The Effect of Shaving Body Hair on the Physiological Cost of Freestyle Swimming (2024)

Abstract

The purpose of this study was to determine if shaving of body hair would have an effect on the physiological cost of standard swimming velocities. Physiological effort required to swim at a given velocity was assessed using determinations of blood lactate concentration 2 min after each of four 200 yard freestyle swims. Six subjects volunteered and were asked to swim four 200’s with 15 min rest between each and reducing their time by roughly 10 sec on each consecutive swim. On the next day, subjects shaved their body hair from arms, legs and exposed torso and repeated this swimming protocol. Blood lactate accumulation at a submaximal speed of 1.08 m/sec was significantly reduced by an average of 28% by shaving. Blood lactate accumulation at a maximal swimming speed of 1.30 m/sec was significantly reduced by an average of 23%. This much change in the physiological cost of submaximal and maximal swimming speeds is nearly as great as that resulting from a season of collegiate swimming training. It was1 concluded that there is indeed a physical benefit to shaving-down (most likely a reduction in body drag) and that the benefits are not solely due to a psychological response.

Since the late 1950’s competitive swimmers have prepared for major competition by removing the hair from their arms, legs, torso and sometimes also from their head on the day of competition. It is likely that only a very small percentage of American and world records over the past 20 years have been set by swimmers who were unshaved. Perhaps following the lead of their elite counterparts, even novice level swimmers will shave for regional and State championships. In addition, many coaches on the collegiate level advise their swimmers to shave for an early season competition so they can meet qualifying standards for championship meets held later in the season.

Despite the obvious importance that competitive swimmers have placed on shaving down, there does not exist any published literature which either supports or refutes the notion that this technique can enhance the performance of competitive swimmers. It is therefore unknown whether this practice is effective in reducing body drag enough to make a difference in performance or if it persists simply out of convention. In 1968, Counsilman (3), stated that there is no valid evidence to substantiate the theory that shaving down can decrease skin resistance enough to influence performance and that any improvements in performance thought to be due to shaving were likely normal improvements resulting from training or from the psychological effect the shaving might induce in the swimmer. He further speculated that if there is an advantage to shaving, it may be that it “increases the swimmer’s sensitivity to the feel or pressure of the water and consequently improves his coordination.”

In 1933, Karpovich determined that water resistance encountered by the body during passive towing is proportional to the square of velocity, indicating that overcoming resistance at high speeds would require energy expenditure to increase exponentially (6). An exponential increase in energy expenditure as a function of velocity was later demonstrated by Holmer (4) who attributed this relationship to the effect of body drag. Other studies sought to determine to what extent certain anthropometric characteristics contributed to body drag (1,2,5,8). Using a multiple regression analysis, Clarys showed that passive drag was most closely related to the greatest cross-sectional diameter of the swimmer but had a non-significant relationship with total body surface area (1). This should not, however, be taken to mean that other anthropometric characteristics are not significant contributors to body drag. Observations on body drag of female swimmers, for instance, have shown that females experience less body drag than males at any given velocity of towing or of free swimming (9). In part this difference was due to differences in body size. Such differences were reduced but not abolished by correcting drag measurements for body surface area and body density. It has also been shown that body drag can be reduced independent of changes in cross-sectional diameter by measuring drag on female swimmers with and without swimming suits (10). These studies showed that a typical female competitive swimming suit adds roughly 9% to body drag across all velocities.

Since body drag provides the primary component of external workload during swimming, reductions in body drag would be expected to reduce the metabolic demand of any given intensity. Thus, if shaving the hair from the body reduces drag, blood lactic acid accumulation at a given velocity should decrease. It was therefore the purpose of this study to assess the effect of denuding the skin of hair on the physiological responses to submaximal and maximal swimming velocities.

Methods

Four males and two females aged;. 20–34 years volunteered as subjects for this study. None of the subjects was engaged in swimming training at the time of the experiments and all but one were competitive swimmers (1 month to 10 years in the past.) Each of the subjects was fully informed of the possible risks and benefits of their participation in the study before giving their written consent.

