It is known that swimmers, swimming at the same speed, consume more oxygen when swimming fully clothed than when wearing a traditional swimsuit (Andersen, 1960). An increase in energy consumption when swimming while wearing clothes probably results from increased water resistance, which hinders movement of the arms and legs (Keatinge, 1961).
In Japan, more people drown when wearing clothes than when wearing a swimsuit. In 1998, police officials reported that 1,200 people drowned in Japan; 25% of them drowned wearing a swimsuit, and the other 75% drowned wearing clothes while doing activities such as fishing, boating, or working near the water. The increased physical exertion required when swimming while wearing clothes may have been a factor in their deaths. The difference between the energy costs of swimmers wearing clothes versus those not wearing clothes has not been fully investigated.
It is generally accepted that the energy supply for short-term, high-intensity exercise originates from stored adenosine triphosphate (ATP) and high-energy phosphagen breakdown, which would cause an increase in blood ammonia concentration (Dudley & Terjung, 1985; Itoh & Ohkuwa, 1990; Lowenstein, 1972). However, there are no reports on the differences in swimming performance and energy supply of individuals swimming wearing clothes and those wearing a traditional swimsuit. Therefore, the purpose of this investigation was to compare swimming speed and blood lactate levels for individuals swimming in clothes or a swimsuit using two different strokes (crawl stroke and breaststroke).
The participants for this experiment were 6 moderately trained male swimmers who swam using either crawl stroke or breaststroke. The purpose and protocol of the study and the possible risks were fully explained to each participant before they signed an informed consent document.
All participants swam in either a swimsuit typically used by competitive swimmers or in shirts, pants, and shoes (clothes). Swimsuits and clothes were provided to participants for this experiment.
The age, height, and weight of the participants were as follows:
M age = 19.2 years, SD = 0.9; M height = 170.9 cm, SD = 4.3; and M weight 61.2 kg, SD = 5.0. Participants' mean body mass index (BMI) was 19.83, SD = 2.2. The water temperature during the experiment was 29.3°C [+ or -] 0.5°C.
All participants were tested at the same time of day. Each participant did two swimming tests in a 25-in swimming pool after 30 min of warming up. The warming up consisted of stretching exercises for 10 mm and swimming at a self-selected pace for 20 mm. The participants were instructed to push off from the end of the pool without diving. For each test, the participants were asked to swim as fast as they could for 60 s either in a swimsuit or in clothes.
All testing was performed in randomized order. Each testing session was separated by a minimum of 3 days. The 60-s swimming distance for each participant was timed with a stopwatch and measured with a tape measure. Stroke frequency, expressed as the number of complete arm cycles per minute, was measured by a videotape recorder (CCD TR2NTSC, Sony, Tokyo, Japan).
The distance per stroke was calculated from the measured total distance covered and the stroke frequency during each 60-s swimming test. On completing the swim, the participants left the pool, dried, and immediately laid in the supine position on a bed for blood sampling. To obtain venous blood, a 21-gauge butterfly needle with a sampling vinyl tube was inserted into the antecubital vein.
While participants were at rest, blood samples (3 ml) were obtained using disposable syringes at intervals of 2.5, 5, 7.5, 10, 12.5, and 15 min during recovery. To protect against coagulation of blood, 0.1 ml of blood was drawn every 30 s during recovery. The samples were immediately put into iced heparinized test tubes. Lactate and ammonia concentrations in the blood were measured within 5 min of collection. Lactate concentrations were measured using a lactate analyzer (Lactate Pro, Kyoto Daiichi Kagaku, Co., Ltd., Kyoto, Japan). Ammonia concentrations were measured using an ammonia analyzer (Amicheck Meter, Kyoto. Daiicbi Kagaku Co., Ltd., Kyoto, Japan). The remaining 2 ml of blood was centrifuged, and the plasma was separated out. Plasma catecholamines were measured by high performance liquid chromatography, using the electrochemical detection method described by Lin et al. (1984).
To obtain statistical comparisons, an analysis of variance with repeated measurements was made using the Scheffe post hoc comparison to determine the significance of the differences in the mean value. The level of significance was set at p<.05. All values are expressed as means and standard deviations (M [+ or -] SD).
When performing the crawl stroke, participants could swim 88.8 [+ or -]3.8 m in a swimsuit and 42.0 [+ or -] 4.2 m while wearing clothes during the 60-s period. When performing the breaststroke, participants could swim 73.6 [+ or -] 8.4 m in a swimsuit and 50.9 [+ or -] 4.5 m in clothes.
The participant's velocity when performing the crawl stroke in clothes (0.70 [+ or -] 0.07 m/min) was significantly lower than when wearing a swimsuit (1.48 [+ or -] 0.06 m/min, p<.01). Their velocity when performing the breaststroke in clothes (0.85 [+ or -] 0.08 m/min) was also significantly lower than when wearing a swimsuit (1.23 [+ or -] 0.14 m/min, p<.01).
The mean percentage of mean velocity decreased 52.7% during the crawl stroke and 30.8% during the breaststroke for participants wearing clothes as compared to wearing a swimsuit. The mean velocity of both strokes was significantly lower when wearing clothes rather than a swimsuit.
When the participants performed the crawl stroke wearing clothes, stroke frequency (61.2 [+ or -] 7.1 strokes/min) was significantly lower (p<.01) than that when wearing a swimsuit (77.0 [+ or -] 6.9 strokes/min).
However, no significant difference was found between the stroke frequency of participants performing the breaststroke wearing clothes (43.4 [+ or -] 6.9 strokes/min) and when wearing a swimsuit (43.4 [+ or -] 6.2 strokes/min). The stroke frequency of both the crawl stroke and breaststroke was significantly lower (p<.01) when participants wore clothes rather than a swimsuit.
