E.L. Reed, E.K. Whittman, T.E. Park, C.L. Chapman, E.A. Larson, B.W. Kaiser, L.N. Comrada, K. Wiedenfeld-Needham, J.R. Halliwill, FACSM, C.T. Minson, FACSM

University of Oregon, Eugene, OR

Cold water immersion (CWI) may provide benefits for both physical (i.e., vascular) and mental (i.e., mood) health similar to exercise. There are limited data for the effects of CWI on peripheral shear stress patterns and using objective measures of mood. PURPOSE: To investigate the effects of an acute bout of CWI on peripheral shear stress and positive and negative affect in healthy, young adults. METHODS: Sixteen healthy adults (age: 23±4; BMI: 22±2 kg/m2; 7 females) completed one 15-min bout of CWI (10.5±0.2°C). Rectal temperature (Tr), heart rate (HR), and mean arterial pressure (MAP) were recorded every 5 min. Mood was assessed with the Positive and Negative Affect Schedule survey at pre-CWI (PRE), during the last min of CWI (CWI), 30 min post-CWI (POST 1) and 3 hours post-CWI (POST 2). Participants were randomized into one of two groups due to the COVID-19 pandemic research restrictions. In group 1, brachial artery ultrasound was completed at pre-CWI, CWI, and POST 1 (n=8). Diameter and blood velocity were recorded for 1 min at each timepoint. Shear stress patterns (total, antegrade, and retrograde), oscillatory shear index (OSI) and forearm vascular conductance (FVC) were calculated. In group 2, venous blood samples were collected at PRE, CWI, POST 1, and POST 2 (n=8). Serum was assayed for cortisol and β-endorphins. Data were analyzed by one-way ANOVA with post-hoc Dunnett’s multiple comparisons. Values are reported as the change from PRE (mean ± SD). RESULTS: At the end of CWI, Tr (-0.4­±0.2°C), HR (-11­±7 bpm), and FVC (-0.32­±0.30 mL•min-1•mmHg-1) were reduced (all p<0.05). At POST 1, Tr (-1.0±0.4°C), HR (-16±7 bpm), total shear (-51.9±49.6 s-1) and FVC (-0.37±0.35 mL•min-1•mmHg-1) were reduced (all p<0.05) but MAP (9±7 mmHg) and OSI (0.08±0.06 au) were elevated (both p<0.02). At POST 2, negative affect (-1­±1 au) was improved and cortisol (-680±595 pg/ml) was reduced (both p<0.04). Positive affect, antegrade shear, retrograde shear, and β-endorphins did not differ across all timepoints of the protocol (p>0.40). CONCLUSION: These data indicate that during CWI there were no changes to shear stress patterns or affect but FVC was reduced compared to pre-immersion. After CWI, total shear stress and FVC were reduced but OSI was elevated 30 minutes post-CWI. Negative affect was mildly improved only at 3 hours post-CWI.

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