Cold-Water Immersion Does Not Improve Running Performance During Intensified Training

The aim of this study was to investigate whether daily post-exercise cold-water immersion (CWI) preserves high-intensity running performance and modulates physiological and perceptual stress responses during an eleven-day intensified training period with limited recovery. Seventeen recreational male runners completed an eleven-day program comprising two five-day blocks separated by one rest day. Each session included 30 min of continuous running, one self-regulated maximal 300 m bout, and ten 300 m high-intensity intervals. Participants were assigned to CWI (10 °C for 15 min post-exercise) or control (seated rest). The primary outcome was time to complete the 300 m bout. Secondary outcomes included training output, peak heart rate (HR), rating of perceived exertion, muscle soreness, and plasma activities of creatine kinase (CK) and lactate dehydrogenase (LDH). Performance did not change over time and did not differ between groups (p > 0.05). Training induced time-dependent increases in muscle soreness and CK/LDH levels and a reduction in peak HR (p < 0.05), while training volume was maintained. CWI did not affect these physiological or perceptual responses. Daily CWI did not improve high-intensity running performance or attenuate most physiological stress responses during intensified training, suggesting limited additional benefit under these conditions.