Rapid Cooling Of An NFL Defensive Linemen With A Core Temperature Of 40.9 2C During A Full Padded Practice

Abstract

HISTORY The athlete is a 9 yr veteran defensive lineman in the National Football League (NFL) with age = 30 yr, height =182.9 cm and body fat = 24%. He arrived at pre-season training camp 2004 with mass = 149 kg, similar to his 2003 pre-season mass (147.7 kg). He gained 5.6 kg by the 5th morning, 3.76% above baseline (BL). His sweat rate was 1.7 l·hr-1 in 2003 with ambient temperature = 23.7 °C and 83% RH. In pre-season 2003 his mean percent dehydration (%Dehy) after practice was 0.87% ranging from 0.0 to 1.85% in 23 consecutive practices. During the first 3 days of the 2004 pre-season this player's core temperature (Te) was monitored using ingestible sensors (HQ, Inc.). On Day 1 of two-a-days, his Te was >39.5°C (103°F) at the end of a one h indoor morning (AM) practice. Wet bulb globe temperature (WBGT) was 24.4°C and he was dressed in a helmet, shorts and shell. He denied a history of heat associated illness. PHYSICAL EXAMINATION The subjects' Te was closely monitored during the afternoon (PM) full padded practice due to his elevated AM Te. While dressed in shorts and a Tee-shirt, his resting Te recorded in an air-conditioned area 45 min prior to PM practice was 37.8°C (100°F). His Te was monitored approximately every 8 min during PM practice and he was questioned frequently about heat-related symptoms. His Te steadily increased to 40°C (104°F) by 1 h and 30 min into practice and he denied symptoms other than he felt hot. When his Te increased to 40.6°C (105°F) he was removed from practice against his will. His equipment was removed and he was transported to the on-field medical tent. Mean WBGT assessed three times during practice was 28.3°C. DIFFERENTIAL DIAGNOSIS Malignant hyperthermia Exercise induced heat stroke Exercise associated hyperthermia (benign) TEST AND RESULTS Te monitoring (40.9°C which decreased with cooling) Cognitive testing (−) Visual assessment (+ mild visual disturbance) % Dehydration (0% from baseline) FINAL WORKING DIAGNOSIS Benign exercise associated hyperthermia. TREATMENT AND OUTCOMES The athlete was removed from practice and rapidly cooled with ice-water soaked vests, neck collars and caps. His Te increased from 40.6°C when removed from practice to 40.9°C (105.7°F) just prior to aggressive cooling. While Te was continuously monitored the ice-water vests, collars and caps were changed approximately every 45 – 90 sec. A total of 6 changes were used for this player. Tc decreased from 40.9°C to 38.7°C (101.7°F) within 10 min of cooling. He had no residual symptoms or subsequent heat-associated problems. His post-practice % Dehy was 1.36% from pre-practice but 0% from BL. The highest Te recorded in this athlete on the 10th day of pre-season was 39.4°C (103°F).