In the world of endurance running, success is often attributed to mileage, discipline, and mental grit. But for athletes preparing for half marathons and marathons in hot and humid climates, like those across the Indian subcontinent, environmental stressors can be the silent saboteurs of performance. Among these, humidity stands out as a critical, yet often underestimated, factor.
Humidity: The Invisible Load on Performance
The impact of humidity on endurance performance has been widely studied, particularly in relation to thermoregulation and exercise-induced cramping. High humidity impairs the body’s ability to cool itself through sweat evaporation, leading to elevated core temperatures, increased heart rate, and accelerated dehydration. These physiological changes significantly increase the risk of muscle cramping, electrolyte imbalance, and heat-related illnesses (Knechtle et al., 2021);(Muhamed et al., 2016)).
Research by Gutiérrez-Vargas et al. (Gutiérrez-Vargas et al., 2020) shows that dehydration in humid conditions is associated with increased hematocrit levels post-marathon, indicating reduced plasma volume—a key contributor to cramping and performance decline. Nikolaidis et al. (Nikolaïdis et al., 2019)further highlight that even a 1°C increase in temperature can slow race times, underscoring the compounded effects of heat and humidity on running efficiency.
Case Study: Wipro Bangalore Marathon, 21st September 2025
The recently concluded Wipro Bangalore Marathon offered a real-time example of how humidity can impact race outcomes. Despite a relatively pleasant ambient temperature of 21°C, the humidity levels ranged from 88% to a peak of 94% during the mid-phase of the race. This created a deceptively challenging environment for runners, especially those unacclimated to such conditions.
Medical tents at the event recorded a high rate of medical incidents, particularly among half marathon and marathon participants. The distribution of medical cases by race category is shown below:
Cramping and Other Medical Issues: A Closer Look
Half Marathon Medical Data
Among half marathon participants, muscle cramps accounted for nearly half (46.2%) of all medical issues. Dizziness, fainting, and breathing difficulties were also prominent, highlighting the physiological toll of humidity even in mid-distance events.
Marathon Medical Data
In the full marathon, the numbers were even more striking. Muscle cramps made up 55.6% of all reported issues, followed by sprains (22.2%) and dizziness/fainting (9.3%). These figures align with global research on the physiological risks of prolonged exertion in humid environments (Maughan et al., 2011); (Hermand et al., 2019)).
Perception vs. Reality: The Training Load Disconnect
Interestingly, when we assessed training perception among recreational runners preparing for these events, most rated the difficulty as “moderate(3 out of 5).” This suggests a disconnect between perceived effort and actual physiological demand, especially under environmental stress.
This misalignment often leads to underpreparedness, particularly in hydration and fueling strategies. Many runners mistakenly believe that hydration is only important in the final weeks before the race or worse even ,only on race day. In reality, hydration and fueling should be integral to the entire training cycle.
Hydration and Fueling: Not Just a Race-Day Concern
In our Enerjiva High Performance programme, which supports elite Indian ultramarathoners who represent Team India in various Asian and World championships, we have seen firsthand how structured hydration and carbohydrate strategies can transform outcomes. Athletes like Amar Singh Devanda, who recently set national records for 12hr race and is current national record holder for 24hr race, follow meticulously monitored protocols that include:
- Carbohydrate periodization: Tailoring intake based on training intensity and duration matching substrate utilization during performance and recovery.
- Pre-, during-, and post-run fueling: Using energy gels(Enerjiva Energy gels), salt capsules(Enerjiva Salt caps), and electrolyte solutions(Enerjiva Hydro).
- Hydration testing: Measuring sweat rate and electrolyte loss to personalize fluid intake.
These strategies aren’t just for elites. Recreational runners can benefit immensely from:
- Practicing fueling during long runs to train the gut and avoid GI distress.
- Using salt capsules and electrolyte drinks to maintain sodium balance.
- Tracking body weight pre- and post-run to estimate fluid loss and rehydration needs.
