One practice advocated for achieving faster performances during a triathlon has been the use of wet suits during the swimming portion. Initially, wet suits were worn to prevent hypothermia during cold water swimming, but recently they have been used to provide buoyancy and enhance swimming performance. Research has shown that wet suits decrease drag(11) and oxygen consumption at a given speed(13) while increasing buoyancy and the distance swum in a given time (9). Collectively, these investigations provide evidence supporting the use of wet suits to improve performance during open water swimming. This has convinced many athletes to wear a wet suit regardless of water temperature and environmental conditions. Since wet suits act as thermal insulators (15), they increase body heat storage when worn in warm water conditions (14). The resulting mild hyperthermia from a warm water wet suit swim may be detrimental to subsequent cycling and running performance (8) and potentially negate the time saved by wearing a wet suit during the swimming stage.
Trappe et al. (14) have compared the thermal responses of wearing a wet suit with wearing a swim suit during the swimming portion of the triathlon. They reported an elevation in mean body temperature when a wet suit is worn during the swimming portion. Additionally, immediately after the swim, they tracked the thermal responses of the triathletes during a 15-min bike ride. However, they did not monitor the thermal responses during a complete cycle stage or run. The latter portions of the cycle and the entire run are the critical points at which any negative effects of hyperthermia would begin to manifest themselves. Additionally, the bike ride was completed in a mild environment (21.1°C) which did not provide the thermal stress associated with a higher environmental temperature or humidity. Using a wet suit during a triathlon completed in a hot and humid environment would increase the likelihood of thermal stress and possibly hinder triathlon performance.
Since the triathlon will be an official sport at the 2000 Olympic games, information on the use of wet suits similar to the conditions that may be encountered in Sydney, Australia, is warranted. In addition, this research may provide a scientific basis for future triathlon rules committee decisions on wet suit usage. The triathlon federation has historically considered water greater than 78°F (25.6°C) as too warm for wet suit usage, although few data are available to justify this threshold. Therefore, the purpose of this project was to determine whether mild heat stress induced by wearing a wet suit while swimming in warm water increases the risk of heat injury during the cycling and running stages of an international distance triathlon (swim = 1.5 km; bike = 40 km; run = 10 km). In addition, overall triathlon performance was assessed in relation to wearing a wet suit in a hot and humid environment as compared to a swim suit.
Subjects. Five healthy males were recruited to participate in this investigation. All subjects were highly trained experienced triathletes. The subjects had been training for and competing an average of 6.8 ± 2.3 yr and had competed at a variety of levels of competition, from local to international. Subjects signed an informed written consent in accordance with the University Institutional Review Board. Subject characteristics are presented in Table 1.
Maximal aerobic capacity testing. The maximal aerobic capacity(˙VO2max) of each triathlete was determined for each mode of a triathlon. Swimming ˙VO2max was determined using a flume (SwimEx, Inc., Warren, RI), cycling ˙VO2max using a stationary ergometer(Lode NV, Groningen, The Netherlands), and running ˙VO2max using a treadmill (Quinton, Seattle, WA). All tests used an incremental protocol to volitional exhaustion and were completed on separate days with >48 h between each test.
Both cycling ˙VO2max and running ˙VO2max tests were conducted with expired respiratory gas samples collected on-line at 30-s intervals. Inspired air volume was measured using a Parkinson-Cowan dry gas meter (Instrumentation Associates, Inc., NY, NY). Expired air was analyzed from a 3 L mixing chamber for gas concentrations using electronic oxygen(Ametek S3A, Applied Electrochemistry, Sunnyvale, CA) and carbon dioxide(SensorMedics LB2, Yorba Linda, CA) analyzers, which were interfaced to an IBM computer for all metabolic calculations. During the cycling ˙VO2max and running ˙VO2max tests, ˙VO2max was defined as a plateau in oxygen consumption with an increase in work rate and an RER value exceeding 1.10. Analyzers were calibrated before each test using a standard reference gas with known concentrations.
During the swimming ˙VO2max, expired air was collected at 30-s intervals using Douglas Bags and immediately analyzed for gas concentrations and volume. Volume was measured using a Parkinson-Cowan dry gas meter and O2 and CO2 concentrations were determined using the same electronic oxygen and carbon dioxide analyzers. ˙VO2max was defined as the peak ˙VO2 measured during the swimming ˙VO2max with an RER > 1.10.
Orientation session. Before each experimental trial, each subject participated in an orientation session in which the experimental protocol was explained. Each subject completed a cycle bout and treadmill run to familiarize himself with each mode and to minimize a learning effect from Trial 1 to Trial 2.
