Decreased submaximal oxygen uptake during short duration oral contraceptive use: a randomized cross-over trial in premenopausal women

Long-term oral contraceptive (OC) use is known to be associated with changes in haemostasis, cardiovascular dynamics, and carbohydrate and lipid metabolism. Less well documented are the short-term variations in cardiorespiratory responses to exercise during the menstrual cycle of OC users. In this study the short-term effects of the usage of OC on cardiorespiratory and ventilatory responses to submaximal exercise were examined. Ten women (age= 23 ± 3 years) on monophasic OC were tested at three different times during their ‘cycle’ : during menstruation, off OC use (off OC: days 2 –; 4), early on OC use (EOC: days 7 – 9) and late on OC use (LOC: days 19 – 21). Times of testing were assigned randomly. On each occasion participants performed a continuous 12-min run exercise on a treadmill at three submaximal intensities (averaging 7, 8 and 9 km h^?1), each for 4 min. Heart rate, ventilation ([Vdot]E), oxygen uptake ([Vdot]O₂), carbon dioxide output ([Vdot]CO₂), respiratory exchange ratio and running economy were assessed in the last minute of each stage of exercise. No significant variations were observed between the different times for heart rate, [Vdot]E, and [Vdot]CO₂ irrespective of the stage of exercise (p > 0.05). Using two-way analysis of variance (ANOVA) with repeated measures on both factors (three stages and three times), [Vdot]O₂ (ml kg^?1 min^?1) was lower by 3% to 5.8% when participants were on early and late OC use compared to off OC regardless of the stage of the exercise (F(2,18)= 6.3; p= 0.008). Running economy (ml O₂ kg^?1 km^?1) was significantly improved (lower values) when women were on late OC use compared to off OC regardless of the stage of exercise. No significant interaction effect between stage of exercise and time of pill usage was demonstrated in any of the parameters studied. Results suggest that oral contraceptive users may expect lower [Vdot]O₂ and better running economy during the pill ingestion phase and consequently have implications for exercise performances.     

Physiological factors affecting upper body aerobic exercise

This study examined the influence selected physiological measurements have upon peak oxygen uptake (peak [Vdot]O₂) elicited by upper body (arm crank) exercise employing crank rates of 30 and 70 r.p.m. Nine male volunteers completed: two maximal effort arm crank tests, one cycle exercise maximal aerobic power (AP) test, measurements of isokinetic elbow extension strength (ES), isometric grip strength (GS) and arm volume (AV). Partial correlation coefficients (R) were obtained from a multiple regression analysis. For the 30 r.p.m. protocol, peak [Vdot]O₂ was strongly related to AP (r=0·80; R = 0·51) and moderately related to ES (r=?0·41; R =?0·41) and GS (r=0·40; R = 0·30). For the 70 r.p.m. protocol, peak [Vdot]O₂ was found to be strongly related to AP (r=0·94; R=0·88). AV values were not found to have a marked influence on upper body peak [Vdot]O₂ at either crank rate. These data indicate that aerobic power for cycle exercise is the most important determinant of upper body aerobic exercise performance.     

Evaluation of metabolism from heart rate in industrial work

Oxygen consumption ([Vdot]O₂) and heart rate (HR) were measured in 40 men performing different types of industrial work in eight factories

A [Vdot]O₂-HR relationship was established for each subject using an exercise test on a bicycle ergometer. HR measured during the industrial work was entered in the [Vdot]O₂-HR function, and [Vdot]O₂ thus calculated. A systematic comparison of the calculated [Vdot]O₂ (c[Vdot]O₂) with the actual measured [Vdot]O₂ (m[Vdot]O₂), showed that c[Vdot]O₂ significantly overestimated the [Vdot]O₂ during industrial work. The degree of overestimation was related to the type of work performed. The static muscular activity and the non-steady-state characteristics of the work were responsible for most of the overestimation

A more reliable technique for estimating metabolic rate is to make simultaneous measurements of [Vdot]O₂ and HR at different times during the work day and then from these recordings establish a function: [Vdot]O₂=f(HR). Continuous HR recordings can then be used to calculate a more accurate estimate of the metabolic rate.     

