that, as a means of progression, walking is suitable for lower speeds

Transcription

1 2 6I ENERGY EXPENDITURE IN WALKING AND RUNNING. BY M. OGASAWARA. (From the Department of Industrial Physiology, London School of Hygiene and Tropical Medicine.) (Received February 28, 1934.) IT is well known that speed has a considerable influence on energy expenditure in walking and running. It is generally and correctly understood that, as a means of progression, walking is suitable for lower speeds up to a certain limit, while running is suitable for higher speeds. The average man cannot walk at very high speeds, nor can he execute the normal movements of running at very low speeds. The muscular mechanism of the body is adapted to run instead of walk when higher speeds are required, and to walk instead of run at low speeds. There is, however, a range of speeds, within which walking and running are equally possible, and Benedict and Murschhauser [191] and Furusawa, Hill, Long and Lupton [1924] have shown that, at such speeds running is more efficient than walking from the view point of energy cost. The former's results showed the energy expenditure of running to be about 1 p.c. less than for walking at a speed of 144 m. per min., while in the case of the latter, running at m. per min. was only about 60 p.c. as expensive as walking at approximately the same speed. In the present investigation the total energy expenditure and the oxygen requirement per minute were compared when walking and running at the same speeds. The oxygen requirement for the effort was measured as in the experiments of Furusawa, Hill, Long and Lupton, rather than the oxygen intake during the effort, which was the method of investigation adopted by Benedict and Murschhauser. The subject in the present experiments performed his exercise as naturally as possible, namely by walking or running a given distance on a horizontal track in the open air.

2 26 M. OGASAWARA. EXPERIMENTAL METHOD. The Douglas-Haldane method was used, the expired air of the subject being collected before, during and after each bout of exercise. The experiments were carried out in the morning, between 9.30 a.m. and p.m. All experiments were made with the same subject, who is a laboratory assistant and a healthy, athletic young man of 26 years of age, 126 lb. in weight, ft. 6 in. in height, and having a good deal of experience as a subject in metabolism experiments. In order to ensure that the walking or the running should be as natural as possible, a course was set out on the roof of the School of Hygiene instead of using a treadmill in the laboratory. The course was 0 m. in length per lap and the subject walked or ran 00 m. or 10 laps in each experiment. It was decided not to have any artificial control of the speed which might absorb the attention of the subject when executing the effort. It is not easy to keep the same speed in walking and running in a natural way, but it was fortunately noticed in preliminary experiments that the subject showed nearly the same speed in walking as in running when he tried to walk as quickly as possible or to run as slowly as possible. This fact justified the subsequent carrying out of all experiments in such a way that the subject walked or ran at his quickest or slowest rate respectively, the actual speeds being accurately measured by stopwatch. The number of steps was counted during each 10 sec. of effort on five occasions per walk or run of 00 m., and the mean values were calculated in order to determine and check the rate of muscular movement per minute. In addition to experiments with the quickest walk and slowest run, slower rates of walking and more rapid rates of running were also studied in a few experiments, for purposes of comparison and control. Generally, two experiments were carried out in one mornig, one walking and the other running, or in the reverse order on different days, so that any effects due to fatigue or training could be eliminated in averaging the results. After a foreperiod of 30 mi. resting sitting in a chair with feet up, the first collection of the subject's expired air was taken during 10 min. further resting in the same position. The subject was then fitted with a portable Douglas bag and took up his position at the start of the course to which he moved very slowly. At the moment he started to walk or to run the tap of the bag was turned on and the second collection of expired air commenced. After finishing the exercise the subject returned to the

3 ENERGY EXPENDITURE IN WALKING AND RUNNING. 27 chair and took up the resting position. The time of the second or exercise collection was in the majority of cases mi., i.e. 1 or 2 mi. longer than the exercise itself. This collection was immediately followed by a third collection during a period of 30 min. throughout which the subject maintained the resting posture as before. On the conclusion of the recovery collection a further 10 min. collection was taken as a check on the resting value. Two sample tubes for each bag were analysed, the mean value for the percentage composition being used when the results differed in the two samples from a bag. As a general rule the difference did not exceed 0*06 p.c. in the two analyses, and experiments in which a greater difference appeared have been omitted from this paper. In some of the experiments with a very slow rate of walking the time of the exercise collection had to be slightly prolonged. It will be noted that the base line from which the excess oxygen used for the exercise was assessed, was that of the oxygen consumption per minute of the subject when sitting resting in a chair with the legs raised. It would have been impossible to use the standing posture or work position for the resting and recovery collections owing to the length of time involved, for it has been noted that subjects vary a good deal in their ability to maintain a steady posture when standing and that fatigue materially influences metabolism. DATA OF EXPERIMENTS. The results are given in Tables I and II in which the experiments are listed in order of decreasing speed, except in the case of Exps. 1, 16, 17, 30 and 31, in which rubber shoes were worn. The oxygen requirements in relation to speed is given in Fig. 1, from which it is clear that the difference between the oxygen requirement for walking and running increases with the speed of progression. DIscusSION. The data given in Tables I and II, and the curves in Fig. 1 show that when the rates of progression are substantially the same the increased oxygen requirement for walking as compared with running varies from approximately 4 p.c. at a speed of m. per min. to 1 p.c. at 11- and 20 p.c. at 172*4 m. per min. These results are similar to those of Furusawa, Hill, Long and Lupton, and are also in good accord with the findings of Benedict and Murschhauser. Benedict and Murschhauser determined the

