The effect of O2 breathing on maximal aerobic power

Summary Time of performance, blood lactic acid concentration (L.A.), heart rate (H.R.) and maximal oxygen consumption ( ) were measured during air and oxygen breathin in 11 subjects performing a supramaximal exercise with an O₂ requirement of 70 to 80 ml/kg·min to exhaustion. In addition the subjects were tested for maximal aerobic power with an indirect method. In one subject the rate of lactic acid increase in blood was also measured.The measured with both the direct and the indirect method appears to be about 8% higher when breathing pure oxygen; lactic acid production rate decreases correspondingly. Maximal H.R. and maximal L.A. concentration were found to be the same.In submaximal exercise steady state H.R. is lower by about 8–9 beats/min when breathing oxygen. Also when breathing oxygen H.R. is a linear function of the work load.From experimental data obtained in subjects of different , breathing both air or O₂, the energy equivalent of L.A. could be calculated as amounting to about 47 ml of O₂ or 235 cal per g of L.A. produced.This work was supported by a grant from the National Research Council of Italy (C.N.R.)     

Influence of heat stress and acclimation on maximal aerobic power

Summary Thirteen male volunteers performed cycle ergometer maximal oxygen uptake ( tests) in moderate (21 C, 30% rh) and hot (49 C, 20% rh) environments, before and after a 9-day heat acclimation program. This program resulted in significantly decreased (P<0.01) final heart rate (24 bt·min^–1) and rectal temperature (0.4 C) from the first to last day of acclimation. The was lower (P<0.01) in the hot environment relative to the moderate environment both before (8%) and after (7%) acclimation with no significant difference (P>0.05) shown for maximal power output (PO max, watts) between environments either before or after acclimation. The was higher (P<0.01) by 4% after acclimation in both environments. Also, PO max was higher (P<0.05) after acclimation in both the moderate (4%) and hot (2%) environments. The reduction in in the hot compared to moderate environment was not related to the difference in core temperature at between moderate and hot trials, nor was it strongly related with aerobic fitness level. These findings indicate that heat stress, per se, reduced the . Further, the reduction in due to heat was not affect be state of heat acclimation, the degree of elevation in core temperature, or level of aerobic fitness.     

Changes in maximal aerobic power,aerobic capacity,and muscle enzyme activities at two stages of the annual training cycle in ski-runners

Summary Changes of cardiorespiratory capacity, of the activity of seven enzymes involved in energy metabolism and of laboratory endurance were investigated in a group of nine male ski-runners before and after exhausting training and a competing period during the winter.Despite the decrease in laboratory endurance and total work oxygen consumption between the investigations, O₂ max, O₂-pulse max and O₂ debt did not change; and O₂-pulse per kg b.w. showed a significant increase.In biopsy samples of the vastus lateralis muscle, the activity of enzymes of carbohydrate metabolism, both anaerobic and total (triose phosphate dehydrogenase — TPDH, lactate dehydrogenase — LDH, hexokinase — HK), and of total aerobic metabolism (citrate synthetase — CS, malate dehydrogenase — MDH), was decreased during this period by 27 to 59% (mean values for different enzymes). The mean activity of cytoplasmic glycerol phosphate dehydrogenase (GPDH) and of hydroxyacyl — CoA dehydrogenase (HOADH) did not change, although the activity of the latter enzyme was decreased in the muscle of those ski-runners who were trained predominantly for speed, and it was increased in those trained mainly for endurance.The changes in activity of the muscle enzymes associated with glycolysis (TPDH and LDH) and of MDH, connected with metabolism and hydrogen transport between cytoplasmic and aerobic mitochondrial compartments, correlate inversely with those of aerobic capacity (total work O₂ consumption).     

Effects of simulated altitude training on aerobic and anaerobic power

Summary Five trained males aged 20–23 years undertook successive phases (2–5 weeks duration) of daily training in normoxia or hypoxia. Weekly exhaustive tests alternately in normoxia or hypoxia, throughout, assessed the comparative efficacy of the training. The relative contribution to endurance, aerobic (peak VO₂) and anaerobic (La) power made by exercise or hypoxia separately was studied.In a stepwise increasing work test to exhaustion relative bradycardia developed during the first minute of exhaustive work at 1800 kgm/min in all subjects and aerobic power increased both in normoxia and hypoxia significantly by the end of the first phase hypoxic training. Endurance for exhaustive work increased in both environments as did aerobic and anaerobic power.     