Energy expenditure and clearing snow: a comparison of shovel and snow pusher

In order to assess the energy demands of manual clearing of snow, nine men did snow clearing work for 15 min with a shovel and a snow pusher. The depth of the snowcover was 400–600 mm representing a very heavy snowfall. Heart rate (HR), oxygen consumption ([Vdot]O₂), pulmonary ventilation ( [Vdot]O_E), respiratory exchange ratio (R), and rating of perceived exertion (RPE) were determined during the work tasks. HR, [Vdot]O_E, R, and RPE were not significantly different between the shovel and snow pusher. HR averaged (± SD) 141 ± 20bmin_-1 with the shovel, and 142 ± 19 beats-min_-1 with the snow pusher. [Vdot]O₂was 2·1 ± 0·41 min_-1 (63 ± 12% [Vdot]O₂max) in shovelling and 2·6 ± 0·51 min_-1 (75 ± 14% [Vdot]O₂max) in snow pushing (p< 0·001). In conclusion manual clearing of snow in conditions representing heavy snowfalls was found to be strenuous physical work, not suitable for persons with cardiac risk factors, but which may serve as a mode of physical training in healthy adults.     

Metabolic and respiratory profile of the upper limit for prolonged exercise in man

For high-intensity cycling, power (P) can be well described as a hyperbolic function of tolerable work duration (t): P=(W'/t) + P _LL W' is a constant and P _LL is the lower limit (asymptote) for P which is shown to occur at an O₂ uptake ([Vdot]O₂) lying above the estimated threshold for sustained blood [lactate] increase (Θ_Iac) but below the maximum [Vdot]O₂ ([Vdot]O₂max) obtained during incremental cycling. This relation suggests that, above P _LL, only a certain amount of work (W') can be accomplished regardless of its rate of performance, with [Vdot]O₂ max being attained at fatigue. Hence, P _LL defines a point of discontinuity in the [Vdot]O₂-P relation for supra-Θ_Iac exercise. In order to determine the factors responsible for the continued increase in [Vdot]O₂ (to the maximum fatiguing value) at power outputs >P _LL, we documented the temporal profiles of metabolic (rectal temperature; blood [lactate], [pyruvate], [norepinephrine], [epinephrine]) and respiratory ([Vdot]_E; [Vdot]O₂; [Vdot]CO₂; blood pH, PCO₂, [HCO₃ ^?]) responses to constant-load cycling in eight healthy males at P _LL (24 min) and slightly above P _LL (to exhaustion, i.e. < 24 min). [Vdot]O₂ manifested a delayed steady state at P _LL, despite catecholamine levels and core temperature continuing to increase throughout; blood [lactate] and pH plateaued, however. In contrast, [Vdot]O₂ continued to increase slowly for the duration of the exercise > P _LL and attained [Vdot]O₂max. The response patterns at P _LL, and > P _LL suggest that the slow phase of the [Vdot]O₂ response is best correlated with the temporal profile of blood [lactate], and hence the site and route of metabolism of this variable may play a major role in the [Vdot]O₂ kinetics for high-intensity exercise.     

Can accelerometry accurately predict the energy cost of uphill/downhill walking?

To evaluate whether an activity monitor based on body acceleration measurement can accurately assess the energy cost of the human locomotion, 12 subjects walked a combination of three diVerent speeds (preferred speed±1 km/h) and seven slopes (-15 to + 15% by steps of 5%) on a treadmill. Body accelerations were recorded using a triaxial accelerometer attached to the low back. The mean of the integral of the vector magnitude (norm) of the accelerations (mIAN) was calculated. [Vdot]O₂ was measured using continuous indirect calorimetry. When the results were separately analysed for each incline, mIAN was correlated to [Vdot]O₂ (average r = 0.87, p < 0.001, n = 36). [Vdot]O₂ was not significantly correlated to mIAN when data were globally analysed (n = 252). Large relative errors occurred when predicted [Vdot]O₂ (estimated from data of level walking) was compared with measured [Vdot]O₂ for different inclines (-53% at + 15% incline, to + 55% at -15% incline). It is concluded that without an external measurement of the slope, the standard method of analysis of body accelerations cannot accurately predict the energy cost of uphill or downhill walking.     

