- Running a marathon significantly increases breathing and heart rate to supply muscles with more oxygen and nutrients, alongside an increase in stroke volume.
- Some runners may experience 'cardiac drift', where heart rate rises disproportionately, often indicating dehydration or overheating and increased cardiovascular strain.
- Marathons heavily engage lower body, core, and arm muscles, causing micro-tears that lead to muscle adaptation and potential delayed onset muscle soreness post-race.
- The body's core temperature rises due to heat generation, triggering sweating and redirection of blood flow to the skin for cooling, which can result in fluid and electrolyte loss.
- Initially, glycogen is the main fuel source, but as stores deplete, the body switches to slower fat oxidation, and insufficient fuelling can lead to 'hitting the wall' around miles 18-20 due to energy depletion.
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