The use of whole-body cryotherapy: time- and dose-response investigation on circulating blood catecholamines and heart rate variability
Authors: Julien Louis
Marielle Volondat
Dimitri Theurot
Benoit Dugué
Olivier Dupuy
Jean-Robert Filliard
Journal: European journal of applied physiology (2020)
Discipline: CLINICAL MEDICINE
Keywords: Autonomic nervous system; Body temperature; Cryostimulation.
Affiliations: Research Institute for Sport and Exercise Sciences (RISES), Liverpool John Moores University, Byrom Street, Liverpool, L3 3AF, UK. ., Laboratoire MOVE (EA 6314), Faculté des Sciences du Sport, Université de Poitiers, Poitiers, France., Medical Department, French Institute of Sport (INSEP), 11 avenue du tremblay, 75012, Paris, France.

Abstract:  Purpose: A predominance of parasympathetic drive is observed following cold exposure. Such modulation of the autonomic nervous system (ANS) is associated with faster post-exercise recovery. Within this context, whole-body cryotherapy (WBC) has been spreading in sport medicine, though the optimal temperature and frequency are unclear. The aim of this study was to examine the effects of different cryotherapy conditions on the sympathovagal balance. Methods: Forty healthy males were randomly assigned into five different groups (- 110 °C, - 60 °C, - 10 °C, control temperature [≃ 24 °C]) and undertook 5 WBC sessions over 5 consecutive days. Cardiac autonomic activity was assessed through heart rate variability (HRV) using power density of high frequency (HF), root-mean square difference of successive R-R intervals (RMSSD) and sympathovagal balance (LF/HF). Systemic sympathetic activity was assessed via circulating blood catecholamines. Results: Mean weekly RMSSD (pre: 48 ± 22 ms, post: 68 ± 29 ms) and HF (pre: 607 ± 692 ms2, post: 1271 ± 1180 ms2) increased (p &lt; 0.05) from pre to post WBC, only in the - 110 °C condition. A rise in plasma norepinephrine was found after the first - 110 °C WBC session only (pre: 173 ± 98, post: 352 ± 231 ng L-1, p &lt; 0.01); whereas, it was not significant after the 5th session (pre: 161 ± 120, post: 293 ± 245 ng L-1, p = 0.15). Conclusion: These results suggest that one - 110 °C WBC exposure is required to stimulate the ANS. After five daily exposures, a lower autonomic response was recorded compared to day one, therefore suggesting the development of physiological habituation to WBC. 

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 Recently, a [study] was retracted by authors because they did not obtain an approval from a Comitu00e9 de Protection des Personnes (CPP) for a study related to cryotherapy.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. * Forty healthy males were randomly assigned into five different groups (u2212u2009110 u00b0C, u2212u200960 u00b0C, u2212u200910 u00b0C, control temperature [u2243u200924 u00b0C]) and undertook 5 WBC sessions over 5 consecutive days. Cardiac autonomic activity was assessed through heart rate variability (HRV) using power density of high frequency (HF), root-mean square difference of successive Ru2013R intervals (RMSSD) and sympathovagal balance (LF HF). Systemic sympathetic activity was assessed via circulating blood catecholamines. * 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.  *All participants were volunteers and were informed about the study protocol, and their rights according to the Declaration of Helsinki. Participants gave their written informed consent and the study was approved by the local Ethics Committee (Ile-de-France, Paris). * 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. ,