Jay, Ollie

Objective To develop best-practice recommendations using thermal indices to determine work-to-rest ratios and facilitate further implementation of environmental monitoring for heat safety in secondary school athletics in the United States. Data Sources A narrative review of the current literature on environmental monitoring for heat safety during athletics was conducted by content experts. A list of action-oriented recommendations was established from the narrative review and further refined using the Delphi method. Conclusions Assessment of wet bulb globe temperature at the site of activity and throughout the duration of the event is recommended to assist clinicians and administrators in making appropriate decisions regarding the duration and frequency of activity and rest periods. Activity-modification guidelines should be predetermined and approved by stakeholders and should outline specific actions to be followed, such as the work-to-rest ratio, frequency and timing of hydration breaks, and adjustment of total exercise duration, equipment, and clothing. Furthermore, integration of exertional heat illness injury data with environmental condition characteristics is critical for the development of evidence-based heat safety guidelines for secondary school athletics. Athletic trainers play an essential role in conducting prospective injury data collection, recording onsite wet bulb globe temperature levels, and implementing recommendations to protect the health and safety of athletes.

Heart failure (HF) patients are susceptible to heat strain during exercise, secondary to blunted skin blood flow (SkBF) responses, which may be explained by impaired nitric oxide (NO)-dependent vasodilation. Folic acid improves vascular endothelial function and SkBF through NO-dependent mechanisms in healthy older individuals and patients with cardiovascular disease. We examined the effect of folic acid supplementation (5 mg/day for 6 wk) on vascular function [brachial artery flow-mediated dilation (FMD)] and SkBF responses [cutaneous vascular conductance (CVC)] during 60 min of exercise at a fixed metabolic heat production (300 ẆHprod) in a 30°C environment in 10 patients with HF (New York Heart Association Class I–II) and 10 healthy controls (CON). Serum folic acid concentration increased in HF [preintervention (pre): 1.4 ± 0.2; postintervention (post): 8.9 ± 6.7 ng/ml, P = 0.01] and CON (pre: 1.3 ± 0.6; post: 5.2 ± 4.9 ng/ml, P = 0.03). FMD improved by 2.1 ± 1.3% in HF ( P < 0.01), but no change was observed in CON postintervention ( P = 0.20). During exercise, the external workload performed on the cycle ergometer to attain the fixed level of heat production for exercise was similar between groups (HF: 60 ± 13; CON: 65 ± 20 external workload, P = 0.52). Increases in CVC during exercise were similar in HF (pre: 0.89 ± 0.43; post: 0.83 ± 0.45 au/mmHg, P = 0.80) and CON (pre: 2.01 ± 0.79; post: 2.03 ± 0.72 au/mmHg, P = 0.73), although the values were consistently lower in HF for both pre- and postintervention measurement intervals ( P < 0.05). These findings demonstrate that folic acid improves vascular endothelial function in patients with HF but does not enhance SkBF during exercise at a fixed metabolic heat production in a warm environment.

AbstractHeart failure (HF) patients appear to exhibit impaired thermoregulatory capacity during passive heating, as evidenced by diminished vascular conductance. Although some preliminary studies have described the thermoregulatory response to passive heating inHF, responses during exercise in the heat remain to be described. Therefore, the aim of this study was to compare thermoregulatory responses inHFand controls (CON) during exercise in the heat. TenHF(NYHAclasses I–II) and eightCONwere included. Core temperature (Tc), skin temperature (Tsk), and cutaneous vascular conductance (CVC) were assessed at rest and during 1 h of exercise at 60% of maximal oxygen uptake. Metabolic heat production (Hprod) and the evaporative requirements for heat balance (Ereq) were also calculated. Whole‐body sweat rate was determined from pre–post nude body mass corrected for fluid intake. WhileHprod(HF: 3.9 ± 0.9;CON: 6.4 ± 1.5 W/kg) andEreq(HF: 3.3 ± 0.9;CON: 5.6 ± 1.4 W/kg) were lower (P < 0.01) forHFcompared toCON, both groups demonstrated a similar rise inTc(HF: 0.9 ± 0.4;CON: 1.0 ± 0.3°C). Despite this similar rise inTc,Tsk(HF: 1.6 ± 0.7;CON: 2.7 ± 1.2°C), and the elevation inCVC(HF: 1.4 ± 1.0;CON: 3.0 ± 1.2 au/mmHg) was lower (P < 0.05) inHFcompared toCON. Additionally, whole‐body sweat rate (HF: 0.36 ± 0.15;CON: 0.81 ± 0.39 L/h) was lower (P = 0.02) inHFcompared toCON. Patients withHFappear to be limited in their ability to manage a thermal load and distribute heat content to the body surface (i.e., skin), secondary to impaired circulation to the periphery.