Edited by: Sebastien Racinais, Aspetar Hospital, Qatar
Reviewed by: Ashley Paul Akerman, University of Ottawa, Canada; Roy T. H. Cheung, Hong Kong Polytechnic University, Hong Kong
This article was submitted to Elite Sports and Performance Enhancement, a section of the journal Frontiers in Sports and Active Living
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The New Balance Falmouth Road Race held in Falmouth, Massachusetts, U.S. is a short distance race (11.26 km) that is well-known for high rates of exertional heat stroke (EHS). Previous research has documented the increased EHS rates with hotter and more humid weather conditions, yet did not explore the influence of race pacing on EHS risk. In this study, we leverage 15 years of data to investigate if runners who experienced an EHS moderate their average paces based on weather conditions and if there is a difference in average race pace between participants who experienced an EHS and other runners. Results indicate that runners who experience an EHS do not appear to reduce their average pace with increasing WBGT warning flag categories. In addition, runners who suffer an EHS run at a faster average pace than others, even when controlling for age, gender, race performance, and starting time WBGT. This suggests the important role of metabolic heat production as a risk factor of EHS. Since race pacing is a modifiable risk factor, our findings support the need for race organizers to actively encourage runners to adjust race pacing based on weather conditions.
Exertional heat stroke (EHS) becomes a major concern for race day medical service, especially in warm and hot weather races, where a rapid increase in number of medical tent visits is observed (DeMartini et al.,
We studied the interrelationship between meteorological conditions, race pacing, and cases of EHS at the New Balance Falmouth Road Race. The race is 11.26 km in length and is held annually in August in Falmouth, Massachusetts, USA (41.52°N, 70.67°W). Each year, ~10,000 runners, ranging in status from novice to elite, participate in the race.
Data on EHS cases were obtained from medical tent records for 15 years between 2003 and 2018 (no finish times were recorded in 2006). EHS was clinically determined based on a rectal temperature ≥40°C and associated signs of central nervous system dysfunction (e.g., delirium, altered mental status, aggression, hysteria). Only EHS cases where the participant finished the race were included in this analysis. The finish time was obtained for each of these individuals and average pacing was calculated by dividing finish time by race distance (11.26 km). In addition, information on the age, gender, and race status as elite or non-elite were available for both EHS and non-EHS finishers for the years 2014–2018 (New Balance Falmouth Road Race,
Lastly, incidence rates were computed as number of EHS finishers per 1000 finishers for the years 2003–2018, with the exception of 2012 and 2013 when the number of finishers were not available. The number of finishers for 2003–2011 were obtained from published results in DeMartini et al. (
Meteorological data (e.g., dry bulb temperature, dewpoint temperature, and cloud cover) were collected from the nearest available weather observing station located at Otis Air National Guard Base (41.65°N, −70.52°W), which is ~18.8 km from the race start and operated in joint effort between the National Weather Service, the Federal Aviation Administration, and the Department of Defense. Wet bulb globe temperatures (WBGT) were not routinely recorded during race events and were therefore computed from meteorological data using the Heat Stress Adviser (version 2005; Zunis Foundation, Tulsa, OK) software package (Coyle,
The WBGT was classified using the International Institute for Race Medicine (IIRM) heat stress flag color warnings for runners as low (green, <18°C), moderate (yellow, <18–23°C), high (red, 23–28°C), and extremely high (black, >28°C) risk for hyperthermia (Mears and Watson,
All statistical analyses were performed using SPSS (Version 26; IBM Corporation, Aramonk, NY). The relationship between EHS incidence rates and starting time WBGT was assessed both graphically and using regression analysis.
Descriptive statistics (e.g., mean, standard deviation) were used to characterize average race pacing for EHS cases under different flag color warnings. Group differences in race pacing among flag warning categories for faster and slower EHS finishers were determined using one-way ANOVA. Statistical significance was set a priori at an alpha level of ρ <0.05. The Shapiro-Wilk test of normality and Levene's test for equality of variances were used to ensure that conditions of the statistical test were met. For slow EHS finishers, four participants with race finish times over 1:50 were excluded from analysis as these outliers had average paces consistent with walking rather than running.
Finally, a one-way ANCOVA was conducted to compare any difference in average pacing between EHS and non-EHS finishers for the years 2014–2018 while controlling for age, gender, status as elite or non-elite and starting time WBGT. Statistical significance was set a priori at an alpha level of ρ <0.05. Levene's test for equality of variances and normality checks were used to ensure that conditions of the statistical test were met.
