Post-warm-up muscle temperature maintenance: blood flow contribution and external heating optimisation

PURPOSE: Passive muscle heating has been shown to reduce the drop in post-warm-up muscle temperature (T(m)) by about 25 % over 30 min, with concomitant sprint/power performance improvements. We sought to determine the role of leg blood flow in this cooling and whether optimising the heating procedure would further benefit post-warm-up T(m) maintenance. METHODS: Ten male cyclists completed 15-min sprint-based warm-up followed by 30 min recovery. Vastus lateralisT(m) (T(mvl)) was measured at deep-, mid- and superficial-depths before and after the warm-up, and after the recovery period (POST-REC). During the recovery period, participants wore water-perfused trousers heated to 43 °C (WPT43) with either whole leg heating (WHOLE) or upper leg heating (UPPER), which was compared to heating with electrically heated trousers at 40 °C (ELEC40) and a non-heated control (CON). The blood flow cooling effect on T(mvl) was studied comparing one leg with (BF) and without (NBF) blood flow. RESULTS: Warm-up exercise significantly increased T(mvl) by ~3 °C at all depths. After the recovery period, BF T(mvl) was lower (~0.3 °C) than NBF T(mvl) at all measured depths, with no difference between WHOLE versus UPPER. WPT43 reduced the post-warm-up drop in deep-T(mvl) (−0.12 °C ± 0.3 °C) compared to ELEC40 (−1.08 ± 0.4 °C) and CON (−1.3 ± 0.3 °C), whereas mid- and superficial-T(mvl) even increased by 0.15 ± 0.3 and 1.1 ± 1.1 °C, respectively. CONCLUSION: Thigh blood flow contributes to the post-warm-up T(mvl) decline. Optimising the external heating procedure and increasing heating temperature of only 3 °C successfully maintained and even increased T(mvl), demonstrating that heating temperature is the major determinant of post-warm-up T(mvl) cooling in this application.