Cerebral, cardiac and skeletal muscle stress associated with a series of static and dynamic apnoeas

Trends in competitive freediving accidents

Introduction

Understanding safety issues in competitive freediving is necessary for taking preventive actions and to minimise the risk for the athletes.

Methods

We analysed occurrence of loss of consciousness (LOC) and pulmonary barotrauma (PBt) in various freediving disciplines in 988 competitions over five years (from 2019 to 2023 inclusive), with 38,789 officially registered performances (starts): 26,403 in pool disciplines and 12,386 in depth disciplines.

Results

Average incident rate in competitive freediving (all cases: LOCs plus PBt, 2019-2023) was 3.43% (1,329 incidents / 38,789 starts). The average incident rate of LOC and PBt within five years were 3.31% and 0.38% respectively for all disciplines. Two disciplines present higher risk for LOC: dynamic without fins (DNF) (mean risk ratio (RR) = 1.48, 95% CI, 1.13 to 1.96, P < 0.01) and constant weight without fins (CNF) (mean RR = 2.02, 95% CI, 1.39 to 2.94, P < 0.001). The RR for PBt was not higher in any discipline. The overall risk of all types of incidents (LOC plus PBt) was also higher for DNF (mean RR = 1.55, 95% CI, 1.18 to 2.04, P < 0.01) and CNF (mean RR = 2.80, 95% CI, 1.70 to 5.04, P < 0.001).

Conclusions

The disciplines without fins in the pool (DNF) and at depth (CNF) appear to be the most dangerous in terms of LOC. We may recommend that organisers and safety teams should pay a special attention to no-fin disciplines as most risky for possible LOC.

Stress biomarker changes following a series of repeated static and dynamic apneas in non-divers

PURPOSE

This study examined the magnitude of physiological strain imposed by repeated maximal static and dynamic apneas through assessing a panel of stress-related biomarkers.

METHODS

Eleven healthy men performed on three separate occasions (≥72-h apart): a series of five repeated maximal (i) static (STA) or (ii) dynamic apneas (DYN) or (iii) a static eupneic protocol (CTL). Venous blood samples were drawn at 30, 90, and 180-min after each protocol to determine ischaemia modified albumin (IMA), neuron-specific enolase (NSE), myoglobin, and high sensitivity cardiac troponin T (hscTnT) concentrations.

RESULTS

IMA was elevated after the apnoeic interventions (STA,+86%;DYN,+332%,p ≤ 0.047) but not CTL (p = 0.385). Myoglobin was higher than baseline (23.6 ± 3.9 ng/mL) 30-min post DYN (+70%,38.8 ± 13.3 ng/mL,p = 0.030). A greater myoglobin release was recorded in DYN compared with STA and CTL (p ≤ 0.035). No changes were observed in NSE (p = 0.207) or hscTnT (p = 0.274).

CONCLUSIONS

Five repeated maximal DYN led to a greater muscle injury compared with STA but neither elicited myocardial injury or neuronal-parenchymal damage.