Physiological background of the change point in VO2 and the slow component of oxygen uptake kinetics.

It is generally believed that oxygen uptake during incremental exercise--until VO2max, increases linearly with power output (see eg. Astrand & Rodahl, 1986). On the other hand, it is well established that the oxygen uptake reaches a steady state only during a low power output exercise, but during a high power output exercise, performed above the lactate threshold (LT), the oxygen uptake shows a continuous increase until the end of the exercise. This effect has been called the slow component of VO2 kinetics (Whipp & Wasserman, 1972). The presence of a slow component in VO2 kinetics implies that during an incremental exercise test, after the LT has been exceeded, the VO2 to power output relationship has to become curvilinear. Indeed, it has recently been shown that during the incremental exercise, the exceeding of the power output, at which blood lactate begins to accumulate (LT), causes a non-proportional increase in VO2 (Zoladz et al. 1995) which indicates a drop in muscle mechanical efficiency. The power output at which VO2 starts to rise non-proportionally to the power output has been called "the change point in VO2" (Zoladz et al. 1998). In this paper, the significance of the factors most likely involved in the physiological mechanism responsible for the change point in oxygen uptake (CP-VO2) and for the slow component of VO2 kinetics, including: increase of activation of additional muscle groups, intensification of the respiratory muscle activity, recruitment of type II muscle fibres, increase of muscle temperature, increase of the basal metabolic rate, lactate and hydrogen ion accumulation, proton leak through the inner mitochondrial membrane, slipping of the ATP synthase and a decrease in the cytosolic phosphorylation potential, are discussed. Finally, an original own model describing the sequence of events leading to the non-proportional increase of oxygen cost of work at a high exercise intensity is presented.     

Physiological Criteria in Defining the Standards for Training and Competition Loads in Elite Sports

Adaptation to training loads can be quantitatively described by a dose-effect dependence, with the gain in the training function over a certain period regarded as the effect and the dose expressed as a product of the energy spent during exercise and the stimulus duration. The duration combines the periods of exercises, pauses, and recovery needed to compensate for the fast fraction of the oxygen debt. In addition to direct measurements of the energy spent, quantitative assessment of the load intensity can be based on the total pulse cost of exercise, which accurately reflects the changes in the oxygen demand and the energy cost of the physical load. To quantitate and standardize training and competition loads, we suggest the use of correlations found between the pulse and energy costs of exercises and their relative power determined in critical modes of muscle activity: at the anaerobic threshold; the critical power, associated with the maximum oxygen consumption; the alactic anaerobic threshold; the power of exhaustion, when blood lactic acid reaches its maximum; or at maximum aerobic power, when the muscle reserves of ATP and creatine phosphate are the most depleted.     

Influence of L-carnitine administration on maximal physical exercise

The effects of L-carnitine administration on maximal exercise capacity were studied in a double-blind, cross-over trial on ten moderately trained young men. A quantity of 2 g of L-carnitine or a placebo were administered orally in random order to these subjects 1 h before they began exercise on a cycle ergometer. Exercise intensity was increased by 50-W increments every 3 min until they became exhausted. After 72-h recovery, the same exercise regime was repeated but this time the subjects, who had previously received L-carnitine, were now given the placebo and vice versa. The results showed that at the maximal exercise intensity, treatment with L-carnitine significantly increased both maximal oxygen uptake, and power output. Moreover, at similar exercise intensities in the L-carnitine trial oxygen uptake, carbon dioxide production, pulmonary ventilation and plasma lactate were reduced. It is concluded that under these experimental conditions pretreatment with L-carnitine favoured aerobic processes resulting in a more efficient performance. Possible mechanisms producing this effect are discussed.     

