By Roy Stevenson 
Why should distance runners run on trails? Well it’s as close as you’ll ever get to using the term “fun” while running. Within five minutes of starting your run on a forest trail, as the hum of the city traffic gradually recedes behind you into blissful silence, your feet softly pattering beneath you, and birds singing above, you’ll know why you should run on trails. But aesthetic reasons aside, there are physiological benefits to running on soft surfaces whenever possible.
Here are seven reasons why you should include some sort of trail or soft surface running in your weekly training schedule, whether you’re a hardcore road racer, track “sprinter”, or marathoner.
1Trails have better shock absorption.
Softer surfaces reduce our impact on the ground. This impact, known as ground reactive force, is one of running’s most pernicious side effects. As we age, especially past 50, many runners may not have any choice but to run on softer surfaces, as the wear and tear on our hip and knee joints sta
rts to manifest itself as the beginning stages of osteoarthritis. Trail running is much easier than road running on our feet, ankles, knees, hips, and back.
The high ground reactive force (bounce) from road running causes far more muscle soreness and inflammation than trail running. A survey (Beckstead et al 2005) given to trail runners on their training habits and surfaces was most revealing. A typical comment from ultra trail runners in the survey was that their legs were not nearly as sore after a 50-mile trail race, compared with running a marathon on the road. They also reported that their body recovered slower after a marathon. Electron microscope photos of muscle biopsies taken from the legs of marathon road runners look horrendous—post-marathon muscle tissue is a war zone with widespread disruption to the muscle sarcomere, breached cell membranes, swollen muscle fibers, and damage to the actin-myosin mechanism in the muscle fibers.
2 Trail runners experience fewer injuries than road runners.
There are other disadvantages to running on hard surfaces other than from high impact. When running on level concrete sidewalks or asphalt roads, we continuously put our lower extremity through the same repetitive contractions with little variation in the movement. This manifests itself in several ways. First, we stress the same muscles, ligaments, and tendons constantly, causing any weak spots to eventually revolt in the form of tendonitis or muscle strain—called overuse injuries by sports medicine physicians. The most common injuries in this group are chondromalacia, patellar tendonitis, iliotibial band syndrome, shin splints, stress fractures, back problems, and plantar fasciitis.
When we run on trails and uneven surfaces, the undulations force you to repeatedly change your stride length, stride speed, knee lift, foot plant, and foot contact time with the ground. By constantly making adjustments to your running leg cycle, running on changing surfaces alters your running biomechanics. Although you use the same muscle groups in your legs as when road running, you are now using them in a different way. On trails, your legs run through a wider “band” of movement, making your lower extremities more adapted to a wider range of motion. Thus stress is taken off the same old muscles and tendons that road running forces on them, and disperses it more evenly throughout your legs and hips, reducing your injury potential.
Beckstead’s survey (2005) given to trail runners showed that some of them did as little as 30% of their training off road, with the majority doing 80% to 100% on natural surfaces. They reported virtually no injuries, including ankle sprains, which is what you would expect to find with this population.
3 Running on trails and softer surfaces uses more energy per unit of distance run.
We burn more calories running on soft surfaces like dirt, gravel, sand, or snow, than on hard surfaces. Energy utilization while running on a soft surface like dirt, is 1.15 times more than running on a hard surface at the same speed. This additional energy cost of 15% while trail running may not seem like much, but mathematically it translates into the equivalent of an extra mile run for every 6.6 miles you run on trails.
Why this added energy cost on soft surfaces? Dirt absorbs more of the impact during the landing phases, and thus absorbs more energy—so we require more energy to push off again.
Incidentally, if you want the ultimate cardiovascular workout, strap on snowshoes. Walking in snow triples the metabolic cost when compared with walking on a treadmill!
4 Trail running recruits stabilizer and synergist muscles.
When we run, certain muscles and muscle groups support our trunk and body, holding it steady for the movement to take place. These muscles are called stabilizers. Stabilizers have become the hot item on personal trainers’ programs. The main stabilizer muscles for running are the back, abdominal, gluteal, hip, lateral thigh muscles, and connective tissue (Iliotibial band). Running on uneven and undulating terrain uses stabilizers, big time.
Synergist muscles are closely related to stabilizers, except they play a slightly more active role in the movement by assisting the movement itself. Without the coordinating and balancing actions by our synergists, our movements would be loose and wouldn’t generate much power. Synergists are used heavily when we run on rugged terrain. They help with peripheral movements of our ankles, knees, thighs, and hips when we change direction and accelerate or decelerate. Trail runners have excellent synergist muscle balance and development.
5 Trail running improves flexibility and ankle, knee, and hip strength.
The ever-changing terrain of trail running with its undulations, varying densities, and irregularities, like rocks and tree roots, causes our ankle, knee, and hip joints to become stronger. This is because our joints and tendons get thicker as they adapt to the irregular surface and obstacles. Thus our joints can survive more “play” or torsion before they become strained.
6 Trail running improves balance and agility.
Perhaps these might not seem like critical attributes for runners, but a good sense of balance and agility are most important as we age. Aging people report a decline in balance and agility, and one of their most common problems is losing their balance and falling down, which can lead to serious injuries. Running on a changing surface helps retain and improve balancing skills.
7Trail running offers physical and mental variety.
Being in nature may be a major reason why trail runners choose this sport over road running. The chance to explore beautiful places while temporarily escaping the hustle and bustle of the outside world is an opportunity to find peace, solitude, and tranquility. There’s something calming about cruising through wooded trails.
Roy Stevenson has a master’s degree in exercise physiology and coaching from Ohio University. He teaches exercise science at Seattle University in Washington State and has coached hundreds of serious and recreational runners and triathletes in the Seattle area. As a freelance writer, Roy has over 200 articles on running, triathlons, sports, fitness and health published in over fifty regional, national and international magazines.
