The Acute Effect of Warm-Up with Cold Water Immersion upon Calf Raise Performance, Muscle Tension, and Oxygen Saturation

<b>Objectives:</b> This study investigated the acute effects of pre-exercise cold-water immersion (CWI) on performance, muscle oxygen saturation, and mechanical muscle tension during calf raise training. <b>Method:</b> Twenty-four trained individuals (5 females, 19 males) were randomly assigned to either a CWI group (5 min at 10 ± 1 °C) or a non-CWI group (no intervention). Both groups performed three sets of standing calf raises to failure using a standardized protocol. Load lifted, repetitions, and rate of perceived exertion (RPE) were recorded. Muscle oxygenation (SmO₂, total hemoglobin) and mechanical muscle properties (frequency and stiffness) were measured before and after each set. <b>Results:</b> The CWI group showed a significantly greater increase in barbell load from set 1 to set 2 compared to the non-CWI group (from 94.5 ± 18.1 kg to 98.0 ± 18.7 kg, <i>p</i> < 0.01). Repetitions decreased and RPE increased across sets in both groups. The non-CWI group exhibited earlier increases in muscle stiffness and frequency, whereas these responses were delayed in the CWI group. Gastrocnemius SmO₂ increased during the protocol in the non-CWI group only. Total hemoglobin change was greater in the CWI group in set 1. <b>Conclusions:</b> These findings suggest that pre-exercise CWI may acutely enhance performance and delay neuromuscular fatigue without negatively affecting perceived effort.