On the kinetics of anaerobic power

ABSTRACT: BACKGROUND: This study investigated two different mathematical models for the kinetics of anaerobic power. Model 1 assumes that the work power is linear with the work rate, while model 2 assumes a linear relationship between the alactic anaerobic power and the rate of change of the aerobic power. In order to test these models, a cross country skier ran with poles on a treadmill at different exercise intensities. The aerobic power, based on the measured oxygen uptake, was used as input to the models, whereas the simulated blood lactate concentration was compared with experimental results. Thereafter, the metabolic rate from phosphocreatine break down was calculated theoretically. Finally, the models were used to compare phosphocreatine break down during continuous and interval exercises. RESULTS: Good similarity was found between experimental and simulated blood lactate concentration during steady state exercise intensities. The measured blood lactate concentrations were lower than simulated for intensities above the lactate threshold, but higher than simulated during recovery after high intensity exercise when the simulated lactate concentration was averaged over the whole lactate space. This fit was improved when the simulated lactate concentration was separated into two compartments; muscles + internal organs and blood. Model 2 gave a better behavior of alactic energy than Model 1 when compared against invasive measurements presented in the literature. During continuous exercise, model 2 showed that the alactic energy storage decreased with time, whereas model 1 showed a minimum value when steady state aerobic conditions were achieved. During interval exercise the two models showed similar patterns of alactic energy. CONCLUSIONS: The current study provides useful insight on the kinetics of anaerobic power. Overall, our data indicates that blood lactate levels can be accurately modeled during steady state, and suggests a linear relationship between the alactic anaerobic power and the rate of change of the aerobic power.     

Effect of blood lactate concentration and the level of oxygen uptake immediately before a cycling sprint on neuromuscular activation during repeated cycling sprints

The purpose of this study was to determine whether neuromuscular activation is affected by blood lactate concentration (La) and the level of oxygen uptake immediately before a cycling sprint (preVO(2)). The tests consisted of ten repeated cycling sprints for 10 sec with 35-sec (RCS(35)) and 350-sec recovery periods (RCS(350)). Peak power output (PPO) was not significantly changed despite an increase in La concentration up to 12 mmol/L in RCS(350). Mean power frequency (MPF) of the power spectrum calculated from a surface electromyogram on the vastus lateralis showed a significantly higher level in RCS(350). In RCS(35), preVO(2) level and La were higher than those in RCS(350) in the initial stage of the RCS and in the last half of the RCS, respectively. Thus, neuromuscular activation during exercise with maximal effort is affected by blood lactate concentration and the level of oxygen uptake immediately before exercise, suggesting a cyclic system between muscle recruitment pattern and muscle metabolites.     

Effects of progressive exercise and hypoxia on human muscle sarcoplasmic reticulum function.

This study examined the effects of progressive exercise to fatigue in normoxia (N) on muscle sarcoplasmic reticulum (SR) Ca(2+) cycling and whether alterations in SR Ca(2+) cycling are related to the blunted peak mechanical power output (PO(peak)) and peak oxygen consumption (Vo(2 peak)) observed during progressive exercise in hypoxia (H). Nine untrained men (20.7 +/- 0.42 yr) performed progressive cycle exercise to fatigue on two occasions, namely during N (inspired oxygen fraction = 0.21) and during H (inspired oxygen fraction = 0.14). Tissue extracted from the vastus lateralis before exercise and at power output corresponding to 50 and 70% of Vo(2 peak) (as determined during N) and at fatigue was used to investigate changes in homogenate SR Ca(2+)-cycling properties. Exercise in H compared with N resulted in a 19 and 21% lower (P < 0.05) PO(peak) and Vo(2 peak), respectively. During progressive exercise in N, Ca(2+)-ATPase kinetics, as determined by maximal activity, the Hill coefficient, and the Ca(2+) concentration at one-half maximal activity were not altered. However, reductions with exercise in N were noted in Ca(2+) uptake (before exercise = 357 +/- 29 micromol x min(-1) x g protein(-1); at fatigue = 306 +/- 26 micromol x min(-1) x g protein(-1); P < 0.05) when measured at free Ca(2+) concentration of 2 microM and in phase 2 Ca(2+) release (before exercise = 716 +/- 33 micromol x min(-1) x g protein(-1); at fatigue = 500 +/- 53 micromol x min(-1) x g protein(-1); P < 0.05) when measured in vitro in whole muscle homogenates. No differences were noted between N and H conditions at comparable power output or at fatigue. It is concluded that, although structural changes in SR Ca(2+)-cycling proteins may explain fatigue during progressive exercise in N, they cannot explain the lower PO(peak) and Vo(2 peak) observed during H.     