Comparison of three field methods for measuring oxygen consumption

The Oxylog (OX) and the Kofranyi-Michaelis ( KM) field methods for measuring oxygen consumption ( [Vdot]O₂) were compared with the conventional Douglas Bag (DB) technique in standardized walking and lifting work in the laboratory. Subjects comprised six men. According to the mean differences in [Vdot]O₂ the OX underestimated ( 41% and 6.4% ) and the KM overestimated (3.8% and 0.8% ) [Vdot]O₂in walking and lifting work, respectively. The linear regression equations between the DB and the OX as well as between the DB and the KM revealed a good agreement (r= 0.91-0.99) of the [Vdot]O₂values. The OX and the KM are accurate for reliable [Vdot]O₂measurements under field conditions. Some practical improvements for the OX use, based on several field studies, are recommended.     

The effect of hyperoxia on submaximal exercise with the self-contained breathing apparatus

The e^ffects of hyperoxia on submaximal exercise with the self-contained breathing apparatus (SCBA) were studied in 25 males. Each participant completed a graded exercise test for the determination of ventilatory threshold (VT) and then a submaximal practice trial with a normoxic gas mixture. The normoxic (20.93 ± 0.22% O₂ ; SUB₂₁) and hyperoxic (40.18 ± 0.73% O₂; SUB₄₀) submaximal trials were then administered in a random order. All exercise tests were completed on separate days while wearing firefighting gear and the SCBA. Compared with SUB₂₁, hyperoxia significantly reduced minute ventilation ([Vdot]_E ), mask pressure (P_mask), heart rate, blood lactate concentration, perceived exertion, and perceived breathing distress. As expected, hemoglobin saturation remained higher (p<0.05) during SUB₄₀. The reductions in both [Vdot]_E and P_mask with hyperoxia imply a reduction in the work of breathing during exercise. Total gas consumption was 10.3 ± 8.1% lower during SUB₄₀ when compared to SUB₂₁, another finding that has significant practical implications for occupational safety.     

Interrelationships of respiratory variables of coal miners during work

Abstract

The respiratory responses of expiratory volume ([Vdot] _E), respiratory frequency (f _R), oxygen consumption ([Vdot] O₂), and carbon dioxide elimination ( [Vdot]CO₂) were measured for coal miners while they were performing a variety of work tasks (walking, carrying, shovelling, cranking and running). Because of the difficulties in relating the respiratory variables to external work rate and a close dependence of the respiratory responses on metabolic activity, oxygen consumption was chosen as an independent variable in the predictors for pulmonary ventilation, respiration frequency, and carbon dioxide elimination. It was necessary to use nonlinear equations for [Vdot] _E and [Vdot]Co₂ owing to exercise hyperpnoea above the anaerobic threshold.f _R did not correlate well with [Vdot]O₂ or any of the other respiratory variables. The relationship between [Vdot]_E and [Vdot]CO₂ was linear.     

Metabolic and perceptual responses while carrying external loads on the head and by yoke

Abstract

The purpose of this study was to determine the metabolic efficiency and perceptual acceptability of transporting external loads on the head and by yoke. Ten young males (24·2 ±3·9 years) of average physical fitness ([Vdot]O_2max=49·8 ± 6·5ml kg^-1 min^-1) walked for 6min on a level motor-driven treadmill at 53·6, 73·8 and 93·9m min^-1. Subsequently, all subjects carried external loads (11·6, 16·1 and 20·6 kg) at the same speeds using the headpack (HP), transverse yoke (TY) and frontal yoke (FY) modes of load carriage. Measurements were obtained for oxygen uptake ([Vdot]O₂ l min^-1), local ratings of perceived exertion (RPE-L) and the overall perceived exertion (RPE-O). The [Vdot]O₂ was used in the computation of the metabolic efficiency ([Vdot]O₂ ml kg total weight^-1 min^-1).

