Heat shock factor activation in human muscles following a demanding intermittent exercise protocol is attenuated with hyperthermia

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.