4 28 M. OGASAWARA. TABLE I. Walking. Time, Speed and No. Step rate 1 2 min. 4 sec m./min. 198/min. 2 2 min. 4 sec m./min. 198/min. 3 2 min. 7 sec m./min. 194/min. 4 3mm m./mln. 190/mm. 3 min. 3 sec m./min. 186/min. 6 3 min. 6 sec m./mln. 190/min. 7 3 min. 1 sec m./mln. 186/m min.18sec. 11- m./min. 186/min. 9 3 min. 30 sec m./min. 180/min min. 4 sec. 133*3 m./min. 174/min min. 6 sec. 122 m./mln. 144/min min. 4 sec. 102 m./min. 132/min. Collection time 6 20 rest Ventilation I/min intake c.c./min B.Q requirement c.c./min

5 ENERGY EXPENDITURE IN WALKING AND RUNNING. 29 Time, Speed and No. Step rate 13 min. 1 sec. 9-2 m./mln. 120/min min. 33 sec m./min. 100/min. 1* 3min. 10sec m./min. 18/min. 16* 3min. 12sec. 16*2 m./mln. 186/min. 17* 3 min. 6 sec. 161*3 m./min. 190/min. TABLE I (cont.). Collection 02 time Ventilation intake min. 1/min. c.c./mi rest * rest R.Q * * *07 0* srequirement c.c./min min.30sec. 200 m./mln. 168/min min. 48 sec m./mln. 16/min min. 4 sec m./min. 162/min min. 4 sec m./mln. 160/min min. 166'7 m./min. 160/min min. 6 sec. 161*3 m./min. 160/min min. 10 sec m./min. 16/min. TABLE II. Running * *89 4*48 4* * * *8 1*11 0* * * X * * * *79 * These experiments were carried out with the subject wearing a pair of light rubber shoes. PH. LXXXI

6 260 M. OGASAWARA. TABLE II (cont.). Time, Speed Collection reand time Ventilation intake quirement No. Step rate min. 1/min. c.c./min. R.Q. c.c./min. 2 3 min. 1 sec m./min. 42* /min min. 1sec *8 m./min /min min. 18 sec. 3* m./min /min. * min. 30 sec m./min /min min. 40sec. 4* m./mln. 39* /min * 3 min. 4 sec m./min *89 10/min * * 4 min. 7 sec m./min. 3* /min. 20 rest * * These experiments were carried out with the subject wearing a pair of light rubber shoes. -d 0 '40 XA 0 ai 2rH<. I~~~~~~~~~~ u a0) lu Speed, m./min. Fig. 1. Speed and 0 requirement of walking and running. *-* Walking. o-o Running.

7 ENERGY EXPENDITURE IN WALKING AND RUNNING. 261 oxygen consumption per minute as measured during the exercise; while in the experiments recorded in this paper the oxygen requirement was determined from the excess oxygen used in exercise and recovery. Benedict and Murschhauser's subject was no doubt in a steady state during the working collection, but at some of the higher speeds in the present study a steady state could not have been attained. The min. collection of expired air, the exercise collection in the present investigation, included a minute or more recovery as well as the exercise, so that it is not possible to calculate the actual oxygen intake during exercise. It must be borne in mind, however, that the above comparison of the oxygen requirement per minute for walking and running is not a true comparison of the oxygen used or required per unit muscular movement, namely per stride, when walking and running. In the case of running fewer movements are performed than in walking although the speed of progression and the total distance covered may be the same. Calculations of the actual excess oxygen required per stride show that at the same speed of progression, whether in walking or running, each stride necessitates approximately the same expenditure of energy as judged by the oxygen requirements. Inasmuch as the length of stride in walking is less than in running more strides must be taken to maintain the speed and cover the distance, and the difference in oxygen requirement appears to be directly related to the number of strides taken in each case. Table III shows a comparison of the oxygen requirements per stride when walking and running at various speeds. TABLE III. Oxygen requirement (c.c.) per stride in walking and running at various speeds. Speed Running Speed Running m./min. Walking c.c. m./min. Walking c.c * * *4 21* * * * 166* * *1-16* 161* *7 18* * - 66* * Tbese figures were obtained when the subject wore a pair of light rubber shoes. A strict comparison of walking and running could only be made if the same length of stride and frequency of stride were adopted in each case, but as this is almost impossible and certainly unnatural at high 17-2

