Effects of Swimming at Different Water Temperatures on Muscle and Adipose Tissue Adaptation in Diet-Induced Obese Mice.

BACKGROUND: Obesity is a major global health concern, leading to increased risk of metabolic diseases and mortality. Swimming, as a low-impact exercise, may provide metabolic benefits. However, the influence of water temperature on the metabolic and physiological responses remains underexplored. This study investigated the effects of water temperatures on muscle and adipose tissue adaptations in high-fat diet-induced obese mice. METHODS: Obese mice were subjected to swimming at different water temperatures: 15°C, 25°C, or 32°C. Changes in body and tissue weight, grip strength, exhaustive swimming performance, and key metabolic parameters were assessed. Epididymal fat pads (EFP) and gastrocnemius muscles were collected for histological analyses (muscle fiber composition and adipose tissue remodeling), gene expression (Ucp1, Pgc-1α, Prdm16, Cidea), and western blot analyses (SIRT1-PGC-1α-FNDC5 pathway). RESULTS: Swimming at 25°C and 32°C significantly reduced body weight and EFP weight, improved metabolic profiles and grip strength, whereas cold-water swimming (15°C) enhanced endurance performance. Histological analysis revealed reduced adipocyte size in the 25°C group, accompanied by increased oxidative (Type I) fibers across all swimming groups. Elevated Pgc-1α expression in EFP was particularly prominent at 25°C, and FNDC5 in muscle was most pronounced at 15°C. These findings highlight distinct temperature-dependent metabolic and muscular adaptations during swimming in obese mice. CONCLUSION: Moderate (25°C) and warm (32°C) water temperatures are optimal for reducing obesity-related metabolic dysfunctions and enhancing muscle strength, while cold water (15°C) improves endurance through oxidative muscle adaptation.