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Impact of Weather on Marathon-Running Performance
Abstract
Marathon running performance slows in warm weather conditions, but the quantitative impact of weather has not been established.
To quantify the impact of weather on marathon performance for different populations of runners.
Marathon results and weather data were obtained for the Boston, New York, Twin Cities, Grandma's, Richmond, Hartford, and Vancouver Marathons for 36, 29, 24, 23, 6, 12, and 10 yr, respectively. The race results were broken into quartiles based on the wet-bulb globe temperature (Q1 5.1-10 degrees C, Q2 10.1-15 degrees C, Q3 15.1-20 degrees C, and Q4 20.1-25 degrees C). Analysis of the top three male and female finishers as well as the 25th-, 50th-, 100th-, and 300th-place finishers were compared with the course record and then contrasted with weather.
Marathon performances of top males were slower than the course record by 1.7 +/- 1.5, 2.5 +/- 2.1, 3.3 +/- 2.0, and 4.5 +/- 2.3% (mean +/- SD) for Q1-Q4, respectively. Differences between Q4 and Q1, Q2, and between Q3, and Q1 were statistically different (P < 0.05). The top women followed a similar trend (Q1 3.2 +/- 4.9, Q2 3.2 +/- 2.9, Q3 3.8 +/- 3.2, and Q4 5.4 +/- 4.1% (mean +/- SD)), but the differences among quartiles were not statistically significant. The 25th-, 50th-, 100th-, and 300th-place finishers slowed more than faster runners as WBGT increased. For all runners, equivalence testing around a 1% indifference threshold suggests potentially important changes among quartiles independently of statistical significance.
There is a progressive slowing of marathon performance as the WBGT increases from 5 to 25 degrees C. This seems true for men and women of wide ranging abilities, but performance is more negatively affected for slower populations of runners.
... Among these variables, the ambient temperature significantly influences marathon running performance [3,10]. Concerning the impact of temperatures on marathon running performance, it has been reported that differences between genders [6,9,11] and performance levels of athletes [3,11,12] seem to exist. The influence of temperature has been mainly reported for amateur marathoners [6,13], where increasing temperatures negatively impacted slower runners more than faster runners [3,9]. ...
... In controlled laboratory settings, investigations have highlighted reduced maximal aerobic capacity under elevated temperatures and varying humidity conditions [37]. The impact of humidity on marathon performance has also been explored in previous studies [9,12]. Our findings confirm that a decrease in humidity was associated with a decrease in running performance. ...
... For instance, in the 'Stockholm Marathon,' there was a noteworthy and adverse correlation between rain and the anomaly in marathon finishing times [38]. Interestingly, contrasting these findings, the 'Boston Marathon' witnessed record times accomplished under the influence of drizzle [12]. ...
Extensive research has delved into the impact of environmental circumstances on the pacing and performance of professional marathon runners. However, the effects of environmental conditions on the pacing strategies employed by marathon participants in general remain relatively unexplored. This study aimed to examine the potential associations between various environmental factors, encompassing temperature, barometric pressure, humidity, precipitation, sunshine, cloud cover, wind speed, and dew point, and the pacing behavior of men and women. The retrospective analysis involved a comprehensive dataset comprising records from a total of 668,509 runners (520,521 men and 147,988 women) who participated in the ’Berlin Marathon’ events between the years 1999 and 2019. Through correlations, Ordinary Least Squares (OLS) regression, and machine learning (ML) methods, we investigated the relationships between adjusted average temperature values, barometric pressure, humidity, precipitation, sunshine, cloud cover, wind speed, and dew point, and their impact on race times and paces. This analysis was conducted across distinct performance groups, segmented by 30-minute intervals, for race durations between 2 hours and 30 minutes to 6 hours. The results revealed a noteworthy negative correlation between rising temperatures and declining humidity throughout the day and the running speed of marathon participants in the ’Berlin Marathon.’ This effect was more pronounced among men than women. The average pace for the full race showed positive correlations with temperature and minutes of sunshine for both men and women. However, it is important to note that the predictive capacity of our model, utilizing weather variables as predictors, was limited, accounting for only 10% of the variance in race pace. The susceptibility to temperature and humidity fluctuations exhibited a discernible increase as the marathon progressed. While weather conditions exerted discernible influences on running speeds and outcomes, they did not emerge as significant predictors of pacing.
... The majority of the most popular worldwide sports events (e.g., FIFA World Cup, Summer Olympics, Tour de France, New York Marathon) are held during summer months. Heat, especially without acclimatisation, might impair cardiopulmonary exercise capacity relevantly [1][2][3][4][5][6][7][8][9][10]. Therefore, strategies to overcome heat-induced restrictions of physical attainment are of great interest to professional as well as recreational athletes in regard to peak performance levels. ...
... Data about dehydration due to fluid restriction and assessment of exercise capacity without heat are sparse. The reviews state that moderate weight loss due to fluid restriction would not cause a restriction of exercise capacity [6,7]. This interpretation has to be handled with caution. ...
... Cheuvront [6] refers to five trials studying exercise capacity in a cycle ergometer setting after hypohydration due to fluid restriction but without heat [8][9][10][11][12]. The five studies included a total of only 51 participants (10,8,8,8,7). Some of these studies saw trends for a reduction of exercise capacity [8,11], but no one saw a significant reduction. ...
Background:
Heat induces a thermoregulatory strain that impairs cardiopulmonary exercise capacity. The aim of the current study is to elucidate the effect of isolated dehydration on cardiopulmonary exercise capacity in a model of preparticipating hypohydration.
Methods:
Healthy recreational athletes underwent a standardised fluid deprivation test. Hypohydration was assessed by bioelectrical impedance analysis (BIA) and laboratory testing of electrolytes and retention parameters in the blood and urine. The participants underwent cardiopulmonary exercise testing (CPET) with a cycle ramp protocol. Each participant served as their own control undergoing CPET in a hypohydrated [HYH] and euhydrated [EUH] state.
Results:
Fluid deprivation caused a mild (2%) but significant reduction of body water (38.6 [36.6; 40.7] vs. 39.4 [37.4; 41.5] %; p < 0.01) and an increase of urine osmolality (767 [694; 839] vs. 537 [445; 629] mosm/kg; p < 0.01). Hypohydration was without alterations of electrolytes, serum osmolality or hematocrit. The oxygen uptake was significantly lower after hypohydration (-4.8%; p = 0.02 at ventilatory threshold1; -2.0%; p < 0.01 at maximum power), with a corresponding decrease of minute ventilation (-4% at ventilatory threshold1; p = 0.01, -3.3% at maximum power; p < 0.01). The power output was lower in hypohydration (-6.8%; p < 0.01 at ventilatory threshold1; -2.2%; p = 0.01 at maximum power).
Conclusion:
Isolated hypohydration causes impairment of workload as well as peak oxygen uptake in recreational athletes. Our findings might indicate an important role of hypohydration in the heat-induced reduction of exercise capacity.
... Runner's demographics, environmental conditions [1][2][3], training status [4,5], time of day [6], sunlight exposure [7,8], wind [9], and perceptual comfort [10] are some of the myriad of factors that could influence marathon performance. In particular, marathon performance suffers as temperature rises, especially if held in hot and humid climates [1,2,11]. ...
... Runner's demographics, environmental conditions [1][2][3], training status [4,5], time of day [6], sunlight exposure [7,8], wind [9], and perceptual comfort [10] are some of the myriad of factors that could influence marathon performance. In particular, marathon performance suffers as temperature rises, especially if held in hot and humid climates [1,2,11]. Furthermore, the physiological challenge of running a marathon is vastly different than running shorter distance races [12]. ...
... Climatic conditions can influence marathon performance [1][2][3]. The impact of temperature on marathon runners can be ascertained through measurements of dry bulb temperature (T db ), wet bulb temperature (T wb ), dewpoint temperature (T d ), and wet bulb globe temperature (WBGT). ...
We examined marathon performance of the same group of runners in relation to small changes in dry bulb temperature (Tdb) and wet bulb temperature (Twb) across 3 consecutive y, and investigated whether performance was poorer during an evening marathon compared with morning marathons. Marathon results were obtained from the 2017, 2018, and 2019 Standard Chartered Singapore Marathons. Tdb, Twb, Td, relative humidity, and absolute humidity were gathered for each marathon. K-means clustering and linear regressions were performed on 610 runners who participated in all three marathons. Analysis of the 610 runners’ marathon performance was contrasted with Tdb and Twb. Linear regressions were also performed on 190 runners filtered by percentile, yielding similar results. For clusters with similar Tdb from all runners K-means clustering, an increase in mean Twb by 1.5°C coincided with an increase in finishing time by 559 s (9.3 min) (p < 0.033). Twb hinders marathon performance more than Tdb, with each percentage rise in Tdb and Twb resulting in an increase in net time by 7.6% and 39.1%, respectively (p < 0.025). Male and female runners’ response to Tdb and Twb changes were similar (overlap in 95% confidence intervals for the respective regression coefficients). In conclusion, small variations in environmental parameters affected marathon performance, with Twb impairing marathon performance more than Tdb. Marathon performance was likely better in the morning than evening, possibly due to time of day differences, along with unfavorable Tdb that superseded training effects and the effects of lower Twb.
... Commonly, elite marathon runners' competition results were obtained at different marathon races with different meteorological conditions, which are characterized by variables such as ambient temperature, atmospheric pressure, relative humidity and solar radiation [6][7][8][9][10][11][15][16][17][18] . Approaches used in existing studies conventionally focus on the results and weather conditions of the marathon events at certain locations (analogous to Eulerian representation of fluid dynamics), yet runners participated in these events that held at the same places usually differ greatly across time 9,17,18 , leading to substantially uncertain conclusions. ...
... When it rises beyond 15°C, MFT sharply increases by 0.39 and 0.71 min°C −1 in average with ambient temperature for men and women athletes, respectively. Such a nonlinear relationship is different from those reported previously using Eulerian representation 6,20 , which show that the MFT increases monotonously as ambient temperature rises for all temperatures and for both men and women athletes. Moreover, these previous reports show that the MFT increases by~0.2 and 0.3 min°C −1 in average when ambient temperature rises from 15 to 25°C for men and women 6,20 , respectively, substantially smaller than the current 0.38 and 0.70 min°C −1 . ...
Meteorological conditions exert influences on sport performances via complex processes. Previous studies conventionally investigate the effects of weather conditions on marathon performance by following events held at the same places, which brings large uncertainties due to the changed participants. Via following each athlete to eliminate these uncertainties, we show that elite athletes’ marathon-running performance tends to monotonically worsen as ambient temperature rises except when it is extremely cold based on the best 16 athletes from each of the sex continents. It worsens by 0.56 (0.39 for men and 0.71 for women) min/°C when it rises beyond 15 °C. Theoretical analysis based on global marathon performance and weather observation datasets shows that more than half of this effect is mediated by reduced oxygen partial density as warmer temperature expands air and increases vapor pressure for both the men and women athletes, which is confirmed by the methods of Baron–Kenny. This atmospheric thermodynamic mechanism has not been emphasized previously. We also show that world-top athletes’ marathon performance approximately linearly worsens as ambient pressure decreases and slightly worsens as relative humidity rises if not extremely wet. These results substantially differ from the previous ones following the events instead of each athlete. Multi-variable changes in climate system are projected to slow Olympic marathon athletes by 2.51 and 1.06 min by the end of the 21 st century in relative to 2020 under the high and intermediate emission scenario, respectively. Therefore, future progression of marathon performance is likely to be substantially slowed or even halted by climate changes without efficient greenhouse gas mitigation.
... Prolonged exercise in a hot (H) environment [ambient temperature (T a ) ≥ 25 • C] increases skin and core body (T core ) temperatures and induces extreme disturbances to homeostasis, such as increases in heart rate (HR) and cardiac output to adequately perfuse active skeletal muscle to support metabolism while simultaneously perfusing the skin to sustain heat loss (SAWKA et al., 2011). Therefore, environmental heat stress and muscle metabolic heat production can interact synergistically to increase T core , accelerate fatigue, and degrade endurance performance (Ely et al., 2007;Tatterson et al., 2000). In contrast, the most critical intervention to alleviate heat strain and optimize endurance performance is heat acclimation (HA) training, which is developed following exposure to an H environment during exercise for 1-2 weeks (Pryor et al., 2019;Racinais et al., 2015). ...
... It has been extensively shown that acute exposure to an H environment has an ergolytic effect on endurance performance (Ely et al., 2007;Guy et al., 2015;Macaluso et al., 2011;Maia-Lima et al., 2017). GUY et al. (2015) have shown that marathon running exhibited the most considerable performance impairment in the heat, with a mean reduction of ~3 % for males and females. ...