Caffeine increases maximal anaerobic power and blood lactate concentration

Summary The aim of this study was to specify the effects of caffeine on maximal anaerobic power (W _max). A group of 14 subjects ingested caffeine (250 mg) or placebo in random double-blind order. TheW _max was determined using a force-velocity exercise test. In addition, we measured blood lactate concentration for each load at the end of pedalling and after 5 min of recovery. We observed that caffeine increasedW _max [964 (SEM 65.77) W with caffeine vs 903.7 (SEM 52.62) W with placebo;P<0.02] and blood lactate concentration both at the end of pedalling [8.36 (SEM 0.95) mmol · l^–1 with caffeine vs 7.17 (SEM 0.53) mmol · l^–1 with placebo;P<0.011 and after 5 min of recovery [10.23 (SEM 0.97) mmol · l^–1 with caffeine vs 8.35 (SEM 0.66) mmol · l^–1 with placebo;P<0.04]. The quotient lactate concentration/power (mmol · l^–1 · W^–1) also increased with caffeine at the end of pedalling [7.6 · 10^–3 (SEM 3.82 · 10^–5) vs 6.85 · 10^–3 (SEM 3.01 · 10^–5);P<0.01] and after 5 min of recovery [9.82·10^–3 (SEM 4.28 · 10^–5) vs 8.84 · 10^–3 (SEM 3.58 · 10^–5);P<0.02]. We concluded that caffeine increased bothW _max and blood lactate concentration.     

The effects of acute phosphate supplementation in subjects of different aerobic fitness levels

Six trained cyclists (high-fitness group) and six untrained individuals (low-fitness group), performed a 20-min cycle ergometer exercise test at 70% of maximum oxygen consumption ( followed by a 30-min rest period and then an incremental ride to exhaustion on two occasions, 1 week apart. Ninety minutes prior to exercise subjects consumed a drink containing either 22.2 g dibasic calcium phosphate (DCP; treatment) or calcium carbonate (placebo). Blood was drawn prior to drink ingestion, during submaximal exercise, during recovery and at exhaustion for determination of blood 2,3-DPG, blood ATP, plasma lactate, plasma phosphate, haemoglobin and haematocrit. Throughout exercise, cardiorespiratory variables [oxygen uptake ( minute ventilation, ( ), respiratory exchange ratio, heart rate and oxygen pulse] were monitored, and ratings of perceived exertion obtained. Although there was a trend for the low-fitness group to have a higher plasma phosphate concentration prior to treatment ingestion, no treatment effects on plasma phosphate were noted at any sample time in either group. 2,3-DPG, oxygen pulse, time to exhaustion and were significantly higher in the high-fitness group; however, no differences in these variables were observed as a result of phosphate ingestion. Plasma lactate was significantly lower in the high-fitness group during the submaximal exercise and the recovery period, but again phosphate ingestion had no effect. These results suggest that acute DCP supplementation is not effective as an ergogenic aid and that aerobic fitness level does not affect the response to phosphate supplementation.     

Specificity of maximal aerobic power

Summary Several types of work tasks are used to assess maximal aerobic power (MAP) in humans. Although it is well established that these work tasks may yield different absolute MAP values, little is known about the extent of the specificity of each MAP work task. 30 moderately active young men were tested at random for MAP with five commonly used work tasks: cycling supine, cycling sitting, alternate arm cranking standing, walking on a treadmill, and stepping on a bench. Statistical analyses show that these five tests do not give equal MAP means, equal variances or equal covariances. Various correlation techniques indicate, furthermore, that the common variance between the five aerobic power measurements is at best moderate. It was estimated that the overall common variance for Max ml O₂·kg^–1·min^–1 reached about 50% of the total variance. The most efficient linear loading of each test in the first principal component could account only for 75% of the observed variance in MAP. It is concluded that these five work tasks do not yield parallel test forms, that the practice of transforming one MAP value into another should be abandoned, and that the practice of generalizing from one MAP value to a theoretical general MAP of the human body is not justified.This work was supported by the Quebec Department of Education and by the Research grant program of Laval University     

Leisure time sport activities and maximal aerobic power during late adolescence

Summary The pattern of leisure time sport activity was estimated by retrospective recalls and expressed in terms of an annual sport activity score. The activity score was related to the development of maximal aerobic power during the period of late adolescence in German children. Both girls and boys reduced their activity pattern from 14 to 18 years of age, boys more than girls. At each age boys were more active than girls. A slight tendency towards better fitness with increased habitual physical activity was noticed, but many sedentary children exhibited a good performance capacity and some children with a high level of leisure time sport activity were characterized by a low level of maximal aerobic power. A statistical analysis revealed that the observed tendency to better fitness with increased habitual physical activity could be explained by an age factor with no additional effect of variation in sport activity score.     

