title: Physiological and perceptual responses to exercise and cold stress with special reference to climatic and textile factors
Creators: name: Georgiades, Evelina
Publisher: name: University of Glasgow
Year: 2000
Subjects: subject: Kinesiology, physiology.

description: The primary objective of the first three studies was to provide an indirect assessment of the properties of garments designed for wear in cold environments using human trials. The study design incorporated a specific protocol that allowed for evaluation of specific garment properties, based on physiological and subjective responses. Based on some interesting trends in VO2 response that were noted in the earlier studies, the fourth study aimed to determine the effects of cooling on the VO2 response to exercise in moderate and heavy intensity domains. The first two studies compared the performance of three garments that differed in the degree to which they were air-permeable: high (HP), medium (MP) and low (LP) permeability. The studies were conducted in two sub-zero environmental temperatures, against a constant wind speed. The protocol consisted of a 30 min rest period followed by 30 min of brisk walking on an inclined treadmill. The results suggest that HP was the least favourable garment in the imposed conditions, based on higher values for rating of cold perception (RPC) and elevated VO2 (indicating a more marked shivering response). Furthermore, it appeared that MP was the most effective of the suits, despite having a greater air permeability than LP. This indicates that factors other than wind resistance properties may have a significant effect on garment performance in this particular environment, taking into consideration duration of exposure, ambient temperature, wind-speed and physical activity status. The third study compared the wicking capacity of four garments (polyamide/nylon, capilene polyester, polyester and cotton), designed for wear as a base-layer, that varied in their physical properties and physical characteristics. It is recognised that evaporation of sweat taking place after cessation of exercise in the cold will cool the body, during a period where heat preservation is especially important. The design of the present study incorporated a 20 min exercise period, followed by a subsequent 45 min rest period in cool environment (1° C), during which the garments were evaluated. Lower RPC values and a tendency for a lower VO2 during rest, indicated that the polyester garment, which combined good wicking qualities with a high thermal resistance, was superior to the other garments in its capacity at offsetting heat loss. The results do not imply that heat transfer was prevented by the favourable garment, but rather that it was diminished in magnitude. The principal aim of the final study was to investigate the influence of body cooling on the VO2 response to exercise above and below the lactate threshold, employing square-wave cycle-ergometer exercise transitions for the two intensity domains. The design also allowed for determination of the influence of sub-normal temperatures on incremental cycling performance. The results showed that the induced cooling had detrimental effects on maximal aerobic performance. VO2 during moderate constant-load exercise was significantly elevated following cooling; a similar effect, however, was observed only during the initial stages of heavy intensity constant-load exercise. Furthermore, the characteristic VO2 slow-component observed during constant-load exercise above the lactate threshold remained unaltered by sub-normal temperatures. The results suggest that a graded suppression of shivering occurs with increasing exercise intensity. Furthermore, the findings indicate that temperature is likely to contribute to the slow-component of VO2 by only a trivial amount.