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This study investigated the impact of long-term heat acclimation (HA) training on mouse thermoregulation, metabolism, and running performance in temperate (T) and hot (H) environments. Male Swiss mice were divided into 1) Sedentary (SED) mice kept in T (22 °C; SED/T), 2) Endurance Trained mice (ET, 1 h/day, 5 days/week, 8 weeks, 60 % of maximum speed) in T (ET/T), 3) SED kept in H (32 °C; SED/H), and 4) ET in H (ET/H). All groups performed incremental load tests (ILT) in both environments before (pre-ET) and after four and eight weeks of ET. In the pre-ET period, H impaired (∼30 %) performance variables (maximum speed and external work) and increased (1.3 °C) maximum abdominal body temperature compared with T. In T, after four weeks, although ET/H exercised at a lower (∼30 %) absolute intensity than ET/T, performance variables and aerobic power (peak oxygen uptake, VO2peak) were similarly increased in both ET groups compared with SED/T. After eight weeks, the external work was higher in both ET groups compared with SED/T. Only ET/T significantly increased VO2peak (∼11 %) relative to its pre-ET period. In H, only after eight weeks, both ET groups improved (∼19 %) maximum speed and reduced (∼46 %) post-ILT blood lactate concentrations compared with their respective pre-ET values. Liver glycogen content increased (34 %) in both ET groups and SED/H compared with SED/T. Thus, ET/H was performed at a lower absolute intensity but promoted similar effects to ET/T on metabolism, aerobic power, and running performance. Our findings open perspectives for applying HA training as part of a training program or orthopedic and metabolic rehabilitation programs in injured or even obese animals, reducing mechanical load with equivalent or higher physiological demand.
... suggests that higher temperatures may hurt performance. This is in line with what [17] found, which is that too much heat can hurt performance because it causes more thermal stress and dehydration. ...
p>This case study examines the use of wearable technology to monitor physiological and performance metrics during a 100+ km pilgrimage on the Camino de Santiago. The subject, a 34-year-old female amateur triathlete recovering from an ankle injury, used a Garmin Enduro device to track key data over five days. The study focuses on heart rate, speed, cadence, caloric expenditure, and environmental factors, shedding light on how wearable devices can provide valuable insights into endurance performance. Correlation analysis highlights significant relationships between physical performance and physiological markers, offering a deeper understanding of how such technology can enhance both athletic performance and the overall pilgrimage experience.</p
... led to better performances [16]. In marathon running, performance progressively slowed down with increasing air temperature, especially for slower [17] and older [18] runners. Regarding triathlon, an actual study investigating the Olympic distance triathlon showed differences between the split disciplines and the sexes regarding the ambient temperatures. ...
Background
The IRONMAN® (IM) triathlon is a popular multi-sport, where age group athletes often strive to qualify for the IM World Championship in Hawaii. The aim of the present study was to investigate the location of the fastest IM racecourses for age group IM triathletes. This knowledge will help IM age group triathletes find the best racecourse, considering their strengths and weaknesses, to qualify.
Objective
To determine the fastest IM racecourse for age group IM triathletes using descriptive and predictive statistical methods.
Methods
We collected and analyzed 677,702 age group IM finishers’ records from 228 countries participating in 444 IM competitions held between 2002 and 2022 across 66 event locations. Locations were ranked by average race speed (performance), and countries were sorted by number of records in the sample (participation). A predictive model was built with race finish time as the predicted variable and the triathlete’s gender, age group, country of origin, event location, average air, and water temperatures in each location as predictors. The model was trained with 75% of the available data and was validated against the remaining 25%. Several model interpretability tools were used to explore how each predictor contributed to the model’s predictive power, from which we intended to infer whether one or more predictors were more important than the others.
Results
The average race speed ranking showed IM Vitoria-Gasteiz (1 race only), IM Copenhagen (8 races), IM Hawaii (18 races), IM Tallinn (4 races) and IM Regensburg (2 races) in the first five positions. The XG Boost Regressor model analysis indicated that the IM Hawaii course was the fastest race course and that male athletes aged 35 years and younger were the fastest. Most of the finishers were competing in IM triathlons held in the US, such as IM Wisconsin, IM Florida, IM Lake Placid, IM Arizona, and IM Hawaii, where the IM World Championship took place. However, the fastest average times were achieved in IM Vitoria-Gasteiz, IM Copenhagen, IM Hawaii, IM Tallin, IM Regensburg, IM Brazil Florianopolis, IM Barcelona, or IM Austria with the absolutely fastest race time in IM Hawaii. Most of the successful IM finishers originated from the US, followed by athletes from the UK, Canada, Australia, Germany, and France. The best mean IM race times were achieved by athletes from Austria, Germany, Belgium, Switzerland, Finland, and Denmark. Regarding environmental conditions, the best IM race times were achieved at an air temperature of ∼27°C and a water temperature of ∼24°C.
Conclusions
IM age group athletes who intend to qualify for IM World Championship in IM Hawaii are encouraged to participate in IM Austria, IM Copenhagen, IM Brazil Florianopolis, and/or IM Barcelona in order to achieve a fast race time to qualify for the IM World Championship in IM Hawaii where the top race times were achieved. Most likely these races offer the best ambient temperatures for a fast race time.
... Allerdings bietet Training unter kalten Temperaturen potenzielle Vorteile, darunter eine gesteigerte Leistungsfähigkeit im Ausdauersport, bei ca. 5°C [15] oder eine Schonung der Herzarbeit durch eine erhöhte Ausschüttung von Serotonin bei Kälte [26]. Trotz dieser Erkenntnisse fehlen bisher Studien, die den Einfluss von Kälte oder auch von Hitze auf miRNAs näher analysieren. ...
Zusammenfassung
In den vergangenen Jahren hat sich die Forschung verstärkt der Identifizierung von MicroRNAs (miRNAs) als Biomarker gewidmet. Auch die physiologischen Anpassungen an körperliche Ausdauerbelastungen wurden in diesem Kontext untersucht. miRNAs sind kleine nichtkodierende RNAs, die eine Schlüsselrolle bei der posttranskriptionellen Genregulation spielen. Diese kurze Übersichtsarbeit gibt einen Überblick über die Grundlagen der miRNAs, ihre biogenetischen Wege und ihre Funktionen sowie aktuelle Erkenntnisse über ihre Rolle bei der Anpassung an Ausdauertraining. Die Forschung zeigt, dass miRNAs, die im Blut und anderen Körperflüssigkeiten zirkulieren, als Reaktion auf sportliche Betätigung in spezifischen Mustern exprimiert werden. Diese Veränderungen sind abhängig von der Art (z. B. anaerobe oder aerobe Belastung, Ausdauer- vs. Krafttraining), Intensität und Dauer des Trainings. Darüber hinaus gibt es Hinweise darauf, dass miRNAs geschlechtsspezifische Reaktionen auf körperliche Belastungen zeigen. Die Erkenntnisse über miRNAs als Biomarker bieten nicht nur Einblicke in die Mechanismen der Trainingsanpassung, sondern könnten auch praktische Anwendungen in der präventiven Gesundheitsförderung und im betrieblichen Gesundheitsmanagement finden. Langzeitstudien und weitere Forschung sind jedoch erforderlich, um die genauen Zusammenhänge und das Potenzial von miRNAs als therapeutische Ziele vollständig zu verstehen.
... Heat stress affects several parameters vital for exercise endurance, leading to performance impairment in prolonged events [10,24,39]. Athletes participating in these events frequently face considerable thermoregulatory strain, as they must maintain high-intensity exercise for extended periods under high heat stress [42,52,58]. ...
We previously developed the FAME Lab PHS software (PHSFL), a free offline software to calculate the predicted heat strain for a group of individuals based on the ISO 7933. The objectives of this study were to: upgrade the PHSFL from an offline (desktop-version) tool to a web-based platform, as well as assess its validity in recreational athletes in different forms of exercise and across various temperature recording methodologies and environmental conditions. The web PHSFL was developed as browser-based software developed using HTML, CSS, and JavaScript, and included several updates from the previous offline version. Its validity was assessed in 83 healthy non-smoking males and females during rest, exercise, and post-exercise recovery in 165 trials (cycling: 97; running: 68). Trials were performed in an environmental chamber under varying environmental conditions: 19.1 to 40.6 °C air temperature, 30.0% to 60.0% relative humidity, 0.1 to 0.5 m/s wind speed, and 0 or 800 W/m2 solar radiation. Comparison of actual vs. predicted core body temperature showed 0.85 Willmott’s Index of Agreement, 0.76 (P < 0.001) correlation coefficient, and 95% limits of agreement of 0.16 ± 0.83 °C (mean difference ± 95% limits). Results for rectal temperature showed 0.79 Willmott’s Index of Agreement, 0.68 (P < 0.001) correlation coefficient, and 95% limits of agreement of 0.18 ± 0.76 °C. Results for skin temperature showed 0.77 Willmott’s Index of Agreement, 0.75 (P < 0.001) correlation coefficient, and 95% limits of agreement of − 0.24 ± 2.28 °C. We conclude that the web PHSFL provides acceptably accurate predictions of core body temperature and skin temperature to be used as indicators of physiological heat strain.
... First, trainees can be educated to recognize that despite their best efforts, it will be impossible in hot and humid conditions for them to replicate their best performance from cool or temperate conditions and that they should adjust their pace (and performance expectations) accordingly. 37 Second, the role of acclimatization should also be emphasized in education regarding EHS prevention. Indeed, two of the cases outlined above involved Soldiers who had arrived at Fort Moore from cooler areas of the country less than one week prior to commencing their training. ...
Exertional heat stroke (EHS) is a medical emergency characterized by elevated body temperature and central nervous system dysfunction, and it can include dizziness, confusion and loss of consciousness, as well as long-term organ and tissue damage. EHS is distinct from classic, or passive, heat stroke and is most commonly observed during intense physical activity in warfighters, athletes, and laborers. EHS is an ongoing non-combat threat that represents a risk to both the health and readiness of military personnel. Potential risk factors and their mitigation have been the subject of investigation for decades. One risk factor that is often mentioned in the literature, but not well quantified, is that of individual motivation to excel, wherein highly trained military personnel and athletes exert themselves beyond their physiological limits because of a desire to complete tasks and goals. The motivation to excel in tasks with high standards of achievement, such as those within elite military schools, appears to create an environment in which a disproportionately high number of exertional heat illness casualties occur. Here, we review existing biomedical literature to provide information about EHS in the context of motivation as a risk factor and then discuss five cases of EHS treated at Martin Army Community Hospital at Fort Moore, GA, from 2020 to 2022. In our discussion of the cases, we explore the influence of motivation on each occurrence. The findings from this case series provide further evidence of motivation to excel as a risk factor for EHS and highlight the need for creative strategies to mitigate this risk.
... There has been a body of work establishing the effects of weather and environmental conditions on running performances, particularly in marathons [Suping et al., 1992, Ely et al., 2007, Vihma, 2010, Knechtle et al., 2019, Berke, 2019, Weiss et al., 2022. While most focus on effects of high temperatures and humidity, not relevant to cross country running in the North East of England, Knechtle et al. [2019] investigated performances in the Boston marathon and found significant negative effects of windspeed and rainfall. ...
Cross country running races are different to track and road races in that the courses are not typically accurately measured and the condition of the course can have a strong effect on the finish times of the participants. In this paper we investigate these effects by modelling the finish times of all participants in 28 cross country running races over 5 seasons in the North East of England. We model the natural logarithm of the finish times using linear mixed effects models for both the senior men's and senior women's races. We investigate the effects of weather and underfoot conditions using windspeed and rainfall as covariates, fit distance as a covariate, and investigate the effect of time via the season of the race, in particular investigating any evidence of a pre- to post-Covid effect. We use random athlete effects to model the participant to participant variability and identify the most difficult courses using random course effects. The statistical inference is Bayesian. We assess model adequacy by comparing samples from the posterior predictive distribution of finish times to the observed distribution of finish times in each race. We find strong differences between the difficulty of the courses, effects of rainfall in the month of the race and the previous month to increase finish times and an effect of increasing distance increasing finish times. We find no evidence that windspeed affects finish times.
... This study explored that master runners (men aged ≥65 years and women aged ≥45 years) may not yet have reached the limits of marathon performance (Lepers and Cattagni, 2012). A reference by Matthew, comprising 60 citations in our dataset, indicates that marathon running tends to decelerate in warm weather (Ely et al., 2007). The remaining references predominantly examine various aspects of marathon performance, including the impact of factors such as body composition, training techniques, pacing strategies, gender differences, and temperature regulation. ...
Background: When marathon runners break the 2-h barrier at the finishing line, it attracts global attention. This study is aimed to conduct a bibliometric analysis of publications in the field of marathon running, analyze relevant research contributors, and visualize the historical trends of marathon performance research over the past 15 years.
Methods: On 8 December 2023, we extracted high-quality publication data from the Web of Science Core Collection spanning from 1 January 2009 to 30 November 2023. We conducted bibliometric analysis and research history visualization using the R language packages biblioshiny, VOSviewer, and CiteSpace.
Results: A total of 1,057 studies were published by 3,947 authors from 1,566 institutions across 63 countries/regions. USA has the highest publication and citation volume, while, the University of Zurich being the most prolific research institution. Keywords analysis revealed several hotspots in marathon research over the past 3 years: (1) physiology of the elite marathon runners, (2) elite marathon training intensity and pacing strategies, (3) nutritional strategies for elite marathon runners, (4) age and sex differences in marathon performance, (5) recovery of inflammatory response and muscle damage.
Conclusion: This study presents the first comprehensive bibliometric analysis of marathon performance research over the past 15 years. It unveils the key contributors to marathon performance research, visually represents the historical developments in the field, and highlights the recent topical frontiers. The findings of this study will guide future research by identifying potential hotspots and frontiers.
