Modern running shoes do an excellent job of reducing impact. A wide variety of technologies—including cushioning materials, gels, air channels, and other design features—are intended to reduce the compressive loads placed on the joints and body while running.

There is a potential drawback, however. If most of your running is done on relatively smooth, paved surfaces, the muscles and joints of the lower leg do not have to work as hard to stabilize the body. Joint stability and lower-leg strength are important components of injury prevention, and this is one reason trail running can be a valuable addition to a runner's training program.

Trail Running as Strength Training for Runners

Running over uneven and constantly changing surfaces forces the muscles of the lower leg to react to the terrain and stabilize the body. In many ways, trail running can function as sport-specific strength training for the lower legs.

If you are new to trail running, you may be surprised by how sore or fatigued your lower legs feel afterward. The calves, feet, ankles, tendons, ligaments, and other stabilizing muscles are exposed to stresses that are not present to the same degree when running on a consistent paved surface.

This varied loading can help develop strength and stability throughout the lower leg. Running on softer surfaces can also challenge the muscles involved in propulsion and help develop strength and power during toe-off.

How to Add Trail Running to Your Training Plan

As with any new training stimulus, trail running should be introduced gradually. Unless you are specifically training for an off-road running event, the base or off-season can be a particularly useful time to introduce trail running.

Start with perhaps one trail workout per week and keep the initial mileage and duration relatively limited. As your body adapts to the new demands, you can gradually increase the amount of trail running in your program.

Not all trails create the same training stimulus. Off-road surfaces can range from crushed gravel and grass to sand, single-track hiking trails, and extremely rough backcountry terrain. Generally, the more uneven and varied the terrain, the greater the demand placed on the lower legs and the rest of the body.

On very rough or steep terrain, hiking may actually be as effective—and safer—than running. You may still reach your aerobic training zones while hiking challenging terrain, so there is no requirement to run every section of a trail workout.

Choosing the Right Trail Running Shoes

Trail running shoes generally provide more traction and protection than traditional road running shoes, although the amount of cushioning and support varies considerably between models.

Some trail shoes are essentially running shoes with a more aggressive tread, while others approach the design of lightweight hiking shoes. The appropriate shoe depends on the type of terrain and training you intend to do.

When purchasing trail shoes, make sure you select a model appropriate for your intended use. A knowledgeable running or outdoor retailer can help you match the shoe to the terrain where you will be training.

I generally do not recommend using trail shoes for regular road running. The aggressive tread and construction that make them useful on trails are not necessarily an advantage on pavement. Conversely, you can often take your regular running shoes off-road when the surface is relatively stable, such as a well-maintained crushed-gravel path.

Trail Running Improves More Than Lower-Leg Strength

The benefits of trail running extend well beyond the lower legs. Constantly adapting to changes in terrain requires coordination between the feet, ankles, knees, hips, and core.

Trail running can challenge lateral knee stability, strengthen many of the muscles involved in running, and improve neuromuscular coordination. Every change in surface, elevation, or direction requires the body to make small adjustments to maintain balance and efficiently produce movement.

These demands make trail running a useful complement to traditional road running.

Use Trail Running for Strength Maintenance

Trail running can be incorporated throughout the training season, although the amount should be adjusted according to your race schedule and goals. During periods when you are emphasizing other forms of training, occasional trail running can provide a useful stimulus for maintaining lower-leg strength, stability, and coordination.

Perhaps the best part is that trail running adds variety to your training. Getting away from the pavement can provide a different physical challenge while also changing the mental experience of a workout.

And, as an added bonus, the scenery is usually better.