In humans, the primary means of cooling the body during exercise is through the evaporation of sweat from the skin surface. Clothing represents a layer of insulation that hinders the evaporation of sweat from the surface of the skin. It follows that clothing that imposes the least amount of resistance to evaporative heat loss may prove beneficial to the thermoregulatory, physiological and perceptual response to exercise, particularly in elite endurance-trained athletes. Thus, the purpose on this study is to examine the influence of wearing a sportswear garment made of a fabric (100% nylon) with superior evaporative characteristics on detailed thermoregulatory, cardiorespiratory, metabolic and perceptual responses to maximal exercise testing at normal room temperature and relatively humidity in a group of 25 endurance-trained cyclists and triathletes aged 20-60 years. It is hypothesized that wearing a garment made of 100% nylon will improve exercise performance (e.g., exercise endurance time) and that this improvement will reflect improvements in thermoregulatory, cardiorespiratory, metabolic and perceptual responses to exercise. Athletes will be recruited via contact with coaches of the McGill University Cycling and Triathlon teams as well as through contact with coaches of competitive cycling and triathlon teams/training groups in the Montreal and surrounding area. Initial contact will consist of a thorough explanation of the study procedures and pre-screening for the inclusion/exclusion criteria prior to study consent by the Principal Investigator and/or his delegate, either in person or by telephone or email. Eligible participants will visit McGill's Clinical Exercise & Respiratory Physiology Laboratory on 3 separate occasions over a period of 10-14 days. Visit 1 will include a maximal incremental bicycle exercise test for familiarization purposes and to determine maximal power output (MPO). Visits 2 and 3 will include a constant-power-output bicycle exercise test at 85% MPO under one of two conditions, in randomized order: (1) while wearing a garment made of 100% polyester, i.e., placebo; and (2) while wearing a garment made of 100% nylon, i.e., cooling fabric. At rest and during exercise at visits 2 and 3, detailed assessments of core body temperature will be made using a temperature sensor placed into the esophagus, while skin temperature and other physiological and perceptual parameters will be measured using standard techniques.

Inclusion Criteria:

• Male or Female
• Non-smoker
• Aged 20-60 years
• Competitive cyclist and/or triathlete competing at the regional, provincial, national and/or international level.
• Maximal rate of oxygen uptake on incremental cycle exercise testing greater than or equal to 60 ml/kg/min.
• Forced expiratory volume in 1 second greater than or equal to 80% predicted.
• Forced expiratory volume in 1 second/forced vital capacity ratio greater than or equal to 70%.
• Women: taking an oral contraceptive for at least 6 months prior to study enrolment.

Exclusion Criteria:

• History or presence of cardiovascular, vascular, respiratory, renal, liver, musculoskeletal, endocrine, neuromuscular, metabolic, menstrual cycle and/or sleep related disease/disorder/dysfunction.
• Inability to perform exercise and pulmonary function testing.
• Taking doctor prescribed medication, other than oral contraceptives for women.
• Allergy to lidocaine or its 'caine' derivatives.