Validation of upper thermal thresholds for outdoor sports using thermal physiology modelling

Figures & data

Table 1. Summary of literature review on six sports.

Sport	Marathon	Football	Rowing	Rugby	Tennis	Triathlon	Total (6 sports)
Search words	(marathon) AND ((rectal temp*) OR (core temp*)) NOT (TitleCombined:(swim*)) NOT (TitleCombined:(ultra*)) NOT (TitleCombined:(ironman))	((football) OR (soccer)) AND ((rectal temp*) OR (core temp*))	(rowing) AND ((rectal temp*) OR (core temp*))	(rugby) AND ((rectal temp*) OR (core temp*))	(tennis) AND ((rectal temp*) OR (core temp*))	(triathlon) AND ((rectal temp*) OR (core temp*))	N/A
Search condition 1	Scholarly & Peer-Reviewed	Scholarly & Peer-Reviewed	Scholarly & Peer-Reviewed	Scholarly & Peer-Reviewed	Scholarly & Peer-Reviewed	Scholarly & Peer-Reviewed	N/A
Search condition 2	Full Text Online	Full Text Online	Full Text Online	Full Text Online	Full Text Online	Full Text Online	N/A
Search condition 3	English	English	English	English	English	English	N/A
Search date	October 31st, 2022	October 31st, 2022	October 31st, 2022	October 31st, 2022	October 31st, 2022	October 31st, 2022	N/A
# of references found	138	305	22	137	93	38	733
# of references for which the title and abstracts were reviewed	50	50	22	50	50	38	260
# of references for which the full text was reviewed	19	5	4	4	23	7	62
# of references identified in the review above	3	2	1	1	3	1	11
# of references identified from literature review of other sports	0	1	0	0	0	0	1
# of references identified for the sport(s)	3	3	1	1	3	1	12

Table 2. Settings for unknown parameters.

Parameters		Settings for unknown parameters
Environmental factors	Mean radiant temperature	Ambient temperature [Ta] +20°C (for outdoor daytime) or the same as Ta (for indoor/outdoor nighttime)
	Wind speed	Three patterns of 0, 1.0, and 3.0 m/s (outdoor) or 0 (indoor)
	Trend of Ta	Three constant patterns at average Ta, low (average – standard deviation [SD]) in the first half and high (average + SD) in the second half, high (average + SD) in the first half of the game and low (average – SD) in the second half of the game.
Exercise factors	Metabolic rate	In running-type exercises, American College of Sports Medicine (ACSM) formula was used [16]. If the SD of the running speed was unknown, 7% [16] of the average metabolic rate was considered the SD. For other types of exercise, metabolic rate was set referring to the typical METs values by Ainsworth et al. (2011) [17] and adjusted them as necessary; 10% of the average metabolic rate was considered the SD.
	Duration	For marathons and triathlons, where metabolic rate and duration are considered related, the assumption is that if the metabolic rate is high (average + SD), the duration is short (average – SD), and if the metabolic rate is low (average – SD), the duration is prolonged (average + SD).

Table

Abbreviations in equations CIs, confidence intervals; LOA, limits of agreement; n, sample size; SD, standard deviation; tn-1, t-value for a two-sided probability of 5% in a t-distribution with n-1 degrees of freedom

Table 3. Sport selection results.

Outdoor sports in Tokyo Olympics 2020	Thermal safety guidelines with upper thresholds			References with core temperature and calculation parameters (number of references and sample size [n])	Selected sports
	Guidelines identified	Index (upper threshold)	Author(s) (*other than IFs)
Archery	F	N/A	N/A	N/A	F
Athletics (marathon)	T	WBGT (28°C)	ACSM*, IIRM*	T (3, n = 99)	T
Baseball/softball	F	N/A	N/A	N/A	F
Beach volleyball	T	WBGT (31°C)	FIVB	F	F
Canoe	F	N/A	N/A	N/A	F
Cycling (mountain bike, road, BMX)	F	N/A	N/A	N/A	F
Equestrianism	F	N/A	N/A	N/A	F
Field hockey	T	Ta (42°C)/ RH (75%)	FIH	F	F
Football	T	WBGT (32°C)	FIFA	T (3, n = 38)	T
Golf	T	Ta (37°C)	IGF	F	F
Modern pentathlon	F	N/A	N/A	N/A	F
Rowing	T	Ta (38°C)/ WBGT (32°C)	FISA	T (1, n = 4)	T
Rugby seventh	T	HIS (150)	World Rugby	T (1, n = 22)	T
Tennis	T	WBGT (32.2°C)/ Tap (34°C)	ITF	T (3, n = 25)	T
Triathlon	T	WBGT (32.2°C)	World Triathlon	T (1, n = 14)	T
Sailing	F	N/A	N/A	N/A	F
Shooting	F	N/A	N/A	N/A	F
Skateboarding	F	N/A	N/A	N/A	F
Sport climbing	F	N/A	N/A	N/A	F
Surfing	F	N/A	N/A	N/A	F
3×3 basketball	F	N/A	N/A	N/A	F

Abbreviations: ACSM, American College of Sports Medicine; FIFA, International Federation of Association Football; FIH, International Hockey Federation; FIVB, International Volleyball Federation; HSI, Heat Stress Index; IGF, International Golf Federation; Ifs, international sports federations; ITF, International Tennis Federation; IIRM, International Institute for Running Medicine; T_a, ambient temperature; UIPM, Union Internationale de Pentathlon Moderne; WBGT, Wet Bulb Globe Temperature; T, True; F, False.

Figure 1. Bland-Altman plot of measured and simulated core temperature in 29 experiments: 11 for general exercise experiments and 18 for six selected sports.

Abbreviations: CI, confidence interval; SD, standard deviation

Figure 2. Predicted core temperature in six sports at the upper thresholds of the thermal safety guidelines (99.7^th percentile).

Abbreviations: prep, preparation; RH: relative humidity; T_a: ambient temperature; WU: warm-up

Figure 3. Current and revised upper thermal thresholds for football, marathons, and triathlons.

Abbreviations: PCTL, percentile; WBGT, Wet Bulb Globe Temperature

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Data availability statement

The datasets generated and analyzed during the current study are available from the corresponding author upon reasonable request.