Abstract

The relationship between rectal (Tre) and infrared tympanic-derived "rectal-equivalent" (Tty) temperatures was investigated in seven adult subjects during cycle ergometer exercise in a mild environment (air temperature 21ø to 24øC, relative humidity approximately 60%). The experiment involved three phases: exercise in minimal airflow (duration approximately 50 minutes, air speed <0.05 m/s) (Phase 1); same workload for a further 10 minutes with facial airflow of 0.7 m/s (Phase 2); and recovery in minimal airflow (Phase 3). Tty was significantly lower than Tre in the last four minutes of Phase 1 (p<0.01) and throughout Phases 2 and 3 (p<0.0005). In Phase 1 Tty correlated significantly with Tre (r=0.92, p<0.001) and was on average (+/-SE) 0.16+/-0.02øC lower than Tre. In Phase 2 Ty continued to correlate significantly with Tre (r=0.83, p<0.001) but the mean underestimation of Tre by Tty (0.73+/-0.05øC) was significantly greater than in Phase 1 (p<0.001). During Phase 3 the difference between Tre and Tty was even greater (1.07+/-0.05øC); a significant correlation between Tre and Tty was still evident (r=0.78, p<0.001). The application of a cotton wool pad to the ear significantly raised Tty values for each phase of the experiment (average increase Phase 1, 0.37øC; Phase 2, 0.56øC, Phase 3, 0.68øC, p<0.001 for each phase). These data suggest that exercise core temperature can be estimated to within 0.2øC of Tre by infrared tympanic thermometry provided airflow is minimal and ambient temperatures are mild. Where moderate facial airflow exists, however, as in many sports contexts, this method can considerably underestimate core temperature. This limitation of infrared tympanic-derived core temperature could result in misdiagnosis of heat exhaustion. Further research should be undertaken to refine this method in its application to sports and exercise. Verf.-Referat