Allopurinol intake does not modify the slow component of V(.)O(2) kinetics and oxidative stress induced by severe intensity exercise

The aim of this study was to test the hypothesis that allopurinol ingestion modifies the slow component of V(.)O(2) kinetics and changes plasma oxidative stress markers during severe intensity exercise. Six recreationally active male subjects were randomly assigned to receive a single dose of allopurinol (300 mg) or a placebo in a double-blind, placebo-controlled crossover design, with at least 7 days washout period between the two conditions. Two hours following allopurinol or placebo intake, subjects completed a 6-min bout of cycle exercise with the power output corresponding to 75 % V(.)O(2)max. Blood samples were taken prior to commencing the exercise and then 5 minutes upon completion. Allopurinol intake caused increase in resting xanthine and hypoxanthine plasma concentrations, however it did not affect the slow component of oxygen uptake during exercise. Exercise elevated plasma inosine, hypoxanthine, and xanthine. Moreover, exercise induced a decrease in total antioxidant status, and sulfhydryl groups. However, no interaction treatment x time has been observed. Short term severe intensity exercise induces oxidative stress, but xanthine oxidase inhibition does not modify either the kinetics of oxygen consumption or reactive oxygen species overproduction.     

Circulating plasma VEGF response to exercise in sedentary and endurance-trained men.

The skeletal muscle capillary supply is an important determinant of maximum exercise capacity, and it is well known that endurance exercise training increases the muscle capillary supply. The muscle capillary supply and exercise-induced angiogenesis are regulated in part by vascular endothelial growth factor (VEGF). VEGF is produced by skeletal muscle cells and can be secreted into the circulation. We investigated whether there are differences in circulating plasma VEGF between sedentary individuals (Sed) and well-trained endurance athletes (ET) at rest or in response to acute exercise. Eight ET men (maximal oxygen consumption: 63.8 +/- 2.3 ml x kg(-1) x min(-1); maximum power output: 409.4 +/- 13.3 W) and eight Sed men (maximal oxygen consumption: 36.3 +/- 2.1 ml x kg(-1) x min(-1); maximum power output: 234.4 +/- 13.3 W) exercised for 1 h at 50% of maximum power output. Antecubital vein plasma was collected at rest and at 0, 2, and 4 h postexercise. Plasma VEGF was measured by ELISA analysis. Acute exercise significantly increased VEGF at 0 and 2 h postexercise in ET subjects but did not increase VEGF at any time point in Sed individuals. There was no difference in VEGF between ET and Sed subjects at any time point. When individual peak postexercise VEGF was analyzed, exercise did increase VEGF independent of training status. In conclusion, exercise can increase plasma VEGF in both ET athletes and Sed men; however, there is considerable variation in the individual time of the peak VEGF response.     

Effect of changes in arterial oxygen content on circulation and physical performance.

To evaluate the effect of different levels of arterial oxygen content on hemodynamic parameters during exercise nine subjects performed submaximal bicycle or treadmill exercise and maximal treadmill exercise under three different experimental conditions: 1) breathing room air (control); 2) breathing 50% oxygen (hyperoxia); 3) after rebreathing a carbon monoxide gas mixture (hypoxia). Maximal oxygen consumption (Vo2 max) was significantly higher in hyperoxia (4.99 1/min) and significantly lower in hypoxia (3.80 1/min) than in the control experiment (4.43 1/min). Physical performance changes in parallel with Vo2 max. Maximal cardiac output (Qmax) was similar in hyperoxia as in control but was significantly lower in hypoxia mainly due to a decreased stroke volume. A correlation was found between Vo2 max and transported oxygen, i.e., Cao2 times Amax, thus suggesting that central circulation is an important limiting factor for human maximal aerobic power. During submaximal work HR was decreased in hyperoxia and increased in hypoxia. Corresponding Q values were unchanged except for a reduction during high submaximal exercise in hyperoxia.     

