There is nothing better than physical exercise to stay in shape and reduce the risks associated with many pathologies. However, how do you choose the type of daily physical activity you want to practice? Is it better to walk or run? Is one more effective in terms of health benefits than the other? Does running really damage the joints as we can read everywhere? Fortunately for those who are still questioning the merits of these two activities, science has repeatedly looked into the subject in order to clarify and detail the contributions and risks of these.
The idea that running is the best exercise for humans has many supporters. Among them is Daniel Lieberman of Harvard University, who argues that we evolved to run long distances. He believes our now largely untapped talent for sustained hunting — chasing animals over long distances — in hot conditions gives us an advantage over other animals and has shaped our evolutionary history.
And we're not just good at running because we're good at walking. A range of adaptations such as sweat glands and hairless skin to help with cooling, the right balance of muscle types and a special ligament to keep our head stable when running means that over long distances we can outrun almost all other animals.
“Thanks to our evolutionary history, we all have the anatomy and physiology necessary to walk and run — assuming we are not disabled. In today's world, we have medicalized, commodified, and commercialized exercise, but physical activity, at its heart, is something we evolved to be says Lieberman.
Current US and UK government physical activity guidelines recommend adults get at least 2.5 hours of moderate exercise or 75 minutes of vigorous exercise each week. In the United States, only half the population meets these guidelines and the situation is only slightly better in the United Kingdom. But what is moderate and vigorous exercise?
In the late 1980s, Bill Haskell of Stanford University in California asked the same question and developed a gold standard for comparing exercise and quiet sitting. When seated, we expend about 1 kilocalorie per hour for each kilogram of body mass. Haskell and his colleagues called this a metabolic equivalent, or 1 MET. For an 80 kilogram person, this resting metabolic rate is approximately 1920 kcal per day.
All physical activities can be expressed in METs, and there is now a Compendium of Physical Activities which contains an eclectic mix of these, described using this system. This elegant solution to the definition of exercise includes three categories:light exercise up to 3 METs, moderate exercise between 3 and 6 METs, and vigorous exercise — for anything over 6 METs.
Walking around, at about 2 METs, is light exercise, while brisk walking is at 5 METs. The transition to running at around 7 km/h is where the exercise falls into the vigorous category. A very brisk walk and a slow run are roughly equivalent, in terms of effort and calories burned. But is this also true for their health benefits?
At first glance, it may seem like the race is winning. A study from January, for example, would be enough to entice anyone to sign up for a marathon. This looked at 138 first-time marathon runners and found that training and completing the 41km run, even at a slow pace, equates to a 4-year reduction in the age of the cardiovascular system, or even more for those who are older and less fit.
Running also gets a surprising health check in several large-scale studies that follow people for many years:they show that this exercise has a dose-related effect. Running more often is better, but with diminishing returns. However, the greatest gains occur when transitioning from no physical activity to some exercise. “The greatest health benefits are seen with just a little bit of running each week, less than 60 minutes, an amount that would fit most schedules “, explains Angelique Brellenthin, researcher at Iowa State University.
Other benefits are clear from long-term US studies. In studies of the health of National Walkers and National Runners, Paul Williams and Paul Thompson of Lawrence Berkeley National Laboratory tracked the health status of approximately 16,000 walkers and 33,000 runners over six years. Compared to walkers, runners had a 38% lower risk of high blood pressure and a 71% lower risk of type 2 diabetes.
However, when the researchers controlled for energy expenditure and weight difference between the groups, the benefits of walking and running were comparable. Williams later analyzed data on breast and brain cancer, and the reductions in risk of death from running or walking were, again, similar if energy expenditure was the same.
Even a small amount of exercise brings significant health gains. This was the case in a massive 2011 study that followed more than 400,000 people in Taiwan over an average of eight years, noting their exercise habits and the number of deaths from different causes. This showed that just 15 minutes a day of moderate exercise, such as brisk walking, was enough to reduce the risk of death by 10% compared to sedentary participants. This effect could also be achieved by about 5 minutes of vigorous exercise such as running, giving a time-benefit ratio between running and walking of three to one.
“The fact that running provides similar benefits to walking, but in half the time is one of the main reasons why running is attractive for health. There may be additional benefits of running, particularly for cardiovascular health, related to the higher intensity of running. However, intensity is relative to individual fitness, and a brisk walk will provide many health benefits for people like beginners and older adults says Brellenthin.
There is no doubt that running is a high impact activity. When the foot hits the ground, a force equivalent to two or three times your body weight acts through the body. Bones, joints, muscles and ligaments must absorb this force. The question is whether it wears down your joints, as many of us believe.
Alister Hart, surgeon at Royal National Orthopedic Hospital, London , recruited 82 runners participating in the London Marathon, all over the age of 40 and having never run this distance before. Using MRI, the runners' knees were scanned in detail six months before the race and again a few weeks after. The scans revealed that the main load-bearing compartments of the knee — the parts most susceptible to long-term arthritis — had become stronger as a result of marathon training.
The ball and socket portion (patella) of the joint, however, showed damage, but follow-up examinations revealed that this was reversed six months later when the participants returned to less intense running regimens. Hart's take home message is "running can have long term benefits for your knees".
The team also carried out a study on the hips, which found that a 560 km marathon training program, ending in running, did not cause pre-arthritic changes in the hip joint. “Our results suggest that high impact forces during marathon running were well tolerated by the hip joint says Horga.
