Gastrointestinal temperature trends in football linemen during physical exertion under heat stress.
BACKGROUND
Exertional heat stroke is the third leading cause of death in US athletes. Elevations in core temperature in the digestive tract (TGI) have correlated with core temperature and are possible indicators of those at increased risk of heat stroke.


OBJECTIVE
The primary objective was to compare a.m. vs. p.m. TGI variation in collegiate football linemen during intense "two-a-day" preseason practice. A secondary objective was to compare longitudinal TGI in offensive and defensive linemen.


METHODS
Cross-sectional observational study.


METHODS
Division I Intercollegiate Athletics Football Program.


METHODS
TGI was monitored during consecutive preseason sessions.


METHODS
TGI, heat illness, weight changes, environmental stress, and subjective symptoms.


RESULTS
Mean TGI were 37.8°C and 38.3°C during a.m. and p.m. practices, respectively. The a.m. practices revealed higher TGI gain (1.8°C) compared to p.m. (1.4°C). The p.m. practices had higher maximum TGI than a.m. practices (39.1°C versus 38.8, P=0.0001). Mean time to maximum temperature (Tmax) was 1 hr and 30 min for a.m. and 1 hr and 22 min for p.m. practices. Offensive linemen trended toward higher mean TGI than defensive players (38.0°C vs. 36.7°C, P = 0.069). The rate of rise in TGI was significantly greater in a.m. practices. A decrease in rate of TGI rise was seen from the first to last a.m. practices of the week (P = 0.004).


CONCLUSIONS
Significant TGI elevations in asymptomatic athletes are common in extreme heat during football practice. Intense a.m. practices in full gear result in higher net temperature gain and rate of temperature gain than p.m. practices. Offensive linemen trended toward higher TGI than defensive linemen. As players acclimatized, a decrease in the rate of TGI increase was appreciable, particularly in a.m. practices. Appreciating cumulative heat stress and variations in heat stress related to scheduling of practice is critical.
Coris
Eric E
EE
Department of Family Medicine, The University of South Florida College of Medicine, Tampa, FL 33612, USA. ecoris@health.usf.edu
Mehra
Shabnam
S
Walz
Stephen M
SM
Duncanson
Robert
R
Jennings
Jason
J
Nugent
Dylan
D
Zwygart
Kira
K
Pescasio
Michele
M
D001831:Body Temperature / Q000502:physiology*; D001833:Body Temperature Regulation / Q000502:physiology; D003430:Cross-Sectional Studies; D005538:Football / Q000502:physiology*; D041981:Gastrointestinal Tract / Q000502:physiology; D018883:Heat Stroke / Q000517:prevention & control; D018869:Heat-Shock Response / Q000502:physiology*; D006358:Hot Temperature / Q000009:adverse effects; D006801:Humans; D008297:Male; D005082:Physical Exertion / Q000502:physiology*; D010809:Physical Fitness / Q000502:physiology; D055815:Young Adult