8 262 M. OGASAWARA. speeds the results of such an experiment would be of little if any significance. The curves shown in Fig. 1 for the oxygen requirement in relation to speed and Fig. 2 for the number of strides taken in walking and running in relation to speed, possess similar characteristics, and it is _ *~ C0 120 _ too Speed, m./min. Fig. 2. Speed and stride frequency for walking and running. * Walking. o-o Running. therefore thought that the increased oxygen required per minute for walking at high speeds as compared with running is substantially due to the fact that more muscular movements are exerted per minute in order to maintain the same rate of progression. INFLUENCE OF FOOTWEAR. In some experiments which I have carried out marked differences have been found in energy expenditure when light rubber or heavy walking shoes were worn. It may be pointed out in this connection that Exps. 1, 16 and 17 (Table I) and 30 and 31 (Table II) were carried out with the subject wearing a pair of light rubber shoes instead of the leather walking shoes which were used in all the other experiments. In these experiments using rubber shoes the oxygen requirement for the effort was less than that when leather shoes were worn, particularly so in the case of the walking experiments. Difficulty was found by the subject in running at low speeds unless rubber shoes were worn.

9 ENERGY EXPENDITURE IN WALKING AND RUNNING. 263 INFLUENCE OF ARM SWING. Benedict and Murschhauser claimed that the arm swing in walking caused a marked increase in energy expenditure, and attempted to allow for the effect of arm swing in their computations of the energy expenditure by determining the oxygen used by their subject when standing and swinging the arms as in walking. They stated that with the oxygen consumption for arm swing as the base line the energy cost of walking proved to be some 3 p.c. less than for running at the same speed. In walking at high speeds the arms must be swung quite vigorously across the chest in order to provide a reaction so that the opposite leg can be brought forward without bending at the knee as in running. Otherwise, at high speeds, walking degenerates into running. The extra expenditure m walking may possibly be due partly to the swinging of the arms, and also partly to the maintained contraction of the muscles of the leg, but the actual number of muscular movements appears to be the main cause. I carried out a few experiments to determine the energy cost of arm swinging at the rates executed when walking, and the results showed the oxygen requirement per minute for arm swing to be on the aggregate 906 c.c. for 3 min. 6 sec., swinging at the rate of 190 arm swings per min. Subtracting this figure for the oxygen requirement per minute of standing arm-swinging exercise, the energy cost of the remaining movements of progression in walking at the speed of 161x3 m. per min. would be about 11 p.c. less than the cost of running at the same speed-a result which appears difficult to believe. As the accurate estimation of the oxygen requirement for arm swinging alone is practically impossible, owing to other factors increasing oxygen usage, as for example postural balance and increased respiratory movements, I do not think that this result is of any value. Moreover, inasmuch as arm swinging is an essential feature of walking at high speeds the isolated study of the movement is without significance in comparing the relative oxygen requirements for walking and running at the same speed. SUMMARY. The oxygen requirements for walking and running at the same speed under natural conditions in the open air have been investigated by the Douglas-Haldane method. The results are similar to those of

10 264 M. OGASAWARA. Furusawa, Hill, Long and Lupton, and in good accordance with the laboratory treadmill experiments of Benedict and Murschhauser. With increasing speed of progression the oxygen requirement for walking increases at a greater rate than for running. The increased oxygen requirement for walking as compared with that for running at the same rate varied from 4 p.c. at a speed of m. per min. to 1 p.c. at 11- and 20 p.c. at m. per mn. It was noticed in walking at high speeds that the oxygen requirement for the effort was less when light rubber shoes were worn than when leather walking shoes were used. The vigorous arm swinging across the chest adopted when walking at high speeds may necessitate increased oxygen usage, but it is not thought to be a material cause of the difference in oxygen requirement observed in walking and running at the same rates of progression. The isolated study of the energy expenditure in arm swinging is considered to be of little if any significance. The oxygen requirement per stride when walking or running at the same speed is shown to be substantially the same, and therefore it is thought that the increased oxygen requirement for walking is essentially due to the fact that more muscular movements are necessary because the length of stride is less. I should like to express my deep indebtedness and thanks to Dr G. P. Crowden for his kind help, without which this investigation could not have been carried out. REFERENCES. Benedict, F. G. and Murschhauser, H. (191). Carnegie In8t. of Washington, No Furusawa, K., Hill, A. V., Long, C. N. H. and Lupton, H. (1924). Proc. Roy. Soc. B, 97, 168, 17.