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.     

Metabolic,cardiovascular and spinal strain of a representative fuel replenishment task

The metabolic, cardiovascular and spinal strain of a representative fuel replenishment task for a tank crew were assessed using nine military subjects wearing coveralls in a comfortable ambient climate. The task involved lifting 5 gal jerry cans (weighing 23·4?kg) from the ground to a height representing a tank deck (1·676 m) at a rate of two lifts per minute for 15 min. Oxygen uptake ([Vdot]O₂), minute ventilation ([Vdot]E), heart rate (HR) and intra-abdominal pressure (IAP) were monitored continuously. After 15 min of lifting the mean [Vdot]O₂ was 0·821 min^?1 (S.D. 0·18). This was 27% of the predicted [Vdot]O₂ max. The mean [Vdot]E was 21·81 min^?1 (S.D.4·1) and the HR was 111·3 beats min^?1 (S.D. 17·8). The mean peak IAP was 105·6?mmHg, with 56% of the peak IAPs exceeding 90?Hg. The mean intrasubject coefficient of variation was 10·7% (range 7·2–24·2). In a separate series of 20 consecutive bimanual straight arm vertical lifts of 10?kg at 15 s intervals, the mean intrasubject COV% was 7·2% (range 3·2–11·2%). The replenishment task was considered acceptable in terms of the metabolic and cardiovascular strain. In terms of spinal strain, there may be an unacceptable risk of back injury if the task was normally undertaken as part of a soldier's full-time occupation over many years     

The physical strain of dairy farming

The aim of this study was to estimate the physical stress and strain in dairy farming, using ambulatory heart rate and oxygen consumption measurements. The rate of perceived exertion was estimated with Borg scale. The maximal oxygen consumption was measured in the laboratory. The study group consisted of eight male and 15 female farmers. The handling of feed and manure was the heaviest work task in dairy farming. The aerobic capacity ([Vdot]O₂ max) of female farmers (26 ± 3 ml/min/kg) was below average, and their work required over 50% of [Vdot]0₂ max during most of the tasks. The [Vdot]0₂ max of male fanners (32±10 ml/min/kg) was moderate, and most work tasks required below 50% of [Vdot]0₂ max. The mean heart rate in dairy farming tasks was 99 beats min^-1 in men and 116 beats min^-1 in women. However, according to the rate of perceived exertion, the men experienced the same work tasks as subjectively more heavy than did the women. The physical strain of female farmers in dairy farming seems to be too high because of heavy work tasks and relatively low [Vdot]0₂ max of women. Special attention should be paid to these factors in the occupational health services for farmers.     

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.     

Permissible loads based on energy expenditure measurements

The literature is reviewed and, based on this, it is suggested that the upper general tolerance limit over an 8-hour work day, consisting of mixed physical work, including handling operations, is approximately 30–35% [Vdot]O₂ max (on bicycle legwork or treadmill). Therefore, the individual tasks must be adjusted to a metabolic level not exceeding 30–35% [Vdot]O₂ max in the majority of the labour force or may be more realistic in specific groups within the labour force (young/ old, male/female). The following metabolic values are suggested (1 [Vdot]O₂ ): males <40 years: 0·7males>40 years: 0·6; females < 40 years: 0·6; females >40 years: 0·5. It is important to notice that even with a metabolic rate below 30–35% [Vdot]O₂ max it is possible that local overstrain and/ or fatigue in the back muscles during, for example, manual handling operations of long duration can occur     

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     

Aerobic capacity of urban women homemakers in Bombay

Twenty-six healthy women homemakers residing in the metropolitan city of Bombay were studied on a treadmill and a cycle ergometer to determine their aerobic capacity ([Vdot]O₂ max) with a view to evaluating their cardio-respiratory fitness and ascertaining the job-demand-fitness-compatibility in household activities. The [Vdot]O₂ max was found to be significantly higher in treadmill experiments, i.e. 15% in absolute value and 18% in relative value, as compared with that obtained by cycle ergometry (p < 0·001). A much higher difference was observed in values derived from the two methods on the same subjects (i.e. 28% in absolute value and 31% in relative value). Thus, the [Vdot]O₂max obtained from treadmill experiments may be regarded as the maximal aerobic power or the highest oxygen uptake that an individual can attain during exercise, which in the sample of the present study was recorded as 1·901 min ^?1 (33·9 ml kg ^?1 min ^?1). The findings also revealed that age and body weight have a direct influence on [Vdot]O₂max, which was found to be significantly correlated, positively with the latter and negatively with the former (p<0·01 in both cases). The physiological job-demand of household activities seems to be compatible in relation to the [Vdot]O₂max of the homemakers.     

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.     

