Most people consider running a pretty easy sport to get into. You lace up some shoes and go—how much simpler could it be? Well, for runners of every ability and skill level, from casual weekend joggers to ultramarathoners, it’s a little more complicated than that. Runners fret over their form, how to protect their joints, and the proper footwear to keep them safe from injury.
Runners are also concerned with finding the best places to run. Some prefer to jog in the woods, while others like the safety and security of a treadmill. Some enjoy the feeling of a run on the beach; others would rather take in the sights on a city sidewalk. It’s possible to run on just about any surface—grass, dirt, gravel, pavement, sand, treadmill, or track—but each one has its advantages and disadvantages. For getting the best possible workout  and preventing joint damage, what’s the best bet?
Run for Your Life
As we run, the muscles in our feet and legs act like springs, redirecting our bodies’ momentum from downward to upward each time one of our feet strikes the ground. The average runner has about 180 footfalls per minute, and with each stride, some of that energy from the body is transferred into the ground as well. Springy, cushioned surfaces absorb some of the shock while reflecting energy upward to help propel our bodies along. Hard, inflexible surfaces neither absorb the energy of the impact nor bounce momentum back into our legs. Soft, slippery surfaces tend to be easier on joints in the long term, while rigid, inflexible surfaces are better for preventing injuries in the short term.
Most biomechanics experts and professional runners prefer to run on softer, more cushioned surfaces, like grass and wooded trails; these types of terrain are easiest on the joints because they absorb impact. In addition, their tiny variances help build strength in the small muscles of your calves and thighs, which have to work harder to stabilize your legs on unstable, uneven surfaces. For activating these small muscles, sand is the ultimate workout.
When it’s impossible to run outside, most runners prefer to stay indoors on a treadmill. It might not provide much in the way of scenery, but a treadmill does have a spring-mounted band that absorbs shock and protects joints; however, because it doesn’t allow you to turn, it won’t exercise the same muscles that irregular outdoor surfaces do.
Unevenness and unpredictability may make grass and dirt trails a good workout, but these characteristics also make them a potentially bad choice, especially for novice runners. Bumps, divots, and tree roots can be like an obstacle course for a runner. It’s easy to end up with a pulled muscle or a sprained ankle, since such inconsistencies in the terrain are unavoidable. People who regularly use outdoor trails report that they often can’t appreciate the beautiful scenery, since they’re focusing their attention on the trail and making sure they avoid pits and other dangerous obstructions in their path. Also, when grass gets wet or dirt gets muddy, slipperiness is an additional hazard. Running on the beach often requires people to run at an angle, and forcing one’s legs to compensate for the gradual slope of the shoreline can lead to overuse injuries on one side of the body. Runner’s World magazine gives grass the highest rating of any terrain, although it acknowledges that the best grass for running, such as that of well-manicured golf courses, is usually off-limits.
Pounding the Pavement
Harder surfaces like asphalt, concrete, and athletic tracks provide considerably less shock absorption, but they do offer stable, predictable running surfaces. They might not be everyone’s favorite, but they are ubiquitous and free. People who live in urban areas may not have access to earthen trails, but they can always find an unbroken stretch of concrete on which to run. While hard surfaces are more punishing to the joints, they make it easy to measure distance and keep up a steady pace. They’re also usually free of hills or obstacles that might get in the way.
Unfortunately, running on hard surfaces is sometimes unavoidable. Most races and marathons are held on roads, so runners need to be accustomed to the experience of running on pavement. Runner’s World ranks pavement, which is ten times as hard as asphalt, as one of the worst surfaces to run on. (Snow is the only one that’s worse.) Most experts recommend limiting the amount of time you spend running on hard surfaces, if possible, since they’re hardest on the body.
However, some biomechanics studies have found that it doesn’t really matter what surface a person runs on—the human body will accommodate by adjusting its stride to equalize the shock. In other words, when running on an unyielding sidewalk, our bodies adapt our gait to minimize impact, and when running on loose terrain, they adapt to stiffen our legs and keep motion constant.
Another important factor besides the terrain is footwear—shoes with lateral support are better on unstable trail surfaces, while those with only heel support are more appropriate for tracks and treadmills. Some podiatrists and exercise experts even believe that the best way to run is barefoot.
Ultimately, surfaces that are soft and cushioned are better for our bodies than those that are flat and rigid. But the best practice, according to physicians and runners alike, is to run on a mixture of surfaces. Using soft outdoor trails part of the time can relieve pressure on the joints, and resorting to hard concrete and asphalt surfaces sometimes helps you avoid strains and sprains. A treadmill is a good compromise, if perhaps a little boring. Ultimately, there are as many ways to run as there are types of runners. A “trial run” is, literally and figuratively, the best way to know what’s right for you.