Heat acclimatisation on UK exercise SAIF SAREEA 3

UK Exercise SAIF SAREEA 3 saw components of first Armoured Infantry Brigade conduct kinetic armoured infantry manoeuvres in Oman in temperatures that at times exceeded 50°C. This paper presents the methods of acclimatisation, recreational physical training in the heat, and reacclimatisation training conducted in theatre during this exercise. In order to reduce the risk of heat illness, individuals underwent either validated heat acclimatisation training in accordance with current policy, or adapted training as dictated by musculoskeletal restrictions or job specification. Direction was issued regarding recreational training. There was a theatre medical consensus agreed for the practice of returning soldiers to the exercise after admission to a medical treatment facility due to the effects of heat and data were collated on all LAND (Army) acclimatisation and heat illness presentations. The rates of climatic effect were much lower than expected in the medical estimate based on Exercise SAIF SAREEA 2 and similar exercises. Only five LAND patients fulfilled the in-theatre case definition of exertional heat illness of a deployed LAND forces population at risk of 2550. Zero patients who were returned to the exercise after symptoms associated with climatic exposure were subsequently readmitted with heat illness.

Risk perceptions for exertional heat illnesses in junior cricket in Sri Lanka

ObjectivesExertional heat illnesses (EHI) can occur when sport is played in hot and humid environments, such as those common across Asia. Measures to reduce the risk of EHI are important; however, causal data on EHI occurrence are limited and challenging to capture. To gain an initial understanding of EHI risks, we aimed to assess the risk perceptions of EHI of youth cricketers.MethodsA descriptive cross-sectional survey, comprised of 14 questions on EHI risks, was conducted with 365 Sri Lankan junior male cricketers (age=12.9±0.9 years) who typically play in hot and humid conditions.ResultsFor climate related risks, relative humidity was perceived as having a low risk of EHI compared with ambient temperature. The EHI risk associated with wearing protective gear, as commonly used in cricket, was perceived as low. Most junior cricketers perceived a low level of risk associated with recommended preventive measures such as body cooling and heat-acclimatisation.ConclusionThis is the first study to explore EHI risk perceptions in any sporting context. Young players may not be mindful of all risks. Therefore, leadership and initiative from competition organisers and parents is required to promote countermeasures.

Heart rate variability and plasma nephrines in the evaluation of heat acclimatisation status

Purpose Heat adaptation (HA) is critical to performance and health in a hot environment. Transition from short-term heat acclimatisation (STHA) to long-term heat acclimatisation (LTHA) is characterised by decreased autonomic disturbance and increased protection from thermal injury. A standard heat tolerance test (HTT) is recommended for validating exercise performance status, but any role in distinguishing STHA from LTHA is unreported. The aims of this study were to (1) define performance status by serial HTT during structured natural HA, (2) evaluate surrogate markers of autonomic activation, including heart rate variability (HRV), in relation to HA status. Methods Participants (n = 13) were assessed by HTT (60-min block-stepping, 50% VO2peak) during STHA (Day 2, 6 and 9) and LTHA (Day 23). Core temperature (Tc) and heart rate (HR) were measured every 5 min. Sampling for HRV indices (RMSSD, LF:HF) and sympathoadrenal blood measures (cortisol, nephrines) was undertaken before and after (POST) each HTT. Results Significant (P < 0.05) interactions existed for Tc, logLF:HF, cortisol and nephrines (two-way ANOVA; HTT by Day). Relative to LTHA, POST results differed significantly for Tc (Day 2, 6 and 9), HR (Day 2), logRMSSD (Day 2 and Day 6), logLF:HF (Day 2 and Day 6), cortisol (Day 2) and nephrines (Day 2 and Day 9). POST differences in HRV (Day 6 vs. 23) were + 9.9% (logRMSSD) and − 18.6% (logLF:HF). Conclusions Early reductions in HR and cortisol characterised STHA, whereas LTHA showed diminished excitability by Tc, HRV and nephrine measures. Measurement of HRV may have potential to aid real-time assessment of readiness for activity in the heat.