Physiological responses and physical performance during football in the heat.
OBJECTIVE
To examine the impact of hot ambient conditions on physical performance and physiological responses during football match-play.


METHODS
Two experimental games were completed in temperate (∼ 21°C; CON) and hot ambient conditions (∼ 43°C; HOT). Physical performance was assessed by match analysis in 17 male elite players during the games and a repeated sprint test was conducted after the two game trials. Core and muscle temperature were measured and blood samples were obtained, before and after the games.


RESULTS
Muscle and core temperatures were ∼ 1°C higher (P<0.05) in HOT (40.3 ± 0.1 and 39.5 ± 0.1°C, respectively) compared to CON (39.2 ± 0.1 and 38.3 ± 0.1°C). Average heart rate, plasma lactate concentration, body weight loss as well as post-game sprint performance were similar between the two conditions. Total game distance declined (P<0.05) by 7% and high intensity running (>14 km ⋅ h(-1)) by 26% in HOT compared to CON), but peak sprint speed was 4% higher (P<0.05) in HOT than in CON, while there were no differences in the quantity or length of sprints (>24 km ⋅ h(-1)) between CON and HOT. In HOT, success rates for passes and crosses were 8 and 9% higher (P<0.05), respectively, compared to CON. Delta increase in core temperature and absolute core temperature in HOT were correlated to total game distance in the heat (r = 0.85 and r = 0.53, respectively; P<0.05), whereas, total and high intensity distance deficit between CON and HOT were not correlated to absolute or delta changes in muscle or core temperature.


CONCLUSIONS
Total game distance and especially high intensity running were lower during a football game in the heat, but these changes were not directly related to the absolute or relative changes in core or muscle temperature. However, peak sprinting speed and execution of successful passes and crosses were improved in the HOT condition.
Sport and Health Sciences, College of Life and Environmental Sciences, St. Lukes Campus, University of Exeter, Exeter, United Kingdom. M.Mohr@exeter.ac.uk
Magni
M
Mohr
Lars
L
Nybo
Justin
J
Grantham
Sebastien
S
Racinais
D000328:Adult; D001786:Blood Glucose; D001831:Body Temperature; D015444:Exercise / Q000502:physiology*; D005538:Football / Q000502:physiology*; D006339:Heart Rate; D006358:Hot Temperature; D006801:Humans; D019344:Lactic Acid / Q000097:blood; D008297:Male; D012420:Running; D012964:Sodium / Q000097:blood; D013546:Sweating / Q000502:physiology
D001786:Blood Glucose; D019344:Lactic Acid; D012964:Sodium