Influence of body mass on maximal oxygen uptake: effect of sample size

Basal metabolic rate is scaled to body mass to the power of 0.73, and we evaluated whether a similar scaling applies when the O₂ transport capacity of the body is challenged during maximal exercise (i.e. at maximal O₂ uptake, V˙O _2max). The allometric relationship between V˙O _2max and body mass (y=a · x ^b, where y is V˙O _2max and x is body mass) was developed for 967 athletes representing 25 different sports, with up to 157 participants in each sport. With an increasing number of observations, the exponent approached 0.73, while for ventilation the exponent was only 0.55. By using the 0.73 exponent for V˙O _2max, the highest value [mean (SD)] for the males was obtained for the runners and cyclists [234 (16) ml · kg^−0.73 · min⁻¹], and for the females the highest value was found for the runners [189 (14) ml · kg^−0.73 · min⁻¹]. For the females, aerobic power was about 80% of the value achieved by the males. Scaling may help both in understanding variation in aerobic power and in defining the physiological limitations of work capacity. Accepted: 3 November 2000     

Anaerobic and aerobic peak power output and the force-velocity relationship in endurance-trained athletes: effects of aging

The aim of this investigation was to test the hypothesis that the anaerobic peak power output (P _{an, peak}) declines more than the peak aerobic power (P _{aer, peak}) with increasing age. In addition, the force-velocity (F-) relationship was studied to determine which of these two factors is primarily responsible for the expected alterations in anaerobic power. TheP _{an, peak}, the maximalF when is equal to zero (F ₀) and the maximal whenF is equal to zero (₀) were assessed byF- test i.e. a brief intense intermittent exercise test using incremental braking forces. TheP _{aer, peak} was measured by a maximal increment exercise test. A group of 12 young athletes (YA) and 12 master athletes (MA) mean age 24.8 (SEM 1.3) and 65.1 (SEM 1.2) years, respectively, participated in this study. The YA and MA had similar body masses, heights and endurance training schedules. The results showed thatP _{an, peak} was 42.7% lower in the older subjects, corresponding to mean values of 1089 (SEM 40) compared to 624 (SEM 33) W (t = 8.9,P < 0.001) for YA compared to MA, respectively. TheF ₀ andV ₀ indices showed values that were lower by 30.3% and 15.2%, respectively. TheP _{aer, peak} was 35 % lower with mean values of 323 (SEM 12) W for YA compared to 210 (SEM 6) W for MA (t = 8.3,P < 0.001). The mean maximal oxygen uptake was 34.7% lower with 4240 (SEM 160) ml · min^–1 for YA compared to 2770 (SEM 120) ml · min^–1 for MA(t = 7.2,P < 0.001).TheP _{an, peak}:P _{aer, peak} ratio and ₀/F ₀coefficient were 12.1% lower and 18.4% higher, respectively. In summary, this study showed that in endurance-trained athletes, the age-related difference inP _{an, peak} was significantly greater than that ofP _{aer, peak}. Similarly, the age-related difference inF was significantly greater than that in .     

Neuromuscular,anaerobic, and aerobic performance characteristics of elite power athletes

Summary Various aspects of neuromuscular, anaerobic, and aerobic performance capacity were investigated in four powerlifters, seven bodybuilders, and three wrestlers with a history of specific training for several years. The data (means ± SD) showed that the three subject groups possessed similar values for maximal isometric force per unit bodyweight (50.7±9.6, 49.3±4.1, and 49.3±10.9 N/kg, respectively).However, significant (P<0.05) differences were observed in the times for isometric force production, so that e.g., times to produce a 30% force level were shorter for the wrestlers and bodybuilders (28.3±3.1 and 26.4±6.6 ms) than that (53.3±23.7 ms) for the powerlifters. Utilization of elastic energy by the wrestlers was significantly (P<0.05) better than that of the other two subject groups, as judged from differences between the counter-movement and squat jumps at 0, 40, and 100 kg's loads. No differences were observed between the groups in anaerobic power in a 1-min maximal test, but the values for max were higher (P<0.05) among the wrestlers and bodybuilders (57.8±6.6 and 50.8±6.8 ml·kg^–1·min^–1) as compared to the powerlifters (41.9±7.2 ml ·kg^–1·min^–1). Within the limitations of the subject sample, no differences of a statistical significancy were observed between the groups in fibre distribution, fibre areas, or the area ratio of fast (FT) and slow (ST) twitch fibres in vastus lateralis. In all subjects the vertical jumping height was positively (P<0.01) correlated with the FT fibre distribution, and negatively with the time of isometric force production (P<0.05). Maximal force was correlated (P<0.001) with thigh girth. Muscle cross-sectional area did not correlate with mean fibre area. It was assumed that the selected aspects of neuromuscular, anaerobic, and aerobic performance capacity may be influenced by muscle structure, but also specifically and/or simultaneously by training lasting for several years.     

