This blog provides an overview of a recently published study on the “Association between feels-like temperatures and injury risk during international outdoor athletic championships: A prospective cohort study on 29,579 athlete starts during 10 championships” [1].

Why is this study important?

Anecdotal field experiences report that when the environmental temperatures are cold, athletes get more injuries than when it is hot. Athletes, coaches and medical staff, try to have this in mind when they are training and competing. 

However, there were few scientific events about this, which does not allow us to argue and support about this potential external environmental risk factor. Experimental animal studies show increased tissue damage (i.e., muscle or tendon) with decreased tissue temperature [2–4]. In athletics, lower rates of hamstring injuries were reported when temperatures were above 25°C, with higher rates when temperatures were between 10-14.9°C [5]. An improved understanding of the potential association between environmental temperatures and injuries would be of great interest to help the development of injury risk reduction strategies. Such a knowledge is important for both 1) clinical applications and 2) scientific knowledge.

How did the study go about this?

This study was a total population study. We used i) injury data routinely collected by medical teams using the same methods during 10 international outdoor athletics championships from 2007 to 2022, ii) feels-like temperatures data using the Universal Thermal Climate Index (UTCI) [6] from Di Napoli et al., [7] (who combined the meteorological variables air temperature, humidity, wind speed and solar radiation as provided in the ERA5-HEAT dataset [8], extracted hourly during each championship), and iii) exposure data (i.e., number of athlete starts of each round and event of each championship). 

We then performed Poisson regressions with incidence rates (number of injuries per 1,000 athlete starts) as outcomes and UTCI as a predictive variable adjusted for sex, for all and time-loss injuries, for different injured tissue types (i.e., muscle, tendon, ligament, articular, bone, and skin) and specific discipline (i.e., sprints, hurdles, jumps, throws, middle distance, long distance, marathon, and race walking).

What did the study find?

During 10 international outdoor athletics championships from 2007-2022, a total of 1,203 in-competition injuries were reported for 29,579 athlete starts. 

The main findings of the present study were that:

• • For all in-competition injuries (i.e., all injured tissue types and all disciplines), higher UTCI was associated with lower incidence rates for time-loss injuries (Incidence Rate Ratio (IRR)=0.98, 95%CI: 0.97-0.98) but not for all injuries (IRR=1.00, 95%CI: 1.00-1.01). 
  • Based on injured tissue type with all disciplines included, higher UTCI was associated with lower incidence rates for all (IRR=0.97, 95%CI: 0.97-0.98) and time-loss (IRR=0.96, 95%CI: 0.96-0.96) muscle injuries.
  • Based on the specific discipline, higher UTCI was associated with lower incidence rates for all and time-loss muscle injuries for sprints (IRR=0.95, 95%CI: 0.95-0.96, and IRR=0.94, 95%CI: 0.93-0.94, respectively), hurdles (IRR=0.97, 95%CI: 0.96-97, and IRR=0.95, 95%CI: 0.94-0.96, respectively), and throws (IRR=0.97, 95%CI: 0.97-0.98).

What are the key take-home points? 

From a clinical perspective, these results can be presented as: for every 10°C decrease in feels-like temperature (in the whole UTCI data range from 1.1°C to 38.9°C), the risk of time-loss injury increased by about 20%, and the risk of muscle injury increased by 30-40% [1]. Specific analyses of each discipline revealed that this association was also found for sprints, hurdles and throws, where for every 10°C decrease (in the whole UTCI data range from 1.1°C to 38.9°C), the risk of injury or muscle injury increased by 20-60% according to disciplines [1]. 

The present results may inform injury risk reduction strategies at athletics competitions, and especially for muscle injuries which are the predominant in athletics [9,10]. Although the precise mechanism for higher muscle injury rates with lower feels-like temperatures requires further investigation, the present results provide an additional opportunity for risk reduction strategies.

Since lower feels-like temperatures were associated with a higher risk of muscle injuries, we can suggest improving the strategies to manage with lower feels-like temperatures, by, for instance, i) adapting clothing by wearing warmer clothing in cold outdoor environments with the aim of limiting muscle temperature decrease, ii) active and/or passive methods with the aim of increasing muscle temperature (e.g., improving and increasing warm-up quality and duration, using devices to heat the body) [11], and/or iii) adapting the timing of the event to the weather conditions or by anticipating preparation according to the weather conditions to avoid/limit environmental heat or cold stress conditions.

