Upper body sweat mapping provides evidence of relative sweat redistribution towards the periphery following hot-dry heat acclimation

Figures & data

Table 1. Physiological data (mean ± SD) on days 1 and 6 of heat acclimation (HA).

HA	Gross Sweat Loss (g.m^−2⋅h^−1)	Final Tcore (ºC)	Final mean Tsk (ºC)	Av. Exercise HR (bpm)	Av. Exercise Metabolic Rate (W)	Av. Work Performed (Kj)
Day 1	621 ± 73	38.4 ± 0.2	37.4 ± 0.7	141 ± 9	659 ± 135	2374 ± 485
Day 6	708 ± 80***	38.5 ± 0.3	37.3 ± 0.4	136 ± 9	763 ± 155	2746 ± 558

Significant versus day 1: *** p < 0.001. Heart rate (HR) and metabolic rate data are averages of all three exercise bouts completed during each heat acclimation session. Final core temperature (T_core) and mean skin temperature (T_sk) were the average values recorded during the final minute of the protocol.

Table 2. Physiological data (mean ± SD) during pre and post heat acclimation (HA) sweat mapping experimentation. Surface area weighted gross sweat loss (SA weighted GSL) was calculated from regional sweat rates for the surface area covered by pads only.

	Time Point	Baseline	Intensity 1	Intensity 2
Tcore (°C)	Pre HA	37.1 ± 0.3	38.0 ± 0.2	38.4 ± 0.3
	Post HA	36.9 ± 0.4	37.6 ± 0.3	37.9 ± 0.1
Heart Rate (bpm)	Pre HA	65 ± 11	136 ± 2	156 ± 3
	Post HA	58 ± 7	132 ± 3*	157 ± 4
Work Rate (%VO2max)	Pre HA	-	54 ± 3	73 ± 4
	Post HA	-	57 ± 5	76 ± 7
Gross sweat loss (g.m^-2.h^-1)	Pre HA	-	350 ± 83	599 ± 97
	Post HA	-	376 ± 56	795 ± 121**
SA Weighted GSL (g.m^-2.h^-1)	Pre HA	-	312 ± 102	521 ± 108
	Post HA	-	517 ± 153**	807 ± 174**

Significantly different versus pre-HA values: * P < 0.05; ** P < 0.01

Figure 1. Absolute gross sweat loss (GSL; g ⋅ h⁻¹) and metabolic rate (W kg⁻¹) at exercise intensity 1 (I1) and intensity 2 (I2) during pre- and post- heat acclimation (HA) sweat mapping experiments. * indicates p < 0.05.

Table 3. Significance level of pre- versus post- heat acclimation regional sweating rates. Gray shading indicates a significant decrease whilst no shading indicates a significant increase.

	Intensity 1		Intensity 2
	Absolute data (g.m^−2.h^−1)	Normalised ratio data	Absolute data (g.m^−2.h^−1)	Normalised ratio data
Shoulders	*	-	***#	-
Lat upper chest	**$	-	*	-
Med upper chest	-	-	-	-
Lat mid chest	*	-	*	-
Med mid chest	**	-	-	-
Sides	**#	-	**$	-
Ant lower	-	-	**	-
Lat upper back	-	*	***#	**
Med upper back	*	**	**	-
Lat mid upper back	**$	-	**#	-
Lat mid lower back	*	-	*	-
Med mid back	-	-	**	-
Pos lower back	-	-	-	-
Ant upper arm	**	*	**$	**
Pos upper arm	**	-	**$	*
Ant lower arm	**#	-	**	-
Pos lower arm	**	-	**#	**$

Significance level for uncorrected data: *P ≤ 0.05; **P ≤ 0.01; ***P ≤ 0.001; Significance level following Bonferroni correction: # P ≤ 0.05; ## P ≤ 0.01; ### P ≤ 0.001; $ 0.1 > P ≥ 0.05

Figure 2. Absolute pre- and post-acclimation regional median sweat rates of the torso and arms in male athletes at exercise intensity 1 and 2. Image created by Gavin Williams.

Figure 3. Normalized pre-and post-acclimation regional median sweat rates of the torso and arms in male athletes at exercise intensity 1 and 2. Image created by Gavin Williams.

Figure 4. Individual normalized pre- and post- heat acclimation sweating rates for central (torso) versus peripheral (arms) regions at intensity 1 (I1) and intensity 2 (I2). * indicates p < 0.05.

Table 4. Pre and post heat acclimation (HA) regional skin temperature during sweat mapping experiments at 5 measurement periods: baseline (BL), pre I1 pad application (Pre I1), post I1 pad application (Post I1), pre I2 pad application (Pre I2), and post I2 pad application (Post I2). Significant changes within regions from the previous measurement period are indicated by the symbols listed below the table. A significant decrease is indicated by grey shading ().

		Skin Temperature (°C)
		Pre-HA					Post HA
Region		BL	Pre I1	Post I1	Pre I2	Post I2	BL	Pre I1	Post I1	Pre I2	Post I2
Torso	Anterior medial upper	31.3	32.3	32.7*	32.9	33.5	33.4	31.8	33.1	31.5**#	33.2
	Anterior lateral upper	31.6	31.7	32.2*	31.7*	32.8	32.9	31.3	32.8	30.5***##	32.9
	Anterior medial lower	30.4	31.0	31.7**#	30.0**#	31.8	32.1	30.1	32.0	28.9***#	31.9*
	Anterior lateral lower	30.7	32.0	32.3*	31.6*	32.5	32.7	31.2	32.7*	30.2**#	32.4
	Posterior medial upper	31.9	32.4	33.4*	33.7	34.5	33.1	32.7	34.6**#	33.0**#	35.2***##
	Posterior lateral upper	32.0	31.6	33.0**$	32.7*	34.0	32.8	31.5**#	34.2***##	32.0**#	35.0***##
	Posterior medial lower	30.6	32.2	33.3***##	33.5	34.2	32.6	32.7	34.7***##	32.9***##	35.1***###
	Posterior lateral lower	30.2	31.4	32.6**#	32.3*	33.5	31.7	31.3	33.8***##	31.4***##	34.4***###
	Sides	30.6	31.5	32.5*	31.5*	32.9**#	32.0	31.0	32.8**$	30.7**#	33.3**#
Arms	Anterior upper	32.4	31.8	32.9*	31.5*	32.7*	33.1	31.2	32.4	30.8**#	32.8*
	Posterior upper	31.6	31.9	32.9	31.8	32.9*	31.0	31.0*	32.6**$	31.8	33.5**$
	Anterior lower	31.4	31.7	33.0*	32.1	33.1	32.4	30.7**	32.1**#	30.8**	32.0
	Posterior lower	31.7	31.9	32.8	32.5	33.0	31.7	31.0	32.2*	31.7	33.3**#
	Unweighted Mean	31.0 ± 3.0	31.7 ± 1.5	33.3 ± 1.8	32.1 ± 1.5	33.0 ± 1.1	31.7 ± 0.6	31.1 ± 0.4	32.2 ± 1.0	31.7 ± 1.0	33.2 ± 1.4

No correction: *P < 0.05; **P < 0.01; ***P < 0.001;

Bonferroni correction: # P < 0.05; ## P < 0.05; ### P < 0.001; $ 0.1 > P ≥ 0.05