An investigation of the impact of the LineBreak Sportswear.

( On thermoregulation during exercise in a warm and humid environment followed by recovery in a cooler environment. ) School of Exercise, Biomedical and Health Sciences, Edith Cowan University Michael R. McGuigan, Ph.D., Lecturer, Exercise Physiology, Robert U. Newton Ph.D., Professor of Exercise Science. May 2005.

EXECUTIVE SUMMARY
The purpose of this research project was to determine the effect of the LineBreak garment on body temperature and exercise performance during exercise in the heat and also during a rest period in a cool environment following a bout of exercise. Ten men were recruited for this investigation. Testing utilized the LineBreak High Performance Tee, with a cotton tee as the control garment.

Three conditions of garment were worn (LineBreak only, Cotton Tee only and both LineBreak and Cotton Tee) during an exercise and recovery bout which were conducted over three separate days. Several  significant and important effects were revealed for the LineBreak garment.

• Skin temperature was significantly decreased using the LineBreak garment condition compared to the cotton tee.
• Sweat rate was decreased by 31% when using the LineBreak garment.
• The overall rating of perceived exertion for the exercise session was reduced when using the LineBreak garment.

This randomised, controlled study shows that wearing the LineBreak High Performance Tee results in a significant and meaningful reduction in heat stress with subsequent reduction in fluid loss and increased comfort.

Introduction.
It is well documented that heat strain, as a result of an elevated core body temperature, is a major cause of reduced exercise performance and heat related illnesses (Gonzalez-Alonso et al., 1999). A variety of clothing combinations have been used by athletes while exercising in different climatic conditions. The theory behind using different clothing conditions is that it may be possible to lessen the impact of hot and/or humid conditions on the body’s thermoregulatory system and subsequently exercise performance. A number of different fabrics have been introduced to the athletic apparel market with claims made by manufacturers of improved exercise performance due to their evaporative characteristics. It has been suggested that these improved evaporative characteristics are a result of improved vapor permeation, which leads to increased sweat evaporation, and potentially lower skin and core temperatures, as well as reduced evaporative water loss. It has also been shown that increases in skin wetness can affect thermal comfort (Pascoe et al., 1994).

It has been proposed that when using these types of garments that the evaporation can occur faster because of the faster transfer of sweat from the skin to the fabric (Otomasu et al., 1997). Once there, the sweat will then be transported through the fabric and dispersed more quickly and evenly over a larger area and evaporation is maximized. As a result, during exercise the athlete will feel cooler and perceive the exercise as being less difficult. This will lead to increased performance due to more efficient thermoregulation during the exercise and thus greater blood availability to the working muscles. LineBreak Performance Sportswear provides apparel designed to improve body thermoregulation during exercise, in addition to enhancing performance using principles of muscle compression (Doan et al., 2003). The purpose of this investigation was to examine the thermoregulatory properties of the LineBreak garment during exercise in a warm and humid environment and during recovery in cooler conditions.

Methods.
Subjects included ten men (mean height, 176.0 cm; mean age, 21.3 years; mean body mass, 76.3 kg) who were classified as recreationally trained (exercise at least 5 days per week for minimum of 30 minutes).

The Garment.
The High Performance Tee (LineBreak, Sydney, Australia) was used in this investigation. The garments were custom fit based on height, weight and waist girth. The garment material is made to be light, strong, compressive and consists of materials that promote evaporation of sweat in a more efficient manner.

Experimental Approach.
Testing utilized three conditions including the LineBreak tee, cotton tee or cotton tee worn over the LineBreak tee. All conditions involved the subjects performing 60 minutes of treadmill running in a climate chamber set at 26ºC and 50% humidity during each session. After the exercise bout, the subjects were placed in a colder room (15º C) and monitored for a further 30 minutes. The principle outcome measures were thermoregulation in terms of skin and core temperature, physiological stress as measured by heart rate, perceived exertion, and sweat response as determined from fluid loss during the exercise intervention.