The influence of flywheel weight and pedalling frequency on the biomechanics and physiological responses to bicycle exercise†

The physiological, subjective and biomechanical effects of altering flywheel weight and pedalling rate on a Quinton Model 870 bicycle ergometer were studied. Steel plates were added to the flywheel to increase its weight to 35·9 kg with a moment of inertia of 1·65 kg m². A 1·5 kg spoked wheel with a moment of inertia of 0·1 kg m² was used as the light flywheel. Eight subjects pedalled on two separate occasions for 6 min at 40, 50, 60, 70, 80 and 90 r.p.m. with workload levels representing 30 and 60% of their [Vdot]O₂max with each flywheel. Force plate pedals were used to measure the total resultant force on the pedals (F_R ) and the component perpendicular to the crank arm (F_T). A force effectiveness index (FEI) was denned as the average of F_T/F_R over a crank cycle. The result showed no statistically significant change (p<0·05) in [Vdot]O₂, heart rate and rating of perceived exertion of the FEI as a function of flywheel weight except for the [Vdot]O₂ at 50 r.p.m. for the light workload. As the r.p.m. increased from 40 to 90 r.p.m., the FEI decreased from 0·5 to 0·35 with the heavy load and from 0·36 to 0·22 with the light load. Measured physiological, subjective and biomechanical indices did not change significantly with flywheel weight. Increasing the pedalling rate caused a significantly less effective application of forces to the crank arm with only a small change in [Vdot]O₂.     

A new kayak ergometer based on wind resistance

Abstract

An ergometer for kayak paddlers has been developed and used for winter training, measurements of work capacity and maximal oxygen uptake ([Vdot]O₂ max). Force is transmitted from the paddle by means of a wire connected to a flywheel mounted with six 9 × 9cm blades. Resistance, therefore, is based on wind turbulence generated by the flywheel. The mechanical efficiency of the ergometer at 63% (range 48-77) of [Vdot]O₂ max was 17% (range 16-18) (n= 13). The [Vdot]O₂ max was similar during bicycling (median 4·9; range 4·4-5·4l/min), arm cranking (median 4·8; range 4·3-5·11/min), on-water rowing in a kayak (median 4·7; range 4·0-4·91/min) and during rowing the kayak ergometer (median 4·8; range 4·3-5·21/min), (n = 6, p> 0·05). Work capacity during a 5 min ‘all-out’ test was 272 W (range 253–304 W) on the kayak ergometer (n = 17). The use of the ergometer for training helped to increase the aerobic power during arm exercise of Danish paddlers. Before introduction of the ergometer (February 1986), their VO₂ max was 4·6 (range 3·8-5·2) 1/min while 12 months later, it was 50 (range 4·2–5·7) 1/min (n = 14, p < 0·01). The ergometer has thus been found.useful for training and evaluation of work capacity in kayak paddlers.     

Estimated aerobic performance and energy cost of severe exercise of 24 h duration

Abstract

The maximal aerobic performance ([Vdot]O₂max) and energy cost of running at various speeds of two ultra-distance athletes were measured in the laboratory on a motor driven treadmill and the results related to observations made during a 24 h race. The athletes finished 1st and 2nd in the event and covered distances of 251·46 km and 234·56 km respectively during the 24 h period. From the measurements in the laboratory it was calculated that the average speeds sustained by the athletes during the competition were equivalent to an O₂ cost of 36·4 ml kg^?1 min^?1 and 35·3 ml kg^?1 min^?1 which represented approximately 50% of their [Vdot]O₂max. During the race the winner expended an estimated 77,829 kJ (18.595 kcal) which is three times the highest recorded value in the most severe industrial work. By the nature of the activity this figure must be regarded as at or near the upper limit of sustainable energy expenditure by man during a complete uninterrupted 24 h circadian cycle.     

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 ([Vdot]O₂) 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 [Vdot]O₂ measurements were made. Linear regression analyses revealed high correlations between HR and [Vdot]O₂ 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 [Vdot]O₂ 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-[Vdot]O₂ 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 [Vdot]O₂ may be estimated from individual HR-[Vdot]O₂ regression lines during non-steady state exercise.     

The energy cost of women walking and running in shoes and boots∗

The purpose of this study was to determine the difference in energy cost for women walking and running in shoes versus heavier boots. Seven subjects wore athletic shoes (mean weight = 514 ± 50g) and leather military boots (mean weight = 1371 ± 104g) at three walking speeds (4·0, 5·6 and 7·3km/hour) and two running speeds (8middot;9 and 10·5 km/hour). During each walking and running trial oxygen uptake ([Vdot]O₂ ml kg^?1 min^?1) was measured. The [Vdot]O₂ for women wearing boots were significantly higher (P < 0·05) than for shoes for both walking and running, with the exception of the slowest walking speed. The average increment in energy cost was 1·0% per 100-g increase in weight per pair of footwear. These results are similar to those reported for men from other studies which found increments in energy cost of 0·7 to 0·9% per 100-g increase in weight of footwear.     

