 3.4) % than that in N [4.15 (SD 0.18) l · min^–1] . This decrease agrees well with previous investigations that have studied centrally limited exercise, such as running and cycling, under similar levels of hypoxia.     

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) .     

Specificity of physiological adaptation to endurance training in distance runners and competitive walkers

Summary The present study was designed to evaluate the specificity of physiological adaptation to extra endurance training in five female competitive walkers and six female distance runners. The mean velocity ( ) during training, corresponding to 4 mM blood lactate [onset of blood lactate accumulation (OBLA)] during treadmill incremental exercise (training was 2.86 m·s^–1 SD 0.21 in walkers and 4.02 m·s^–1, SD 0.11 in runners) was added to their normal training programme and was performed for 20 min, 6 days a week for 8 weeks, and was called extra training. An additional six female distance runners performed only their normal training programme every day for about 120 min at an exercise intensity equivalent to their lactate threshold (LT) (i.e. a running of about 3.33 m·s^–1). After the extra training, there were statistically significant increases in blood lactate variables (i.e. oxygen uptake ( O₂) at LT, at LT, O₂ at OBLA, at OBLA; P<0.05), and running F for 3,000m (P<0.01) in the running training group. In the walking training group, there were significant increases in blood lactate variables (i.e., at LT, at OBLA; P<0.05), and walking economy. In contrast, there were no significant changes in lactate variables, running and economy in the group of runners which carried out only the normal training programme. It is suggested that the changes in blood lactate variables such as LT and OBLA played a role in improving F of both the distance runners and the competitive walkers. Furthermore, the significant improvement in walking economy brought about by extra endurance training might be a specific phenomenon for competitive walkers compared to runners.     

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.     

Oxygen uptake during running as related to body mass in circumpubertal boys: a longitudinal study

Summary To investigate the effect of endurance training on physiological characteristics during circumpubertal growth, eight young runners (mean starting age 12 years) were studied every 6 months for 8 years. Four other boys served as untrained controls. Oxygen uptake ( O ₂) and blood lactate concentrations were measured during submaximal and maximal treadmill running. The data were aligned with each individual's age of peak height velocity. The maximal oxygen uptake ( O _2max; ml · kg^–1 · min^–1) decreased with growth in the untrained group but remained almost constant in the training group. The oxygen cost of running at 15 km · h^–1 ( O ₂₁₅, ml · kg^–1 · min^–1) was persistently lower in the trained group but decreased similarly with age in both groups. The development of O _2max and O ₂₁₅ (1 · min^–1) was related to each individual's increase in body mass so that power functions were obtained. The mean body mass scaling factor was 0.78 (SEM 0.07) and 1.01 (SEM 0.04) for O _2max and 0.75 (SEM 0.09) and 0.75 (SEM 0.02) for O ₂₁₅ in the untrained and trained groups, respectively. Therefore, expressed as ml · kg^–0.75 · min^–1, O ₂₁₅ was unchanged in both groups and O _2max increased only in the trained group. The running velocity corresponding to 4 mmol · 1^–1 of blood lactate ( _la4) increased only in the trained group. Blood lactate concentration at exhaustion remained constant in both groups over the years studied. In conclusion, recent and the present findings would suggest that changes in the oxygen cost of running and O _2max (ml · kg^–1 · min^–1) during growth may mainly be due to an overestimation of the body mass dependency of O ₀₂ during running. The O ₂ determined during treadmill running may be better related to kg^0.75 than to kg¹.     

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      

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.