The Hsp72 and Hsp90α mRNA responses to hot downhill running are reduced following a prior bout of hot downhill running, and occur concurrently within leukocytes and the vastus lateralis
The leukocyte heat shock response (HSR) is used to determine individual’s
thermotolerance. The HSR and thermotolerance are enhanced following interventions
such as preconditioning and/or acclimation/acclimatization. However, it is unclear
whether the leukocyte HSR is an appropriate surrogate for the HSR in other tissues
implicated within the pathophysiology of exertional heat illnesses (e.g., skeletal muscle),
and whether an acute preconditioning strategy (e.g., downhill running) can improve
subsequent thermotolerance. Physically active, non-heat acclimated participants were
split into two groups to investigate the benefits of hot downhill running as preconditioning
strategy. A hot preconditioning group (HPC; n = 6) completed two trials (HPC1HOTDOWN
and HPC2HOTDOWN) of 30 min running at lactate threshold (LT) on −10% gradient in
30◦C and 50% relative humidity (RH) separated by 7 d. A temperate preconditioning
group (TPC; n = 5) completed 30 min running at LT on a −1% gradient in 20◦C and
50% (TPC1TEMPFLAT) and 7 d later completed 30 min running at LT on −10% gradient
in 30◦C and 50% RH (TPC2HOTDOWN). Venous blood samples and muscle biopsies
(vastus lateralis; VL) were obtained before, immediately after, 3, 24, and 48 h after each
trial. Leukocyte and VL Hsp72, Hsp90a, and Grp78 mRNA relative expression was
determined via RT-QPCR. Attenuated leukocyte and VL Hsp72 (2.8 to 1.8 fold and 5.9
to 2.4 fold; p < 0.05) and Hsp90a mRNA (2.9 to 2.4 fold and 5.2 to 2.4 fold; p < 0.05) responses accompanied reductions (p < 0.05) in physiological strain [exercising rectal
temperature (−0.3◦C) and perceived muscle soreness (∼ −14%)] during HPC2HOTDOWN
compared to HPC1HOTDOWN (i.e., a preconditioning effect). Both VL and leukocyte Hsp72
and Hsp90a mRNA increased (p < 0.05) simultaneously following downhill runs and
demonstrated a strong relationship (p <0.01) of similarmagnitudes with one another. Hot
downhill running is an effective preconditioning strategy which ameliorates physiological
strain, soreness and Hsp72 and Hsp90a mRNA responses to a subsequent bout.
Leukocyte and VL analyses are appropriate tissues to infer the extent to which the HSR
has been augmented