Influence of training status on maximal accumulated oxygen deficit during all-out cycle exercise

The influence of training status on the maximal accumulated oxygen deficit (MAOD) was used to assess the validity of the MAOD method during supramaximal all-out cycle exercise. Sprint trained (ST; n = 6), endurance trained (ET; n = 8), and active untrained controls (UT; n = 8) completed a 90 s all-out variable resistance test on a modified Monark cycle ergometer. Pretests included the determination of peak oxygen uptake ( O_2peak) and a series (5–8) of 5-min discontinuous rides at submaximal exercise intensities. The regression of steady-state oxygen uptake on power output to establish individual efficiency relationships was extrapolated to determine the theoretical oxygen cost of the supramaximal power output achieved in the 90 s all-out test. Total work output in 90 s was significantly greater in the trained groups (P<0.05), although no differences existed between ET and ST. Anaerobic capacity, as assessed by MAOD, was larger in ST compared to ET and UT. While the relative contributions of the aerobic and anaerobic energy systems were not significantly different among the groups, ET were able to achieve significantly more aerobic work than the other two groups, while ST were able to achieve significantly more anaerobic work. Peak power and peak pedalling rate were significantly higher in ST. The results suggested that MAOD determined during all-out exercise was sensitive to training status and provided a useful assessment of anaerobic capacity. In our study sprint training, compared with endurance training, appeared to enhance significantly power output and high intensity performance over brief periods (up to 60 s), yet few overall differences in performance (i.e. total work) existed during 90 s of all-out exercise.     

Comparison of oxygen uptake at the onset of decrement-load and constant-load exercise

The purpose of the present study was to examine whether the level of oxygen uptake (V(.)(O2) at the onset of decrement-load exercise (DLE) is lower than that at the onset of constant-load exercise (CLE), since power output, which is the target of V(.)(O2) response, is decreased in DLE. CLE and DLE were performed under the conditions of moderate and heavy exercise intensities. Before and after these main exercises, previous exercise and post exercise were performed at 20 watts. DEL was started at the same power output as that for CLE and power output was decreased at a rate of 15 watts per min. V(.)(O2) in moderate CLE increased at a fast rate and showed a steady state, while V(.)(O2) in moderate DLE increased and decreased linearly. V(.)(O2) at the increasing phase in DLE was at the same level as that in moderate CLE. V(.)(O2) immediately after moderate DLE was higher than that in the previous exercise by 98+/-77.5 ml/min. V(.)(O2) in heavy CLE increased rapidly at first and then slowly increased, while V(.)(O2) in heavy DLE increased rapidly, showing a temporal convexity change, and decreased linearly. V(.)(O2) at the increasing phase of heavy DLE was the same level as that in heavy CLE. V(.)(O2) immediately after heavy DLE was significantly higher than that in the previous exercise by 156+/-131.8 ml/min. Thus, despite the different modes of exercise, V(.)(O2) at the increasing phase in DLE was at the same level as that in CLE due to the effect of the oxygen debt expressed by the higher level of V(.)(O2) at the end of DLE than that in the previous exercise.     

