Running and other strenuous activities are believed to raise the risk of osteoarthritis (OA), relative to less strenuous activities such as walking, but is it really so?
A new study published in the journal Medical Science Sports Exercise examines whether running, walking and other exercise affect OA and hip replacement risk and evaluates the role of Body Mass Index (BMI) in mediating these relationships.
The study tracked 74,752 runners over 7.1 years and 14,625 walkers over 5.7 years, looking at the number of OA and hip replacement cases in each group.
The results showed that the runners (excluding injury-prone Olympic-class athletes who are at higher risk of developing OA and who formed a very small portion of the 90,000 study participants) had half the risk of OA and hip replacement relative to walkers who spent equal amount of energy, measured in metabolic equivalent hours per day (METhr/d).
Surprisingly, other forms of exercise were found to be more damaging to the knee than either walking or running.
Many people think of exercise as wearing down our body the same way a car engine´s bearings wear down from extensive use, says Paul Williams, an epidemiologist at the Lawrence Berkeley Laboratory in Berkeley, California. But studies of animal models have demonstrated that exercise leads to thickening of the cartilage and increase of its elasticity. So, instead of wearing down our bearings, running may oil them, Williams says.
Running may have some special protective properties, but half of the positive effect comes from weight loss. You will still have these protective properties if you are lean no matter how you have achieved it. In fact, the OA risk increases by 5% for every point increase in a person´s BMI, which is generally related to the increased stress on the joints as a result of heavier weight.
The study also found that people involved in forms of strenuous activities other than running were at a 21% greater risk of OA and 99% greater risk of hip replacement relative to those who exercised the least.
In fact, what makes injury-free walking and running safer than going to the gym relates to the way we bend our knee. In the gym, we do the deep knee bending (the same moves a carpet layer performs while doing their job). When we are running, however, we are not bending our knees to the same degree.
Even though OA risk rises by 3.9% per year for men and by 6.1% per year for women, the benefits of running are greater than the risks for 70 years, Williams says, as quoted by health and fitness and travel news website outsideonline.com.