Significant main effects (mode, load and speed) and three interaction effects (mode × load, mode × speed and load × speed) were obtained for metabolic efficiency. Scheffé post hoc analysis revealed that the metabolic efficiency for the TY and HP were greater than the FY while transporting the 16·1 and 20·6kg loads at all walking speeds (p <0·05). No significant loss in metabolic efficiency was found while carrying the 20·6kg load at 53·6 m min^-1. At 93·9 m min^-1, all external loads transported were associated with a loss in metabolic efficiency. The RPE-L for the HP was lower than the FY (p < 0·05). Both the RPE-0 and RPE-L increased as the walking speeds and external loads were increased. The findings suggest that load transportation using the FY system is both physiologically and perceptually unacceptable.     

Energy cost and physiological responses of males snowshoeing with rotating and fixed toe-cord designs in powdered snow conditions

The purpose of this study was to measure the energy cost and physiological responses of males while snowshoeing with two separate toe-cord designs (rotating toe-cord system vs. fixed toe-cord design) in powdered snow conditions. Eight males snowshoed at self-selected intensity for two, 1600 m trials in two snowshoes, with a rotating toe-cord system and a fixed-toe cord design. It was found that heart rate (HR) (140 vs. 134 beats min^-1), oxygen consumption ([Vdot]O₂) (63.4 vs. 34.0 ml kg^-1min^-1), energy cost (56.0 vs. 52.4 kJ min^-1), and ratings of perceived exertion (RPE) (13 vs. 12) were significantly (p<0.05) higher while snowshoeing with the fixed toe-cord design than with the rotating toe-cord system. Snowshoeing with the rotating toe-cord system at an average speed of 3.96 km h^-1 produced mean &Vdot;O₂ values that were 56% of [Vdot]O₂ max, while snowshoeing with the fixed toe-cord design at 3.86 km h^-1 evoked mean [Vdot]O₂ values that were 60% of [Vdot]O₂ max. Mean HR while snowshoeing with the rotating toe-cord system was 70% of HR max, while the mean HR when snowshoeing with the fixed toe-cord design was 74% of HR max. These findings suggest that snowshoeing with a rotating toe-cord system results in lower cardiorespiratory strain in powdered snow conditions compared to snowshoeing with a fixed toe-cord design.     

Characterization of the metabolic demands of simulated shipboard Royal Navy fire-fighting tasks

The purpose of this study was to quantify the metabolic demand of simulated shipboard fire-fighting procedures currently practised by men and women in the Royal Navy (RN) and to identify a minimum level of cardiovascular fitness commensurate with satisfactory performance. Thirty-four males (M) and 15 females (F) volunteered as subjects for this study (n = 49). Maximal oxygen uptake ([Vdot]O_2max) and heart rate (fc _max) of each subject was assessed during a standardized treadmill test. During the main trials, volunteers were randomly assigned to complete several 4-min simulated shipboard fire-fighting tasks (boundary cooling (BC), drum carry (DC), extinguisher carry (EC), hose run (HR), ladder climb (LC)), at a work rate that was endorsed as a minimum acceptable standard. Heart rate (fc) and oxygen uptake ([Vdot]O2) were recorded at 10-s intervals during rest, exercise and recovery. Participants completed all tasks within an allocated time with the exception of the DC task, where 11 subjects (all females) failed to maintain the endorsed work rate. The DC task elicited the highest (p< 0.01) group mean peak metabolic demand (PMD) in males (43 ml min^-1 kg^-1) and females (42 ml min^-1 kg^-1) who were able to maintain the endorsed work rate. The BC task elicited the lowest PMD (23 ml min^-1 kg^-1), whilst the remaining three tasks elicited a remarkably similar PMD of 38–39 ml min^-1 kg^-1. The human endurance limit while wearing a self-contained breathing apparatus (SCBA) dictates that RN personnel are only able to fire-fight for 20–30 min, while wearing a full fire-fighting ensemble (FFE) and performing a combination of the BC, HR and LC tasks, which have a group mean metabolic demand of 32.8 ml min^-1 kg^-1. Given that in healthy subjects fire-fighting can be sustained at a maximum work intensity of 80% [Vdot]O_2max when wearing SCBA for this duration, it is recommended that all RN personnel achieve a [Vdot]O_2max of 41 ml min^-1 kg^-1 as an absolute minimum standard. Subjects with a higher [Vdot]O_2max than the above quoted minimum are able to complete the combination of tasks listed with greater metabolic efficiency and less fatigue.     