... Elite athletes must also consider time efficiency when choosing event preparation amongst their demanding training and performance schedules. Despite the addition of valuable material in recent studies about this neglected field [3,4] , it is well acknowledged that endurance activities are often hindered by high temperatures [1,2] . The most probable mechanism for this effect is a comprehensive thermoregulatory response that occurs when exposed to heat. ...
... Prominent examples include the FIFA world cup in Brazil (2014), the Olympic games in Beijing (2008), Rio de Janeiro (2016), and Tokyo (2021), along with the World Athletics Championships in Beijing (2015) and Doha (2019). It is well-documented that increasing ambient temperatures and/or humidity elevates the risk of heat-related injuries and impair exercise performance [7,12,14,27,42]. Notably, recent work indicate that athletes with a history of exertional heat illnesses may be more susceptible to in-race medical events [42]. ...
Heat acclimation (HA) is regarded as the most important countermeasure to protect athlete health and performance when exercising in hot ambient conditions. HA involves passive or exercise heat stress applied intentionally to increase sweating, core temperature, and skin temperature. However, these responses can lead to significant physiological stress, increasing the risk of accumulated fatigue and overreaching. Post-exercise cooling is an effective strategy to restore neuromuscular function and perceptive recovery following hyperthermia-induced fatigue. However, the influence of post-exercise cooling on heat adaptation remains largely unexplored. This review discusses the potential impact of this recovery modality on heat adaptation. Studies investigating the interaction between hot and cold exposures in the context of thermal adaptation were reviewed. The examined literature collectively indicates: (1) no impairments in heat adaptation when cold exposures did not interfere with the physiological responses attained during the heat stress, (2) marginal compromises in thermal impulse during heat stress did not diminish the magnitude of heat adaptation, and may be compensated through enhanced absolute training intensity (3) while substantial cooling during heat stress can potentially impair sudomotor adaptations to HA, it is reasonable to expect no impairments in this context as recovery-based cooling does not influence the physiological responses garnered during heat stress. It is acknowledged that this conclusion is based on exploratory findings, as direct data on the effects of recovery cooling interventions on heat adaptations are currently lacking.
... There are studies that individual performance depends on endogenous factors such as anthropometric, genetic and physiological characteristics [9,10] and environmental factors that affect all athletes [11][12][13]. In this regard, it is of interest to observe the athletes who are engaged in marathon running [14]. ...
It is well known that only man is capable of endurance running and in this sense he has no equal among animals. Why do other animals have us beat over short distances, but are not able to run long distances as long as humans? There are different answers. Walking upright has allowed us to become some of the best distance runners in the world, but at the expense of speed. It is also believed that to run long distances on the African savannah man needed to have an effective cooling system and it is believed that man has developed one. Firstly, heat exchange improved due to the disappearance of fur. Secondly, humans learned to sweat intensively. They also attach importance to the diet and the lifestyle. There are other answers, but they have little relevance to the question discussed here. Can the above answers be considered exhaustive? We believe that there is another important factor unique to man, which ultimately allowed him to occupy the top of the food chain. This factor is the peculiarity of the heat-conducting ability of the human body. Man became a good long-distance runner because among animals he has the most highly heat-conducting body, which allowed him to effectively dissipate excess heat outside the body.
... Similar patterns have been reported for the full marathon distance (Berndsen, Lawlor, & Smyth, 2020;Deaner, Carter, Joyner, & Hunter, 2015;March, Vanderburgh, Titlebaum, & Hoops, 2011;Smyth, 2021). On the full marathon distance, Ely, Cheuvront, Roberts, and Montain (2007) investigated the impact of weather and temperature and found trends towards slowing with increased wet-bulb globe temperature. Trubee, Vanderburgh, Diestelkamp, and Jackson (2014) found that for non-elite full marathon runners, female runners pace better than male, and that this was magnified in peak temperature. ...
The Gothenburg Half Marathon is one of the world’s largest half marathon races with over 40 000 participants each year. In order to reduce the number of runners risking over-straining, injury, or collapse, we would like to provide runners with advice to appropriately plan their pacing. Many participants are older or without extensive training experience and may particularly benefit from such pacing assistance. Our aim is to provide this with the help of machine learning. We first analyze a large publicly available dataset of results from the years 2010 - 2019 (n = 423 496) to identify pacing patterns related to age, sex, ability, and temperature of the race day. These features are then used to train machine learning models for predicting runner’s finish time and to identify which runners are at risk of making severe pacing errors and which ones seem set to pace well. We find that prediction of finish time improves over the current baseline, while identification of pacing patterns correctly identifies over 70% of runners at risk of severe slowdowns, albeit with many false positives.
... In competitive road cycling, elite cyclists can experience substantial thermal strain, with peak core temperatures (T core ) exceeding 40°C [1]. It is well documented that hyperthermia elevates the risk of heat-related injuries [2] and impairs exercise performance [3][4][5]. Appropriate heat mitigation strategies are thus necessary to safeguard the health and safety of athletes constantly during training and competing in hot environmental conditions [6,7]. ...
This study compared the effects of precooling via whole-body immersion in 25°C CO2-enriched water (CO2WI), 25°C unenriched water (WI) or no cooling (CON) on 10-km cycling time trial (TT) performance. After 30 min of precooling (CO2WI, CON, WI) in a randomized, crossover manner, 11 male cyclists/triathletes completed 30-min submaximal cycling (65%VO2peak), followed by 10-km TT in the heat (35°C, 65% relative humidity). Average power output and performance time during TT were similar between conditions (p = 0.387 to 0.833). Decreases in core temperature (Tcore) were greater in CO2WI (-0.54 ± 0.25°C) than in CON (-0.32 ± 0.09°C) and WI (-0.29 ± 0.20°C, p = 0.011 to 0.022). Lower Tcore in CO2WI versus CON was observed at 15th min of exercise (p = 0.050). Skin temperature was lower in CO2WI and WI than in CON during the exercise (p < 0.001 to 0.031). Only CO2WI (1029 ± 305 mL) decreased whole-body sweat loss compared with CON (1304 ± 246 mL, p = 0.029). Muscle oxygenation by near-infrared spectroscopy (NIRS), thermal sensation, and thermal comfort were lower in CO2WI and WI versus CON only during precooling (p < 0.001 to 0.041). NIRS-derived blood volume was significantly lower in CO2WI and WI versus CON during exercise (p < 0.001 to 0.022). Heart rate (p = 0.998) and rating of perceived exertion (p = 0.924) did not differ between conditions throughout the experiment. These results suggested that CO2WI maybe more effective than WI for enhanced core body cooling and minimized sweat losses.
... Along these lines of cool environments and thereby cooler muscle temperatures, it is well known that the fastest endurance runs are recorded with lower ambient temperatures around 5-10°C (11), whereas progressively slower times that occur in higher temperatures are related to central factor-mediated fatigue. Interestingly, previous research has shown that even sport climbing performance, which relies dominantly on localized finger flexor endurance capacity, was greater at an ambient temperature of 10°C than during a thermoneutral condition (24°C) (18), showing that localized mechanisms are responsible for performance enhancement with respect to thermoneutral conditions as well. ...
Baláš, J, Kodejška, J, Procházková, A, Knap, R, and Tufano, JJ. Muscle cooling before and in the middle of a session: there are benefits on subsequent localized endurance performance in a warm environment. J Strength Cond Res XX(X): 000–000, 2023—Localized cold-water immersion (CWI) has been shown to facilitate recovery in the middle of a session of exhaustive repeated forearm contractions. However, it has been suggested that these benefits may be attributed to “precooling” the muscle before an activity, as opposed to cooling a previously overheated muscle. Therefore, this study aimed to determine how precooling and mid-cooling affects localized repeated muscular endurance performance in a warm environment. Nineteen subjects completed a familiarization session and 3 laboratory visits, each including 2 exhaustive climbing trials separated by 20 minutes of recovery: PRE CWI (CWI, trial 1; passive sitting [PAS], trial 2); MID CWI (PAS, trial 1; CWI, trial 2); and CONTROL (PAS, trial 1; PAS, trial 2). Climbing trial 1 in PRE CWI was 32 seconds longer than in CONTROL ( p = 0.013; d = 0.46) and 47 seconds longer than in MID CWI ( p = 0.001; d = 0.81). The time of climbing trial 2 after PAS (PRE CWI and CONTROL) was very similar (312 vs. 319 seconds) irrespective of the first trial condition. However, the time of the second trial in MID CWI was 43 seconds longer than in PRE CWI ( p < 0.001; d = 0.63) and 50 seconds longer than in CONTROL ( p < 0.001; d = 0.69). In warm environments, muscle precooling and mid-cooling can prolong localized endurance performance during climbing. However, the effectiveness of mid-cooling may not be as a “recovery strategy” but as a “precooling” strategy to decrease muscle temperature before subsequent performance, delaying the onset of localized heat-induced neuromuscular fatigue.
... This performance decrement extends to military populations [4][5][6], who are expected to complete physical work whilst wearing protective clothing and equipment, which reduces their evaporative heat loss capacity [7,8] and increases their metabolic rate and, therefore, heat production [9]. The increase in thermal strain associated with exercise or work performed in the heat hinders aerobic exercise performance [3,[10][11][12] due to alterations in the cardiovascular, central nervous system and skeletal muscle function [13], as well as heightening the risk of exertional heat illness [14,15]. Consequently, strategies to mitigate the adverse effects of thermal strain on performance and heat illness risk in sporting and military contexts have been developed, with a key physiological intervention being heat acclimation/acclimatisation [16,17]. ...
Background
Athletes and military personnel are often expected to compete and work in hot and/or humid environments, where decrements in performance and an increased risk of exertional heat illness are prevalent. A physiological strategy for reducing the adverse effects of heat stress is to acclimatise to the heat.
Objective
The aim of this systematic review was to quantify the effects of relocating to a hotter climate to undergo heat acclimatisation in athletes and military personnel.
Eligibility Criteria
Studies investigating the effects of heat acclimatisation in non-acclimatised athletes and military personnel via relocation to a hot climate for < 6 weeks were included.
Data Sources
MEDLINE, SPORTDiscus, CINAHL Plus with Full Text and Scopus were searched from inception to June 2022.
Risk of Bias
A modified version of the McMaster critical review form was utilised independently by two authors to assess the risk of bias.
Data Synthesis
A Bayesian multi-level meta-analysis was conducted on five outcome measures, including resting core temperature and heart rate, the change in core temperature and heart rate during a heat response test and sweat rate. Wet-bulb globe temperature (WBGT), daily training duration and protocol length were used as predictor variables. Along with posterior means and 90% credible intervals (CrI), the probability of direction (Pd) was calculated.
Results
Eighteen articles from twelve independent studies were included. Fourteen articles (nine studies) provided data for the meta-analyses. Whilst accounting for WBGT, daily training duration and protocol length, population estimates indicated a reduction in resting core temperature and heart rate of − 0.19 °C [90% CrI: − 0.41 to 0.05, Pd = 91%] and − 6 beats·min⁻¹ [90% CrI: − 16 to 5, Pd = 83%], respectively. Furthermore, the rise in core temperature and heart rate during a heat response test were attenuated by − 0.24 °C [90% CrI: − 0.67 to 0.20, Pd = 85%] and − 7 beats·min⁻¹ [90% CrI: − 18 to 4, Pd = 87%]. Changes in sweat rate were conflicting (0.01 L·h⁻¹ [90% CrI: − 0.38 to 0.40, Pd = 53%]), primarily due to two studies demonstrating a reduction in sweat rate following heat acclimatisation.
Conclusions
Data from athletes and military personnel relocating to a hotter climate were consistent with a reduction in resting core temperature and heart rate, in addition to an attenuated rise in core temperature and heart rate during an exercise-based heat response test. An increase in sweat rate is also attainable, with the extent of these adaptations dependent on WBGT, daily training duration and protocol length.
PROSPERO Registration
CRD42022337761.
... It has been shown that heat, especially without acclimatization, might impair cardiopulmonary exercise capacity [2][3][4][5][11][12][13][14][15][16][17]. Nevertheless, most studies evaluated the effects of dehydration on exercise capacity in models of exercise-induced dehydration (with dehydration resulting from intense sweating) or dehydration after heat exposure. ...
Background:
Sports-related concussion is a relevant risk of contact sports, with several million cases per year worldwide. Prompt identification is crucial to prevent complications and late effects but may be impeded by an overlap with dehydration-associated impairment of cognitive function. Researchers have extensively studied the effects of pronounced dehydration in endurance sports, especially in the heat. However, little is known about the effects of isolated and mild dehydration.
Methods:
Healthy recreational athletes underwent a standardized fluid deprivation test. Hypohydration was assessed by bioelectrical impedance analysis (BIA) and laboratory testing of electrolytes and retention parameters. Participants underwent cardiopulmonary exercise testing (CPET) with a cycle ramp protocol. Each participant served as their own control undergoing CPET in a hypohydrated [HYH] and a euhydrated [EUH] state. Effects were assessed using a shortened version of Sport Concussion Assessment Tool 3 (SCAT3).
Results:
Fluid deprivation caused a mild (2%) reduction in body water, resulting in a calculated body mass loss of 0.8% without alterations of electrolytes, serum-osmolality, or hematocrit. Athletes reported significantly more (1.8 ± 2.2 vs. 0.4 ± 0.7; p < 0.01) and more severe (4.4 ± 6.2 vs. 1.0 ± 1.9; p < 0.01) concussion-like symptoms in a hypohydrated state. Balance was worse in HYH by trend with a significant difference for tandem stance (1.1 ± 1.3 vs. 0.6 ± 1.1; p = 0.02). No relevant differences were presented for items of memory and concentration.
