The use of whole-body cryotherapy: time- and dose-response investigation on circulating blood catecholamines and heart rate variability.
Level 2 - randomized trial
Randomized controlled trial
PubMed 32474683 · doi:10.1007/s00421-020-04406-5
What was done
Forty healthy males were randomly assigned to five different temperature groups (-110 °C, -60 °C, -10 °C, and a control temperature of ~24 °C) and completed five whole-body cryotherapy (WBC) sessions over five consecutive days. Cardiac autonomic activity was measured using heart rate variability (HRV) metrics, specifically high-frequency power density (HF), root-mean square of successive R-R interval differences (RMSSD), and LF/HF ratio. Systemic sympathetic activity was assessed via circulating blood catecholamines (plasma norepinephrine).
What was found
Autonomic changes occurred only in the -110 °C condition. Mean weekly RMSSD increased from 48 ± 22 ms pre-WBC to 68 ± 29 ms post-WBC (p < 0.05), and HF increased from 607 ± 692 ms² pre-WBC to 1271 ± 1180 ms² post-WBC (p < 0.05). Plasma norepinephrine increased after the first session at -110 °C from 173 ± 98 ng L⁻¹ to 352 ± 231 ng L⁻¹ (p < 0.01), but the increase after the fifth session was not statistically significant (pre: 161 ± 120 ng L⁻¹ vs. post: 293 ± 245 ng L⁻¹, p = 0.15). No significant autonomic modulation was reported for warmer exposure temperatures.
Why it matters
The findings indicate a temperature threshold (-110 °C) is required to stimulate the autonomic nervous system during WBC, while demonstrating rapid physiological habituation within five daily sessions.
Limits
The study had a small sample size (n = 40 across multiple groups, approximately 8 participants per arm) and included only young, healthy males. It measured surrogate physiological and autonomic markers rather than functional athletic recovery or clinical outcomes, and long-term adaptation beyond five days was not assessed.
Cited by
- supports Norepinephrine levels increase in humans after just two minutes of cold exposure.