Maximal aerobic capacity for repetitive lifting: comparison with three standard exercise testing modes

Summary A multi-stage, repetitive lifting maximal oxygen uptake ( ) test was developed to be used as an occupational research tool which would parallel standard ergometric testing procedures. The repetitive lifting test was administered to 18 men using an automatic repetitive lifting device. An intraclass reliability coefficient of 0.91 was obtained with data from repeated tests on seven subjects. Repetitive lifting test responses were compared to those for treadmill, cycle ergometer and arm crank ergometer. The mean±SD repetitive lifting of 3.20±0.42 l · min^–1 was significantly (p<0.01) less than treadmill ( = 0.92 l · min^–1) and cycle ergometer ( = 0.43 l· min^–1) and significantly greater than arm crank ergometer ( = 0.63 l · min^–1). The correlation between repetitive lifting oxygen uptake and power output wasr = 0.65. correlated highly among exercise modes, but maximum power output did not. The efficiency of repetitive lifting exercise was significantly greater than that for arm cranking and less than that for leg cycling. The repetitive lifting test has an important advantage over treadmill or cycle ergometer tests in the determination of relative repetitive lifting intensities. The individual curves of vs. power output established during the multi-stage lifting test can be used to accurately select work loads required to elicit given percentages of maximal oxygen uptake.     

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

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

Standardization of work intensity for evaluation of exercise-induced bronchoconstriction

Summary Reactivity of airways to 6 min of graded intensity treadmill work was studied in nine asthmatic and 15 non-asthmatic subjects. After performing a progressive max treadmill test, each subject completed five 6-min exercise tests at selected intensities: 40, 60, 80, and 100% max; and at 80% of max predicted from heartrate. Pulmonary function measures recorded after exercise demonstrated a direct relationship between work intensity and exercise induced bronchoconstriction (EIB) for both groups, with the asthmatics showing their lowest values at 80% max. Heartrate-set work intensities produced a wide range of aerobic demand, thus significantly increasing the variability of the EIB response recorded.     

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      

Changes in ventilation at the start and end of moderate and heavy exercise of short and long duration

Summary These experiments examined the effect of exercise intensity and duration on the magnitude of the abrupt change in ventilation at the start ( ) and end ( ) of exercise. Five subjects performed constant load treadmill exercise at 50% and 80% of their maximum oxygen consumption ( ) for 6 and 10 min while inspiring atmospheric air. The subjects also completed additional exercise tests at 80% for 10 min while inspiring an oxygen-enriched gas mixture. During each exercise trial ventilation was measured breath-by-breath. The and were determined by using non-linear curve-fitting techniques. The results showed that was greater at the start of the 80-% exercise tests compared to the 50-% tests and that at each level of exercise was greater than . The results also demonstrated that was inversely related to the intensity and duration of exercise. Furthermore, the was not altered subsequent to the inspiration of oxygen-enriched air. These findings have led us to postulate that the stimulus responsible for is reduced during exercise and that the degree of reduction is related to the intensity and duration of exercise. In addition, it was concluded that these changes might occur independently of peripheral chemoreceptor activity.     

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

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

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.     

Standards and predicted values of anaerobic threshold

Summary Mean values for body size, body composition and endurance indices have been obtained from a homogeneous group of 125 physically active men to find predicted values of AT (age 23.4±4.3 years; height 175.9±6.5 cm; weight 72.2±8.9 kg; body fat 17.9±4.7% body weight, muscularity index 19.0±1.5 kg fat-free mass/cm² · 10^–4 height; forced vital lung capacity 5667±815 cm³; 48.5±6.0 cm³ · kg^–1 · min^–1; anaerobic threshold 61.0±7.8% ). Endurance performance and fitness indices were a little higher than average, but about 10% lower than in endurance-trained athletes. The authors suggest that standards of anaerobic threshold (AT) for ergonomics and endurance training should be about 55–65% , but not lower than 1800 cm³ O₂ · min^–1. The coefficients of correlation of AT relating to , and submaximal load were significant at the 0.01 level. Using regression analysis, predicted values of AT were developed. A predicted value of AT can be obtained from the regression line of AT on L_submax used as a nomogram, during a simple PWC₁₇₀ exercise test without blood or gas analysis.     

Aerobic performance capacity in paraplegic subjects

Summary To determine adaptation to prolonged exercise in paraplegics, maximal O₂ uptake ( ) and lactate threshold (LT) were evaluated during an arm cranking exercise in nine patients (P) and nine able-bodied (AB) subjects.Mean averaged 25.1 and 31.6 ml · min^–1 · kg^–1 in P and AB groups respectively. in P was found to be directly related to the level of spinal injury: the higher the lesion the lower the uptake. Lactate threshold expressed as a percentage of was higher in P (59%) than in AB (43%), and close to that observed in armtrained athletes.Since training has less effect on in paraplegics than in able-bodied subjects, attributable to a deficiency in the circulatory adaptation of paraplegics to exercise, the observed differences between AB and P in lactate threshold and submaximal exercise indicate that the possible effect of training in paraplegics is located at the level of intracellular chemistry, with a diminution in glycogenolysis (higher LT) and a higher rate of lipid utilization (lower RQ).     

