What causes running injuries?
A running injury occurs when part of the body is exposed to a force that’s beyond its tolerance or prolonged loads that are more than it can repair over time.
That all may sound a little complex but essentially an injury is the end result of the body struggling to cope with the forces it’s exposed to.
In the category of sudden injuries, you’ve got injuries like ankle sprains and muscle tears. They happen suddenly (as the name suggests) and the damage is caused by a single force greater than the tissue can handle. For that reason, the moment of injury and its cause tend to be fairly obvious.
For gradual injuries, they come on over a period of time due to consistently abnormal forces. Those forces aren’t strong enough to cause damage in a single incident. The body might slowly break down over time due to an inability to keep up with the rate of repair needed or the forces begin to generate an inflammatory reaction in the injured area. This group of injuries includes things like bone stress fractures and tendon reactions.
How are road and trail different?
Road and trail cause different loading patterns and stresses on the body. However it’s not just about the surface but the way the brain and body adapt to that surface.
Road running, which includes pavement and cycle paths, is often on smooth, hard surfaces that are fairly consistent over the course of a run. Because the surface is consistent, runners are able to stride out confidently and can generate good power with a stable surface underneath them.
Unfortunately that consistency also means that the same loading patterns are occurring throughout the entire run without a great deal of variation. The running technique used in road running also tends to take the major joints through a larger range of motion than trail running.
Trail running, which describes a wide variety of surfaces like dirt, gravel and loose rocks, provides a more varied experience. This can be helpful in spreading the load across a wider range of areas or to modify the pressure on a specific area. That variability will also mean less controlled loading and more spikes in pressure on some areas of the body.
As an example, running along a rocky fire trail will occasionally bend your toes back and overwork your hip stabilisers on the loose rocky sections. But you won’t be able to stride out too much, so there’s less stretch on your hamstrings and hip joints.
Which surface is best for?
Flat technical single trail is perfect for PF. It encourages good muscular stability around the foot and ankle, supporting the fascia.
Flat road allows better control of Achilles tendon forces, so you can maintain a consistent pressure on it by monitoring pacing and gradient.
Funnily enough, the jury is out on this one. Trail is more unpredictable but we tend to pay more attention during risky situations. Road is consistent but that means we’re not expecting a small dip in the pavement or stray garden hose.
This one is a big “it depends”. Pain on the front of the knee (Patellofemoral pain) is better suited to road running as you can run with straighter knees. Pain on the side of the knee goes better on trails where good stability is required, which improves knee control, and the forces aren’t as consistent.
Lower back pain
Lower back pain tends to like the variability of trails and the slightly more forward trunk position. Trails also limit your opportunity to stride out, taking away another common cause of back pain.
Hamstrings like flat trails, particularly technical trails. The constant stretch and loading experienced with road running can be a trigger for many hamstrings injuries.
The term “shin splints” actually covers a number of injuries. One cause is bone stress injuries, which goes best on trails due to the reduced impact forces and power generation.
Another cause is muscle overload (which can cause Compartment Syndrome or Tibial Periostitis), which goes better on the road as you can determine the amount of pressure on the injury by controlling the parameters of the run.
Pete has over 20 years experience as a Physiotherapist and specialises in running biomechanics and complex injuries. He believes that you must identify and fix the underlying cause of an injury, to recover faster, prevent recurrences and improve performance.