Effect of nutritionally enriched coffee consumption on aerobic and anaerobic exercise performance

The purpose of this study was to compare nutritionally enriched JavaFit coffee (JF) to commercially available decaffeinated coffee (P) with regard to impact on endurance and anaerobic power performance in a physically active, college-aged population. Ten subjects (8 men, 2 women) performed two 30-second Wingate anaerobic power tests and 2 cycle ergometer tests (75% VO2 max) to exhaustion. Mean VO2 was measured during each endurance exercise protocol. Excess postexercise oxygen consumption (EPOC) and respiratory exchange ratio (RER) were recorded for 30 minutes following all exercise sessions. Area under the curve analysis was used to compare EPOC between JF and P for all exercise sessions. No differences were seen between JF and P in any of the power performance measures. However, time to exhaustion was significantly (p = 0.05) higher in JF (35.3 +/- 15.2 minutes) compared with P (27.3 +/- 10.7 minutes). No difference between JF and P were seen in EPOC in either the aerobic or anaerobic exercise sessions. A significant (p < 0.05) difference in average 30-minute postanaerobic power exercise RER was seen between JF (0.87 +/- 0.04) and P (0.83 +/- 0.03), but not following endurance exercise. A nutritionally-enriched coffee beverage appears to enhance time to exhaustion during aerobic exercise, but does not provide an ergogenic benefit during anaerobic exercise.     

Relationship in humans between spontaneously chosen crank rate and power output during upper body exercise at different levels of intensity

The aim of this study was to assess the relationship between spontaneously chosen crank rate (SCCR) and power output during two upper body exercise tests: firstly, an incremental maximal aerobic power test (T1), with an initial intensity of 50 W followed by 15-W increases at each subsequent 90-s stage and secondly, a test (T2) with consecutive exercise periods set at 50%, 60%, 70%, 80%, 110% and 120% of maximal power (Pmax) separated by passive recovery periods. Eight nationally and internationally ranked kayakers, aged 20 (SD 2) years, performed the tests. During both T1 and T2, mean SCCR values were correlated (r = 1) and increased significantly (P < 0.05) in association with the increases in power output. The finding that the subjects consistently increased their crank rate as the power output increased in different tests, i.e. at submaximal, maximal and supramaximal intensities, strongly suggests that SCCR depended on power output and not on the type of exercise (incremental or rectangular exercise). Moreover, the equation relating crank rate and power output determined from T1 suggests that it may be used to predict the crank rate which will be chosen in upper body exercise, whatever the intensity. Finally, the results of testing at 110% and 120% of Pmax would suggest that a high crank rate (>90 rpm) should be used during the test procedure using supramaximal exercises where accumulated oxygen deficit is calculated, and more particularly when exercise is performed using the upper body.     

Effects of acute hypobaric hypoxia on the appearance of ingested deuterium from a deuterium oxide-labelled carbohydrate beverage in body fluids of humans during prolonged cycling exercise

To determine whether or not acute hypobaric hypoxia alters the rate of water absorption from a carbohydrate beverage ingested during exercise, six men cycled for 80 min on three randomly assigned different occasions. In one trial, exercise was performed in hypoxia (barometric pressure, P(B) = 594 hPa, altitude 4,400 m) at an exercise intensity selected to elicit 75% of the individual's maximal oxygen uptake (VO2max) previously determined in such conditions. In the two other experiments, the subjects cycled in normoxia (P(B) = 992 hPa) at the same absolute and the same relative intensities as in hypoxia, which corresponded to 55% and 75%, respectively, of their VO2max determined in normoxia. The subjects consumed 400 ml of a 12.5% glucose beverage just prior to exercise, and 250 ml of the same drink at 20, 40 and 60 min from the beginning of exercise. The first drink contained 20 ml of deuterium oxide to serve as a tracer for the entry of water into body fluids. The heart rate (HR) during exercise was higher in hypoxia than in normoxia at the same absolute exercise intensity, whereas it was similar to HR measured in normoxia at the same relative exercise intensity. Both in normoxia and hypoxia, plasma noradrenaline concentrations were related to the relative exercise intensity up to 40 min of exercise. Beyond that duration, when exercise was performed at the highest absolute power in normoxia, the noradrenaline response was higher than in hypoxia at the same relative exercise intensity. No significant differences were observed among experimental conditions, either in temporal profiles of plasma D accumulation or in elimination of water ingested in sweat. Conversely, elimination in urine of the water ingested appeared to be related to the severity of exercise, either high absolute power or the same relative power combined with hypoxia. We concluded that water absorption into blood after drinking a 12.5% glucose beverage is not altered during cycling exercise in acute hypobaric hypoxia. It is suggested that the elimination of water ingested in sweat and urine may be dependent on local circulatory adjustments during exercise.     

