Resistance training (RT) increases muscle fiber size and induces angiogenesis to maintain capillary density. Cold water immersion (CWI), a common postexercise recovery modality, may improve acute recovery, but it attenuates muscle hypertrophy compared with active recovery (ACT). It is unknown if CWI following RT alters muscle fiber type expression or angiogenesis. Twenty-one men strength trained for 12 wk, with either 10 min of CWI ( n = 11) or ACT ( n = 10) performed following each session. Vastus lateralis biopsies were collected at rest before and after training. Type IIx myofiber percent decreased ( P = 0.013) and type IIa myofiber percent increased with training ( P = 0.012), with no difference between groups. The number of capillaries per fiber increased from pretraining in the CWI group ( P = 0.004) but not the ACT group ( P = 0.955). Expression of myosin heavy chain genes ( MYH1 and MYH2), encoding type IIx and IIa fibers, respectively, decreased in the ACT group, whereas MYH7 (encoding type I fibers) increased in the ACT group versus CWI ( P = 0.004). Myosin heavy chain IIa protein increased with training ( P = 0.012) with no difference between groups. The proangiogenic vascular endothelial growth factor protein decreased posttraining in the ACT group versus CWI ( P < 0.001), whereas antiangiogenic Sprouty-related, EVH1 domain-containing protein 1 protein increased with training in both groups ( P = 0.015). Expression of microRNAs that regulate muscle fiber type (miR-208b and -499a) and angiogenesis (miR-15a, -16, and -126) increased only in the ACT group ( P < 0.05). CWI recovery after each training session altered the angiogenic and fiber type-specific response to RT through regulation at the levels of microRNA, gene, and protein expression.
Keywords: capillaries; microRNA; molecular mechanisms; postexercise recovery; resistance training.