Each subject was asked to perform four 200 yard freestyle swims with 15 min rest between each on two consecutive days. On the first day, the subject was asked to swim the first 200 at a mild pace, the second 200 at medium pace, the third 200 at a moderately hard pace and the fourth 200 at an all-out pace. In addition, the subjects were advised to decrease their time by roughly 10 sec on each consecutive 200. The swims were timed from the instant the feet broke contact with the starting wall until the hand touched the finish wall. At the same time on the second day, after shaving all the hair from the arms, legs and exposed torso, the subjects performed the same protocol and were asked to duplicate the times recorded for the first three 200’s from the previous day. For the fourth 200, the subjects were asked to exert an all-out effort. Two min after each of the swims, a 20 microliter fingertip blood sample was obtained and immediately deproteinized in perchloric acid. The blood samples were later centrifuged and analyzed for lactic acid concentration using an enzymatic spectrophotometric method (7). All of the blood samples for each subject were analyzed in the same assay in order to eliminate any inter-assay variability.

Because the subjects could not exactly duplicate their trial times of the first day, we used a regression of log lactate on velocity to compare the blood lactate responses at standardized speeds. Briefly, this procedure requires that blood lactate concentration be converted to common logarithm and then treating the relationship between log lactate and velocity with linear regression analysis followed by prediction of lactate concentration at standard speeds for each subject in each condition. An example of how such a plot looks is shown in Fig. 1. We have chosen the log lactate technique over others because we have found that this usually gives us the best curve fit and least error in prediction. The correlation coefficients for these trials ranged between 0.91 to 0.99.

The regression equations were used to determine blood lactate at speeds of 1.08 ± 0.06 m/sec and 1.30 ± 0.06 m/sec both pre- and post-shave. These velocities were chosen for comparison because the former corresponds to the pre-shave velocity at a blood lactate of 4 mM and the latter represents the maximum pre-shave velocity. Group means for blood lactate at these velocities were compared between pre- and post-shave using repeated measures ANOVA. The greatest velocity achieved pre-shave was compared with that of post-shave using a paired t-test. Likewise, blood lactate after the fastest pre-shave swim and post-shave were compared. The null hypothesis was rejected when P < 0.05. All data are reported as mean ± SE.

Results

Performance speeds and blood lactate concentrations for the pre-shave and post-shave conditions are shown in Table 1. In spite of our instruction to the subjects to swim the same speed on the second day (shaved) for the first three 200’s, the velocities were significantly faster. Blood lactate concentration was, however, significantly lower after the first three swims in the shaved trial. There was no significant difference in blood lactate concentration after the fourth swim between pre-shave and post-shave in spite of the fact that the subjects swam significantly faster after shaving.

At the pre-shave velocity corresponding to a blood lactate concentration of 4mM (1.08 ± 0.06 m/sec), blood lactate was significantly lower post-shave (2.90 ± 0.29 mM) and represents an average decrease in blood lactate at this velocity of 28 ± 7%. At the pre-shave maximum velocity of 1.30 ± 0.06 m/sec, blood lactate was also observed to be significantly lower post-shave (7.99 ± 0.47 mM) than pre-shave (10.56 ± 0.84 mM). The group mean percentage decrease in lactate at this speed was 23 ± 3%. These data are shown in Fig. 2.

A group mean lactate/velocity profile for both pre-shave and post-shave is shown in Fig. 3 and shows a significant rightward shift in the profile with the magnitude of shift appearing roughly equal at all speeds.

Discussion

The major finding of this study is that shaving the hair from arms, legs and torso substantially reduced the physiological cost (as judged by accumulation of blood lactate) of both submaximal and maximal freestyle swimming speeds. The reduction in blood lactate accumulation at standard speeds is generally taken as evidence of 1) improved aerobic fitness which either increases lactate clearance or reduces lactate production, 2) improved mechanical efficiency, or 3) muscle glycogen depletion as a result of heavy training. Since these swimmers were not engaged in swimming training at the time of this experiment and since the trials were conducted on consecutive days, it is very unlikely that changes in aerobic fitness or muscle glycogen depletion could account for the changes in blood lactate that were observed. We have also found that when this protocol is used on consecutive days without shaving, the blood lactate accumulation at standard speeds is identical between days. For these reasons, we favor a reduced physiological cost as the explanation for decreased blood lactate accumulation observed in this study.

