Science of Sport: Clothing - Technical clothing offers limited benefits

The so-called 'technical' athletic clothing fabrics which purport to promote sweat evaporation from the skin provide no thermoregulatory, physiological or comfort advantages when compared with traditional cotton clothing during or after exercise in a moderately warm environment.

This was the clear and somewhat surprising conclusion of a new study on eight well-trained, well-hydrated men, carried out in the Human Performance Laboratory of Indiana University.

The researchers were investigating the hypothesis that: 'important physiological variables classically accepted to be affected by exercise in the heat (ie skin temperature, core temperature, heart rate and sweat loss) would show less perturbation with garments made from a fabric with improved evaporative characteristics as compared with ensembles of more traditional fabrics'.

Each subject carried out three identical submaximal treadmill tests wearing different ensembles, plus running shoes, as follows:

* short-sleeved T-shirt, cycling shorts and anklet socks made from an evaporative polyester fabric;

* the same items of clothing made from a traditional cotton fabric;

* lycra swim suit and anklet socks (the 'semi-nude' condition).

Each trial consisted of 20 minutes of quiet seated rest in an environmental chamber, 30 minutes of treadmill running at 70% of VO2max, 15minutes of treadmill walking at 40% of VO2max and 15 minutes of seated rest. The chamber was heated to 30¼C, with a relative humidity of about 35. Wind speeds were applied to match the subjects' activity - ie highest during running and lowest during rest.

A variety of measurements - including clothing mass, body mass and body temperature - were taken before and after the trials. Key results were as follows:

* l Temperature. There were no differences in any temperature variables between ensembles during running, walking and postexercise rest. In response to changes in exercise conditions, there were similar rates of change in body, rectal and skin temperature between all ensembles;

* Metabolic requirements. There were no differences in oxygen consumption or heart rate between ensembles at any point;

* Comfort. There were no differences in thermal comfort or sweating sensations between ensembles.

However, there was a difference in the retention of sweat by the clothing ensembles, with the cotton outfit retaining approximately three times more sweat than either the synthetic or the semi-nude variants.

'It is therefore evident,' point out the researchers, 'that the synthetic material...does promote greater evaporation, as claimed by the manufacturer. In spite of this, the [cotton] ensemble did not impair temperature regulation in a warm environment.'

They acknowledge, though, that the same might not be true of cold environments 'where postexercise evaporation may create a significant cooling effect, especially during intermittent exercise. Thus, the use of fabrics that promote evaporation may have a potentially greater benefit during exercise in a cold environment'.

This latter theory remains to be demonstrated. Meanwhile, the main message from the current study is that 'neither modest differences in the amount of clothing worn nor the fabric characteristics of the clothing alter physiological, thermoregulatory or comfort sensation responses during exercise in a moderately warn environment'.

Reference:

Med Sci Sports Exerc 2001 Dec 33(12), pp2124-2130

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