We investigated the effect of daily cold water immersion (CWI), during a typical training week, on parasympathetic activity and subjective ratings of well-being.
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.
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.
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.
Hani Al Haddad and Martin Buchheit are with the Université de Picardie Jules Verne Research Laboratory, EA 3300 “Exercise Physiology and Rehabilitation,” Faculty of Sport Sciences, Amiens, France, and with the Sport Science Section, Physiology Unit, Aspire Academy for Sports Excellence, Doha, Qatar. Jonathan Parouty is with Talent Swimming Center, Amiens Métropole Natation, Amiens, France, and with Sport Development and Analysis, Swim Force One Association, Berk, France.