The influence of exercise intensity on the power spectrum of heart rate variability

The power spectral analysis of R-R interval variability (RRV) has been estimated by means of an autoregressive method in seven sedentary males at rest, during steady-state cycle exercise at 21 percent maximal oxygen uptake (%VO2max), SEM 2%, 49% VO2max, SEM 2% and 70% VO2max, SEM 2% and during recovery. The RRV, i.e. the absolute power of the spectrum, decreased 10, 100 and 500 times in the three exercise intensities, returning to resting value during recovery. In the RRV power spectrum three components have been identified: (1) high frequency peak (HF), central frequency about 0.24 Hz at rest and recovery, and 0.28 Hz, SEM 0.02, 0.37 Hz, SEM 0.03 and 0.48 Hz, SEM 0.06 during the three exercise intensities, respectively; (2) low frequency peak (LF), central frequency about 0.1 Hz independent of the metabolic state; (3) very low frequency component (VLF), less than 0.05 Hz, no peak observed. The HF peak power, as a percentage of the total power (HF%), averaged 16%, SEM 5% at rest and did not change during exercise, whereas during recovery it decreased to 5%-10%. The LF% and VLF% were about 50% and 35% at rest and during low exercise intensity, respectively. At higher intensities, LF% decreased to 16% and VLF% increased to 70%. During recovery a return to resting values occurred. The HF component may reflect the increased respiratory rate and the LF peak changes the resetting of the baroreceptor reflex with exercise. The hypothesis is made that VLF fluctuations in heart rate might be partially mediated by the sympathetic system.     

Structural and functional characteristics of the heart of professional soccer players after retirement from long-term sports activity

The structural and functional characteristics of the heart of 51 retired soccer players who ceased training 3–15 years ago are presented. A number of structural and functional signs of “athlete’s heart” detected in the subjects indicate more efficient heart functioning at rest and during exercise. The myocardium requires less oxygen per unit power of muscle work, and each gram of the myocardium of retired athletes performs more mechanical work than the myocardium of untrained subjects of the same age. This indicates long-term adaptation of the heart of retired athletes to muscle work. The heart functioning at rest and during exercise in retired athletes becomes less efficient with age, this trend being more pronounced in older former athletes than in younger ones. This is expressed in an increased oxygen consumption by the myocardium, a higher occurrence of atypical electrocardiogram patterns, age-related changes in myocardial contractility, and a decreased capacity of each gram of the myocardium for generating mechanical work.     

Human femoral artery diameter in relation to knee extensor muscle mass, peak blood flow, and oxygen uptake