During the orientation session, swimming work rates (flume speed) were determined for the two experimental trials. ˙VO2 and heart rate(HR), at various steady state swimming rates, were measured with a wet suit and with a swim suit. This ˙VO2 matching was done to ensure similar metabolic heat production for both the swim suit and wet suit trials. Once this data was gathered, flume speed for the experimental trials was determined by a combination of the following criteria: (1) subject feedback was considered when choosing a rate with which the subjects felt they could swim continuously at for 30 min and was what they considered “race pace” and (2) a pace was chosen at which ˙VO2 measurements could be equal in both experimental conditions.
Experimental protocol. Subjects randomly completed two simulated triathlons (swim = 30 min; bike = 40 km; run = 10 km) in the laboratory using a swimming flume, cycle ergometer, and running treadmill. In both trials all conditions were identical except for the swimming event in which a 3- to 4-mm thick neoprene wet suit (Long John, Quintana Roo, San Marcos, CA) which covered the torso and legs to the ankles was worn during one trial (WS) and traditional competitive swimming suit during the other trial (SS). Trials were completed in the morning and 1 wk apart.
Each subject reported to the laboratory well rested after abstaining from vigorous exercise for a 24-h period. Subjects were instructed to record and replicate their diets 2 d before each experimental trial. The day before each trial subjects consumed three commercially available energy bars (Powerbar, Powerfood Inc., Berkeley, CA).
Subjects were asked to void and a nude weight was obtained (Toledo ID1, Toledo Scale Co., Worthington, OH) before exercise. The subjects were then fitted with a heart rate telemetry unit (Polar Vantage XL, Polar Electronics, Port Washington, NY), and a rectal thermocouple (TX-2, Columbus Instruments, Columbus, OH) was inserted 10 cm beyond the anal sphincter. Skin thermocouples were positioned on the chest, upper arm, thigh, and calf with a transparent, waterproof dressing (Bioclusive, Johnson & Johnson Medical, Arlington, TX) which allowed for heat exchange. Pretrial temperature measurements were recorded (Iso-Thermex Model 256, Columbus Instruments) which included rectal(Tc) and skin (Tsk) temperatures.
After baseline temperature measurements were recorded, subjects began a 30-min swim (H2O = 25.4 ± 0.1°C) wearing either the swim suit or the wet suit. Subjects wore the same standard latex swimming cap and goggles for each trial. Steady-state HR was recorded during the swimming portion. Subjects were stopped briefly (2 min) for ˙VO2, a rating of perceived exertion (RPE) (1), thermal sensation (TS)(10), and temperature (Tsk, Tc) measurements at 15 and 30 min. ˙VO2 was determined using the backward extrapolation technique (7).
After the 30-min measurements, subjects quickly proceeded to the environmental chamber to complete the cycling and running portions. Environmental conditions were maintained inside the chamber at 31.9 ± 0.1° C and 65% humidity. Subjects were instructed to maintain a competition pace and complete the given distances in as short a time as possible. No feedback, other than accumulated distance, was given to the subjects during the remainder of the triathlon. Transition times were standardized at 4 min from water to bike and 1.5 min from bike to treadmill.
Once inside the chamber, subjects began a self-paced 40-km bike ride on an electronically braked isokinetic cycle ergometer (Met-100, Cybex, Ronkonkoma, NY). A fan (Marathon Electronics, Wausau, WI) was placed directly in front of the subjects to simulate the air flow and evaporative effects normally experienced during actual competition (12 mph). Subjects were given H2O(150 mL) at the start, and at 15, 30, and 45 min of the bike ride. Sixty-second Douglas bags were collected every 15 min and during the final kilometer. Expired air was analyzed using the previous described analyzers, which were interfaced to an IBM computer for all metabolic calculations. Also during this time, Tc, Tsk, RPE, HR, and TS were recorded every 15 min. After completion of the 40 km bike ride, total bike time was recorded.
After the cycle stage each triathlete began a self-paced 10-km run on a treadmill. The treadmill was equipped with photocells at the front and back of the treadmill. If the subject moved to the front of the treadmill, the light beam to the photocells would be blocked which would increase the treadmill speed. If the subject moved to the back of the treadmill, the back light beam to the photocells would be blocked and decrease the treadmill speed. This setup allowed the subject to control the treadmill speed and still maintain a natural running motion. The treadmill was also interfaced to an IBM computer. With software developed at the laboratory, total distance and time were displayed. Expired air was collected every 15 min and during the final 0.5 km. As with the cycling portion, Tc, Tsk, RPE, HR, and TS were recorded every 15 min and during the final minute. Following the running portion, treadmill time and total time was recorded. After completion of the triathlon each subject dried off before a post-trial nude weight was recorded. Sweat rate (SR) was calculated from this data (6).