The effect of aerodynamic handlebars on oxygen consumption while cycling at a constant speed

Abstract

In this study, the oxygen consumption ([Vdot]O₂) of bicycling was measured at a fixed speed (40 km·h^?1on level terrain, with normal and aerodynamic handlebars using a Douglas bag collection system. Eleven elite (USCF category I or 2) men cyclists age 24 to 40 years (X¯=28·5, SD±4·6) performed four consecutive (two with each bar in alternating order) steady state rides at 40 km· h^?1over a 4 km flat course (same direction each trial). Expired gases were collected in a 1501 Douglas bag attached to a following vehicle during the last 45 s (approx. 0·5 km) of each trial. A repeated measures analysis of variance revealed a significant (p<0·02) handlebar effect. Specifically, [Vdot]O₂was 2% lower under the aerodynamic handlebar treatment (X¯=4·26, SD±0·36 1 min^?1when compared with that of the normal handlebar treatment (X¯=4·34, SD±0·35 1 min^?1The results of this study demonstrate that the reported aerodynamic advantage of the aerodynamic handlebars produces a small but significant reduction in the [Vdot]O₂of bicycling at 40 km·h^?1     

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Abstract

The role of heart rate (f _H) in the perception of exertion (RPE) during short term progressive and prolonged (l h) exercise has been studied in healthy male subjects by observing the effects of experimentally changingf _H, using intravenous injections of either atropine or practolol to modify the influence of the autonomic system.

In short term exercise the results showed that independently of the large changes produced f _H for a given oxygen intake, the subjects rated their exertion in accordance with the relative work performed (i.e. % [Vdot]o₂max) in all experiments with and without drug administration. In prolonged exercise the association of RPE and %[Vdot]o₂max was less clear. After 10min of prolonged exercise at the same [Vdot]o₂ the RPE scores were lower than those observed in the progressive work tests and with atropinisalion and β-blockade RPE tended to rise during the exercise to reach a maximum value at the 60th min though [Vdot]o₂ remained unchanged.

It was concluded that heart rate per sehas little influence on RPE and is not an important factor underlying the perception of effort. Nor can it be used to explain the close association between RPE and relative work load found in short term exercise. During prolonged exercise more research is required before any definitive conclusion can be reached particularly bearing in mind the importance of RPE scales to the study of industrial and occupational stress.     