Conclusions:
Mild dehydration caused relevant alterations of concussion-like symptoms and balance in healthy recreational athletes in the absence of endurance exercise or heat. Further research is needed to clarify the real-life relevance of these findings and to strengthen the differential diagnosis of concussion.
... This performance decrement extends to military populations [4][5][6], who are expected to complete physical work whilst wearing protective clothing and equipment, which reduces their evaporative heat loss capacity [7,8] and increases their metabolic rate and, therefore, heat production [9]. The increase in thermal strain associated with exercise or work performed in the heat hinders aerobic exercise performance [3,[10][11][12] due to alterations in the cardiovascular, central nervous system and skeletal muscle function [13], as well as heightening the risk of exertional heat illness [14,15]. Consequently, strategies to mitigate the adverse effects of thermal strain on performance and heat illness risk in sporting and military contexts have been developed, with a key physiological intervention being heat acclimation/acclimatisation [16,17]. ...
... When athletes perform or train in thermally challenging conditions, they are subject to added physiological strain when compared with the same work in temperate conditions [24][25][26][27]. Endurance exercise performance is particularly compromised by high thermal strain (i.e. ...
Background
Hyperthermia (and associated health and performance implications) can be a significant problem for athletes and teams involved in intermittent sports. Quantifying the highest thermal strain (i.e. peak core body temperature [peak Tc]) from a range of intermittent sports would enhance our understanding of the thermal requirements of sport and assist in making informed decisions about training or match-day interventions to reduce thermally induced harm and/or performance decline.
Objective
The objective of this systematic review was to synthesise and characterise the available thermal strain data collected in competition from intermittent sport athletes.
Methods
A systematic literature search was performed on Web of Science, MEDLINE, and SPORTDiscus to identify studies up to 17 April 2023. Electronic databases were searched using a text mining method to provide a partially automated and systematic search strategy retrieving terms related to core body temperature measurement and intermittent sport. Records were eligible if they included core body temperature measurement during competition, without experimental intervention that may influence thermal strain (e.g. cooling), in healthy, adult, intermittent sport athletes at any level. Due to the lack of an available tool that specifically includes potential sources of bias for physiological responses in descriptive studies, a methodological evaluation checklist was developed and used to document important methodological considerations. Data were not meta-analysed given the methodological heterogeneity between studies and therefore were presented descriptively in tabular and graphical format.
Results
A total of 34 studies were selected for review; 27 were observational, 5 were experimental (2 parallel group and 3 repeated measures randomised controlled trials), and 2 were quasi-experimental (1 parallel group and 1 repeated measures non-randomised controlled trial). Across all included studies, 386 participants (plus participant numbers not reported in two studies) were recruited after accounting for shared data between studies. A total of 4 studies (~ 12%) found no evidence of hyperthermia, 24 (~ 71%) found evidence of ‘modest’ hyperthermia (peak Tc between 38.5 and 39.5 °C), and 6 (~ 18%) found evidence of ‘marked’ hyperthermia (peak Tc of 39.5 °C or greater) during intermittent sports competition.
Conclusions
Practitioners and coaches supporting intermittent sport athletes are justified to seek interventions aimed at mitigating the high heat strain observed in competition. More research is required to determine the most effective interventions for this population that are practically viable in intermittent sports settings (often constrained by many competing demands). Greater statistical power and homogeneity among studies are required to quantify the independent effects of wet bulb globe temperature, competition duration, sport and level of competition on peak Tc, all of which are likely to be key modulators of the thermal strain experienced by competing athletes.
Registration
This systematic review was registered on the Open Science Framework (https://osf.io/vfb4s; https://doi.org/10.17605/OSF.IO/EZYFA, 4 January 2021).
... As expected, aerobic performance was hindered, the magnitude of which correlated with the WBGT during the race (R 2 = 0.89); with only 1 athlete, out of 219 matching their PB. WBGT has been found to be a strong predictor of performance decrement (42,43), with similar R 2 values found across a wider range of conditions during numerous 20 km (R 2 = 0.77) and 50 km (R 2 = 0.70) racewalk events (44). It may be that pace slowed over time because the requirement for cutaneous blood flow results in a reduction in skeletal muscle blood flow, ultimately inhibiting the ability to continue exercise at the same intensity (45). ...
Purpose: To characterise thermoregulatory and performance responses of elite road-race athletes, while competing in hot, humid, night-time conditions during the 2019 IAAF World Athletic Championships. Method: Male and female athletes, competing in the 20 km racewalk (n=20 males, 24 females), 50 km racewalk (n=19 males, 8 females) and marathon (n=15 males, 22 females) participated. Exposed mean skin (Tsk) and continuous core body (Tc) temperature were recorded with infrared thermography and ingestible telemetry pill, respectively. Results: The range of ambient conditions (recorded roadside) were 29.3-32.7°C air temperature, 46-81 % relative humidity, 0.1-1.7 m∙s-1 air velocity and 23.5-30.6°C wet bulb globe temperature. Tc increased by 1.5 ± 0.1°C but mean Tsk decreased by 1.5 ± 0.4°C over the duration of the races. Tsk and Tc changed most rapidly at the start of the races and then plateaued, with Tc showing a rapid increase again at the end, in a pattern mirroring pacing. Performance times were between 3 to 20 % (mean = 113 ± 6%) longer during the championships compared to the personal best (PB) of athletes. Overall mean performance relative to PB was correlated with the wet-bulb globe temperature (WBGT) of each race (R2 = 0.89), but not with thermophysiological variables (R2 ≤ 0.3). Conclusion: As previously reported in exercise heat stress, in this field study Tc rose with exercise duration, whereas Tsk showed a decline. The latter contradicts the commonly recorded rise and plateau in laboratory studies at similar ambient temperatures, but without realistic air movement.
... In addition, VF build and VF tree were larger in the locations where WBGT was suppressed. Because Ely et al. showed that there is a progressive slowing of marathon performance as the WBGT increases from 5 to 25 • C [50], if WBGT can be suppressed by high VF build and VF tree , athletes' performance can be improved. Minimum WBGT for Sapporo is 21 • C for the 5:00 a.m. ...
A marathon is a grueling endurance race, and runners are at risk of heatstroke. Therefore, the thermal environment of the marathon course should be accurately assessed. Solar radiation, a factor in the thermal environment, is particularly affected by the surrounding environment. In this study, we proposed a method to calculate wet-bulb globe temperature (WBGT) in a short period of time using geographic information system (GIS) data, considering changes in solar radiation. WBGT is used as an indicator of heat stroke. This method was used to assess the risk of heat stroke due to weather conditions, span of time, and location on the marathon course of the Tokyo 2020 Olympics. According to the analysis results, in Sapporo, trees and buildings can suppress WBGT by about 2 °C, but on days when the average temperature exceeded 26 °C, WBGT exceeded 21 °C from 5:00 to 13:00. On the contrary, even in August, the hottest month of the year, there were days when WBGT was almost always below 21 °C from 5:00 to 13:00. In other words, it is concluded that the risk of heat stroke can be reduced if the marathon is held in accordance with the weather conditions of the day. In addition, by mapping and identifying locations where there is little change in attenuated WBGT, it is possible to identify locations where the thermal environment should be improved.
... Hot environmental conditions impair exercise performance by raising thermal and physiological strain (Ely et al. 2007;Mohr et al. 2012; Morante and Brotherhood 2008;Périard et al. 2014a;Racinais et al. 2015). Repeated exposure to heat stress (heat acclimation (HA)) can lessen this strain (Guy et al. 2015;Chalmers et al. 2014;Tyler et al. 2016), by inducing beneficial adaptations to the heat (Taylor 2014;Sawka et al. 2011). ...
Purpose
This study investigated the effects of acute hyperthermia and heat acclimation (HA) on maximal and rapid voluntary torque production, and their neuromuscular determinants.
Methods
Ten participants completed 10 days of isothermic HA (50 °C, 50% rh) and had their knee-extensor neuromuscular function assessed in normothermic and hyperthermic conditions, pre-, after 5 and after 10 days of HA. Electrically evoked twitch and octet (300 Hz) contractions were delivered at rest. Maximum voluntary torque (MVT), surface electromyography (EMG) normalised to maximal M-wave, and voluntary activation (VA) were assessed during brief maximal isometric voluntary contractions. Rate of torque development (RTD) and normalised EMG were measured during rapid voluntary contractions.
Results
Acute hyperthermia reduced neural drive (EMG at MVT and during rapid voluntary contractions; P < 0.05), increased evoked torques ( P < 0.05), and shortened contraction and relaxation rates ( P < 0.05). HA lowered resting rectal temperature and heart rate after 10 days ( P < 0.05), and increased sweating rate after 5 and 10 days ( P < 0.05), no differences were observed between 5 and 10 days. The hyperthermia-induced reduction in twitch half-relaxation was attenuated after 5 and 10 days of HA, but there were no other effects on neuromuscular function either in normothermic or hyperthermic conditions.
Conclusion
HA-induced favourable adaptations to the heat after 5 and 10 days of exposure, but there was no measurable benefit on voluntary neuromuscular function in normothermic or hyperthermic conditions. HA did reduce the hyperthermic-induced reduction in twitch half-relaxation time, which may benefit twitch force summation and thus help preserve voluntary torque in hot environmental conditions.
... These challenges will affect runners increasingly as the race progresses, and may contribute to higher rates of slowing in warmer environmental conditions [8]. Among competitive runners, warmer weather slows both men and women [9]. However, the fastest runners slow more during the second half, whereas others appear to adopt a slower pacing strategy from the outset [10]. ...
... In the future, I believe that the data of fitness platforms will be enriched with additional information. Both additional data from wearables (spatiotemporal, kinematic and kinetic) as well as context information about the run (weather, surface of running track based on GPS) will enable even more detailed insights into the biomechanics and physiology of endurance runners in specific conditions [231,232]. Especially longitudinal studies based on this kind of data will provide new insights into the response of runners to training or running-related injuries, which have not been possible before due to a lack of data [21]. ...
Body-worn sensors, so-called wearables, are getting more and more popular in the sports domain. Wearables offer real-time feedback to athletes on technique and performance, while researchers can generate insights into the biomechanics and sports physiology of the athletes in real-world sports environments outside of laboratories. One of the first sports disciplines, where many athletes have been using wearable devices, is endurance running. With the rising popularity of smartphones, smartwatches and inertial measurement units (IMUs), many runners started to track their performance and keep a digital training diary. Due to the high number of runners worldwide, which transferred their data of wearables to online fitness platforms, large databases were created, which enable Big Data analysis of running data. This kind of analysis offers the potential to conduct longitudinal sports science studies on a larger number of participants than ever before. In this dissertation, both studies showing how to extract endurance running-related parameters from raw data of foot-mounted IMUs as well as a Big Data study with running data from a fitness platform are presented.
... However, one reason that can explain these differences is the higher temperature observed in the 2018 edition. This higher environmental temperature could explain the faster relative speed in the first sections of the race 35,36 , and also a decrease in speed in the second half of the race due to thermal stress 35,37 . Further studies could explore the effect of environmental conditions on pacing in a controlled laboratory study. ...
Running pacing has become a focus of interest over recent years due to its relationship with performance, however, it is still unknown the consistency of each race in different editions. The aim of this study is to analyze the consistency of pacing profile in three consecutive editions of three marathon races. A database of 282,808 runners, compiled from three different races (Chicago, London, and Tokyo Marathon) and three editions (2017, 2018, and 2019) was analyzed. Participants were categorized according to their time performance in the marathon, every 30 min from 2:30 h to sub-6 h. The relative speed of each section for each runner was calculated as a percentage of the average speed for the entire race. The intraclass correlation coefficients (ICC) of relative speed at the different pacing section, taking into account the runner time categories, was excellent over the three marathon editions (ICC > 0.93). The artificial intelligence model showed an accuracy of 86.8% to classify the runners' data in three marathons, suggesting a consistency between editions with identifiable differences between races. In conclusion, although some differences have been observed between editions in certain sections and marathon runner categories, excellent consistency of the pacing profile was observed. The study of pacing profile in a specific marathon can, therefore, be helpful for runners, coaches and marathon organizers for planning the race and improving its organization.
... Additionally, exercise in the heat negatively impacts exercise performance and athlete safety [2]. For example, marathon performance progressively decreases as the Wet Bulb Globe Temperature (WBGT) increases from 5 • C to 25 • C [3]. Furthermore, exertional heat stroke is among the top three leading causes of death in sport, and other exertional heat illnesses, including heat exhaustion, heat syncope, and heat cramps, are prevalent and recurring illnesses across all levels of sport [4,5]. ...