The magnitude of reduction in blood lactate accumulation observed in this study is quite substantial when compared with that normally associated with training. Unfortunately, little literature exists regarding how much of a shift in the lactate/velocity profile we can expect from a season of training. However, we have used these profiles to evaluate the progress made in training of collegiate swimmers. Over the past 4 years we have observed that during a collegiate swimming season, blood lactate at near-maximal standard speed decreases by an average of between 27–35% without shaving. In the present study, the decrease in blood lactate as a result of shaving amounted to 23%. Thus, it can be said that within these subjects the effect of shaving was nearly as great as an entire season of training.

Another way to appreciate the magnitude of this effect is to examine the present data in terms of improvements in time over the distance used. It was stated that velocity on the all-out 200 yard swim was significantly faster after shaving but improvements in speed could have been a result of the subjects expecting to swim faster after shaving and thus exerting a greater effort. If this were the case in the present study, then we would expect such a “placebo effect” to cause an increase in blood lactate in proportion with the faster time. However, as shown in the results, blood lactate was not significantly higher after the all-out post-shave swim. Nevertheless, if we use the maximum blood lactate from the pre-shave trials and determine the post-shave time that would result in this lactate value, then average 200 time would be 2:15.0 ± 6.4 sec. This is significantly faster than the time which occurred pre-shave (2:21.6 ± 6.5 sec) at the same blood lactate concentration and agrees very closely with the average time which was actually achieved on the post-shave all-out trial (2:15.5 ± 6.2 sec). It should be obvious, therefore, that reducing body drag by whatever means available should perhaps occupy a greater portion of coaches efforts in preparing swimmers than it presently does.

A reduction in the physiological effort required to maintain a given swimming speed can be brought about by a decreasing body drag. Earlier research suggests that the primary components of body drag (active drag) are form drag, wave drag, skin resistance and eddy resistance. Of these components, the one that is probably most affected by shaving hair is skin resistance. The present data do not, however, allow us to be certain that shaving body hair reduces body drag enough to account for the amount of decrease we observed in blood lactate accumulation. It could be argued that shaving body hair improves one’s efficiency by improving their ability to sense and thus eliminate non-propulsive and energy consuming movements. Further research employing direct determinations of body drag are therefore needed to identify the mechanism by which removal of body hair reduces the physiological cost maintaining any given swimming speed. It would also be useful to determine if the other strokes are affected as much by shaving.

Practical Applications

Not all swimming coaches agree that there is a physical justification for swimmers to shave their body hair before major competition. In part this may be due to the lack of objective evidence of the effect. The present data provide a beginning to our understanding of why shaving seems to offer such an advantage. Furthermore, since the effects of shaving appear to be due to more than just a psychological boost, shaving down for competition more often during a season can be justified. There is no reason to expect that repeated shaving would diminish the amount of biomechanical and physiological effects that can be derived. This must, however, be counterbalanced with the consideration of possible psychological benefits that might occur from “saving the shave” until the major competition.

These results may also have implications for the way in which we view the role played by body drag in determining a swimmer’s performance capacity. Certainly many coaches already appreciate the need to incorporate strategies for decreasing body drag (i.e., streamlining, body position, etc.) into training programs. But there are many swimming programs that strive to achieve so much daily training yardage that there is little time or energy left for technique training. Some coaches may not realize the extent to which small changes in body drag might affect the physiological effort required to swim fast. The present data demonstrate that the potential return from reductions in body drag can be rather substantial. Thus, it may be wise for some coaches to spend more time working on drag reduction in place of some of the physiological training thereby contributing to greater improvements in performance and minimizing the risk of overtraining.

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