3-min whole body cryotherapy/cryostimulation after training in the evening improves sleep quality in physically active men
Authors: Geoffroy Boucard
Benoit Dugué
Olivier Dupuy
Wafa Douzi
Romain Bouzigon
Maxence Tanneau
Journal: European Journal of Sport Science (2019)
Discipline: CLINICAL MEDICINE
Keywords: Cryotherapy; cold exposure; heart rate variability; pain; parasympathetic system
Affiliations: Laboratoire Mobilité Vieillissement Exercice (MOVE)-EA6314, Faculty of Sport Sciences, University of Poitiers, Poitiers, France, Centre de Recherches sur la Cognition et l’Apprentissage (UMR7295), Université de Poitiers and Université François-Rabelais de Tours, Poitiers, France, Laboratoire C3S (EA 4660), Unité de Promotion, de Formation et de Recherche (UPFR) des Sports, Université de Franche Comté, Besançon, France

Abstract:  Exercise training during evening may disturb sleep patterns and hinder recovery process. The present study aimed to examine the effect of whole body cryotherapy (WBC) exposure after training in the evening on sleep quality and night heart rate variability (HRV). A total of 22 physically active men were randomized to undergo either WBC (3-min at -40°C, wind speed of 2.3 m s-1) or passive recovery (control) following an evening training consisting of 25 min of continuous running at 65% of the maximal aerobic speed (MAS) followed by intermittent running at 85% of the MAS. Each night following the training, the number of movements and HRV during sleeping time were recorded. The next morning, subjective sleep quality and perceived pain were assessed using Spiegel questionnaire and a visual analogue scale, respectively. The number of movements during the night following WBC was significantly reduced (p &lt; 0.05) compared with the control condition. Subjective sleep quality following WBC was significantly better than the control group (p &lt; 0.05). During the estimated slow-wave sleep (SWS), the high frequency power (HF) was higher in the WBC group than the control group (p &lt; 0.05), and the low frequency power (LF) and the LF/HF ratio were lower than the control group (p &lt; 0.05). Pain was significantly reduced following WBC compared to the control (p &lt; 0.01). In conclusion, the use of 3-min WBC after training in the evening improves subjective and objective sleep quality in physically active subjects, which may be due to greater pain relief and improved parasympathetic nervous activity during the SWS period. 

Retracted: No

PubPeer comments:
 Recently, a [study] was retracted by authors because they did not obtain an approval from a Comitu00e9 de Protection des Personnes (CPP) for a study related to cryotherapy. In France, prospective studies on cryotherapy are considered as researches in humans and must obtain an approval from a CPP before to start. In this article, the description of the study highlights a prospective research in human. * we examined the impact of 3-min whole body cryotherapy exposure on subjective and objective sleep quality and night HRV analysis following a standardized training session in physically active men. * The study recruited healthy volunteers and performed several interventions. It clearly is a research in humans as described by the French Health Law. This type of study must obtain an approval from a CPP before to start the recruitment of participants. However, the ethics statement is not really clear. It is mentioned that the authors obtained an approval from a local ethics committee but not mentioned if it was a CPP approval.  *They provided their written informed consent, which conformed to the code of ethics of the Declaration of Helsinki. The study was accepted by the local ethics committee. * Considering this point, can the authors clarify and mention if they obtain an approval from a CPP before to obtain the approval? If not, do they seek an approval from a CPP ? In this case, what was the answer of the CPP and what was the reasons the CPP provided to waive the CPP approval ? Providing a copy of the CPP waiver in the supplementary material could help to raise any ethical concerns. ,