It is not known whether the diameter of peripheral conduit arteries may impose a limitation on muscle blood flow and oxygen uptake at peak effort in humans, and it is not clear whether these arteries are dimensioned in relation to the tissue volume they supply or, rather, to the type and intensity of muscular activity. In this study, eight humans, with a peak pulmonary oxygen uptake of 3.90 +/- 0.31 (range 2.29-5.03) l/min during ergometer cycle exercise, performed one-legged dynamic knee extensor exercise up to peak effort at 68 +/- 7 W (range 55-100 W). Peak values for knee extensor blood flow (thermodilution) and oxygen uptake of 6.06 +/- 0.74 (range 4.75-9.52) l/min and 874 +/- 124 (range 590-1,521) ml/min, respectively, were achieved. Pulmonary oxygen uptake reached a peak of 1.72 +/- 0.19 (range 1.54-2.33) l/min. Diameters of common and profunda femoral arteries determined by ultrasound Doppler were 10.6 +/- 0.4 (range 8.2-12.7) and 6.0 +/- 0.4 (range 4.5-8.0) mm, respectively. Thigh and quadriceps muscle volume measured by computer tomography were 10.06 +/- 0.66 (range 6.18-10.95) and 2.36 +/- 0.19 (range 1.31-3.27) liters, respectively. The common femoral artery diameter, but not that of the profunda branch, correlated with the thigh volume and quadriceps muscle mass. There were no relationships between either of the diameters and the absolute or muscle mass-related resting and peak values of blood flow and oxygen uptake, peak pulmonary oxygen uptake, or peak power output during knee extensor exercise. However, common femoral artery diameter correlated to peak pulmonary oxygen uptake during ergometer cycle exercise. In conclusion, common and profunda femoral artery diameters are sufficient to ensure delivery to the quadriceps muscle. However, the common branch may impose a limitation during ergometer cycle exercise.     

The power-duration product--evaluation of a new reference system for cardiopulmonary exercise testing.

The aim of this study was to assess the discriminatory power of the new reference system, power-duration product (PDP), for the analysis of haemodynamic and metabolic variables derived from cardiopulmonary exercise tests. The PDP was calculated as the cumulative index of the product of power (W) times the duration (minutes) of each individual exercise step. The study comprised 30 healthy male volunteers, who were classified into three groups with respect to their regular physical activity: 10 untrained medical students (students), 10 sprinters and long-jumpers (athletes) and 10 endurance athletes performing triathlon (triathletes). Twenty metabolic and haemodynamic variables were recorded throughout exhaustion-limited cycling ergometry. The data were analysed with respect to five reference systems (heart rate, relative and absolute oxygen consumption/body surface area, power, and PDP). A total of 14 differences between modified time courses of haemodynamic and metabolic variables in the three groups of volunteers were observed by reference to PDP, 12 by reference to relative oxygen consumption/body surface area, 11 by reference to heart rate, 8 by reference to absolute oxygen consumption/body surface area, and 7 by reference to power. When using PDP as the reference, the time courses of 8 parameters differed significantly between students and triathletes, 5 between students and athletes, and 1 between athletes and triathletes. In addition to its discriminatory superiority for the comparison of different groups characterized by different cardiopulmonary training and endurance, it was found that PDP permitted a better characterization of the individually performed exercise than the consideration of power per se.     

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

In two experiments maximal aerobic power (VO2max) calculated from maximal mechanical power (Wmax) 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 VO2max using the equation VO2max = 12.Wmax + 5.weight. 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 VO2max correlated significantly (p less than 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 VO2max (calculated) on VO2max (measured) was less than 3.2%. Two expressions of relative work load (%VO2max and %Wmax) were established and found to be closely correlated. The relative work load in %VO2max could be predicted from the relative work load in %Wmax with an average standard error of 3.8%. The data demonstrate that calculated VO2max based on a maximal multi-stage exercise test provides an accurate and valid estimate of VO2max.     

Strength training and aerobic exercise: comparison and contrast

Most exercise programs for conditioning and rehabilitation are oriented to strength development, aerobic (cardiovascular) fitness, or a combination of the 2. Because the 2 types of exercise are located at the opposite extremes of a muscular power continuum, the design of a program must be highly specific with regard to the exercise to be undertaken, as well as the intensity, duration, and frequency, in order to attain optimal results. Strength exercise programs involve weight training or the use of high-resistance machines with exercise that is limited to a few repetitions (generally less than 20) before exhaustion. Aerobic exercise involves exercise performed for extended periods (e.g., 10-40 minutes) with large muscle activity involving hundreds of consecutive repetitions that challenge the delivery of oxygen to the active muscles. The chronic physiological adaptations and the variables in program design are highly specific to the type of exercise performed.