We compared the effect of programmed (PFI) and thirst-driven (TDFI) fluid intake on prolonged cycling performance and exercise associated muscle cramps (EAMC). Eight male endurance athletes (26 ± 6 years) completed two trials consisting of 5 h of cycling at 61% $\dot{\mathrm{V}}{\mathrm{O}}_{2\mathrm{peak}}$ followed by a 20 km time-trial (TT) in a randomized crossover sequence at 30 °C, 35% relative humidity. EAMC was assessed after the TT with maximal voluntary isometric contractions of the shortened right plantar flexors. Water intake was either programmed to limit body mass loss to 1% (PFI) or consumed based on perceived thirst (TDFI). Body mass loss reached 1.5 ± 1.0% for PFI and 2.5 ± 0.9% for TDFI (p = 0.10). Power output during the 20 km TT was higher (p < 0.05) for PFI (278 ± 41 W) than TDFI (263 ± 39 W), but the total performance time, including the breaks to urinate, was similar (p = 0.48) between conditions. The prevalence of EAMC of the plantar flexors was similar between the drinking conditions. Cyclists competing in the heat for over 5 h may benefit from PFI aiming to limit body mass loss to <2% when a high intensity effort is required in the later phase of the race and when time lost for urination is not a consideration.

This study aimed to determine if the change in heart rate variability from pre- to post-firefighting is modulated by different work cycles. Thirteen male firefighters underwent two firefighting simulations that comprised two identical 25-minute work bouts intercalated by a passive recovery period of either 20 minutes (T20) or 5 minutes (T5). The square root of the mean squared differences of successive R-R intervals (RMSSD) and aural temperature were measured at rest before (PRE) and after (POST) firefighting simulations. The decrease in RMSSD was different between firefighting simulations (T20: -10 ± 21.2 ms, T5: -19.9 ± 20.9 ms, interaction, P = 0.02). Post-firefighting aural temperature was greater (P = 0.05) in T5 (37.18 ± 0.53°C) than in T20 (36.88 ± 0.49°C). In conclusion, a shorter recovery period of 5 minutes between firefighting work bouts decreases post-firefighting heart rate variability possibly attributed to a lower parasympathetic reactivation and a higher absolute value of body temperature.

Objective: Using a cross-sectional correlational study, the purpose was to quantitatively investigate factors associated to firefighters' food behaviors while on duty at the fire station. Methods: Two hundred and fifty-two (252) firefighters (males, 96%; age, 39 ± 11 years) completed an online questionnaire assessing diet and exploring factors that could be associated to firefighters' food behaviors at the fire station. Results: First regression analysis showed that level of education, years of experience, self-perceived nutrition knowledge, autonomous motivation, and accessibility to unhealthy foods were the best predictors of healthy food score. Second regression analysis revealed that body mass index, autonomous motivation, and meals interrupted by emergency calls were the best predictors of fast-food score. Conclusions: This study highlights the various factors associated with firefighters' food behaviors at the fire station.

Background: Leading sports medicine and nutrition organizations recommend replacing sodium losses during prolonged exercise; however, practical guidance for implementing sodium replacement strategies remains limited. Estimating sodium needs during exercise requires assessment of both whole-body sweat sodium concentration (WBSSC) and sweat rate. Objectives: This study focused on WBSSC by examining its temporal stability, reproducibility, and predictability during prolonged cycling exercise while drinking according to two hydration strategies. Methods: Using a randomized, crossover, counterbalanced design, eight highly trained men completed two 5 h cycling sessions (183 ± 14 W, 30 °C) while consuming fluids either in a programmed (P) or ad libitum (A_L) fashion. Sweat was collected with patches applied on the forearm for ~20 min before sampling, which occurred at ~40, 130, 220, and 290 min. Local sweat sodium concentration was converted to WBSSC using a validated equation. Results: A main effect of time was observed for WBSSC (p < 0.05), with only the 40 min time point differing from later measurements; no condition or interaction effects were detected. The within-trial typical variation in WBSSC was 7.2 mmol·L⁻¹ for P and 6.1 mmol·L⁻¹ for A_L, while the between-trial typical variation was 5.6 mmol·L⁻¹. The WBSSC measured at 40 min predicted mean exercise WBSSC with good precision and moderate stability (y = 0.2738 + 1.3397x, R² = 0.87, standard error of the estimate = 5.4 mmol·L⁻¹, 95% confidence interval slope = 0.82–1.86 mmol·L⁻¹). Conclusions: These findings indicate that during prolonged cycling exercise, WBSSC (1) varies trivially within and between trials; (2) can reasonably be predicted using a single sweat sample and; (3) is not influenced by P or A_L drinking.

Objective: The aim of the study is to measure the association between the physical activity (PA) levels and cardiorespiratory fitness on the firefighters’ cardiac autonomic function at rest at the fire station. Methods: Anthropometry, heart rate variability, fitness, and PA levels were assessed at the fire station in 98 career Québec male firefighters. Results: Partial correlations, adjusted for age, waist circumference, and perceived stress revealed that heart rate and several heart rate variability indices were significantly correlated to estimated maximal oxygen consumption and to high-intensity PA but not to moderate-intensity PA. Conclusions: These results suggest that both cardiorespiratory fitness and high-intensity physical training are related to the cardiac autonomic function of firefighters. Therefore, fire department should promote PA programs to improve physical fitness among firefighters.