Differences in skin temperature responses during three different (-135°c) whole body cryotherapy exposure durations in elite rugby league players

Abstract

Background
Growing ever popular within elite sports, Whole Body Cryotherapy (WBC) is the therapeutic application of extreme cold air for a short duration. Minimal evidence is available for determining the physiological effects of WBC, including observation of skin surface and core temperature changes, in particular across specific pre-determined regions of interest. This study aimed to investigate the effects of three different (-135°C) whole body cryotherapy exposure durations on skin surface and core body temperatures in a group of elite rugby league players.
Methods and Results
14 male professional first team super league rugby players were exposed to 1, 2 and 3 minutes of WBC at -135°C. Each WBC exposure was separated by seven days, and followed a competitive league fixture. Via ingestion of a core temperature pill, core body temperature was recorded pre, immediately post and 20 minutes post WBC. Non-contact, digital infrared thermal imaging measured skin surface temperature (Tsk). Tsk was measured pre, immediately post and every five minutes post WBC exposure, up to 20 minutes. Regions of interest were defined by attaching wooden markers to specific anatomical landmarks. Four regions of interest were defined; anterior triangle of the neck (A), torso (B), lower abdomen (C) and the back (D).
Significant reductions (p=<0.05) in mean Tsk were noted after each exposure duration. Average Tsk over time demonstrated significant differences (p=<0.05) between pre and immediately post exposure time points, for each exposure. When comparing regions of interest significant differences (p=<0.05) were found in mean Tsk. When comparing average Tsk of lower abdomen with A, B and D, significant differences (p=<0.05) were determined. No significant differences were noted between B and D. No Significant differences were noted in core temperature.
Discussion and Conclusion
In all four regions of interest, Tsk was reduced following all exposure durations of WBC. The effectiveness of WBC in reducing Tsk has been demonstrated in previous studies; in the current study the lowest Tsk recorded was 12.1°C, in the lower abdomen following a 3 minute exposure of WBC. This demonstrates the ability of WBC to achieve skin cooling within a desired therapeutic range, which is a key claim of WBC, as part of a recovery method within elite sport. The pattern of change and differences in average Tsk across C against A, B and D was interesting. In particular vascular shunting to protect vital organs in areas A and B could be a suggestion as to why Tsk differed following WBC exposures. Core temperature did not significantly fluctuate following exposures of WBC. However, a small rise was observed in all exposures, illustrating a relationship with the drop in Tsk, and the body’s ability to maintain the function of vital organs. A phase of rewarming occurred following WBC exposures with post mean Tsk at 20 minutes not reaching pre exposure mean Tsk. Although lower limb Tsk was not measured in this study, these findings may have implications for clinicians deciding when it is safe to return an athlete to functional tasks following WBC, to reduce the risk of potential injury.