What is the Effect of Cold Water Immersion on Heart Rate Variability in Navy Divers?

Research Paper Title

Diving in the Arctic: Cold Water Immersion’s Effects on Heart Rate Variability in Navy Divers.

Background

Diving close to the Arctic circle means diving in cold water regardless of the time of year. The human body reacts to cold through autonomous nervous system (ANS)-mediated thermoregulatory mechanisms. Diving also induces ANS responses as a result of the diving reflex.

Methods

In order to study ANS responses during diving in Arctic water temperatures, we retrospectively analysed repeated 5-min heart rate variability (HRV) measures and the mean body temperature from dives at regular intervals using naval diving equipment measurement tests in 0°C water. Three divers performed seven dives without physical activity (81-91 min), and two divers performed four dives with physical activity after 10 min of diving (0-10 min HRV recordings were included in the study).

Results

Our study showed a significant increase in parasympathetic activity (PNS) at the beginning of the dives, after which PNS activity decreased significantly (measure 5-10 min). Subsequent measurements (15-20 min and onward) showed a significant increase in PNS activity over time.

Conclusions

Our results suggest that the first PNS responses of the human diving reflex decrease quickly. Adverse effects of PNS activity should be considered on long and cold dives. To avoid concurrent sympathetic (SNS) and PNS activity at the beginning of dives, which in turn may increase the risk of arrhythmia in cold water, we suggest a short adaptation phase before physical activity. Moreover, the researchers suggest it is prudent to give special attention to cardiovascular risk factors during pre-dive examinations for cold water divers.

Reference

Lundell, R.V., Raisanen-Sokolowski, A.K., Wuorimaa, T.K., Ojanen, T. & Parkkola, K.I. (2020) Diving in the Arctic: Cold Water Immersion’s Effects on Heart Rate Variability in Navy Divers. Frontiers in Physiology. doi: 10.3389/fphys.2019.01600. eCollection 2019.

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