Regarding distance per stroke, a significant difference (p<.01) was found between participants performing the crawl stroke wearing clothes (0.70 [+ or -] 0.07 m/stroke) and when wearing a swimsuit (1.15 [+ or -] 0.07 m/stroke). There was a similar finding for participants performing the breaststroke. Distance per stroke was 1.19 [+ or -] 0.19 m/stroke when wearing clothes, and 1.72 [+ or -] 0.29 m/stroke wearing a swimsuit (p<.01).
Participants' blood lactate concentrations after performing the crawl stroke in clothes were significantly lower as compared to wearing a swimsuit, while their lactate concentrations after performing the breaststroke in clothes were similar those after doing it in a swimsuit (see Table 1, A). Blood ammonia concentrations after performing the crawl stroke in clothes were significantly lower than after doing it in a swimsuit, whereas for the breaststroke, no significant difference was found in ammonia levels between participants wearing a swimsuit and clothes (see Table 1, B ). Participants' blood lactate and ammonia concentrations after swimming in clothes were significantly higher when they did the breaststroke compared to when they did the crawl stroke (see Table 1, A and B).
Epinephrine concentrations after participants performed the crawl stroke in clothes were significantly lower than after they did it wearing a swimsuit (see Table 2, A), while, for the breaststroke, no significant difference was found in epinephrine levels between tests performed wearing clothes or a swimsuit. Moreover, the type of apparel had no significant effect on the participants' norepinephrine concentration after either the crawl stroke or breaststroke (see Table 2, B).
This study demonstrated that mean swimming velocity decreased considerably when the participants wore clothes instead of a swimsuit while performing the crawl stroke or the breaststroke. However, the mean swimming velocity of participants wearing clothes decreased more when they did the crawl stroke instead of the breaststroke.
Velocity is produced by stroke frequency and the distance traveled through the water with each complete stroke (Craig & Pendergast, 1979). For the crawl strokes, the stroke frequency of participants wearing clothes was lower than that of those wearing a swimsuit. However, the type of apparel had no significant effect on stroke frequency when participants did the breaststroke. Participants wearing clothes covered less distance per stroke than those wearing a swimsuit for either stroke.
When participants performed the crawl stroke in clothes instead of a swimsuit, the distance covered per stroke decreased by 39.1%; however, when they did the breaststroke in clothes instead of a swimsuit, it only decreased by 30.8%. Mean velocity of the crawl stroke performed in clothes decreased because of the reduction in stroke frequency and distance per stroke. Mean velocity for the breaststroke performed when wearing clothes also decreased as a result of reduced distance per stroke. These findings suggest that the relatively large resistance created by clothes may have a significant effect on swimming performance, especially for the crawl stroke.
Blood lactate levels are a good indicator of glycogen breakdown within working muscles (Medbo, 1993). Participants' blood lactate concentrations were significantly lower after doing the crawl stroke while wearing clothes rather than a swimsuit; however, no significant differences in blood lactate levels were observed after doing the breaststroke in clothes or a swimsuit. This result suggests that glycogen breakdown was suppressed when participants wore clothes while doing the crawl stroke. The lower blood lactate levels measured after participants did the crawl stroke wearing clothes may be a factor in the reduced stroke frequency.
Regarding the breaststroke, no significant differences between blood lactate levels after swimming while wearing clothes or a swimsuit were found. Nor did apparel have a significant effect on stroke frequency of the breaststroke.
In this investigation, a significant linear relationship was-found between blood lactate levels and stroke frequency of participants doing the crawl stroke (r = .91, p<.001).
Exercise intensity is closely related to epinephrine and norepinephrine concentrations, which are signs of an increase in sympathoadrenergic activation (Lehmann, Schmid, & Keul, 1985; Urhausen, Weiler, Coen, & Kindermann, 1994).
Several studies have reported that catecholamine, particularly in the epinephrine derived from the adrenal medulla, may play a major role in regulating muscle glycogen breakdown during exercise (Stainsby, Sumners, & Andrew, 1984; Stainsby, Sumners, & Eitzman, 1985).
Cheetham, Boobis, Brooks, and Williams (1986) also reported that changes in plasma catecholamines correlated to estimated ATP production from glycolysis. Increases in epinephrine and norepinephrine levels correlate with increases in lactate concentrations (Lehmann et al., 1985; Mazzeo & Marshall, 1989).
In the present investigation, the lower blood lactate concentrations found after participants swam while wearing clothes may be attributed to a decrease in epinephrine levels in plasma. Decreases in blood lactate and plasma epinephrine levels after doing the crawl stroke wearing clothes probably result from increased water resistance, which restricts the movement of the limbs (Keatinge, 1961).
From these results, we draw three conclusions.
First, the relatively large resistance presented by clothes during swimming had a significant effect on swimming performance, especially when participants did the crawl stroke instead of the breaststroke.
Second, performing the crawl stroke while wearing clothes may reduce glycogen breakdown.
Finally, when swimming in clothes, in terms of swimming performance and energy supply, the breaststroke is better than the crawl stroke.
Submitted: December 6, 2000
Accepted: October 8, 2001
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This study was supported by the Descent Sports Sciences Promotion Foundation (1997). Please address all correspondence concerning this article to Tetsuo Ohkuwa, Department of General Studies, Nagoya Institute of Technology, Showa-ku, Nagoya, 466-8555, Japan.
Tetsuo Ohkuwa, Hiroshi Itoh, and Yoshihiko Yamazaki are with the Department of General Studies at the Nagoya Institute of Technology. Takako Yamamoto and Yuzo Sato are with the Research Center of Health, Physical Fitness, and Sports at Nagoya University.