From the Guidelines
Feeling sick after running a half marathon is typically due to dehydration, electrolyte imbalances, and glycogen depletion, which can be prevented by proper hydration and nutrition strategies, as supported by recent studies 1. To prevent post-exertional malaise after completing a half marathon, it is essential to understand the physiological factors that contribute to this condition. Prolonged exercise, such as running a half marathon, leads to significant stress on the body, resulting in dehydration, electrolyte imbalances, and glycogen depletion.
Physiological Factors
- Dehydration: occurs when the body loses more fluids than it takes in, leading to an imbalance in electrolytes and a decrease in blood volume 1.
- Electrolyte imbalances: essential minerals such as sodium, potassium, and calcium are lost through sweat, leading to muscle cramps, fatigue, and other symptoms 1.
- Glycogen depletion: the body's stored energy source is depleted, leading to fatigue, weakness, and dizziness 1.
Prevention Strategies
- Proper hydration: drinking 16-20 ounces of fluid 2 hours before running and 6-8 ounces every 20 minutes during the race, preferably with electrolyte drinks like Gatorade or Nuun tablets 1.
- Nutrition: eating a light, carbohydrate-rich meal 2-3 hours before the race and considering consuming energy gels or chews containing 25-30g of carbohydrates every 45-60 minutes during the run 1.
- Recovery: rehydrating with electrolyte-containing fluids and consuming a small meal with a 3:1 carbohydrate-to-protein ratio within 30 minutes after finishing the race 1.
Additional Considerations
- Gastrointestinal distress: intense exercise can divert blood from the digestive system to the muscles, causing nausea, vomiting, and other symptoms 1.
- Stress hormones and inflammatory compounds: produced during prolonged exertion, can trigger nausea and other symptoms 1.
- Proper training, nutrition, and recovery strategies: can significantly reduce post-race symptoms and improve overall performance 1.
From the Research
Post-Exertional Malaise after Completing a Half Marathon
- Post-exertional malaise, a condition characterized by prolonged fatigue and exhaustion after physical activity, can occur after completing a half marathon [(2,3,4)].
- Several factors contribute to post-exertional malaise, including:
- Dehydration and electrolyte imbalance [(5,6)]
- Muscle damage and inflammation 5
- Cardiovascular strain [(2,6)]
- Gastrointestinal symptoms [(2,4)]
- Immune system suppression [(2,3)]
- Changes in biomarkers suggesting pathological events in certain organ systems, such as cardiovascular, renal, gastrointestinal, liver, hematological, immune, musculoskeletal, central nervous, and endocrine systems, can often be observed after a marathon 2.
- These changes are usually temporary, depending on intensity and duration of the performance, and usually normalize within a week [(2,3)].
- Half marathon runners may experience similar physiological and pathophysiological changes as marathon runners, although the severity and duration of these changes may be less pronounced [(2,3)].
- It is essential to note that individual factors, such as training background, pacing, and environmental conditions, can influence the occurrence and severity of post-exertional malaise [(5,6)].