Training effects of cross-country skiing and running on maximal aerobic cycle performance and on blood lipids

Summary Two experiments were carried out to compare the cardiorespiratory and metabolic effects of cross-country skiing and running training during two successive winters. Forty-year-old men were randomly assigned into skiing (n = 15 in study 1,n = 16 in study 2), running (n = 16 in study 1 andn = 16 in study 2) and control (n = 17 in study 1 andn = 16 in study 2) groups. Three subjects dropped out of the programme. The training lasted 9–10 weeks with 40-min exercise sessions three times each week. The training intensity was controlled at 75%–85% of the maximal oxygen consumption (VO_2max) using portable heart rate metres and the mean heart rate was 156–157 beats·min^–1 in the training groups. In the pooled data of the two studies the mean increase in theVO_2max (in ml·min^–1·kg^–1) on a cycle ergometer was 17% for the skiing group, 13% for the running group and 2% for the control group. The increase inVO_2max was highly significant in the combined exercise group compared to the control group but did not differ significantly between the skiing and running groups. The fasting serum concentrations of lipoproteins and insulin did not change significantly in any of the groups. These results suggested that training by cross-country skiing and running of the same duration and intensity at each session for 9–10 weeks improved equally the cardiorespiratory fitness of untrained middle-aged men.     

Oxygen uptake kinetics and maximal aerobic power are unaffected by inspiratory muscle training in healthy subjects where time to exhaustion is extended

The aim of this study was to determine whether 4 weeks of inspiratory muscle training (IMT) would be accompanied by alteration in cardiopulmonary fitness as assessed through moderate intensity oxygen uptake (O₂) kinetics and maximal aerobic power (O_2max). Eighteen healthy males agreed to participate in the study [training group (Tra) n=10, control group (Con) n=8]. Measurements of spirometry and maximal static inspiratory mouth pressure (PI_max) were taken pre- and post-training in addition to: (1) an incremental test to volitional exhaustion, (2) three square-wave transitions from walking to running at a moderate intensity (80% ventilatory threshold) and (3) a maximal aerobic constant-load running test to volitional fatigue for the determination of time to exhaustion (T_lim). Training was performed using an inspiratory muscle trainer (Powerbreathe). There were no significant differences in spirometry either between the two groups or when comparing the post- to pre-training results within each group. Mean PI_max increased significantly in Tra (P<0.01) and showed a trend for improvement (P<0.08) in Con. Post-training T_lim was significantly extended in both Tra [232.4 (22.8) s and 242.8 (20.1) s] (P<0.01) and Con [224.5 (19.6) and 233.5 (12.7) s] (P<0.05). Post-training T_lim was significantly extended in Tra compared to Con (P<0.05). In conclusion, the most plausible explanation for the stability in O₂ kinetics and O_2max following IMT is that it is due to insufficient whole-body stress to elicit either central or peripheral cardiopulmonary adaptation. The extension of post-training T_lim suggests that IMT might be useful as a stratagem for producing greater volumes of endurance work at high ventilatory loads, which in turn could improve cardiopulmonary fitness.     

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.     

Effects of hypoxic training on normoxic maximal aerobic power output

The responses to 1-leg submaximal and maximal exercise have been studied in four male subjects before and after a 5 week training programme. One leg was trained under normoxic conditions and the other under hypoxic ( \(F_{IO_2 } \) =0.12) conditions for 30 min/day, 3 times/week at a fixed absolute work load which approximated to 75% of the limb's normoxic \(\dot V_{O_2 \max } \) . Before and after training both limbs were measured in normoxia, one limb was additionally measured in hypoxia. The aim of the experiments being to use each subject as his own control and to try and elucidate the effects of hypoxia per se as a training stimulus to the improvement of maximal aerobic power output ( \(\dot V_{O_2 \max } \) ) measured in normoxia. The results showed that before training the responses to exercise at submaximal and maximal levels were identical in each limb; the effects of hypoxia being to raise V _E1.5 and f _H1.5, to reduce \(\dot V_{O_2 \max } \) and to leave \(\dot V_{O_2 450} \) unchanged. The effects of the two types of training were to reduce \(\dot V_{O_2 450} \) , decrease f _H1.5 and increase \(\dot V_{O_2 \max } \) , the effects being independent of the \(F_{IO_2 } \) . The changes in \(\dot V_{O_2 \max } \) of the hypoxic and normoxic trained legs were related to the initial \(\dot V_{O_2 \max } \) of each subjects' limb. It was concluded that our investigation lends no support to the view that hypoxia has either an additive or potentiating effect with exercise during a training programme on the improvement of aerobic power output measured under normoxic conditions.     