The relationship between heart rate and oxygen uptake during non-steady state exercise

In this study the validity of using heart rate (HR) responses to estimate oxygen uptake (VO2) during varying non-steady state activities was investigated. Dynamic and static exercise engaging large and small muscle masses were studied in four different experiments. In the first experiment, 16 subjects performed an interval test on a cycle ergometer, and 12 subjects performed a field test consisting of various dynamic leg exercises. Simultaneous HR and VO2 measurements were made. Linear regression analyses revealed high correlations between HR and VO2 during both the interval test (r = 0.90 +/- 0.07) and the field test (r = 0.94 +/- 0.04). In the second experiment, 14 non-wheelchair-bound subjects performed both an interval wheelchair test on a motor driven treadmill, and a wheelchair field test consisting of dynamic and static arm exercise. Significant relationships were found for all subjects during both the interval test (r = 0.91 +/- 0.06) and the field test (r = 0.86 +/- 0.09). During non-steady state exercise using both arms and legs in a third experiment, contradictory results were found. For 11 of the 15 subjects who performed a field test consisting of various nursing tasks no significant relationship between HR and VO2 was found (r = 0.42 +/- 0.16). All tasks required almost the same physiological strain, which induced a small range in data points. In a fourth experiment, the influence of a small data range on the HR-VO2 relationship was investigated: five subjects performed a field test that involved both low and high physiological strain, non-steady state arm and leg exercise. Significant relationships were found for all subjects (r = 0.86 +/- 0.04). Although the r-values found in this study were less than under steady state conditions, it can be concluded that VO2 may be estimated from individual HR-VO2 regression lines during non-steady state exercise.     

The energy cost and heart-rate response of trained and untrained subjects walking and running in shoes and boots

Abstract

To determine the difference in the energy cost of walking and running in a lightweight athletic shoe and a heavier boot, fourteen male subjects (six trained and eight untrained) has their oxygen uptake ([Vdot]O₂) measured while walking and running on a treadmill. They wore each type of footwear, athletic shoes of the subjects' choice (average weight per pair = 616 g) and leather military boots (average weight per pair = 1776g), at three walking speeds (4·0, 5·6 and 7·3 km hour^?1) and three running speeds (8·9, 10·5 and 12·1 km hour^?1). The trials for running were repeated at the same three speeds with the subjects wearing shoes and these shoes plus lead weights. The weight of the shoes plus the lead weights was equal to the weight of the subjects' boots. The [Vdot]O₂values with boots were significantly (p < 0·05) higher (5·9?10·2%) at all speeds, except the slowest walk, 4·0 km hour^?1Also, [Vdot]O₂with shoes plus lead weights were significantly (p<0·05) higher than shoes alone. Weight alone appeared to account for 48-70% of the added energy cost of wearing boots. The relative energy cost ([Vdot]O₂, ml kg^?1?) of trained and untrained subjects were the same at all speeds. These data indicate that energy expenditure is increased by wearing boots. A large portion of this increase may be attributed to weight of footwear. In addition, the increased energy cost of locomotion with boots appears to place a limiting stress on untrained subjects.     

Hyperoxia improves maximal exercise with the self-contained breathing apparatus (SCBA)

The effects of hyperoxia on maximal exercise while breathing from a self-contained breathing apparatus (SCBA) were studied in 25 males. Each participant completed three graded exercise tests (GXT) for the assessment of maximal oxygen uptake (Vdot;O _2max): two with 20.95 ± 0.28% O₂ and the third (GXT₄₀) while breathing hyperoxia (40.64 ± 1.29% O₂). No significant differences were found between the two normoxic tests, except for a 16W increase in maximal power output (PO_max) in the second trial (GXT₂₁). Compared to GXT₂₁, hyperoxia significantly increased Vdot;O _2max and PO_max by 10.0 ± 3.8% and 10.2 ± 7.1%, respectively. This was likely due to an increase in O₂ delivery as suggested by the significantly higher oxyhemoglobin saturation. The increase in Vdot;O _2max with hyperoxia was similar to the increase in carbon dioxide production (9.3 ± 6.5%). No other significant differences were found at maximal exercise. However, at the intensity that elicited Vdot;O _2max in GXT₂₁, pulmonary ventilation and SCBA mask pressure were significantly lower during GXT₄₀, suggesting a decrease in the work of breathing. These findings could have significant implications for occupations that involve heavy work with SCBA.     

