The effects of passive heating and head-cooling on perception of exercise in the heat

Abstract

The capacity to perform exercise is reduced in a hot environment when compared to cooler conditions. A limiting factor appears to be a higher core body temperature (T (core)) and it has been suggested that an elevated T (core) reduces the drive to exercise, this being reflected in higher ratings of perceived exertion (RPE). The purpose of the present study was to determine whether passive heating to increase T (core) would have a detrimental effect on RPE and thermal comfort during subsequent exercise in the heat and whether head-cooling during passive heating would attenuate these unpleasant sensations of an elevated T (core) during subsequent exercise in the heat. Nine physically-active, non-heat-acclimated volunteers [6 males, 3 females; age: 21 +/- 1 year, VO(2max) 50 +/- 9 ml kg(-1).min(-1), peak power output: 286 +/- 43 W (mean +/- SD)] performed two 12-minute constant-load cycling tests at 70% VO(2max) in a warm-dry environment (34 +/- 1 degrees C, relative humidity <30%) separated by a period of passive heating in a sauna (68 +/- 3 degrees C) to increase T (core). In one trial, subjects had their head and face cooled continually in the sauna (HC), the other trial was a control (CON). Passive heating increased T (core) by 1.22 +/- 0.03 degrees C in the CON and by 0.75 +/- 0.07 degrees C in the HC trial (P < 0.01). Passive heating increased weighted mean skin temperature (T (msk)) in both the CON and HC trials (P < 0.01), however, head-cooling lowered T (msk) during passive heating (P < 0.05). Exercise time following passive heating was reduced in both the CON and HC trials (P < 0.05). Passive heating increased RPE (P < 0.01), however, RPE was lower following passive heating with head-cooling (P < 0.05). There was a significant correlation between T (core) and RPE (r = 0.82, P < 0.001). In conclusion, our results suggest increased RPE during exercise in the heat is primarily due to the increase in T (core). Furthermore, head-cooling attenuates the rise in T (core) and the effect on RPE is proportional to the rise on T (core).

The effects of swilling an l(−)-menthol solution during exercise in the heat

“…However, at the point of volitional fatigue, the circulatory system does not appear to be maximally stressed (Nielsen et al 1993), and muscle glycogen or carbohydrate metabolism do not appear to be limited (Parkin et al 1999). Furthermore, we have previously demonstrated by use of a passive heating model with adequate hydration, which greatly reduces the cardiovascular and metabolic alterations exhibited during active heating, that a substantial rise in core temperature is a causative element of the reduced (fixed intensity) exercise capacity in the heat (Armada-da- Silva et al 2004;Simmons et al 2008).…”

Practical neck cooling and time-trial running performance in a hot environment

“…If the magnitude of cooling is sufficient and/or the thermal strain is severe enough, cooling the head and neck can illicit beneficial thermoregulatory (Gordon et al 1990;Shvartz 1970), cardiovascular (Shvartz 1970) and perceptual (Mundel et al 2006;Simmons et al 2008) adjustments. Practical cooling devices have been shown to have no effect on the physiological response to exercise (Bulbulian et al 1999;Gordon et al 1990).…”

The Governor has a sweet tooth – Mouth sensing of nutrients to enhance sports performance

“…Some suggestion of small enhancement with mouth rinse vs. no treatment (60% of subjects did better) Yes -10% Note that exercise protocol measured capacity rather than performance Cycling time to exhaustion was increased by 9% (p = 0.04) in menthol trial (63 ± 14 min) compared with the placebo trial (58 ± 16 min) and was attributed to altered sensation of oropharyngeal temperature. Menthol was associated with increased ventilation and a trend to reduced ratings of perceived effort Bitter taste Gam et al and face can certainly reduce perception of effort (Simmons, Mündel, & Jones, 2008). Mündel and Jones (2010) extended these results by using a menthol-containing solution to induce a sensation of coldness in the mouth without any actual cooling effect.…”