The Goldilocks Dose
How to get the benefits of running - without the complications
A recent article in the Financial Times asked a simple question: Is marathon running actually safe?
It explored the arguments for and against, with thoughts from leading sports and medical specialists including Exercise for Science’s Professor Alister Hart. We sum up the main messages…
The modern marathon is 26.2 miles of steady, repetitive impact, and has an almost mythical appeal. That instinct may run deep: humans may well have evolved as long-distance movers millions of years ago, endurance running to hunt and survive.
But how well does that evolutionary legacy translate to today’s runners?
The health gains
There is solid evidence that marathon training can be profoundly beneficial, particularly for cardiovascular health. A University College London study of first-time marathon runners showed improvements in blood pressure and aortic stiffness — effectively reversing arterial ageing by around four years. Cardiologist Anish Bhuva, who co-led the study, notes that older runners with higher initial blood pressure saw the biggest gains.
The benefits can also extend to the skeleton. As Professor Alister Hart explains: “The kneecap has the thickest cartilage in the body because it takes the greatest load.” In the exercise for Science MRI studies, runners ona four-month marathon training plan showed no joint deterioration, and some improved. “Bones need impact, they strengthen through it,” Alister says.
Psychologically, benefits are just as notable. Sport psychologist Josephine Perry highlights that marathon training adds structure, reduces overthinking and strengthens social belonging. Research from the UCLA Department of Psychiatry and Biobehavioral Sciences even suggests higher fitness correlates with faster information processing - delivering a potential cognitive boost.
The risks
But running a marathon is not automatically healthy. In the article, cardiologist Carl Lavie argues that the “sweet spot” for endurance exercise is far below marathon-training levels: at around 30–40 minutes per day. Consistently exceeding 10 hours a week may increase risks such as atrial fibrillation or coronary artery calcification. It’s suggested that middle-aged runners tackling marathons and ultras, screening tests like ECGs or coronary calcium scoring could help rule out underlying heart disease.
Musculoskeletal strain is another concern. Studies of ultra-endurance athletes show up to half experience issues from temporary cartilage swelling to soft-tissue changes. Ultra-running researcher Guillaume Millet of Jean Monnet University emphasises that extreme distance places athletes near the limits of human physiological adaptation. Fatigue, insufficient recovery and repetitive strain all raise the risks of injury.
Even Professor Daniel Lieberman, an evolutionary biologist at Harvard University cautions that although humans are built for endurance, our ancestors did not run repetitive pavement miles. Natural movement was varied — a mix of walking, running, carrying and lifting.
The Goldilocks Dose
Professor Hart offers a balanced conclusion: that marathon running is a Goldilocks activity. Too much leads to stress fractures and overuse injuries; too little weakens the skeleton. He explains that around 90% of runners will experience injury at some point, most commonly around the kneecap due to poor patellofemoral tracking.
Hart highlights practical solutions: strength drills like glute bridges and cross-training such as cycling can keep kneecap motion aligned and reduce injury risk. It’s important to understand how to train sustainably, not excessively.
So, is it safe?
The Financial Times article suggests that it depends. For many, marathon training brings cardiovascular, psychological and cellular benefits. But overloading the body can tip those benefits into harm.
While humans evolved to move, that didn’t necessarily involve 26 mile distances. For most people, the healthiest choice is to run regularly, mix movement types, and follow Prof Hart’s Goldilocks rule: not too little, not too much - an amount that’s just right.