The subjects were instructed to maintain their regular fluid and food intake during the course of the investigation. Prior to each exercise session they were normally hydrated and instructed to have not eaten for 8 hours, and have not participated in any physical exercise for the past 48 hours. They were instructed not to consume alcohol or drugs 48 h before testing, not to consume caffeine 12 hrs before testing, and to drink water and other non-caffeinated beverages liberally. Prior to the commencement of the study, each subject underwent a familiarization session in the environmental chamber. This session was also used to assess the subjects exercise capacity. The environmental chamber was maintained at 26ºC and 50% humidity. A fan set at a moderate speed was used to simulate outdoor air flow. These conditions were chosen as they are typical for Sydney in January and represented a warm and moderately humid thermal environment. All subjects were tested at the same time of the day to minimize the effects of circadian rhythm on heart rate and body temperature, and at least 2 days passed between testing of the same subject.

The subject commenced exercise on the treadmill at an intensity of approximately 60% VO2 max (previously determined based on heart rate response in the initial familiarization session). This intensity was maintained throughout each exercise session. The same running shoes and shorts were used for all three testing conditions. Subjects were able to consume unlimited amounts of water during the exercise and recovery.

Testing Procedures.
Sweat Rate: An electronic scale (Mettler ID1 MultiRange) was used to measure the subject’s nude body weight and clothing weight before and immediately after both the exercise and recovery periods. The change in body mass was used to calculate sweat rate (loss in body weight•time of exercise-1). All fluid consumed by the subject was included in the calculations to obtain an accurate measure of sweat rate.

Rating of Perceived Exertion: Ratings of perceived exertion (RPE) were acquired every five minutes throughout the testing (Borg, 1975). The RPE values were averaged to give the mean RPE for each exercise session.

Thermal Sensation: A 16 point bipolar scale for rating of thermal comfort (with anchors of 0.0 (unbearably cold) through to 8.0 (unbearably hot) was used to measure thermal comfort (Young et al., 1987). The measures of thermal sensation were acquired every five minutes throughout the testing. The values were averaged to give the mean thermal rating for each exercise session.

Session RPE: Thirty minutes after every exercise session, each subject recorded their RPE for the entire session using the modified 10-point scale developed by Foster and colleagues (Foster et al., 1996; Foster, 1998). In short, this method was designed to provide a measure of the global perception of the intensity, or physical stress, of an entire exercise session.

Core Body Temperature: Tympanic temperature was determined using a Braun ThermoScan proLT every five minutes during exercise and recovery. Tympanic temperature has been demonstrated to represent body core temperature (Newsham et al., 2002).

Skin Temperature: Thermocouples (YSI Tele-thermometer) were placed on the back, chest, and thigh of the subject and the individual skin temperatures recorded throughout the exercise and recovery. The three sites were averaged using a body distribution formula to give the mean skin temperature at each time point. The thermocouples were secured with breathable tape.

Heart Rate: Heart rate was continually monitored throughout the test and recovery period. Measures were obtained every five minutes. The values were averaged to obtain a mean heart rate for the exercise and recovery. In addition blood pressure was monitored throughout the exercise and recovery.

Comfort Index: The subjects were asked to provide feedback regarding the comfort and perceived effectiveness of the LineBreak garment.

Data Analyses.
Means and standard deviations were calculated for all measured variables and grouped by time point and garment condition. Repeated measures analysis of variance (ANOVA) was used to determine time point and garment main effects as well as interactions. In the event of a main effect being significant, follow up testing using Bonferonni post hoc analysis was completed. The criterion for statistical significance was set at an alpha of p < 0.05. To aid interpretation of the data, effect size (ES) was calculated as the difference between means divided by the mean SD of the two samples (Thomas et al., 1991). An ES of greater than 0.7 was interpreted to be a large difference (Thomas et al., 1991).

Results.
Sweat Rate
There was a 17% decrease in sweat rate when using the LinkBreak tee under the cotton tee and a 31% decrease with the LineBreak tee condition.

Rating of Perceived Exertion:
There were no significant differences in RPE.

Thermal Sensation:
There were no significant differences in thermal comfort rating.

Session RPE:
The subjects overall rating of the exercise ie. Session RPE showed there was a significant decrease in session RPE when using the LineBreak tee (p<0.05) compared to cotton tee condition.