References

1 Edouard P, Dandrieux P-E, Klöwer M, et al. Association between feel-like temperatures and injury risk during international outdoor athletic championships: a prospective cohort study on 29 579 athlete starts during 10 championships. Br J Sports Med. Published Online First: 22 October 2024. doi: 10.1136/bjsports-2023-108050

2 LaBan MM. Collagen tissue: implications of its response to stress in vitro. Arch Phys Med Rehabil. 1962;43:461–6.

3 Warren CG, Lehmann JF, Koblanski JN. Elongation of rat tail tendon: effect of load and temperature. Arch Phys Med Rehabil. 1971;52:465–74.

4 Safran MR, Garrett WE, Seaber A V., et al. The role of warmup in muscular injury prevention. Am J Sports Med. 1988;16:123–9. doi: 10.1177/036354658801600206

5 Tokutake G, Kuramochi R. Association of hamstring strain injuries with season and temperature in track and field collegiate athletes in Japan: A descriptive epidemiological study. Asian J Sports Med. 2020;11:e96743. doi: 10.5812/asjsm.96743

6 Klöwer M, Edouard P, Niess AM, et al. Forecasting feels-like temperatures as a strategy to reduce heat illnesses during sport events. Br J Sports Med. 2023;57:559–61. doi: 10.1136/bjsports-2022-106413

7 Di Napoli C, Hogan RJ, Pappenberger F. Mean radiant temperature from global-scale numerical weather prediction models. Int J Biometeorol. 2020;64:1233–45. doi: 10.1007/s00484-020-01900-5

8 Di Napoli C, Barnard C, Prudhomme C, et al. ERA5-HEAT: A global gridded historical dataset of human thermal comfort indices from climate reanalysis. Geosci Data J. 2021;8:2–10. doi: 10.1002/gdj3.102

9 Edouard P, Hollander K, Navarro L, et al. Lower limb muscle injury location shift from posterior lower leg to hamstring muscles with increasing discipline-related running velocity in international athletics championships. J Sci Med Sport. 2021;24:653–9. doi: 10.1016/j.jsams.2021.02.006

10 Edouard P, Reurink G, Mackey AL, et al. Traumatic muscle injury. Nat Rev Dis Primers. 2023;9:56. doi: 10.1038/s41572-023-00469-8

11 Racinais S, Cocking S, Périard JD. Sports and environmental temperature: From warming-up to heating-up. Temperature. 2017;4:227–57.

 

Authors and affiliations:

Pascal Edouard (1,2,3), Pierre-Eddy Dandrieux (1,4,5) Milan Klöwer (6), Astrid Junge (5), Sébastien Racinais (7,8), Pedro Branco (3), Karsten Hollander (5), Laurent Navarro (4)

Affiliations:

1 Université Jean Monnet, Lyon 1, Université Savoie Mont-Blanc, Inter-university Laboratory of Human Movement Biology, EA 7424, F-42023, Saint-Etienne, France

2 Department of Clinical and Exercise Physiology, Sports Medicine Unit, University Hospital of Saint-Etienne, Faculty of Medicine, Saint-Etienne, France

3 European Athletics Medical & Anti-Doping Commission, European Athletics Association (EAA), Lausanne, Switzerland

4 Mines Saint-Etienne, Univ Lyon, Univ Jean Monnet, INSERM, U 1059 Sainbiose, Centre CIS, F-42023 Saint-Etienne France

5 Institute of Interdisciplinary Exercise Science and Sports Medicine, MSH Medical School Hamburg, Hamburg, Germany

6 Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge MA, USA

7 CREPS Montpellier – Font Romeu, Environmental stress unit, Montpellier, France

8 DMEM, Univ Montpellier, INRAE, Montpellier, France

Contact : Pascal Edouard, MD PhD, Department of Clinical and Exercise Physiology, Sports Medicine Unit, IRMIS, Campus Santé Innovations, University Hospital of Saint-Etienne, 42 055 Saint-Etienne cedex 2, France. Tel.: +33 674 574 691; Fax numbers: +33 477 127 229; E-mail: Pascal.Edouard@univ-st-etienne.fr