Biomechanical and metabolic effects of varying backpack loading on simulated marching

Twelve healthy, male Army recruits performed three, 40-min treadmill marches at 6 km/h, under three load carriage conditions: 0%-body weight (BW) backpack load, 15%-BW load and 30%-BW load. Kinematic and kinetic data were obtained, immediately before and after each treadmill march, for computing ankle, knee and hip joint rotations and moments. Metabolic data (oxygen uptake ([Vdot]O₂), expired ventilation ([Vdot]E), respiratory exchange ratio (RER)), heart rate (HR) and ratings of perceived exertion (RPE) were collected continuously during marching. Significant differences (p?0.05) were observed between each load for [Vdot]O₂, HR and [Vdot]E throughout the marches. At 40 min, relative energy costs for 0%-BW, 15%-BW and 30%-BW loads were 30, 36 and 41% [Vdot]O₂max, respectively. RPE responses during marching significantly differed for only the 30%-BW load and were greater than responses at 0%-BW and 15%-BW loads. During load carriage trials prior to treadmill marches (pre-march), peaks in internal, hip extension, knee extension and ankle plantar flexion moments increased with increasing backpack load. Relative to 0%-BW load, percentage increases in knee moments, due to 15%-BW and 30%-BW loads, pre-march, were substantially larger than the percentage increases for hip extension and plantar flexion moments, pre-march. Pre-march and post-march peaks in hip extension and ankle plantar flexion moments were similar with all loads, while notable premarch to post-march declines were observed for knee extension moment peaks, at 15%-BW and 30%-BW load. Pre-march joint loading data suggests that the knee may be effecting substantial compensations during backpack loaded marching, perhaps to attenuate shock or reduce load elsewhere. Post-march kinetic data (particularly at 15%-BW and 30%-BW load), however, indicates that such knee mechanics were not sustained and suggests that excessive knee extensor fatigue may occur prior to march end, even though overall metabolic responses, at 15%BW and 30%-BW load, remained within generally recommended limits to prevent fatigue during prolonged work.     

Estimation of energy expenditure in a work environment: Comparison of accelerometry and oxygen consumption/heart rate regression

The aim of this study was to compare estimation of energy expenditure (EE) in working environments, either from accelerometry or from an individual oxygen consumption/heart rate ([Vdot]O₂/HR) regression curve. The study participants were 46 volunteer workers aged 27±6 years old. A significant correlation between EE predicted by the [Vdot]O₂/HR curve and the accelerometer was observed (r=0.78, p <0.01). However, more disparities were observed between the two methods when the mean job intensity was not within 16% and 23% higher than resting HR. The accelerometer overestimated by a mean of 34.4% the prediction by [Vdot]O₂/HR regression if the intensity of the task was lower than a total of 1000 kcal/shift and underestimated the prediction by a mean of –24.9% if EE estimation of the work shift was higher than a total of 1500 kcal/shift. Despite a high correlation between both methods in the whole group, EE evaluated by accelerometry does not correspond to EE predicted by the [Vdot]O₂/HR regression curves when evaluated individually.     

The Aerobic Capacity of Forty British Women Aged 17-27 Years

Maximum oxygen intake ([Vdot] _{o 2}max), lung ventilation, heart rate, skinfolds, haematocrit and haemoglobin concentration were measured in 40 British women aged 17-27 years during 5?min maximum ergometer exercise. Repeatable values were obtained in 2 or 3 attendances. [Vdot] _{o 2}max for 20 subjects preparing for Alpine skiing was 43.3 ml/kg min (range 37.8-50.8 ml/kg min). [Vdot] _{o 2}max for 20 laboratory technicians was 36.5 ml/kg min (range 30.9-42.2 ml/kg min). The variation in [Vdot] _{o 2} max in subjects followed over 6-12 weeks ranged from + 3 to + 30%. The variation in [Vdot] _{o 2} max in 6 skiers followed over 2-6 years ranged from — 10 to +45%. The results are compared with other series on British women and with published results from other countries.