American football uniforms elicit thermoregulatory failure during a heat tolerance test

Figures & data

Table 1. Subject demographics and descriptive information

	CONTROL	PADS
Demographics
	Age (y)	23 ± 3
	Height (cm)	179.6 ± 7.6
	Body Mass Index (kg/m^2)	24.2 ± 2.6
	Body Density (g·cc^−[^5])	1.08 ± 0.01
	Body Fat (%)	9 ± 2
	Body Surface Area (m^2)	1.97 ± 0.17
	VO2max (mL/kg/min)	51.4 ± 4.7
Hydration Measurements
	Pre-exercise Usg	1.006 ± 0.005	1.005 ± 0.004
	Body Mass Pre-exercise (kg)	78.7 ± 10.4	78.3 ± 11.5
	Body Mass Post-exercise (kg)	77.4 ± 10.4	77.3 ± 11.1
	Fluid Ingested (L)	0.69 ± 0.24	1.15 ± 0.87
	Sweat Rate (L/h)	0.96 ± 0.14	1.24 ± 0.28 ^a
	Post-testing Hypohydration (%)	2.4 ± 0.2	2.8 ± 0.7 ^b
Environmental Conditions
	Ambient Temperature (°C)	39.5 ± 0.9	39.6 ± 0.9
	Relative Humidity (%)	42.4 ± 1.1	41.8 ± 1.8

Data are means ± SD, n = 10. PADS = full American football uniform. Usg = urine specific gravity. ^a = PADS > CONTROL (t₉ = 5.6, P < 0.001). ^b = PADS > CONTROL (t₉ = 1.9, P = 0.047).

Table 2. Heat tolerance test results

	CONTROL	PADS
HTT Failure Data
Number of subjects who failed (n)	5 of 10	10 of 10
Failed because HR >150 bpm (n)	4 of 10	8 of 10
Failed because Trec >38.5°C (n)	1 of 10	2 of 10
Time to failure for those subjects who could not complete the HTT (min)	61.7 ± 23.5 ^a	43.4 ± 14.2
Probability of Heat Tolerance Data
Probability of Heat Tolerance	0.36 ± 0.47 ^a	0 ± 0
Subjects classified as “heat intolerant” (n)	6 of 10	10 of 10
Subjects classified as “borderline” (n)	1 of 10	0 of 10
Subjects classified as “heat tolerant” (n)	3 of 10	0 of 10
TREC and HR Data
First half of HTT, Rate of TREC Increase (°C/min)	0.016 ± 0.005 ^a, b	0.025 ± 0.006 ^b
Second half of HTT, Rate of TREC Increase (°C/min)	0.006 ± 0.003 ^a	0.021 ± 0.005
First half of HTT, Rate of HR Increase (bpm/min)	0.72 ± 0.32 ^a, b	1.34 ± 0.35 ^b
Second half of HTT, Rate of HR Increase (bpm/min)	0.26 ± 0.12 ^a	0.48 ± 0.18

Data are means ± SD, n = 10. HTT = heat tolerance test. ^a = CONTROL different from PADS (P < 0.05). ^b = Different from second half of testing within each condition (P < 0.05).

Figure 1. T_REC (a) and HR (b) responses with (PADS) and without (CONTROL) American football equipment donned during a HTT. X-axis error bars for the final PADS measurements indicate the SD for the exercise duration before T_REC was 39.5°C. Time 0 indicates the start of the HTT. Dashed horizontal lines indicate values indicative of a failed HTT. Data are means ± SD (n = 10). ^a = PADS > Control (P < 0.05)

Adams WM, Belval LN, Geisler PR. Return-to-activity following exertional heat stroke. Athl Train Sports Health Care. 2018;10:5–6.

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Availability of data and material

These data has not been published elsewhere nor is any data set available publicly at this time.