Aerobic Capacity of Steel Workers in India

Abstract

Seventy-six workers, aged 21–43 y. drawn from three major steel plants—two located in the eastern and one in the central region of India (referred to as Group A, Group B and Group C respectively)—were studied on the bicycle ergometer to determine their aerobic capacity ([Vdot]_O2max), Both the direct and indirect methods were employed, the direct one being used only in the case of the workers in Group C. The mean [Vdot]_O2max of these workers was found to be 42·6 cm³ kg^?1 with a standard error of ± 0·71 cm³ kg^?1 min^?1. The highest values were observed among the workers in Group B (mean 47·0± 1·35 (S.E.)cm³kg^?1 min^?1) who are ethnically distinct and have a high level of customary activity, and the lowest among workers in Group C (mean: 39·0±0·74(S.E.) cm³kg^?1 min^?1).

As expected, the [Vdot]_O2max was found to be correlated positively with body weight, and negatively with age in a multiple regression analysis. Furthermore, the active Group B has values for [Vdot]_O2max that are significantly higher than those for the other Groups, a difference that is not attributable to weight or age.     

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.     

Circadian changes in resting heart rate and body temperature,maximal oxygen consumption and perceived exertion

To investigate the existence, magnitude and interplay of rhythmic 24-hour variations in human functions, maximal O₂ uptake (VO₂max), resting heart rate (?_H), body temperature (T_b) and rated perceived exertion (RPE) during exercise were measured twice every 2hours over a full day-night cycle. Thirty-one subjects were randomly administered a treadmill test on 24 separate occasions, 48 hours apart. RPE was observed at heart rates of 130, 150 and 170beats/min. Resting T _b, and/H were lower (p< 005) in the morning than afternoon or evening. Measurement of [Vdot]O₂ max revealed no significant differences throughout 24 hours. RPE was higher (p< 0-05)at 130, 150 and 170HR at 02.00 and 04.00hours than at 20.00, 22.00 and 24.00 hours. T _b and ?_H were apparently in phase.and show a sine wave pattern when expressed on a 24-hour scale. These data demonstrate the significance of the circadian variation for the application of functional tests.     

A comparison of time to exhaustion at [vdot]O2;max in elite cyclists,kayak paddlers,swimmers and runners

Abstract

A recent study has shown the reproducibility of time to exhaustion (time limit: ttime) at the lowest velocity that elicits the maximal oxygen consumption (υ[vdot]O₂ max). The same study found an inverse relationship between this time to exhaustion at υ[vdot]O₂ max and υ[vdot]O₂ max among 38 élite long-distance runners (Billat et al. 1994b). The purpose of the present study was to compare the time to exhaustion at the power output (or velocity) at [vdot]O₂ max for different values of [vdot]O₂ max, depending on the type of exercise and not only on the aerobic capacity. The time of exhaustion at υ[vdot]O₂ max (tlim) has been measured among 41 élite (national level) sportsmen: 9 cyclists, 9 kayak paddlers, 9 swimmers and 14 runners using specific ergometers. Velocity or power at [vdot]O₂ max ( υ[vdot]O₂ max) was determined by continuous incremental testing. This protocol had steps of 2 min and increments of 50 W, 30 W, 0.05ms^? and 2km^? for cyclists, kayak paddlers, swimmers and runners, respectively. One week later, dim was determined under the same conditions. After a warm-up of 10 min at 60% of their υ[vdot]O₂ max, subjects were concluded (in less than 45 s) to their υ[vdot]O₂ max and then had to sustain it as long as possible until exhaustion. Mean values of υ[vdot]O₂ max and dim were respectively equal to 419±49 W (tlim = 222 ± 91 s), 239±56W ( tlim = 376 ± 134 s), l 46±009ms^?1 ( tlim = 287± 160s) and 22.4 ±0.8kmh^?1 ( tlim = 321 ±84s), for cyclists, kayak paddlers, swimmers and runners. Time to exhaustion at υ[vdot]O₂ max was only significantly different between cycling and kayaking (ANOVA test, p<0.05). Otherwise, υ[vdot]O₂max (expressed in ml min^?1 kg^?1) was significantly different between all sports except between cycling and running (p < 0.05). In this study, time to exhaustion at υ[vdot]O₂ max was also inversely related to υ[vdot]O₂ max for die entire group of elite sportsmen (r= ?0.320, p<0.05, n = 41). The inverse relationship between υ[vdot]O₂ max and dim at υ[vdot]O₂ max has to be explained, it seems that dim depends on υ[vdot]O₂ max regardless of the type of exercise undertaken.     

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.     

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.     

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.