Effect of daily cold water immersion on heart rate variability and subjective ratings of well-being in highly trained swimmers.

PURPOSE: We investigated the effect of daily cold water immersion (CWI), during a typical training week, on parasympathetic activity and subjective ratings of well-being. METHODS: Over two different weeks, eight highly trained swimmers (4 men; 19.6 ± 3.2 y) performed their usual training load (5 d/wk, approx. 21 h/wk). Last training session of each training day was immediately followed by 5 min of seated recovery, in randomized order, with CWI (15°C) or without (CON). Each morning before the first training session (6:30 AM) during the two experimental weeks, subjective ratings of well-being (eg, quality of sleep) were assessed and the R-R intervals were recorded for 5 min in supine position. A vagal-related index (ie, natural logarithm of the square root of the mean of the sum of the squares of differences between adjacent normal R-R intervals; Ln rMSSD) was calculated from the last 3-min segment. RESULTS: Compared with CON, CWI effect on Ln rMSSD was rated as possibly beneficial on day 2 [7.0% (-3; 19)], likely beneficial on day 3 [20.0% (1.5; 43.5)], very likely beneficial on day 4 [30.4% (12.2; 51.6)] and likely beneficial on day 5 [24.1% (-0.4; 54.8)]. Cold water immersion was associated with a likely greater quality of sleep on day 2 [30.0% (2.7; 64.6)], very likely on day 3 [31.0% (5.0; 63.1)] and likely on day 4 [38.6% (11.4; 72.4)] when compared with CON. CONCLUSION: Five minutes of CWI following training can reduce the usual exercise-induced decrease in parasympathetic activity and is associated with improved rating of perceived sleep quality.

Effect of cold water immersion on 100-m sprint performance in well-trained swimmers.

The aim of the present study was to examine the effect of cold water immersion (CWI) on sprint swimming performance in simulated competition conditions. Ten well-trained swimmers (5 males, 5 females; 19.0 +/- 3.9 years) performed two 100-m swimming sprints (S1 and S2) interspersed with a 30-min passive recovery period, during which athletes were randomly assigned to 5 min of CWI (14 degrees C) or an out-of-water control condition (CON 28 degrees C). During tests, sprint times, heart rate (HR), pre- and post-race parasympathetic activity via HR variability (natural logarithm of the square root of the mean of the sum of the squares of differences between adjacent normal R-R intervals; Ln rMSSD) and blood lactate accumulation ([La](ac)) and clearance ([La](cle)) were recorded. Rates of perceived recovery (RPR) and exertion (RPE) were evaluated before and after each sprint. CWI was associated with a 'likely' decrease in swimming performance [1.8% (90% CI 0.2, 3.5)], as well as 'likely' lower peak HR [-1.9% (-3.6, -0.2)]. CWI was also associated with a 'likely' smaller decrease in Ln rMSSD after the first sprint [-16.7% (-30.9, -4.1)]. RPR was 'likely' better [+27.2% (-3.7, 68.0)] following CWI. 'unclear' effects were observed for [La](ac) [+24.7% (-13.4, 79.5)], [La](cle) [-7.6% (-24.2, 12.7)] or RPE [+2.0% (-12.3, 18.5)]. Following CWI, changes in sprint times were 'largely' correlated with changes in peak HR (r = 0.80). Despite a subjective perception of improved recovery following CWI, this recovery intervention resulted in slower swimming times in well-trained athletes swimming in simulated competition conditions.