Core Body Temperature:
There were no significant differences in tympanic temperature between conditions during the exercise and during the recovery.

Skin Temperature:
The LineBreak condition resulted in a significant decrease in skin temperature compared to the other conditions (p<0.05) during exercise. There were no significant differences in skin temperature during recovery.

Heart rate:
There were no significant differences between conditions for the average heart rate during exercise. The average heart rate during recovery showed no significant differences between conditions.

Comfort Index:
A number of positive comments were made by the subjects regarding the Linebreak garments. A number of subjects (9/10) made positive comments regarding the comfort level of the garment. One subject commented that the garment “seems to absorb sweat very well” and that “it feels very comfortable”. Another subject made the comment that “the garment made me feel cooler in the hot conditions”. Several subjects also made comments that they felt that the garments had a positive impact on their performance in the warm and humid conditions they encountered.

Discussion.
From the test results of this study we observed several positive benefits of the LineBreak garment. Skin temperature was significantly decreased during the exercise bout while wearing the LineBreak tee. The subjects also perceived the overall exercise bout as being easier while wearing the LineBreak tee. Finally there was a 31% reduction in sweat rate following exercise when wearing the LineBreak tee. Although this change was not statistically significant due to the large variation in this measure, the overall effect does appear to be quite large (Effect Size = 0.68). Through various mechanisms, these findings may translate into a positive effect on athletic performance. Through various mechanisms, these findings may translate into a positive effect on athletic performance.

In humans, the primary means of cooling the body during exercise is through the evaporation of sweat from the skin surface. Clothing can also hinder sweat evaporation from the skin (Gavin et al., 2001). Increases in skin and core temperature and a reduction in cooling efficiency are observed when clothing interferes with the evaporation of sweat from the skin (Gavin et al., 2001). In this investigation we found that the LineBreak tee significantly reduced skin temperature during exercise and also during recovery.

There were no significant differences in core temperature during exercise or recovery between the conditions. It has been suggested that the use of core temperature to assess heat stress imposed by wearing clothing during exercise may lead to erroneous conclusions (Gonzalez-Alonso et al., 1999). Body temperature is a highly regulated physiological variable; therefore a greater thermal disturbance may be needed to see differences in these temperature variables.

Given the suggestion that exercise tolerance can be influenced by perceived exertion and that changes in skin wetness can affect thermal comfort (Gavin et al., 2001), we measured perceived exertion and thermal comfort and sweating sensations. There were no significant differences between conditions for average RPE during the exercise. However, several subjects did comment that they felt more comfortable exercising in the warm and humid conditions while wearing the LineBreak tee. The intensity of exercise was chosen to reflect a moderate intensity that the subjects could perform continuously for 60 minutes. It is unclear if we would have seen different results if the subjects had been exercising at higher intensity levels.

Another method of intensity quantification approach used in this study was the session RPE method developed by Foster and colleagues (Foster, 1998). The session RPE method attempts to quantify the athlete's global perception of the stress of an entire training bout, based on an evaluation performed 30 minutes after training cessation. The subjects overall rating of the exercise was reduced when wearing the LineBreak garment, suggesting that they perceived the exercise as being less difficult in the warm and humid conditions when wearing the apparel. There were no significant differences in average heart rate during exercise or recovery however. Although not significant, the rating of thermal comfort did suggest that this measure was moderately reduced while wearing the LineBreak garment.

The investigation was conducted using warm and humid environmental conditions, which were chosen to reflect typical outdoor conditions that athletes would be exercising in Australia.

In conclusion, wearing the LineBreak garment:
• Significantly reduced skin temperature during exercise.
• Decreases sweat rate by up to 31%.
• The overall rating of perceived exertion is reduced for the exercise session.

Summary.
Wearing the LineBreak garment appears to result in the significant thermoregulatory changes that could be of benefit to the athlete. It is clear that wearing the LineBreak garment reduces skin temperature, possibly due to the absorption of sweat that the material provides. This may have contributed to the overall rating of perceived exertion being less. The session RPE does indicate that under conditions where the LineBreak garment is worn, the subjects perceived the exercise as being less difficult. The overall sweat rate was reduced under the conditions where the LineBreak garment was used.

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