The purpose of this study was to examine the changes in metabolic heat production (Hprod), evaporative heat loss (Hevap), and dry heat loss (Hdry), following heat acclimatization (HAz) and heat acclimation (HA). Twenty-two male endurance athletes (mean ± standard deviation; age, 37 ± 12 y; body mass, 73.4 ± 8.7 kg; height, 178.7 ± 6.8 cm; and VO2max, 57.1 ± 7.2 mL·kg−1·min−1) completed three trials (baseline; post-HAz; and post-HA), which consisted of 60 min steady state exercise at 59 ± 2% velocityVO2max in the heat (ambient temperature [Tamb], 35.2 ± 0.6 °C; relative humidity [%rh] 47.5 ± 0.4%). During the trial, VO2 and RER were collected to calculate Hprod, Hevap, and Hdry. Following the baseline trial, participants completed self-directed outdoor summer training followed by a post-HAz trial. Then, five days of HA were completed over eight days in the heat (Tamb, 38.7 ± 1.1 °C; %rh, 51.2 ± 2.3%). During the HA sessions, participants exercised to maintain hyperthermia (38.50 °C and 39.75 °C) for 60 min. Then, a post-HA trial was performed. There were no differences in Hprod between the baseline (459 ± 59 W·m−2), post-HAz (460 ± 61 W·m−2), and post-HA (464 ± 55 W·m−2, p = 0.866). However, Hevap was significantly increased post-HA (385 ± 84 W·m−2) compared to post-HAz (342 ± 86 W·m−2, p = 0.043) and the baseline (332 ± 77 W·m−2, p = 0.037). Additionally, Hdry was significantly lower at post-HAz (125 ± 8 W·m−2, p = 0.013) and post-HA (121 ± 10 W·m−2, p < 0.001) compared to the baseline (128 ± 7 W·m−2). Hdry at post-HA was also lower than post-HAz (p = 0.049). Hprod did not change following HAz and HA. While Hdry was decreased following HA, the decrease in Hdry was smaller than the increases in Hevap. Adaptations in body heat exchange can occur by HA following HAz.
This article presents a historical overview and an up‐to‐date review of hyperthermia‐induced fatigue during exercise in the heat. Exercise in the heat is associated with a thermoregulatory burden which mediates cardiovascular challenges and influence the cerebral function, increase the pulmonary ventilation, and alter muscle metabolism; which all potentially may contribute to fatigue and impair the ability to sustain power output during aerobic exercise. For maximal intensity exercise, the performance impairment is clearly influenced by cardiovascular limitations to simultaneously support thermoregulation and oxygen delivery to the active skeletal muscle. In contrast, during submaximal intensity exercise at a fixed intensity, muscle blood flow and oxygen consumption remain unchanged and the potential influence from cardiovascular stressing and/or high skin temperature is not related to decreased oxygen delivery to the skeletal muscles. Regardless, performance is markedly deteriorated and exercise‐induced hyperthermia is associated with central fatigue as indicated by impaired ability to sustain maximal muscle activation during sustained contractions. The central fatigue appears to be influenced by neurotransmitter activity of the dopaminergic system, but inhibitory signals from thermoreceptors arising secondary to the elevated core, muscle and skin temperatures and augmented afferent feedback from the increased ventilation and the cardiovascular stressing (perhaps baroreceptor sensing of blood pressure stability) and metabolic alterations within the skeletal muscles are likely all factors of importance for afferent feedback to mediate hyperthermia‐induced fatigue during submaximal intensity exercise. Taking all the potential factors into account, we propose an integrative model that may help understanding the interplay among factors, but also acknowledging that the influence from a given factor depends on the exercise hyperthermia situation. © 2014 American Physiological Society. Compr Physiol 4:657‐689, 2014.
This article emphasizes significant recent advances regarding heat stress and its impact on exercise performance, adaptations, fluid electrolyte imbalances, and pathophysiology. During exercise‐heat stress, the physiological burden of supporting high skin blood flow and high sweating rates can impose considerable cardiovascular strain and initiate a cascade of pathophysiological events leading to heat stroke. We examine the association between heat stress, particularly high skin temperature, on diminishing cardiovascular/aerobic reserves as well as increasing relative intensity and perceptual cues that degrade aerobic exercise performance. We discuss novel systemic (heat acclimation) and cellular (acquired thermal tolerance) adaptations that improve performance in hot and temperate environments and protect organs from heat stroke as well as other dissimilar stresses. We delineate how heat stroke evolves from gut underperfusion/ischemia causing endotoxin release or the release of mitochondrial DNA fragments in response to cell necrosis, to mediate a systemic inflammatory syndrome inducing coagulopathies, immune dysfunction, cytokine modulation, and multiorgan damage and failure. We discuss how an inflammatory response that induces simultaneous fever and/or prior exposure to a pathogen (e.g., viral infection) that deactivates molecular protective mechanisms interacts synergistically with the hyperthermia of exercise to perhaps explain heat stroke cases reported in low‐risk populations performing routine activities. Importantly, we question the “traditional” notion that high core temperature is the critical mediator of exercise performance degradation and heat stroke. Published 2011 This article is a U.S. Government work and is in the public domain in the USA. Compr Physiol 1:1883‐1928, 2011.
Background
Exercise in humid and hot environments (HHEs) may result in decreased perception, motor performance, and memory owing to endogenous heat production and exogenous load. However, whether a single bout of exercise (SBOE) intensity affects the magnitude of changes in the levels of hemocytes remains controversial. In this article, we aimed to investigate the effects of a SBOE of varying intensities on blood cells in HHE.
Methods
Thirty-two volunteers were randomly divided into a quiet control group (QC), 55% VO 2 max intensity exercise group (HHE55%), 70% VO 2 max intensity exercise group (HHE70%), and 85% VO 2 max intensity exercise group (HHE85%). The participants in the exercise groups were assigned to perform an SBOE on the treadmill under HHE conditions for 30 min, whereas participants in the QC remained still under HHE conditions for 30 min (temperature: 28–32 °C, relative humidity: 85–95%).
Results
The net body mass (NBM), perfusion index (PI), mean corpuscular volume (MCV), platelet (PLT), and plateletcrit (PCT) values were affected significantly by the exercise intensity ( P < 0.01) the hemoglobin (HGB) and neutrophil count (NE) were affected significantly by exercise intensity ( P < 0.05). After an SBOE, compared with that before exercise, the sublingual temperature (ST) of all groups, the NBM and MCV of all exercise groups, the PI of the HHE55% and HHE70% groups, the HGB, hematocrit (HCT), and NE of the HHE70% group, the red blood cell count (RBC), PLT, and PCT of the HHE70% and HHE85% groups, and the white blood cell count (WBC) of HHE85% changed very significantly ( P < 0.01). The PCT of QC, blood oxygen saturation (SaO 2 ), and soluble transferrin receptor (sTfR) levels in the HHE55% group, the lymphocyte count (LY) in the HHE70% group, and the HGB and HCT in the HHE85% group changed significantly ( P < 0.05).
Conclusion
Low- and moderate-intensity SBOE in HHE could increase the serum EPO and serum sTfR levels and decrease the serum IL-3 levels. Conversely, a high-intensity load could increase the risk of inflammation. Therefore, low-intensity exercise may be more appropriate for an SBOE in HHE.
Der Marathonlauf ist ein Event, der draußen
stattfindet und bei dem die Läuferinnen und
Läufer den jeweiligen Wetterbedingungen
ausgesetzt sind. Um die negativen Folgen
durch extreme und aktuelle Wettersituationen
zu reduzieren, gibt es die Möglichkeit,
den optimalen Zeitpunkt im Laufe des Jahres
auf Basis klimatischer Bedingungen zu bestimmen
sowie den Zeitpunkt des Laufes zu
optimieren. Der Anstieg der globalen Lufttemperatur
durch den anthropogen verursachten
Klimawandel bringt ein großes gesundheitliches
Risiko mit sich. Durch die
Zunahme von Extremereignissen kommt es
vermehrt zu Hitzewellen. Eine sportliche Ausdauerbelastung
unter Hitze stellt ein gesundheitliches
Risiko dar, das sich in der Zukunft
erhöht. Infolgedessen werden zukünftige Marathonläufe
unter extremeren Wetterverhältnissen
stattfinden.
Thermoregulation is impaired in individuals with a spinal cord lesion (SCI), affecting sweat capacity, heat loss, and core temperature. This can be particularly problematic for athletes with SCI who exercise in hot and humid conditions, like those during the Tokyo 2020 Paralympic Games. Heat acclimation can support optimal preparation for exercise in such challenging environments, but evidence is limited in endurance athletes with SCI. We evaluated whether seven consecutive days of exercise in the heat would result in heat acclimation. Five elite para-cycling athletes with SCI participated (two females, three males, median (Q1-Q3) 35 (31–51) years, four with paraplegia and one with tetraplegia). All tests and training sessions were performed in a heat chamber (30°C and 75% relative humidity). A time-to-exhaustion test was performed on day 1 (pretest) and day 7 (posttest). On days 2–6, athletes trained daily for one hour at 50–60% of individual peak power (PPeak). Comparing pretest and posttest, all athletes increased their body mass loss (p=0.04), sweat rate (p=0.04), and time to exhaustion (p=0.04). Effects varied between athletes for core temperature and heart rate. All athletes appeared to benefit from our heat acclimation protocol, helping to optimize their preparation for the Tokyo 2020 Paralympic Games.
Understanding both positive and negative impacts of climate change is essential for comprehensively assessing and well adapting to the impacts of changing climate. Conventionally, climate warming is revealed to negatively impact human activities. Here, we reveal that human beings’ performance in anaerobic sports may benefit from climate warming. Using global weather observation and athletes’ performance datasets, we show that world-top athletes’ performances in nearly all athletics anaerobic events (i.e., sprints, jumps and throws) substantially improve as ambient temperature rises. For example, 100 m performance monotonically improves by 0.26 s as ambient temperature rises from 11.8° to 36.4 °C. Using Coupled Model Intercomparison Project Phase 6 datasets, we further show that global warming can substantially improve world-top athletes’ performance in eleven of the thirteen Olympics athletics anaerobic events by 0.27%–0.88% and 0.14–0.48% under high-emission and medium-emission scenarios, respectively, during 1979–2100. Among them, the improvements for 100 m are 0.59% (0.063 s) and 0.32% (0.034 s), respectively. Mechanism analysis shows that the warmed ambient atmosphere can improve competitors’ performance through expanding the air and thus reducing the air resistance to the competitors and throwing implements for hummer throw and all the sprints, hurdling and jumps. Quantitative analysis estimates that this thermodynamic process is essential for the impacts of warmed ambient atmosphere on the performances in these events as physiological processes are.
WBGT (Wet Bulb Globe Temperature) was originally championed by the United States military and has been widely implemented in daily training to prevent casualties or injuries among soldiers due to unfavorable high temperature and humidity conditions during the summer, and it has been widely used in various fields, such as marathons, military training, and travel. Starting from the daily periodicity of WBGT, this paper uses the Holt-Winters 24 h, and discusses the feasibility of its autocorrelation prediction. The prediction results were evaluated using the time series cross-validation method and RMSE. Two experiments were conducted with the dataset acquired by NCSCO and the self-collected Dongguan University of Technology dataset(DGUT-D). First, a preliminary experiment was conducted using NCSCO data to explore the feasibility of WBGT autocorrelation pre-diction, and then the DGUT-D was used to predict the 24-h WBGT of the Songshan Lake Campus of the Dongguan University of Technology (DGUT).
Although exercise in the heat and its effect on thermoregulatory responses has been well studied, limited information is available concerning the effect of high environmental temperatures on thermoregulatory responses, cardiovascular strain and cost of locomotion during loaded marching in the heat. Members of the armed forces are wearing protective equipment like bulletproof vests, helmets and tactical vests while performing a loaded march, often in high environmental temperatures, which could potential expose the individual uncompensable heat stress. Therefore, the purpose of this study was to investigate the effect of elevated environmental temperature on core and body temperature, heart rate and cost of locomotion in military service members during a 5 km loaded march. Participants were seven service members of the Canadian Armed Forces Light Infantry (age 24±6 years, height 178±5 cm, weight 78.8±14.7 kg, VO2max 49.2±5.6 ml·min ⁻¹ ·kg ⁻¹ , lean body mass 66.3±8.3 kg, body fat % 14.9±6.5), who performed a loaded march carrying 35 kg of equipment, under two environmental conditions ( NORMAL 21°C and 50 relative humidity (RH), and HOT 30°C and 50% RH). Treadmill speed was set to 5.17km/h and the incline was set to 1% to simulate level ground walking. The 35 kg external load consisted of military boots, uniform, helmet, fragmentation vest, tactical vest, a Colt 7 replica rubber rifle and a loaded day pack. Participants walked on the treadmill for 60 min, or until voluntary termination. Heart rate was measured using a Garmin 310xt heart rate monitor, while energy expenditure was calculated from O2 consumption and CO2 production, using an open circuit flow through metabolic system. Cost of locomotion was calculated as energy expended per kg weight (body weight and external load) per kilometer walked (J·kg ⁻¹ ·km ⁻¹ ). Core temperature was measured using a telemetric pill (Jonah Temperature Capsule). All participants completed the loaded march in the normal condition, however one participant was unable to complete the full hour in the HOT condition due to gastric distress. Heart rate was significantly higher from 25 min until the end of the loaded march when participants performed the loaded march in the HOT condition compared to NORMAL . Heart rate during the last 5 min in the HOT condition was 152±11 bpm, compared to 136.9±13.2 bpm in the NORMAL condition. Core temperature was significantly higher in the HOT condition compared to NORMAL , and was 38.2±0.5°C in the HOT condition compared to 37.7±0.3°C in the NORMAL condition after 60 min of loaded march. Cost of locomotion (J·kg ⁻¹ ·km ⁻¹ ) was also affected by environmental temperature, and was significantly higher in the HOT condition compared to NORMAL (AUC hot 165.5±10.4 vs normal 152. ±8.9). The results from this study shows that performing a loaded march at 30°C and 50% RH wearing military protective equipment lead to uncompensable heat stress, causing an increase in core temperature and heart rate (cardiovascular strain). We also observed that the uncompensable heat stress caused an increase in the cost of locomotion without changing any factors other than environmental temperature.
