We spoke to Dr Richard Blagrove, an expert in the physiology of endurance running, who explained why your physiology will drive your performance, what happens to your body across the 26.2 miles, and the importance of pacing and developing a varied training programme.
What makes a good marathon runner?
“For many years, sports scientists have been able to predict marathon performance with reasonable accuracy by looking at three key physiological factors: a runner’s maximum aerobic capacity (known as ‘VO₂max’), the proportion of that capacity they access at marathon pace, and how efficiently they run.
“More recently, our research at Loughborough University has shown that a fourth factor - known as ‘durability’ - may be just as important, if not more so, than these three classic determinants of performance.”
What is durability and why is it important?
“Durability describes how well your body can maintain its normal physiological performance as the race progresses, compared with when you are fresh. It helps explain why runners feel comfortable early on, only to struggle in the final 10 miles of events like the London Marathon.
“Our research shows that highly trained runners experience only small declines in aerobic capacity and can maintain their running efficiency even after two hours at marathon pace. As a result, runners with greater durability can hold their speed for longer, and sometimes even accelerate towards the finish, while those with worse durability face the often-unavoidable slowdown in the second half of the race.”
What happens to your body across 26.2 miles?
“A runner’s physiology changes during a marathon for several reasons. Carbohydrate stores in the most economical muscle fibres start to run low, so the body recruits less efficient fibres that cost more energy to use.
“Fatigue also subtly alters running technique, shifting work away from the ankle and reducing the natural ‘spring’ in the legs, which makes each stride more demanding. At the same time, the nervous system works harder to activate tired muscles, further increasing energy expenditure.
“The body is forced to rely more on fat stores, which requires more oxygen than carbohydrate to produce the same energy. Together, these gradual changes make holding the same pace increasingly difficult as the miles tick by.”
Pacing can have a huge impact
"Crucially, the physiological effects that cause runners to slow down in a marathon start earlier than most realise. Our research shows that, particularly when starting too fast, running efficiency can decline after around an hour of marathon pace, which for many is well before halfway. So, a pacing strategy that tries to ‘bank some time’ in the early stages is not very sensible!"
Can runners improve their durability?
“The good news is that durability can be improved, even during the marathon itself. Runners who build higher weekly mileage, do regular long runs, and include strength training tend to hold their efficiency better. Their bodies slow down more gradually, allowing them to maintain their performance deeper into the marathon.
“Carbohydrate availability is crucial for durability because it fuels the most efficient muscles even over long distances. That’s why loading up on carbohydrates before the race, and topping them up regularly during the marathon, is essential.
“Runners setting off through the streets of London on Sunday should be aware that efficiency deteriorates earlier than they might expect, but those who pace smartly and fuel well with carbohydrates are more likely to hold their pace and achieve their goal time.”
ENDS
For further comments or interview requests with Dr Richard Blagrove, please email the PR team or call 01509 222224.