Author(s): HOHENAUER, E., DOUZI, W., BURTSCHER, J., Institution: UNIVERSITY OF APPLIED SCIENCES AND ARTS OF SOUTHERN SWITZERLAND, Country: SWITZERLAND, Abstract-ID: 1416

INTRODUCTION:
Cold-water immersion (CWI) induces a coordinated thermoregulatory and stress-response program that may converge on pathways controlling peroxisome proliferator-activated receptor gamma coactivator-1 alpha (PGC-1alpha), a master regulator of mitochondrial biogenesis and a coordinator of angiogenesis, antioxidant defense and substrate metabolism. This mechanistic link is often assumed, but direct human evidence remains limited.
METHODS:
We performed a mechanistic synthesis of the literature on CWI/cold exposure, focusing on upstream neuroendocrine triggers, intracellular signaling, and downstream transcriptional targets related to PGC-1alpha in brown adipose tissue and skeletal muscle. We integrated these pathways into a testable dose-response framework that explicitly considers both adaptive signaling and adverse-event risk.
RESULTS:
CWI activates peripheral cold receptors (e.g., TRPM8), increases sympathetic noradrenaline release and stimulates the hypothalamic-pituitary-thyroid axis (TSH->D2->T3). These inputs plausibly drive beta-adrenergic cAMP-PKA-p38MAPK-CREB signaling and promote PGC-1alpha and uncoupling protein-1 expression, particularly in brown adipose tissue. In parallel, shivering-associated Ca2+ fluxes can activate CaMKII and calcineurin, providing an additional route to increase PGC-1alpha expression. Elevated PGC-1alpha can coactivate nuclear respiratory factors (NRF1/NRF2) and mitochondrial transcription factor A (TFAM) to support mitochondrial biogenesis and oxidative capacity, while inducing antioxidant enzymes (superoxide dismutase, catalase, glutathione peroxidase). Together with estrogen-related receptor alpha (ERRalpha), PGC-1alpha may enhance vascular endothelial growth factor signaling, consistent with angiogenic remodeling. Cold-related metabolic shifts (e.g., increased fatty acid oxidation via CPT1 and PPARalpha/gamma, and fibroblast growth factor 21 secretion) could improve insulin sensitivity and energy expenditure. However, in humans these links are based largely on acute molecular responses, heterogeneous protocols, and indirect evidence; convincing data for increases in mitochondrial content/function and durable health or performance outcomes remain scarce.
CONCLUSION:
We propose a practical dose-response spectrum in which short, progressive immersions may maximize adaptive signaling while minimizing risk, whereas longer or poorly controlled exposures increase the likelihood of hypothermia, arrhythmias, and loss of consciousness. This framework supports hypothesis-driven trials that quantify PGC-1alpha-related outcomes alongside safety endpoints in athletes and clinical populations.