The reliability of sport science tools are important where meaningful change is assessed. However, there is little research identifying the reliability of an intermittent high intensity protocol in a hot environment, therefore the purpose of this study was to investigate these factors using a Wattbike Pro. Twelve healthy, males completed three trials, of intermittent sprint protocols (ISP) of: 18 × 4-s maximal sprints in an environmental chamber (35.9 ± 0.7°C, RH 38.0 ± 1.9 %). Each 4-s sprint was followed by 116-s of active recovery. During each sprint, Power, Heart Rate (HR), thermal comfort and thermal sensation (-3/+3 scales), and RPE were assessed. Peak Average power (highest mean 4s sprint out of 18) 1435W, mean power 1028W, Coefficient of Variation (CV) 3.7 % meaningful change 37W. Peak power (highest instantaneous power of any 4s sprint) peak power 1556W, mean power 1151W, CV4.1 % meaningful change 46W. Average power output (mean average power of 18 sprints) peak power 1355W, mean power 938W, CV4.6 % equating to a meaningful change of 40W and also Average Peak (mean of highest instantaneous power of each 18 sprints) peak power 1454W, mean power 1052W, CV3.6 % 36W. This study confirms the reliability of the intermittent high intensity protocol in a hot environment.
In this third installment of our four-part historical series, we evaluate contributions that shaped our understanding of heat and cold stress during occupational and athletic pursuits. Our first topic concerns how we tolerate, and sometimes fail to tolerate, exercise-heat stress. By 1900, physical activity with clothing- and climate-induced evaporative impediments led to an extraordinarily high incidence of heat stroke within the military. Fortunately, deep-body temperatures > 40 °C were not always fatal. Thirty years later, water immersion and patient treatments mimicking sweat evaporation were found to be effective, with the adage of cool first, transport later being adopted. We gradually acquired an understanding of thermoeffector function during heat storage, and learned about challenges to other regulatory mechanisms. In our second topic, we explore cold tolerance and intolerance. By the 1930s, hypothermia was known to reduce cutaneous circulation, particularly at the extremities, conserving body heat. Cold-induced vasodilatation hindered heat conservation, but it was protective. Increased metabolic heat production followed, driven by shivering and non-shivering thermogenesis, even during exercise and work. Physical endurance and shivering could both be compromised by hypoglycaemia. Later, treatments for hypothermia and cold injuries were refined, and the thermal after-drop was explained. In our final topic, we critique the numerous indices developed in attempts to numerically rate hot and cold stresses. The criteria for an effective thermal stress index were established by the 1930s. However, few indices satisfied those requirements, either then or now, and the surviving indices, including the unvalidated Wet-Bulb Globe-Thermometer index, do not fully predict thermal strain.
Environmental heat stress impairs endurance performance by enhancing exercise-induced physiological and perceptual responses. However, the time course of these responses during self-paced running, particularly when comparing hot and temperate conditions, still needs further clarification. Moreover, monitoring fatigue induced by exercise is paramount to prescribing training and recovery adequately, but investigations on the effects of a hot environment on post-exercise neuromuscular fatigue are scarce. This study compared the time course of physiological and perceptual responses during a 10 km self-paced treadmill run (as fast as possible) between temperate (25°C) and hot (35°C) conditions. We also investigated the changes in countermovement jump (CMJ) performance following exercise in these two ambient temperatures. Thirteen recreational long-distance runners (11 men and 2 women), inhabitants of a tropical region, completed the two experimental trials in a randomized order. Compared to 25°C, participants had transiently higher body core temperature (TCORE) and consistently greater perceived exertion while running at 35°C (p < 0.05). These changes were associated with a slower pace, evidenced by an additional 14 ± 5 min (mean ± SD) to complete the 10 km at 35°C than at 25°C (p < 0.05). Before, immediately after, and 1 h after the self-paced run, the participants performed CMJs to evaluate lower limb neuromuscular fatigue. CMJ height was reduced by 7.0% (2.3 ± 2.4 cm) at 1 h after the race (p < 0.05) compared to pre-exercise values; environmental conditions did not influence this reduction. In conclusion, despite the reduced endurance performance, higher perceived exertion, and transiently augmented TCORE caused by environmental heat stress, post-exercise neuromuscular fatigue is similar between temperate and hot conditions. This finding suggests that the higher external load (faster speed) at 25°C compensates for the effects of more significant perceptual responses at 35°C in inducing neuromuscular fatigue.
Introduction:
The importance of providing wet bulb globe temperature (WBGT) heat stress flag category measurements in real time is well recognized by road race directors, and it is bound to become even more important with the rise of extreme weather and pandemic outbreaks. The purpose of this paper is to describe the WBGT index and its components measured during the 125th running of the Boston Marathon on October 11, 2021, for qualitative comparison to measurements made similarly on its traditional April date, 2014 to 2019.
Methods:
Monitoring occurred at the 7 km, 18 km, and 32 km marks of the race in the towns of Ashland, Natick-Wellesley, and Newton. The outdoor WBGT index was calculated from direct hourly measurements of the dry bulb, black globe, and natural wet bulb temperatures from 0900 to 1500 h.
Results:
The WBGT index was not different among towns; thus, the average hourly values for the 3 towns were compared to historical data averaged identically. Although the black globe temperature fluctuated considerably in response to changing cloud cover, on average, partly cloudy skies kept the solar load comparable to what has been observed in April. Dry bulb and wet bulb temperatures were higher than those on most April dates shown, which resulted in a yellow (or amber) flag day for most of the race.
Conclusions:
The historic October Boston Marathon was among the warmest in recent history. Like the impact of COVID-19 on the 2021 Boston Marathon, future climate challenges around outdoor activities could necessitate rescheduling; they underscore the importance of real-time WBGT index measures.
The wet bulb globe temperature (WBGT) is widely used in athletics for assessing heat stress. Sports governing bodies provide a wide variety of recommendations on how often to take WBGT measurements during activities like practices and competitions. This can leave coaching staff and other sports medicine personnel in a quandary as to what is the “best practice.” Our study is the first to use a large dataset to quantify the variability of WBGT within practice and competition sessions, and to identify the impact of using different measurement rates on the WBGT. The study leverages 6 years of data from thousands of American football practice and competition sessions from across Georgia, USA. We observed that, on average, WBGTs are coolest in the morning (26.67°C) and evening (24.84°C), and hottest in the midday (30.23°C) and afternoon (27.21°C). The variability within sessions tended to be greater for morning, midday, and afternoon than evenings, with session standard deviations of 0.96°C to 1.27°C and ranges of 2.67°C to 3.55°C when controlling for duration. WBGTs also tended to increase over time in morning sessions and decrease over time during afternoon and evening sessions. These changes are clinically important. We found that Georgia High School Association (GHSA) WBGT activity modification categories often changed during sessions, especially in the morning, midday, and afternoon where a change in GHSA category of ≥1 occurred in 57% to 76% of sessions. Considering this variability, our results indicate that more frequent measurements better capture maximum WBGT values over a session and reduce the likelihood of misclassifying activity modification.
Objective:
The aim of the study was to evaluate the effect of a hot environment on several physiological variables of soccer players and suggest feasible solutions to it.
Subjects and methods:
The study is of prospective design, considering 66 participants comprising professional soccer players. All the participants completed the Physical Activity Readiness Questionnaire (PARQ). The participants were assigned to 3 different groups. Each group was assigned 22 participants. They were made to play in three different chambers, maintained at cool, moderate and hot temperatures. Players were made to play and various variables were determined to assess the effect of hot temperature on them.
Results:
Several variables were determined including absolute and relative oxygen uptake, heart rate, minute ventilation, the blood concentration of lactate and time to get exhausted. All the variables of players who played in hot temperatures have revealed higher heart rate, ventilation and increased lactate concentration. Players in a hot environment ran out faster.
Conclusions:
The study was concluded due to the players' dehydration and physiological deteriorated factors in a hot environment, leading to poor performances and also affecting the players' health in the long run. Further, the study suggested improving the environment around the game venues.
The short- and long-term impacts of air pollution on human health are well documented and include cardiovascular, neurological, immune system and developmental damage. Additionally, the irritant qualities of air pollutants can cause respiratory and cardiovascular distress. This can be heightened during exercise and especially so for those with respiratory conditions such as asthma. Meteorological conditions have also been shown to adversely impact athletic performance; but research has mostly examined the impact of pollution and meteorology on marathon times or running under laboratory settings. This study focuses on the half marathon distance (13.1 miles/21.1 km) and utilises the Great North Run held in Newcastle-upon-Tyne, England, between 2006 and 2019. Local meteorological (temperature, relative humidity, heat index and wind speed) and air quality (ozone, nitrogen dioxide and PM2.5) data is used in conjunction with finishing times of the quickest and slowest amateur participants, along with the elite field, to determine the extent to which each group is influenced in real-world conditions. Results show that increased temperatures, heat index and ozone concentrations are significantly detrimental to amateur half marathon performances. The elite field meanwhile is influenced by higher ozone concentrations. It is thought that the increased exposure time to the environmental conditions contributes to this greater decrease in performance for the slowest participants. For elite athletes that are performing closer to their maximal capacity (VO2 max), the higher ozone concentrations likely results in respiratory irritation and decreased performance. Nitrogen dioxide and PM2.5 pollution showed no significant relationship with finishing times. These results provide additional insight into the environmental effects on exercise, which is particularly important under the increasing effects climate change and regional air pollution. This study can be used to inform event organisation and start times for both mass participation and major elite events with the aim to reduce heat- and pollution-related incidents.
Background: The two aspects of the influence of environmental conditions on marathon running performance and pacing during a marathon have been separately and widely investigated. The influence of environmental conditions on the pacing of age group marathoners has, however, not been considered yet.
Objective: The aim of the present study was to investigate the association between environmental conditions (i.e., temperature, barometric pressure, humidity, precipitation, sunshine, and cloud cover), gender and pacing of age group marathoners in the “New York City Marathon”.
Methodology: Between 1999 and 2019, a total of 830,255 finishes (526,500 males and 303,755 females) were recorded. Time-adjusted averages of weather conditions for temperature, barometric pressure, humidity, and sunshine duration during the race were correlated with running speed in 5 km-intervals for age group runners in 10 years-intervals.
Results: The running speed decreased with increasing temperatures in athletes of age groups 20–59 with a pronounced negative effect for men aged 30–64 years and women aged 40–64 years. Higher levels of humidity were associated with faster running speeds for both sexes. Sunshine duration and barometric pressure showed no association with running speed.
Conclusion: In summary, temperature and humidity affect pacing in age group marathoners differently. Specifically, increasing temperature slowed down runners of both sexes aged between 20 and 59 years, whereas increasing humidity slowed down runners of <20 and >80 years old.
Purpose:
The Doha 2019 women's World Championship marathon took place in extreme hot (32 °C), humid conditions (74% relative humidity) culminating in unprecedented (41%) failure rates. We explored whether extreme heat or suboptimal pacing was responsible for diminished performance against a temperate "control" (London 2017: 19 °C, 59% relative humidity) and whether physical characteristics (eg, body surface area, estimated maximal oxygen uptake, habitual heat exposure) explained performance.
Method:
Five-kilometer-pace (km·h-1) data underwent repeated-measures analyses of hot (Doha, n = 40) versus temperate pacing and performance (London, n = 78) within and between marathon pacing (finisher quartiles normalized against personal best; n = 10 per group) and within hot marathon finishers versus nonfinishers (up to 10 km; normalized data). Possible predictors (multiple regression) of hot marathon pacing were explored. Tests to .05 alpha level, partial eta squared (ηp2) indicates effect size.
Results:
Mean (SD) of Doha (14.82 [0.96] km·h-1) pace was slower (London: 15.74 [0.96] km·h-1; P = .00; ηp2=.500). In hot conditions, athletes finishing in positions 1 to 10 (group 1) started more conservatively (93.7% [2.1%] of personal best) than slower runners (groups 3 and 4; 96.6% [2.8%] of personal best; P < .05, ηp2=.303). Groups were not different at 15 km and then slowed immediately (groups 3 and 4) or after 20 km (group 2). Finishers and nonfinishers adopted similar pace up to 10 km (P > .05, ηp2=.003). World ranking predicted (P = .00; r2 = .248) average pace in Doha.
Conclusion:
Extreme hot conditions reduced performance. Top 10 athletes adopted a conservative initial pace, whereas lower-placing athletes adopted a faster, aggressive start. Pacing alone does not explain high failure rates in nonfinishers. Athletes competing in the heat should initially pace conservatively to optimize performance.
Exercise-heat exposure results in significant sweat losses due to large biophysical requirements for evaporative heat loss. Progressive body water losses will increase plasma tonicity and decrease blood volume (hypertonic–hypovolemia). The result is reduced dry and evaporative heat exchange through alterations in the core temperature threshold for initiation of skin blood flow and sweating as well as changes in the sensitivity of these thermo-effectors. Regulation of reduced sweating conserves body water, which reduces heat loss and increases exercise hyperthermia, but the magnitude of this effect is modified by environmental heat transfer capabilities. The focus of this paper is to (1) examine the major mechanisms by which hypohydration alters thermoregulatory responses in the heat, and (2) illustrate how important differences in environmental airflow characteristics between laboratory and field settings may modify these effects.