The relationship between changing body height and growth related changes in maximal aerobic power

Summary In order to analyse the relationship between maximal aerobic power and height, body mass and lean body mass a multi-longitudinal survey was conducted on three different age groups of randomly selected children from a small Czech community. Beginning at the initial ages of 8, 12 and 16 years subjects were subsequently retested three times at 2-year intervals. At overlapping ages there were no differences in the various age groups between height and . By utilizing mean values for the various parameters at specific calendar ages a growth curve was constructed for each sex for the age range 8–20 years. The values were compared with longitudinal studies in various countries and no substantial differences were found. When was then compared to height, body mass and lean body mass it was apparent that the almost linear relationship with height was the most precise. In addition the children remained, generally speaking, in their same rank order for for the three different age groupings.     

The effect of an α-ketoglutarate-pyridoxine complex on human maximal aerobic and anaerobic performance

Summary The administration of 30 mg/kg of body weight of an -ketoglutarate-pyridoxine complex (-KG compl; stoichiometric ratio -KG: pyridoxine 46.35 to 53.65) to trained non-athletic individuals increases max by 6% (p<0.005). The kinetics of the on- and off-responses at the onset and offset of a rectangular work load is not affected by the drug. Peak blood lactate concentration [La_b] following two supramaximal running work loads lasting 60 s and 132±4 s, respectively is significantly (p<0.05 and p<0.005) less after the -KG compl treatment (La_b=–1.1 and –2.7 mmol·1^–1, respectively) than in a control group. The half time (t1/2) of La disappearance from blood during recovery is unaffected by the -KG compl treatment (19.7 min vs 19.5 min). The increase in max and the corresponding decrease of [La_b] are not found after separate administration of either of the components of the complex. It is concluded that -KG complex stimulates aerobic metabolism, probably prompting mitochondrial reabsorption of -KG, which activates the malate-oxalacetate shuttle and the generation of high energy phosphates at the substrate level.     

Effects of varied doses of psilocybin on time interval reproduction in human subjects

Action of a hallucinogenic substance, psilocybin, on internal time representation was investigated in two double-blind, placebo-controlled studies: Experiment 1 with 12 subjects and graded doses, and Experiment 2 with 9 subjects and a very low dose. The task consisted in repeated reproductions of time intervals in the range from 1.5 to 5s. The effects were assessed by parameter kappa of the 'dual klepsydra' model of internal time representation, fitted to individual response data and intra-individually normalized with respect to initial values. The estimates kappa were in the same order of magnitude as in earlier studies. In both experiments, kappa was significantly increased by psilocybin at 90 min from the drug intake, indicating a higher loss rate of the internal duration representation. These findings are tentatively linked to qualitative alterations of subjective time in altered states of consciousness.     

Mechanical power during maximal treadmill walking and running in young and elderly men

This study determined mechanical power during movements specific to maximal walking and running using a non-motorized treadmill in 38 elderly [69.4 (5.0) years] and 50 young [24.3 (3.4) years] men. The mean mechanical power over a period of time covering six steps, during which the belt velocity peaked and then kept almost plateau, was determined as a performance score in each of maximal walking (WP) and running (RP). In terms of the value relative to body mass, the relative difference between the two age groups was greater for RP (61.7%) than for WP (21.4%) or isometric knee extension (34.1%) and flexion torque (43.8%). In the two groups, WP was significantly (P<0.05) correlated to knee extension (r=0.582 for the elderly and r=0.392 for the young) and flexion torque (r=0.524 for the elderly and r=0.574 for the young). Similarly, RP was also significantly (P<0.05) correlated to knee extension (r=0.627 for the elderly and r=0.478 for the young) and flexion torque (r=0.500 for the elderly and r=0.281 for the young). In these relationships, the WP adjusted statistically by thigh muscle torque was similar in the two age groups. However, the corresponding value for RP was significantly higher in the young than in the elderly. The findings here indicate that: (1) the difference between the young and elderly men in mechanical power is greater during maximal running than maximal walking, and (2) although the thigh muscle torque contributes to the power production during the two maximal exercise modes in the two age groups, the RP is greater in the young than in the elderly regardless of the difference in the thigh muscle torque.