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

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

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

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

Cardiorespiratory response to absolute and relative work intensity in untrained men

Summary Twenty young, untrained men performed two tests on cycle ergometer in order to verify whether the kinetics of the cardiorespiratory reactions exhibit any relation to maximal oxygen uptake ( ) in the untrained state. On the 1st day, the subjects exercised at work intensities of 50 and 100 W, the increase as a step function, for periods of 10 min each. The next day, they performed exercise at a relative intensity of 50% for 10 min. Respiratory frequency, tidal volume, minute ventilation ( ), heart rate (HR), stroke volume (SV), and cardiac output ( ) were measured continuously. The SV was measured by impedance plethysmography. All the cardiorespiratory variables increased rapidly at the onset of both absolute and relative intensity of work, with a faster response for than for . The increase in absolute intensity of work from 50 to 100 W caused a significantly slower cardiorespiratory reaction than at the beginning of exercise. The SV increased by 20 ml during first 20 s of both absolute and relative intensities of work and then began to decrease after 6 and 4 min of the exercise, respectively. The decrease in SV was associated with an increase in HR and a stable value of . Acceleration at the beginning of, and deceleration during recovery from, the relative intensity of work for , HR, and were well correlated with individual levels of in the tested men. It is concluded that the kinetics of cardiorespiratory reaction to a constant, relative intensity of work is related to in untrained men, and that the kinetics probably constitute a physiological feature of an individual.     

Blood flow in thigh muscle during bicycling exercise at varying work rates

16 male subjects exercised at 25, 50, 75, 90, 100 and 120% of on a von Döbeln bicycle ergometer. The muscle mass was measured in a whole body counter. Muscle blood flow (MBF) estimated from the rate of¹³³Xe clearance from m. rectus femoris showed a levelling-off at about 0.5 l of blood per min and liter of muscle tissue (equal to an irrigation coefficient of 0.5 min^–1) at work rates above 50 to 60% of . This concurs with clearance data from the literature. However, when MBF is calculated from , muscle mass, and reliable values for differences, MBF in the present subjects would: 1. Not level off before 90 to 100% , 2. reach a value of 1.0 min^–1. The underestimation of MBF calculated from¹³³Xe clearance and the levelling-off shown by this method may be due to a systematic error inherent in the method, the¹³³Xe clearance being diffusion limited at high flow rates.This study was supported by a grant from the Swedish Medical Council and from Statens lægevidenskabelige forskningsråd, Denmark, project no 512–667 and 512–1156.     

Oxygen consumption and metabolic strain in rowing ergometer exercise

Summary Oxygen consumption ( ) when rowing was determined on a mechanically braked rowing ergometer (RE) with an electronic measuring device. was measured by an open spirometric system. The pneumotachograph valve was fixed to the sliding seat, thus reducing movement artefacts. A multi-stage test was performed, beginning with a work load of 150 W and increasing by 50 W every 2 minutes up to exhaustion. Serum lactate concentrations were determined in a 30 s break between the work stages. 61 examinations of oarsmen performing at maximum power of 5 W · kg⁻¹ or more were analysed. and heart rate (HR) for each working stage were measured and the regression line of on the work load (P) and an estimation error (s_xy) were calculated: (ml · min⁻¹) (S_xy = ± 337 ml,r = 0.98) Good reproducibility was found in repeated examinations. Similar spiroergometry was carried out on a bicycle ergometer (BE) with 10 well trained rowers and 6 trained cyclists. of rowing was about 600 ml · min⁻¹ higher than for bicycling in the submaximal stages for both groups. The of RE exercise was 2.6% higher than for oarsmen on BE, and the cyclists reached a greater on BE than the oarsmen. No differences were found between RE and BE exercise heart rate. The net work efficiency when rowing was 19% for both groups, experienced and inexperienced: when cycling it was 25% for cyclists and 23% for oarsmen.     

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.     

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

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

The effect of exercise intensity and duration on the oxygen deficit and excess post-exercise oxygen consumption