The largest mass participation fun run in the world took place in
Auckland, New Zealand where an estimated 80000 participants ran 10.4 km
`Round the Bays' in the early fall of 1982. Even in the relatively mild
climate of Auckland, heat stroke and other types of heat illness occur
during this annual event. Techniques for thermal assessment of human
bioclimate have not been applied to an exercising crowd although it is
widely accepted that crowding will reduce the heat loss of individuals.
To quantify the possible heat load brought about by running in a large
crowd, those components of the microenvironment that affect radiant,
evaporative and convective heat exchange were measured, both within the
mass of runners and separately from it. These data were used as input
for two detailed body-environment heat exchange models which show the
effect of the runners themselves on the thermal environment. Since it is
assumed that changes longwave radiation exchange and convective losses
from the body are likely to be the major causes of differences between
solo and group running, these avenues of heat exchange are carefully
assessed . The results show that longwave radiative losses can be
reduced substantially by running in a lame group compared to solo
running, but the absolute size of the increase in net heat load on the
individual is small. However, heat loss by convection for group runners
is less than half that for sole runners. This may be the result of
entertainment of air within an atmospheric envelope below head level in
which wind speed and direction are the same as the runner's and
direction. For the weather conditions prevailing at the time of the
experiment, jogging in the main bunch of runners is estimated to cause,
on occasions, more than three times the heat stress on the body compared
to that experienced when running solo along the same route at the same
time of day during identical weather conditions.
The sections in this article are:
This study determined whether 1) exhaustion from heat strain occurs at the same body temperatures during exercise in the heat when subjects are euhydrated as when they are hypohydrated, 2) aerobic fitness influences the body temperature at which exhaustion from heat strain occurs, and 3) curves could be developed to estimate exhaustion rates at a given level of physiological strain. Seventeen heat-acclimated men [maximal oxygen uptake (VO2max) from 45 to 65 ml.kg-1.min-1] attempted two heat stress tests (HSTs): one when euhydrated and one when hypohydrated by 8% of total body water. The HSTs consisted of 180 min of rest and treadmill walking (45% VO2max) in a hot-dry (ambient temperature 49 degrees C, relative humidity 20%) environment. The required evaporative cooling (Ereq) exceeded the maximal evaporative cooling capacity of the environment (Emax); thus thermal equilibrium could not be achieved and 27 of 34 HSTs ended by exhaustion from heat strain. Our findings concerning exhaustion from heat strain are 1) hypohydration reduced the core temperature that could be tolerated; 2) aerobic fitness, per se, did not influence the magnitude of heat strain that could be tolerated; 3) curves can be developed to estimate exhaustion rates for a given level of physiological strain; and 4) exhaustion was rarely associated with a core temperature up to 38 degrees C, and it always occurred before a temperature of 40 degrees C was achieved. These findings are applicable to heat-acclimated individuals performing moderate-intensity exercise under conditions where Ereq approximates or exceeds Emax and who have high skin temperatures.
This investigation represents a descriptive summary of a limited number of marathon runners. As preliminary work it warrants the following observations and conclusions: Elite class male and female distance runners have been described as slight in build, with little body fat and large lung volumes. The marathon runners of this study, although not elite performers, did not differ from those previously described. The 'above average' female and 'average' male marathoners studied here were able to work at a high fraction of their aerobic power for a prolonged period. The fractional utilization of aerobic capacity was similar to that reported for elite male performers. The women studied performed the marathon at least as well and perhaps better than men with similar maximal aerobic capacities relative to body weight. It is estimated that male and female subjects expended 2903 and 2191 kcal respectively, to complete the 42.2 km distance.
Marathon races are performed over a broad range of environmental conditions. Hyperthermia is a primary challenge for runners in temperate and warm weather, but hypothermia can be a concern during cool-wet or cold conditions. Body temperature during the marathon is a balance between metabolic heat production and exchange with the environment described by the heat balance equation. During exercise, core temperature is proportional to the metabolic rate and largely independent of a wide range of environmental conditions. In temperate or cool conditions, a large skin-to-ambient temperature gradient facilitates radiant and convective heat loss, and reduces skin blood flow requirements, which may explain the tolerance for high core temperature observed during marathons in cool conditions. However, in warmer environments, skin temperatures and sweating rates increase. In addition, greater skin blood flow is required for heat loss, magnifying thermoregulatory and circulatory strain. The combined challenge of exercise and environment associated with marathon running can substantially challenge the human thermoregulatory system.
Purpose:
The purpose of this study was to assess research aimed at measuring performance enhancements that affect success of individual elite athletes in competitive events.
Analysis:
Simulations show that the smallest worthwhile enhancement of performance for an athlete in an international event is 0.7-0.4 of the typical within-athlete random variation in performance between events. Using change in performance in events as the outcome measure in a crossover study, researchers could delimit such enhancements with a sample of 16-65 athletes, or with 65-260 in a fully controlled study. Sample size for a study using a valid laboratory or field test is proportional to the square of the within-athlete variation in performance in the test relative to the event; estimates of these variations are therefore crucial and should be determined by repeated-measures analysis of data from reliability studies for the test and event. Enhancements in test and event may differ when factors that affect performance differ between test and event; overall effects of these factors can be determined with a validity study that combines reliability data for test and event. A test should be used only if it is valid, more reliable than the event, allows estimation of performance enhancement in the event, and if the subjects replicate their usual training and dietary practices for the study; otherwise the event itself provides the only dependable estimate of performance enhancement. Publication of enhancement as a percent change with confidence limits along with an analysis for individual differences will make the study more applicable to athletes. Outcomes can be generalized only to athletes with abilities and practices represented in the study.
Conclusion:
estimates of enhancement of performance in laboratory or field tests in most previous studies may not apply to elite athletes in competitive events.
Four environmental conditions contribute to climatic heat stress: ambient temperature, air humidity, air movement, and radiant heat from the sun and nearby warm surfaces. If sufficiently great, this climatic heat stress can adversely affect the performance of work or exercise. Particularly for endurance sport activities, such as marathon running, racewalking, and other sustained distance events, the ability to quantify the magnitude of heat stress is of value in helping both coach and athlete plan the safest competitive strategy. Quantification of climatic heat stress is possible through the use of three thermometers, which measure shade temperature (dry bulb temperature [DBT]), the effect of wind and humidity (wet bulb temperature [WBT]), and radiant energy (black globe temperature [BGT]). The three values are incorporated into a heat stress index (HSI), a temperature value comprised of 10% of DBT, 20% of BGT, and 70% of WBT. Extensive HSI monitoring was performed at the 1992 Barcelona Olympic Games, on‐site during all of the endurance competitions (10, 20, 50 km racewalks, marathons, and modem pentathlon cross country). These data provided the first in‐depth assessment of the extent to which the athlete is able to compete successfully under conditions ranging from high risk to extreme risk heat stress with minimal actual heat injury. This success is due in part to the adaptation in tolerating heat stress that occurs with training, as well as the instinctive reduction in pace adopted by the athlete to permit the optimum balance of skin and muscle blood flow that keeps core temperature from rising too high.
Climatic heat stress measurements were made during 1992, 1993, 1994, and 1995 at the Atlanta Centennial Olympic Stadium construction site, using three commercially available heat stress monitoring devices. This venue will be the site of opening and closing ceremonies, as well as all of the athletics competition. The measurement periods were during late July and early August, the period corresponding to the planned 1996 Games competition days. Whereas the 1992 data were of a more general nature, and thus preliminary, in 1993, 1994, and 1995 detailed measurements were made at 5‐minute intervals during selected 4‐hour periods. The potentially high temperature, humidity, and radiant heating in Atlanta during the Games period to which athletes, spectators, officials, and media could be exposed warranted such detailed studies. Measurements included dry bulb temperature, wet bulb temperature, and black globe temperature. From these values, the heat stress index temperature was calculated. The time periods were in the morning (7:00 through 11:00 AM), in the afternoon (12:30 through 4:30 PM), and in the evening (6:00 through 10:00 PM). Also, in 1994 data were obtained during the 50 km Pan American Race Walk Cup held in September as the first official pre‐Olympic athletic test event. Considerable variability in weather occurred during the 4 identical calendar year periods of July and August, which is described. From these data, it is also possible to estimate and compare the average heat stress encountered during specific time periods. In turn, this permits consideration of whether the heat stress during one period might be preferable to another (for example, early morning versus early evening) regarding the staging of an outdoor endurance event that requires a few hours to complete, such as a marathon or walk.
This paper briefly reviews certain aspects of man's response on exposure to a hot climate. The value of applying the concepts of thermal exchange analysis to evaluate the severity of a particular heat stress situation is emphasised. The possible effects of the Rome climate on a marathon runner competing in the 1900 Olympic Games is used as an illustration. It is concluded that with more knowledge of the physiology of athletes the accuracy of such predictions could be much increased, and might then be helpful to the athlete in planning the strategy of his race.
Sex differences in competitiveness are well established, but it is unknown if they originate from sociocultural conditions or evolved predispositions. Testing these hypotheses requires a quantifiable sex difference in competitiveness and the application of a powerful sociocultural manipulation to eliminate it. Study 1 reviews previous work showing that more male distance runners are motivated by competition and maintain large training volumes, suggesting that more males should run fast relative to sex-specific world-class standards. I then use two independent statistical approaches to demonstrate that, in matched populations of male and female U.S. runners, two to four times as many males as females ran relatively fast in 2003. Study 2 investigates whether the growth in opportunities and incentives for female athletes in the past 30 years is eliminating this sex difference. I first show that there was a marked increase in the number of fast female runners in the 1970s and early 1980s, a period during which female participation increased dramatically. However, I found no indication of an absolute or relative increase in the number of fast female distance runners since the mid-1980s. These findings therefore support the hypothesis that sex differences in competitiveness partly reflect evolved predispositions.
The aerobic performance of thirteen male ultramarathon and nine female marathon runners were studied in the laboratory and their results were related to their times in events ranging in distance from 5 km to 84.64 km.
The mean maximal aerobic power output (VO2 max) of the men was 72.5 ml/kg·min compared with 58.2 ml/kg·min (p<0.001) in the women but the O2 cost (VO2) for a given speed or distance of running was the same in both sexes. The 5 km time of the male athletes was closely related to their VO2 max (r=−0.85) during uphill running but was independent of relative power output (%VO2 max). However, with increasing distance the association of VO2 max with male athletic performance diminished (but nevertheless remained significant even at 84.64 km), and the relationship between VO2 max and time increased. Thus, using multiple regression analysis of the form: \begin{gathered} 42.2 km (marathon) time (h) = 7.445 - 0.0338 \dot V{\text{O}}_{{\text{2 max}}} ({\text{ml/kg }} \cdot {\text{ min}}) \hfill \\ - 0.0303\% \dot V{\text{O}}_{{\text{2 max}}} (r = 0.993) \hfill \\ \end{gathered} and \begin{gathered} 84.64 {\text{km (London}} - {\text{Brighton) time (h) = 16}}{\text{.998 }} - {\text{ 0}}{\text{.0735 }}\dot V{\text{O}}_{{\text{2 max}}} \hfill \\ ({\text{ml/kg }} \cdot \min ) - 0.0844\% \dot V{\text{O}}_{{\text{2 max}}} (r = 0.996) \hfill \\ \end{gathered} approximately 98% of the total variance of performance times could be accounted for in the marathon and ultramarathon events. This suggests that other factors such as footwear, clothing, and running technique (Costill, 1972) play a relatively minor role in this group of male distance runners. In the female athletes the intermediate times were not available and they did not compete beyond 42.2 km (marathon) distance but for this event a similar association though less in magnitude was found with VO2 max (r=−0.43) and %VO2 max (= −0.49). The male athletes were able to sustain 82% VO2 max (range 80–87%) in 42.2 km and 67% VO2 max (range 53–76%) in 84.64 km event. The comparable figure for the girls in the marathon was 79% VO2 max (ranges 68–86%). Our data suggests that success at the marathon and ultramarathon distances is crucially and (possibly) solely dependent on the development and utilisation of a large VO2 max.
Ingestion of approximately 30-60 g of carbohydrate during each hour of exercise will generally be sufficient to maintain blood glucose oxidation late in exercise and delay fatigue. Since the average rates of gastric emptying and intestinal absorption exceed 1,250 ml.h-1 for water and solutions containing up to 8% carbohydrate, exercising people can be supplemented with both carbohydrate and fluids at relatively high rates. When cyclists exercise at competitive intensities for 2 h in the heat with a sweat rate of 1,400 ml.h-1, it is clear that the closer that fluid consumption matches sweating rate (at least up to 80% of sweating rate), the better. Increasing dehydration, due to inadequate fluid consumption, directly impairs stroke volume, cardiac output, and skin blood flow, which results in larger increases in body core temperature, heart rate, and ratings of the difficulty of exercise. This same phenomenon probably also applies to running, which argues against the notion that a certain amount of dehydration (i.e., up to 3%) is permissible and without major cardiovascular consequences. However, runners generally drink only 500 ml.h-1 of fluid and thus allow themselves to dehydrate at rates of 500-1,000 ml.h-1. The performance question boils down to "Will the time lost as a result of drinking larger volumes be compensated by the physiological benefits drinking produces and the faster running pace that might be achieved during the last half of the race?" However, if the goal is safety, which means minimizing hyperthermia, there is no question that the closer that the rate of drinking can match the rate of dehydration, the better.