Martínez-Cano et al. (2018) (Martínez-Cano et al., 2018)and Racinais et al. (Racinais et al., 2015)support this approach, noting that individual hydration responses vary, and that electrolyte balance is critical in preventing cramping and sustaining endurance.
Planning the 12-Week Microcycle: A Holistic Approach
A well-structured 12-week training block should include:
- Heat acclimation: At least 10–14 days of exposure to race-like conditions.
- Hydration strategy testing: During key long runs, not just race week.
- Carbohydrate fueling: Practiced and refined across intensities and durations.
- Volume simulation: Long runs that mimic race-day distance and conditions.
This approach ensures that athletes are not only physically prepared but also metabolically and thermally conditioned for the demands of race day.
Conclusion: Prepare for the Environment, Not Just the Distance
Running a marathon or half marathon in humid conditions is not just a physical challenge, it’s a physiological puzzle. Success lies in understanding the environment, respecting the body’s limits, and training with intention. Whether you're chasing a personal best or simply aiming to finish strong, integrating hydration, fueling, and heat adaptation into your training plan is non-negotiable.
Reference:
GUTIéRREZ-VARGAS, R., MARTíN-RODRíGUEZ, S., SáNCHEZ–UREñA, B., RODRíGUEZ-MONTERO, A., CABRERA, J. S., GUTIéRREZ-VARGAS, J. C., ŠIMUNIč, B. & ROJAS‐VALVERDE, D. 2020. Biochemical and Muscle Mechanical Postmarathon Changes in Hot and Humid Conditions. The Journal of Strength and Conditioning Research, 34, 847–856.
HERMAND, É., CHABERT, C. & HüE, O. 2019. Ultra-Endurance Events in Tropical Environments and Countermeasures to Optimize Performances and Health. International Journal of Hyperthermia, 36, 752–759.
KNECHTLE, B., VALERO, D., VILLIGER, E., ALVERO‐CRUZ, J. R., NIKOLAïDIS, P. T., ĆUK, I., ROSEMANN, T. & SCHEER, V. 2021. Trends in Weather Conditions and Performance by Age Groups Over the History of the Berlin Marathon. Frontiers in Physiology, 12.
MARTíNEZ-CANO, J. P., CORTES-CASTILLO, V., MARTINEZ-VILLA, J., RAMOS, J. C. & URIBE, J. P. 2018. Dysnatremia Among Runners in a Half Marathon Performed Under Warm and Humid Conditions. BMJ Open Sport & Exercise Medicine, 4, e000351.
MAUGHAN, R. J., OTANI, H. & WATSON, P. 2011. Influence of Relative Humidity on Prolonged Exercise Capacity in a Warm Environment. European Journal of Applied Physiology, 112, 2313–2321.
MUHAMED, A. M. C., ATKINS, K., STANNARD, S. R., MüNDEL, T. & THOMPSON, M. W. 2016. The Effects of a Systematic Increase in Relative Humidity on Thermoregulatory and Circulatory Responses During Prolonged Running Exercise in the Heat. Temperature, 3, 455–464.
NIKOLAïDIS, P. T., GANGI, S. D., CHTOUROU, H., RüST, C. A., ROSEMANN, T. & KNECHTLE, B. 2019. The Role of Environmental Conditions on Marathon Running Performance in Men Competing in Boston Marathon From 1897 to 2018. International Journal of Environmental Research and Public Health, 16, 614.
RACINAIS, S., ALONSO, J. M., COUTTS, A. J., FLOURIS, A. D., GIRARD, O., GONZáLEZ‐ALONSO, J., HAUSSWIRTH, C., JAY, O., LEE, J., MITCHELL, N., NASSIS, G. P., NYBO, L., PLUIM, B. M., ROELANDS, B., SAWKA, M. N., WINGO, J. E. & PéRIARD, J. D. 2015. Consensus Recommendations on Training and Competing in the Heat. Scandinavian Journal of Medicine and Science in Sports, 25, 6–19.