Human Core Temperature Responses during Exercise and Subsequent Recovery: An Important Interaction between Diurnal Variation and Measurement Site

Abstract

Chronobiological investigations into core temperature during and after exercise can involve ambulatory measurements of intestinal temperature during actual competitions, esophageal temperature measurements in laboratory simulations, or rectal temperature, which can be measured in both the field and laboratory. These sites have yet to be compared during both morning and afternoon exercise and subsequent recovery. At 08:00 and 17:00 h, seven recreationally active males exercised at 70% peak oxygen uptake for 30 min and then recovered passively for 30 min. During the experiment, esophageal, rectal, intestinal, and skin temperatures, plus sweat loss, heart rate, and ratings of perceived exertion (RPE), were monitored. We found that the diurnal variation in intestinal temperature responses (0.45+/-0.32 degrees C; mean+/-SD) was significantly larger compared with rectal (0.33+/-0.24 degrees C) and, particularly, esophageal temperature responses (0.21+/-0.20 degrees C; p= 0.019). This reflected a greater difference of 0.25-0.40 degrees C between the esophagus and the other two sites in the afternoon, compared to inter-site differences of only 0.13-0.16 degrees C in the morning. Diurnal variation was small for skin temperature, heart rate, sweat loss, and RPE responses during exercise (p>0.05). Our data suggest that the relative differences between intestinal, rectal, and esophageal temperature during exercise and subsequent recovery depend on time of day to the extent that inferences from studies on experimental and applied chronobiology will be affected.

A Real-Time Algorithm for Predicting Core Temperature in Humans

“…The core temperature is considered to be an accurate reflection of the thermal state of an individual, although a very recent study [10] suggests that the accuracy may be dependent on time of day.…”

Core temperature response to cycling exercise: Effect of time of day and measurement site

“…More recently, Morris et al (2009) reproduced the procedure initially proposed by Aldemir et al (2000) study, 30 min cycling bout at 70% of the VO 2max , by shifting the time of exercise to 08:00 h and 17:00 h. The authors did not report any significant diurnal difference in the kinetic of temperature data; the morning/evening difference observed at the beginning of the exercise persists until the end of the test.…”

“…The thermal responses for a given exercise differ according to the time of day of the trial. Three studies have attempted to describe the effect of time of day on thermal response to exercise (Aldemir et al, 2000;Waterhouse et al, 2007;Morris et al, 2009). Aldemir et al (2000) proposed a 30 min cycling exercise designed to elicit 70% of individual VO 2max programmed at 08:00 h and 18:00 h. In this case, the diurnal temperature difference observed at the start of the exercise was no longer observed after 20 min of exercise.…”

An Approach to Identify Single Nucleotide Polymorphisms in the Period Circadian Clock 3 (PER3) Gene and Proposed Functional Associations with Exercise Training in a Thoroughbred Horse

“…The screening of PER3 in a Japanese population showed a number of polymorphisms to be associated with delayed sleep-phase syndrome (DSPS) and a circadian rhythm sleep disorder [4,11]. Thus, Thoroughbred breed horse as the model and can be used for possible explanation of the polymorphisms of period circadian clock genes.…”