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Return to Competition after Exertional Heatstroke, Heat Tolerance Testing - Triathlon: 1209June 3 9:20 AM - 9:40 AM

Johnson, Evan C.; Kolkhorst, Fred W. FACSM; Richburg, Allen; Schmitz, Andy; Martinez, John M.; Armstrong, Lawrence E. FACSM

Medicine & Science in Sports & Exercise: May 2011 - Volume 43 - Issue 5 - p 224
doi: 10.1249/01.MSS.0000400605.24620.67
E-20 Clinical Case Slide - Heat-Illness: JUNE 3, 2011 8:00 AM - 10:00 AM: ROOM: 506

1University of Connecticut, Storrs, CT. 2San Diego State University, San Diego, CA. 3US Olympic Training Center, Chula Vista, CA. 4USA Triathlon, Colorado Springs, CO. 5Coastal Sports Medicine, Del Mar, CA.


(No relationships reported)

HISTORY: A 27-year-old United States of America Triathlon sponsored triathlete experienced two incidents of exertional heat stroke (EHS) during 2009. The American College of Sports Medicine recommends heat tolerance testing (HTT; i.e., core temperature and heart rate (HR) observations in a controlled environment) if return to activity is difficult. The value of a single HTT is debated because it does not determine if the athlete can acclimate to heat (i.e., improved physiological responses across days). Therefore, the medical and coaching team chose a novel HTT protocol to allow a conservative decision to be made about the athlete's return to play.

PHYSICAL EXAMINATION: Neither rectal temperatures nor liver enzyme values were recorded after either incident. In each case the athlete lost consciousness for 90-120min, collapsed, was transported to a hospital, and reported nausea and muscle soreness for several days.

DIFFERENTIAL DIAGNOSIS: Due to high motivation to return to competition a triathlon specific HTT was ordered to determine if:

1. prior to acclimation the athlete was able to cycle while in a hot and humid laboratory setting

2. the athlete exhibited classical heat acclimation

3. after acclimation, the athlete was able to endure a longer duration of cycling at the same exercise intensity


Initial HTT (cycling at 70% VO2max, in a 36°C, 50% RH environment)

- starting gastrointestinal temperature (Tgi): 37.22°C

- completed 45 min

- Tgi at 45min: 39.72°C

- rate of Tgi rise: 0.056°C·min-1

- rating of perceived exertion (RPE) at 40min: 17

- HR at 45min: 170bpm

- sweat rate: 1.72 l·hr-1

Acclimatization protocol (9 consecutive days; 36°C, 50% RH)

- Cycling and running (60-90min·d-1)

- Started at lower intensity and duration (day 1) and increased both on subsequent days

Follow up HTT

- starting Tgi: 36.52°C

- completed 70min

- Tgi at 45min: 38.52°C

- rate of Tgi rise: 0.046°C·min-1

- RPE at 40 min: 14

- HR at 45min: 157bpm

- sweat rate: 2.24 l·hr-1

FINAL/WORKING DIAGNOSIS: Based on the favorable responses and adaptations, the athlete was not determined to be "heat intolerant"


1. successfully returned to international competition

2. incorporates acclimation into training

3. adjusts effort level based on understanding of the signs and symptoms of EHS

© 2011 American College of Sports Medicine