Statistical analysis. A two-way ANOVA with repeated measures was used to evaluate the change in temperatures, triathlon times, RPE, TS, VO2, and HR. A one-way ANOVA with repeated measures was used to evaluate any differences between the ˙VO2max tests. For both the one-way and two-way ANOVA, post-hoc comparisons were conducted with Tukey's test when appropriate. A t-test was used to compare SR. All tests for statistical significance were set at an alpha level of P< 0.05. All values are expressed as mean ± SE unless noted.
Maximal aerobic capacity tests. Results from the maximal aerobic capacity tests are presented in Table 2. Maximal aerobic capacity for the swim was 3.63 ± 0.29 L·min-1, which was significantly lower than for the cycle ˙VO2max 4.17 ± 0.26 L·min-1 and run ˙VO2max 4.40 ± 0.24 L·min-1. This same statistical difference was found when expressed as mL·kg-1·min-1. The mean values for swimming ˙VO2max, cycling ˙VO2max, and running˙VO2max were 51.8 ± 2.7, 60.8 ± 3.0, and 64.3± 2.7, respectively.
Temperatures. Mean body temperature (Tb = (0.35 × Tsk) + (0.65 × Tc)) (4) for both the SS and WS trials are presented in Figure 1. These were calculated from the mean skin temperature (Tsk = 0.3(chest + upper arm temperatures) + 0.2 (thigh + calf temperatures)) (8) and core temperatures (Tc) which are presented inFigures 2 and 3, respectively. Although there was no significant difference throughout the trial in Tc, there was a significant difference in Tsk, and therefore Tb, at the 15(Tsk = +4.1°C, Tb = +1.5°C) and 30 min (Tsk =+4°C, Tb = +1.6°C) points of the swim. At these time points the temperature was significantly elevated in the WS as compared with that in the SS. Additionally, Tsk was still significantly elevated (+2.2°) during the precycle measurement. By the 15-min point of the cycle and throughout the rest of both trials, there was no significant difference in Tc, Tb, or Tsk. The greatest increase in Tc occurred during the running portion with a +1.2°C increase during the SS and a +1.0°C increase during the WS.
Triathlon time. There was no difference in total triathlon time between the SS and WS trials (Fig. 4). Additionally, there was no difference in the bike split or run split times. Cycle times were nearly identical, 1:14:46 ± 2:48 for the SS and 1:14:37 ± 2:54 for the WS. The 10-km run times were 1:40 faster in the SS (55:40 ± 1:49 vs 57:20 ± 4:00) as compared with those in the WS. These combined for a total time difference of 1:31 (2:40:26 ± 1:58 vs 2:41:57 ± 1:37) in overall time, with the SS trial having a slight advantage because of the run.
Physiological responses. No significant difference was found in either HR or ˙VO2 when comparing SS with WS. The triathletes'˙VO2 were almost identical at the end of the trials (R Final), with only a 30-mL difference between the two (2.99 ± 0.18 L vs 3.02 ± 0.18 L). It varied by an average of 80 mL throughout the bike and run. At the end of the trials (R-Final), there was a only a 3 beats·min-1 difference between the two trials in HR (176 ± 7 vs 173 ± 5), and HR varied by an average of only 3 beats·min-1 throughout the bike and run. Additionally, there was no significant difference in SR between the trials. SR was 1.0 L·h-1 in the SS and 1.1 L·h-1 in the WS.
Perceptual responses. No significant difference was found in either RPE or TS when comparing SS with WS. RPE was identical for both the SS and WS throughout the bike and run portions. At the end of the trials(R-Final), RPE was identical (17 ± 0.0 vs 17 ± 0.3). TS was 0.2 lower in the SS at the R-Final point (6.8 ± 0.2 vs 7.0 ± 0.2). TS varied by a average of only 0.1 throughout the bike and run stages.
The intent of this project was to determine whether mild heat stress induced by wearing a wet suit while swimming in relatively warm water(25.6°C) affects performance and increases the risk of heat injury during the cycling and running stages of an Olympic distance triathlon. The primary finding was that wearing a wet suit during the swimming stage does not alter the thermoregulatory responses during the subsequent cycling and running stages.
While there was no significant difference between the trials in Tc, there was a significant difference in Tsk, and therefore Tb, at the 15- (Tsk = +4.1°C, Tb = +1.5°C) and 30-min(Tsk = +4°C, Tb = +1.6°C) points of the swim. At these time points, mean body temperature was significantly elevated in the WS as compared with that in the SS. While the data show that the swim portion did produce a significant difference in Tsk, and therefore Tb, this difference was no longer significant by the 15-min point of the bike ride. This finding is supported by data showing no significant difference in Tc and Tsk by 15 min into a bike ride after a 30-min swim which induced a significant difference in Tb (14). Although Tsk and Tb were significantly altered during the swim, Tc was unaffected by the WS or SS trial, suggesting Tc may be a better indicator of thermoregulatory responses.
