Noninvasive assessment of muscle temperature during rest, exercise, and postexercise recovery in different environments

Abstract

Flouris AD, Webb P, Kenny GP. Noninvasive assessment of muscle temperature during rest, exercise, and postexercise recovery in different environments. J Appl Physiol 118: 1310-1320, 2015. First published March 26, 2015 doi:10.1152/japplphysiol.00932.2014.-We introduced noninvasive and accurate techniques to estimate muscle temperature (Tm) of vastus lateralis (VL), triceps brachii (TB), and trapezius (TRAP) during rest, exercise, and postexercise recovery using the insulation disk (iDISK) technique. Thirty-six volunteers (24 men, 12 women; 73.0 Ϯ 12.2 kg; 1.75 Ϯ 0.07 m; 24.4 Ϯ 5.5 yr; 49.2 Ϯ 6.8 ml·kg Ϫ1 ·min Ϫ1 peak oxygen uptake) underwent periods of rest, cycling exercise at 40% of peak oxygen uptake, and postexercise recovery in three environments: Normal (24°C, 56% relative humidity), Hot-Humid (30°C, 60% relative humidity), and Hot-Dry (40°C, 24% relative humidity). Participants were randomly allocated into the "model" and the "validation" groups. Stepwise regression analysis generated models that accurately predicted Tm (predTm) of VL (R 2 ϭ 0.73-0.91), TB (R 2 ϭ 0.85-0.93), and TRAP (R 2 ϭ 0.84 -0.86) using iDISK and the difference between the current iDISK temperature and that recorded between 1 and 4 min before. Cross-validation analyses in the validation group demonstrated small differences (P Ͻ 0.05) of no physiological significance, small effect size of the differences, and strong associations (r ϭ 0.85-0.97; P Ͻ 0.001) between Tm and predTm. Moreover, narrow 95% limits of agreement and low percent coefficient of variation were observed between Tm and predTm. It is concluded that the developed noninvasive, practical, and inexpensive techniques provide accurate estimations of VL, TB, and TRAP Tm during rest, cycling exercise, and postexercise recovery. intramuscular; insulation disk; vastus lateralis; triceps brachii; trapezius DURING EXERCISE, LARGE AMOUNTS of heat are produced in the exercising muscles, leading to increased muscle temperature (Tm) (22). This occurs within the first few seconds of repeated muscle contraction, confirming that Tm is a robust indicator of muscle metabolism. In this light, the strong link between Tm and exercise performance is not surprising. Indeed, a number of studies have shown that Tm is the most important factor in determining the outcome of exercise performance, especially during short-term high-intensity exercise (36 -38, 41). In addition, a 2-5% variation (depending on the contraction type and velocity) in performance has been proposed as a consequence of a change in Tm by 1°C (41). Therefore, knowledge of Tm during work and exercise is crucial to attain performance enhancements. In addition, Tm data have both clinical [in terms of assessing and refining postexercise recovery interventions (39)] and physiological [in terms of improving the assessment of thermometrically derived mean body temperature (26)] value, representing a much-needed source of information in human physiology.At present, measurement of Tm is a time-consuming, invasive, and expensive techniq...

Heat acclimation during low‐intensity exercise increases and Hsp72, but not markers of mitochondrial biogenesis and oxidative phosphorylation, in skeletal tissue

“…In this context, Flouris, Webb, & Kenny (2015) showed that intramuscular temperature did not increase above 39 • C using similar exercise intensity (40%V O 2 max ) and environmental heat stress (39 • C and 27% relative humidity), but shorter exercise duration (90 min).…”

“…Although T core was elevated during all bouts of exercise (38.5–39.5°C), muscle temperature was not measured, meaning we cannot rule out the possibility that muscles did not increase temperature enough to elicit mitochondrial adaptations. In this context, Flouris, Webb, & Kenny (2015) showed that intramuscular temperature did not increase above 39°C using similar exercise intensity (40% ) and environmental heat stress (39°C and 27% relative humidity), but shorter exercise duration (90 min). Also, the current study had no control group, making it impossible to compare a ‘heat + exercise group’ to an ‘exercise only’ group.…”

Superficial warming and cooling of the leg affects walking speed and neuromuscular impairments in people with spastic paraparesis

“…We used non-invasive skin temperature measurement, which has been reported to be associated with deeper intramuscular temperatures [37,38] and was a pragmatic decision in this study. Regardless of the depth of effect, we observed changes in walking speed and neuromuscular impairments, which suggests an effect on neuromuscular structures.…”

Thermoregulatory responses in exercising rats: methodological aspects and relevance to human physiology

“…Considering the latter statement, authors usually do not describe the environment as thermoneutral during exercise experiments and use alternative descriptions, including temperate environments 38 or normal T AMB . 100,101 …”