Effects of Ladder-Climbing Resistance Training on Pyruvate Dehydrogenase Activation in Fast-Twitch Flexor Hallucis...

This study examined whether progressive high-load resistance training (RT) modifies the PDH regulatory axis governing glycolysis-derived pyruvate handling in fast-twitch flexor hallucis longus (FHL) muscles.

Male Wistar rats (n = 18) completed a 5-week progressive high-load RT program using a voluntary ladder-carrying model. FHL muscles were obtained either 24 h after the final session (RT-at-rest) or immediately after the final bout (Post-RT). Enzyme activities, metabolite levels, protein expression, and PDH phosphorylation were assessed using biochemical assays and Western blotting.

High-load RT induced significant FHL hypertrophy despite lower body weight and food intake. RT increased the activities of lactate dehydrogenase, citrate synthase, and PDH and elevated total PDH expression (approximately 30%, P < 0.01). PDK4 expression increased, whereas PDK2 and PDP1 remained unchanged. PDH phosphorylation was significantly higher at rest but markedly reduced immediately after exercise, indicating contraction-associated PDH activation. RT also increased markers related to glucose transport, lactate export, and anabolic/energy signaling, whereas PGC-1α and FAT/CD36 expression remained unchanged.

Progressive high-load RT induces metabolic remodeling in fast-twitch muscle characterized by increased PDH abundance, activity, and dynamic phosphorylation regulation. These findings suggest altered PDH-mediated regulation of glycolysis-derived pyruvate metabolism at the muscle level, rather than direct evidence of increased mitochondrial oxidative capacity. PDH regulation may represent a key regulatory interface linking glycolytic metabolism to downstream mitochondrial metabolism in response to progressive high-load RT.