PT - JOURNAL ARTICLE AU - Michael F Bergeron AU - Kathryn S McLeod AU - John F Coyle TI - Core body temperature during competition in the heat: national boys’ 14s junior tennis championships AID - 10.1136/bjsm.2007.036905 DP - 2007 Nov 01 TA - British Journal of Sports Medicine PG - 779--783 VI - 41 IP - 11 4099 - http://bjsm.bmj.com/content/41/11/779.short 4100 - http://bjsm.bmj.com/content/41/11/779.full SO - Br J Sports Med2007 Nov 01; 41 AB - Objective: To examine on-court core body temperature (TC) and sweat loss, as well as pre- and post-play hydration status, in elite adolescent tennis players during a national championships event in a hot climate.Methods: Eight healthy, fit, young male tennis players (mean (SD) age 13.9 (0.9) years; mass 56.0 (10.7) kg; height 169.2 (14.7) cm) were evaluated during first-round singles competition at the National Boys’ 14s Junior Championships in the heat (wet-bulb globe temperature (WBGT) 29.6 (0.4) °C). Five of those same players were also evaluated during a same-day doubles match (WBGT 31.3 (0.5) °C).Results: During doubles (4.37 (0.35) h after singles), pre-play urine specific gravity (USG) (1.025 (0.002); p = 0.06) and total sweat loss (1.9 (0.2) litres; p = 0.10) tended to be higher before and during doubles, respectively, compared to singles. However, percentage change in body mass (−0.5 (0.3) %) tended to be comparatively less (p = 0.08), even though the doubles matches were generally longer (106.6 (11.2) vs 78.8 (10.9) min; p = 0.09) and the degree minutes total was greater (p = 0.04). TC increased (p<0.001) during singles and remained elevated, even after 10 min following the end of play. Notably, pre-play (singles) USG was strongly associated (p = 0.005) with the players’ final TC (38.7 (0.3) °C) recorded at the end of singles play.Conclusion: Junior tennis players who begin a match not well hydrated could have progressively increasing thermal strain and a greater risk for exertional heat illness as the match advances.