The relationships between the results of Beijing International Marathon Races and the corresponding weather conditions are analysed quantitatively. There are obvious interrelationships between the marathon results and weather factors such as air temperature, wet bulb temperature and human biometeorological indices. For example, the correlation coefficient between the average times of the top ten finishers and temperature is r = 0.8910. The meteorological conditions are classified into three categories, suitable, moderate and unsuitable for running a marathon race, and the optimum meteorological index is given. Also the concept of a meteorological result, i.e. the part of the actual performances fluctuating with the changes in weather conditions, is presented. This plays an important role in some kinds of sports such as marathon racing. Finally, the results of physiological tests are given, which illustrate the physiological reactions of long- and middle-distance runners to the surrounding temperature.
Air temperature and relative humidity have long been suspected of affecting the performance of marathon runners. Though these factors are important in their extremes, we show that other factors are even more indicative of race performances. Performances of the top 3 finishers in the last 30 Boston Marathons were correlated with hourly meteorological data for each race day. These 90 individual performances were classified as: record breaking performances (31), average performances (35), and unusually slow performances (24). The factors that help predict record breaking and unusually slow performances are: (i) wet bulb temperature, (ii) percent sky cover, and (iii) presence or absence of a light precipitation. Record breaking performances are characterized by a wet bulb temperature of less than 7.8 degrees C, and 100% sky cover. A light drizzle is also conducive to better performances. On the other hand, unusually low performances are accompanied by a wet bulb temperature of greater than 7.8 degrees C, and a sky cover of 50% or less. No light precipitation was recorded on any of the unusually slow race days. A graphic analysis clearly shows these relationships to exist. In addition, a multiple regression analysis confirms the importance of these variables. The authors advise that these are reliable predictors; however, when considering marathon races held in various geographical regions and differing climatic regimes, the exact numerical thresholds used here may not apply.
The physiology of marathon running has been extensively studied both in the laboratory and in the field, but these investigations have been confined to elite competitors. In the present study 28 competitors who took part in a marathon race (42.2 km) have been studied; 18 male subjects recorded times from 2 h 19 min 58 s to 4 h 53 min 23 s; 10 female subjects recorded times between 2 h 53 min 4 s and 5 h 16 min 1 s. Subjects visited the laboratory 2-3 weeks after the race and ran on a motor driven treadmill at a series of speeds and inclines; oxygen uptake (VO2) was measured during running at average marathon racing pace. Maximum oxygen uptake (VO2 max) was measured during uphill running. For both males (r = 0.88) and females (r = 0.63), linear relationships were found to exist between marathon performance and aerobic capacity. Similarly, the fraction of VO2 max which was sustained throughout the race was significantly correlated with performance for both male (r = 0.74) and female (r = 0.73) runners. The fastest runners were running at a speed requiring approximately 75% of VO2 max; for the slowest runners, the work load corresponded to approximately 60% of VO2 max. Correction of these estimates for the additional effort involved in overcoming air resistance, and in running on uneven terrain will substantially increase the oxygen requirement for the faster runners, while having a much smaller effect on the work rate of the slowest competitors. Five minutes of treadmill running at average racing pace at zero gradient did not result in marked elevation of the blood lactate concentration in any of the subjects.
Grandma's Marathon has been run each year in June since 1977 in Duluth, MN. It is ranked in the top 20 marathons and in 1993 was ranked the ninth largest and fourth fastest in the United States. As Grandma's Marathon continues to grow each year, so do concerns for the runners' safety. A half marathon was added in 1991 and earlier race times have been implemented to make the race safer for the runners. During the years of 1989-1995, data from the medical tent, weather bureau, and race booklets were analyzed using odds ratios to predict factors associated with a need for medical assistance. The odds of needing assistance were almost two times higher before implementing the half marathon and the odds of needing assistance decreased with earlier start times. Except for 1994 when the race was later, the percent of finishers seeking medical attention has decreased each year, a fact that we feel is a direct result of these race changes. Thus, the addition a half marathon and earlier start times can help decrease the number of people needing medical assistance.
In 1974 two sets of heat stress guidelines, each based on the wet bulb globe temperature (WBGT) index, were designed for men's National Collegiate Athletic Association (NCAA) Championship Division I distance running competitions. One set of guidelines was established to minimize the chance of heat injury during distance running events. A second set was designed to predict heat stress related performance decrements. During the time the heat injury guidelines were used (1974-1993), no heat injuries were reported. The purpose of this study was to assess the accuracy of the performance decrement guidelines and determine whether the WBGT indices were linearly related to men's championship distance running performance. WBGT index data were collected during the 1500-, 3000-steeplechase (SC), 5000-, and 10,000-m events at men's NCAA Division I Track and Field Championships held from 1974 to 1981 (excluding 1975). These data were compared to the average running performance of the top six finishers in each event. Analysis of the accuracy of the NCAA performance decrement guidelines revealed four unexpected performances out of 28 predictions. Pearson product-moment correlation and linear regression analyses between the WBGT indices and performance revealed statistically significant linear relationships for the 3000-SC and 10,000-m events (P < 0.05). A significant linear relationship was also found when the 1500-, 3000-SC, 5000-, and 10,000-m results were pooled (P < 0.05). In conclusion, the NCAA guidelines were effective in preventing heat injury and fairly successful in predicting performance. However, a linear relationship between WBGT indices and distance running performance did not exist in all running events.
Eight healthy males performed four rides to exhaustion at approximately 70% of their VO2max obtained in a neutral environment. Subjects cycled at ambient temperatures (Ta) of 3.6 +/- 0.3 (SD), 10.5 +/- 0.5, 20.6 +/- 0.2, and 30.5 +/- 0.2 degrees C with a relative humidity of 70 +/- 2% and an air velocity of approximately 0.7 m.s-1. Weighted mean skin temperature (Tsk), rectal temperature (Tre), and heart rate (HR) were recorded at rest, during exercise and at exhaustion. Venous samples were drawn before and during exercise and at exhaustion for determination of hemoglobin, hematocrit, blood metabolites, and serum electrolytes and osmolality. Expired air was collected for calculation of VO2 and R which were used to estimate rates of fuel oxidation. Ratings of perceived exertion (RPE) were also obtained. Time to exhaustion was significantly influenced by Ta (P = 0.001): exercise duration was shortest at 30.5 degrees C (51.6 +/- 3.7 min) and longest at 10.5 degrees C (93.5 +/- 6.2 min). Significant effects of Ta were also observed on VE, VO2, R, estimated fuel oxidation, HR, Tre, Tsk, sweat rate, and RPE. This study demonstrates that there is a clear effect of temperature on exercise capacity which appears to follow an inverted U relationship.
Equivalence trials aim to show that two treatments have equivalent therapeutic effects. The approach is to define, in advance, a range of equivalence -d to +d for the treatment difference such that any value in the range is clinically unimportant. If the confidence interval for the difference, calculated after the trial, lies entirely within the interval, then equivalence is claimed. Glaxo Wellcome has carried out a series of trials using this methodology to assess new formulations of inhaled beta-agonists and inhaled steroids in asthma. Eleven of these trials are used to review some practical issues in equivalence trials. For the series of asthma trials, a range for peak expiratory flow rate (PEF) from -15 to +15 l/min was chosen to be the range of equivalence. This fitted well with physicians' opinions and with previously demonstrated differences between active and placebo. The choice of the size of the confidence interval should depend on the medical severity of the clinical endpoints under consideration and the level of risk acceptable in assuming equivalence if a difference of potential importance exists. From this point of view, a recommendation in the CPMP Note for Guidance on Biostatistics that 95 per cent confidence intervals should be used is inappropriate. Intent-to-treat (ITT) and per-protocol (PP) analyses were compared for the eleven asthma trials. Confidence intervals were always wider for the PP analysis and this was entirely due to the smaller number of subjects included in the PP analysis. There was no evidence that the ITT analyses were more conservative in their estimates of treatment difference. The need to demonstrate equivalence in both an ITT and a PP analysis in a regulatory trial increases the regulatory burden on drug developers. The relative importance of the two analyses will depend on the definitions used in particular therapeutic areas. Demonstrating equivalence in one population with strong support from the other would be preferred from the Industry viewpoint. In trials with regulatory importance, prior agreement with regulators on the role of ITT and PP populations should be sought. Trial designs will need to take account of the estimated size of the PP population if adequate power is needed for both analyses. Careful design in the series of asthma trials, particularly identifying a population of patients with potential to improve, resulted in notable increases in lung function during the course of the trials for both treatments. This provided reassurance that equivalence was not due to a lack of efficacy for both treatments. In one trial equivalence was demonstrated overall but a treatment by country interaction was noted. However, this interaction could not be attributed to differences in patient characteristics or baseline data between the countries. Study conduct was also similar in the different countries. The conclusion was that the interaction was spurious and that the trial provided good evidence of equivalence.
The purpose of this study was to assess research aimed at measuring performance enhancements that affect success of individual elite athletes in competitive events.
Simulations show that the smallest worthwhile enhancement of performance for an athlete in an international event is 0.7-0.4 of the typical within-athlete random variation in performance between events. Using change in performance in events as the outcome measure in a crossover study, researchers could delimit such enhancements with a sample of 16-65 athletes, or with 65-260 in a fully controlled study. Sample size for a study using a valid laboratory or field test is proportional to the square of the within-athlete variation in performance in the test relative to the event; estimates of these variations are therefore crucial and should be determined by repeated-measures analysis of data from reliability studies for the test and event. Enhancements in test and event may differ when factors that affect performance differ between test and event; overall effects of these factors can be determined with a validity study that combines reliability data for test and event. A test should be used only if it is valid, more reliable than the event, allows estimation of performance enhancement in the event, and if the subjects replicate their usual training and dietary practices for the study; otherwise the event itself provides the only dependable estimate of performance enhancement. Publication of enhancement as a percent change with confidence limits along with an analysis for individual differences will make the study more applicable to athletes. Outcomes can be generalized only to athletes with abilities and practices represented in the study.
estimates of enhancement of performance in laboratory or field tests in most previous studies may not apply to elite athletes in competitive events.
The typical variation in an athlete's performance from race to race sets a benchmark for assessing the utility of performance tests and the magnitude of factors affecting medal prospects. We report here the typical variation in competitive performance of endurance runners.
Repeated-measures analysis of log-transformed official race times provided the typical within-athlete variation in performance as coefficients of variation (CV). The types of race were cross-country runs (4 races over 9 wk), summer road runs (5 races over 4 wk), winter road runs (4 races over 9 wk), half marathons (3 races over 13 wk and 2 races over 22 wk), and marathons (2 races over 22 wk).
Typical variation of times for the fastest quartile of male runners was 1.2-1.9% in the cross-country and road runs, 2.7% and 4.2% in half marathons, and 2.6% in marathons. Times for the slower half of runners in most events were more variable than those of the faster half (ratio of slower/faster CV, 1.0-2.3). Times of younger adult runners were more variable than times of older runners (ratio of younger/older CV, 1.1-1.8). Times of male runners were generally more variable than those of female runners (ratio of male/female CV, 0.9-1.7).
Tests of endurance power suitable for assessing the smallest worthwhile changes in running performance for top runners need CV < or = 2.5% and < or = 1.5% for tests simulating half or full marathons and shorter running races, respectively. Most of the differences in variability of race times between types of race, ability groups, age groups, and sexes probably arise from differences in competitive experience and attitude toward competing.
Null hypothesis statistical testing (NHST) has been debated extensively but always successfully defended. The technical merits of NHST are not disputed in this article. The widespread misuse of NHST has created a human factors problem that this article intends to ameliorate. This article describes an integrated, alternative inferential confidence interval approach to testing for statistical difference, equivalence, and indeterminacy that is algebraically equivalent to standard NHST procedures and therefore exacts the same evidential standard. The combined numeric and graphic tests of statistical difference, equivalence, and indeterminacy are designed to avoid common interpretive problems associated with NHST procedures. Multiple comparisons, power, sample size, test reliability, effect size, and cause-effect ratio are discussed. A section on the proper interpretation of confidence intervals is followed by a decision rule summary and caveats.
Three subjects walked continuously on a treadmill for periods of 1 hr or more at 180, 300, or 420 kcal/hr in a range of cool and hot climates from corrected effective temperature (CET) 10–32 C. At each rate of work rectal thermal equilibrium was practically independent of the influence of environment over a wide range of climates (“prescriptive” zone); the upper limit of the prescriptive zone appeared to be associated with the minimal bodily thermal gradient compatible with the transfer of adequate amounts of heat from the core to the periphery without placing the thermoregulatory system under disproportionately increased strain, in terms of circulatory response and elevated body core temperature; as such, this seems to be one possible criterion by which thermal environmental limits for everyday work may be assessed. The upper limits of prescriptive zones for work at an energy expenditure of 300 kcal/hr is CET 27.4 C and those for the lower and higher rates of work, respectively, were CET 30.2 C and 26.9 C.
Submitted on June 15, 1962
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