Summary Nine males with mean maximal oxygen consumption ( ) =63.0 ml· kg^–1 · min^–1, SD 5.7 and mean body fat = 10.6%, SD 3.1 each completed nine counterbalanced treatments comprising 20, 50 and 80 min of treadmill exercise at 30, 50 and 70% . The OZ deficit, 8 h excess post-exercise oxygen consumption (EPOC) and EPOC:O₂ deficit ratio were calculated for all subjects relative to mean values obtained from 2 control days each lasting 9.3 h. The O₂ deficit, which was essentially independent of exercise duration, increased significantly (P<0.05) with intensity such that the overall mean values for the three 30%, 50% and 70% workloads were 0.83, 1.89 and 3.09 l, respectively. While there were no significant differences (P>0.05) between the three EPOCs after walking at 30% for 20 (1.01 l), 50 (1.43 l) and 80 min (1.041), respectively, the EPOC thereafter increased (P<0.05) with both intensity and duration such that the increments were much greater for the three 70% workloads (EPOC: 20 min=5.68 l; 50 min=10.04 l; 80 min= 14.59 l) than for the three 50% workload (EPOC: 20 min =3.14 l; 50 min=5.19 l; 80 min= 6.10 l). An analysis of variance indicated that exercise intensity was the major determinant of the EPOC since it explained five times more of the EPOC variance than either exercise duration or the intensity times duration interaction. The mean EPOC:O₂ deficit ratio ranged from 0.8 to 4.5 and generally increased with both exercise intensity and duration. These data imply that the EPOC is more than mere repayment of the O₂ deficit because metabolism is increasingly disturbed from resting levels as exercise intensity and duration increase due to other physiological factors occurring after the steady-state has been attained.     

Ventilatory response during incremental exercise tests in weight lifters and endurance cyclists

Summary The effect of a progressively increasing work rate (15 W·min^–1) up to exhaustion on the time course of O₂ uptake ( ), ventilation ( ) and heart rate (HR) has been studied in weight lifters (WL) in comparison to endurance cyclists (Cycl) and sedentary controls (Sed). and were measured as average value of 30-s intervals by a semiautomatic open circuit method. was 2.55±0.33; 4.29±0.53 and 2.86±0.19·min^–1 in WL, Cycl and Sed respectively. With time and work rate, while and HR increased linearly, changed its slope at two levels. The 1st change occured at a work load corresponding to a mean (± SD) of 1.50±0.26; 1.93±0.34; and 1.23±0.14 l·min^–1 in WL, Cycl, and Sed respectively. values corresponding to the second change of slope were 2.18±0.32 in WL; 3.48±0.53 in Cycl and 2.17±0.28 l·min^–1 in Sed. The first change of slope might be the consequence of the different readjustment of on-response and hence of early lactate in the different subjects. The second change seems to be comparable to the conventional anaerobic threshold and is achieved in all subjects when vs time slope is 7–10 l·min^–1/min of exercise.This work has been supported in part by a grant from the Italian National Research Council (CNR)     

Maximum oxygen consumption in dogs during muscular exercise and cold exposure

Maximum oxygen consumption for a short exhaustive work (Ex max) and for a severe cold stress (Ex max) were investigated in 8 dogs. Heart rate, plasma catecholamines and substrate concentrations were measured under both conditions. Mean C was lower than mean Ex max. Heart rate and plasma lactate were also lower during cold exposure than during exercise. Average plasma epinephrine concentrations were not significantly different and average plasma norepinephrine concentrations were similar under C and Ex max conditions. A positive correlation was found between plasma lactate and epinephrine concentrations measured under both conditions.It may be assumed that maximum oxygen consumption during muscular exercise is higher than during shivering thermogenesis. This difference does not seem to be due to differences in the involvement of the sympathico-adreno-medullary system.     

Fitness as a determinant of oxygen uptake response to constant-load exercise

Summary Exercise performed above the lactate threshold (Θ _La) produces a slowly-developing phase of oxygen uptake ( ) kinetics which elevates above that predicted from the sub-Θ _La -work rate relationship. This phenomenon has only been demonstrated, to date, in subjects who were relatively homogeneous with respect to fitness. This investigation therefore examined whether this behaviour occurred at a given absolute or whether it was a characteristic of supra-Θ _La exercise in a group of subjects with over a threefold range ofΘ _La (990–3000 ml O₂·min⁻¹) and peak (1600–5260 ml O₂·min⁻¹). Twelve healthy subjects performed: 1) exhausting incremental cycle ergometer exercise for estimation ofΘ _La ( ) and peak , and 11) a series of constant-load tests above and below for determination of the profile and efficiency of work. During all tests expired ventilation, and carbon dioxide production were monitored breath-by-breath. The efficiency of work determined during incremental exercise (28.1±0.7%, ,n=12) did not differ from that determined during sub- constant-load exercise (27.4±0.5%,p>0.05). For constant-load exercise, rose above that predicted, from the sub- -work rate relationship, for all supra- work rates. This was evident above 990 ml O₂·min⁻¹ in the least fit subject but only above 3000 ml O₂·min⁻¹ in the fittest subject. As a consequence the efficiency of work was reduced from 27.4±0.5% for sub- exercise to 22.6±0.4% (p<0.05) at the lowest supra- work rate (i.e. +20 W, on average). The efficiency of work generally decreased further at the higher supra- work rates. We conclude that the response to constant-load exercise includes an additional slow phase of the kinetics for all exercise intensities above irrespective of the fitness of the subject. Consequently, measurements of the aerobic efficiency of work during constant-load exercise must rigorously constrain the exercise intensity to the sub- domain. Supported by grants from the John D. and Catherine T. Mac-Arthur Foundation, USPHS RR 00865-15, and NIH HL 07694-01