The significant difference in Tb found in this investigation provided a means for assessing the mild increase in total body heat storage associated with wearing a wet suit during the swim. No significant differences were seen in Tc, Tsk, or Tb after the 15-min cycle point. Therefore, it seems that any additional heat stress provided by the wet suit during the swimming portion, as compared with that by a swim suit, is not a factor during the bike and run portions. Mean body temperature does not continue to rise in a linear fashion after the swim; instead SS Tb and WS Tb reach a common plateau. This is accomplished by a sharp increase in Tsk in the SS trial, along with a flatter response in Tsk in the WS trial, to reach similar Tsk by the 15-min point of the bike ride(Fig. 2). Two factors are probably responsible for the sharp increase seen in SS Tsk. First, the dramatic change in environmental temperature, from H2O of 25.6°C to air of 32°C, caused the skin to warm significantly. Second, the cutaneous blood vessels were able to increase vasodilatation when removed from the water. This vasodilatation allowed the warmer core blood to reach the periphery to dissipate the metabolic heat gained from the swimming bout while simultaneously warming the skin.
Therefore, Tc is probably a more appropriate measure of heat stress placed on the athlete during this investigation. The significance of Tb in this study should be questioned since it is a variable based on Tsk and primarily reflects differences in Tsk. As explained above, Tsk was a measurement that was easily altered with changes in environment. The skin acted as a holding reservoir for the stored heat and was easily dissipated, whereas Tc steadily increased.
All triathletes were able to complete the triathlon with times similar to actual competitions, and there was no statistical difference when comparing total triathlon time between trials. However, the SS trial did provide a 1:31(mm:ss) advantage. As with any timed sport, a difference of 1:31 may not be statistically significant, but it can be a significant margin during actual competition. While the 1:31 faster time in the SS might encourage the triathlete to avoid wet suit usage, one must not forget that the swim times were standardized in this investigation. The time advantage that is gained when wearing a wet suit is well documented(2,3,12,14). Trappe et al.(14) have estimated this advantage to be approximately 1.5-3 min, depending on the skill of the swimmer, in 1500-m swim times(14). Therefore, the faster run times found in this investigation during the SS trial could be offset by the advantages of the wet suit during the swim.
Great individual variability has been reported in the actual time advantage with wearing a wet suit. This individual variability was also found in total time differences (SS vs WS) in this project. Two subjects had virtually identical total times with only 10- and 6-s differences between the SS and WS. If these subjects were able to gain 1.5-3 min with wet suit usage, it would be to their advantage to wear a wet suit. In contrast, two other subjects had 4.3- and 2.5-min slower total times during the WS trial and should personally question whether the swim advantage gained with wet suit usage is being negated during the bike and run portions.
Although mean differences in TS were minimal, one must consider the individual ratings. One subject, who had the highest body fat percentage(11.5), also had the greatest difference in TS between the SS and WS trials(4.0 vs 5.0). The additional insulation provided by the wet suit may have affected this subject's TS the most. Other subjects, who were leaner, reported less of a change in TS during the two trials. This perceptual reporting can also be physiologically explained when looking at the Tb data. During the WS trial, this subject's change in Tb from resting to the 30-min swim point increased 0.5°C, whereas the TB for all other subjects dropped from 0.4-1.0°C, accounting for a 0.9-1.5°C difference between this subject and the other subjects. This finding coincides with that of other researchers who have suggested the most important factor with maintaining body temperature during water immersion is an individual's amount of subcutaneous fat (5).
In summary, wearing a wet suit while swimming in water of 25.6°C does not adversely affect performance or increase the risk of heat injury during the cycling and running stages of an Olympic distance triathlon. Swimming in relatively warm water, 25.6°C, does cause a significant difference between Tsk, and therefore Tb, when wearing a swim suit rather than a wet suit. This difference, however, is eliminated by the 15-min point in the bike ride. Any additional heat stress provided by the wet suit during the swimming portion does not appear to be a factor during the bike and run portions and does not predispose the triathlete to any additional risk for heat injury.
Although the mean data suggest the wet suit does not adversely affect the triathlete, individual responses must be taken into consideration when contemplating wet suit usage. Furthermore, any rulings by governing bodies should recognize the vast range of ages, gender, and fitness levels of triathletes and the effects of these characteristics on the thermal responses of the individual competitors. Any attempt at standardizing wet suit usage to all triathletes would be difficult because of these differences. Future investigations should consider these differences and provide a larger subject pool examining genders, adiposity, and age of the triathlete. The safety of the athlete, along with advancement of the sport, should be considered before any decisions are made.
The authors would like to thank Quintana Roo, Inc. for providing the wet suits and Gary Lee for his technical assistance.
Address for correspondence: Scott W. Trappe, Ph.D., Ball State University, Human Performance Laboratory, Muncie, IN 47306. E-mail:firstname.lastname@example.org.