A total of 247 participants finished the race and experienced an EHS (243 when the four walkers were excluded) over the 2003–2018 period (
Finisher data and exertional heat stroke incidence and rate per 1,000 runners by year.
2003 | 8,058 | 37 | 4.59 |
2004 | 8,171 | 5 | 0.61 |
2005 | 7,532 | 19 | 2.52 |
2007 | 8,926 | 10 | 1.12 |
2008 | 8,743 | 15 | 1.72 |
2009 | 8,864 | 13 | 1.47 |
2010 | 9,653 | 6 | 0.62 |
2011 | 10,930 | 13 | 1.19 |
2012 | 11 | ||
2013 | 15 | ||
2014 | 11,060 | 17 | 1.54 |
2015 | 10,691 | 38 | 3.55 |
2016 | 10,381 | 16 | 1.54 |
2017 | 10,901 | 22 | 2.02 |
2018 | 11,063 | 10 | 0.90 |
9613.31 | 16.47 | 1.80 | |
1289.74 | 9.66 | 1.16 |
WBGTs were computed at the start of the race (
Start time WBGTs and associated flag color warnings indicated by dashed horizontal lines. No finish times were available for EHS cases in 2006 and WBGT data were excluded from the study.
Relationship between start time WBGT and EHS rate per 1000 finishers. IIRM warning flags for runners are categorized as low (green, <18°C), moderate (yellow, <18–23°C), high (red, 23–28°C), and extremely high (black, >28°C) risk for hyperthermia (Mears and Watson,
Average running paces for 243 EHS finishers were compared based on WBGT warning flag category (
Box and whisker plot of average race pacing among IIRM WBGT warning flag categories (Y is yellow, R is red, and B is black) for faster and slower EHS finishers. The dark line in the box is the median, the top and bottom of the box are 75 and 25 percentiles, respectively, the top and bottom lines are the 90th and 10th percentiles, respectively, and the circles represent outliers.
The average running paces for both EHS and non-EHS finishers (elite and non-elite) were compared for the years 2014–2018. During this period, there were 53,369 non-EHS finishers and 100 EHS finishers (93 non-elite and 7 elite). There is a significant difference in average racing pacing between EHS and non-EHS runners, when controlling for age, gender, race performance (fast vs. slow), and starting time WBGT [
The purpose of this study was to identify if pacing played a role in the incidence of EHS at the New Balance Falmouth Road Race. This race provides an excellent case study because of the high rates of EHS compared with other road races (DeMartini et al.,
It has been speculated that the unusually high EHS rates at Falmouth are related to not only the warm conditions but also the high intensity and greater metabolic heat production produced in this shorter (11.26 km) race compared to longer marathons (DeMartini et al.,
Given that these runners competing at faster average paces may be at higher relative risk for EHS, mitigation measures should be attempted. In athletic settings, there are often external motivation and peer pressure (i.e., competition against teammates, desire to impress peer, a pre-set goal to achieve a personal best) that may push the athletes to continue exercise at an intensity that is unmatched to their physical fitness (Adams et al.,
This is a retrospective study that considered many years of data from the Falmouth Road Race. As such, we did not have detailed health information from race participants (e.g., fitness status, heat-acclimatization status, hydration, or pre-existing medical conditions) that may have influenced the risk for an EHS. A key limitation of our study, then, is that we can only provide an association between race pacing and EHS occurrence but not a cause and effect relationship. Even so, we provide a plausible mechanism linking pacing and EHS, and our findings lend support to the well-established practice of weather-based activity modification.
For future work, we hope to add morphological characteristics in our EHS risk stratification since the rate of metabolic heat production and dissipation is directly influenced by body mass and relative body surface area (Cramer and Jay,
The datasets generated for this study are available on request to the corresponding author.
The studies involving human participants were reviewed and approved by University of Connecticut Institutional Review Board. Written informed consent from the participants' legal guardian/next of kin was not required to participate in this study in accordance with the national legislation and the institutional requirements.
YH, AG, and DC conceived of the presented idea. AG, YH, DC, JJ, and RS contributed to the design and implementation of the research, to the analysis of the results, and to the writing of the manuscript.
Falmouth Road Race, Inc. has donated money to the Korey Stringer Institute but not specifically to conduct this study. Falmouth Road Race, Inc. had no influence over the findings or conclusions of the research. The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.