Aim: The present study investigated whether increased activation of heat shock factors (HSF) following exercise relates primarily to the increased muscle temperature or to exercise in general.
Methods: Six subjects completed 40 min of intermittent cycling (15s : 15s exercise:recovery at 300 ± 22 W) at an ambient temperature of either 20.0 ± 1.3 or 40.3 ± 0.7 °C. Muscle biopsies were taken prior to and immediately following the exercise protocol with samples analysed for HSF DNA binding by electrophoretic mobility shift assay.
Results: Exercise at 40 °C resulted in significantly increased oesophageal (39.3 ± 0.2 °C) and muscle temperature (40.0 ± 0.2 °C) at the end of the exercise protocol compared with 20 °C (oesophageal, 38.1 ± 0.1 °C; muscle, 38.9 ± 0.2 °C). However, an increased DNA binding of HSF was not evident following exercise at 40 °C (reduced by 21 ± 22%) whereas it increased by 29 ± 51% following exercise at 20 °C.
Conclusion: It appears that increased temperature is not the major factor responsible for activation of HSF DNA binding.