Effects of 7°C environmental temperature acclimation during a 3-week training period

Abstract

Cold environmental temperatures during exercise and recovery alter the acute response to cellular signaling and training adaptations. Approximately 3 wk is required for cold temperature acclimation to occur. To determine the impact of cold environmental temperature on training adaptations, fitness measurements, and aerobic performance, two groups of 12 untrained male subjects completed 1 h of cycling in 16 temperature acclimation sessions in either a 7°C or 20°C environmental temperature. Fitness assessments before and after acclimation occurred at standard room temperature. Muscle biopsies were taken from the vastus lateralis muscle before and after training to assess molecular markers related to mitochondrial development. Peroxisome proliferator-activated receptor-γ coactivator 1α (PGC-1α) mRNA was higher in 7°C than in 20°C in response to acute exercise before training (P = 0.012) but not after training (P = 0.813). PGC-1α mRNA was lower after training (P < 0.001). BNIP3 was lower after training in the 7°C than in the 20°C group (P = 0.017) but not before training (P = 0.549). No other differences occurred between temperature groups in VEGF, ERRα, NRF1, NRF2, TFAM, PINK1, Parkin, or BNIP3L mRNAs (P > 0.05). PGC-1α protein and mtDNA were not different before training, after training, or between temperatures (P > 0.05). Cycling power increased during the daily training (P < 0.001) but was not different between temperatures (P = 0.169). V̇o_2peak increased with training (P < 0.001) but was not different between temperature groups (P = 0.460). These data indicate that a 3-wk period of acclimation/training in cold environmental temperatures alters PGC-1α gene expression acutely but this difference is not manifested in a greater increase in V̇o_2peak and is dissipated as acclimation takes place.NEW & NOTEWORTHY This study examines the adaptive response of cellular signaling during exercise in cold environmental temperatures. We demonstrate that peroxisome proliferator-activated receptor-γ coactivator 1α mRNA is different between cold and room temperature environments before training but after training this difference no longer exists. This initial difference in transcriptional response between temperatures does not lead to differences in performance measures or increases in protein or mitochondria.

Keywords: PGC-1α; exercise; mRNA; mitochondria; skeletal muscle.

Fig. 1.

Daily training values. Power (W), heart rate, core temperature, and sweat rate during training each day at an rating of perceived exertion (RPE) of 15 in 20°C or 7°C. Data are means ± SE. *P < 0.05 from previous week.

Fig. 2.

A–F: gene expression associated with mitochondrial biogenesis 4-h postexercise relative to preexercise. PGC-1α, peroxisome proliferator-activated receptor-γ coactivator 1α; NRF, nuclear respiratory factor; TFAM, mitochondrial transcription factor A; ERRα, estrogen-related receptor-α; VEGF, vascular endothelial growth factor. *P < 0.05 from preexercise; †P < 0.05 from 20°C; ‡P < 0.05 from day 1 4-h time point.

Fig. 3.

A–D: gene expression associated with mitophagy 4-h after exercise relative to preexercise. PINK1, PTEN-induced kinase-1; BNIP3, Bcl2-interacting protein-3, BNIP3L, Bcl2-interacting protein 3-like; Parkin, an E3 ubiquitin ligase. *P < 0.05 from preexercise; †P < 0.05 from 20°C; ‡P < 0.05 from day 1 4-h time point.