Most people who run understand that running can be hard on the body. It is a weight bearing activity, and so all the lower limb joints and muscles experience some degree of loading with each stride as you land. Muscles are required to work eccentrically(lengthening as they contract to control impact), and then work concentrically(shortening as they contract) to power off the ground as they propel you forward. This loads both the muscle and tendon units. Joints are subject to weight bearing loads via gravity, and must absorb and transmit ground reaction forces, ie as you push off the ground the ground pushes back on you (Newton’s 3rd law of motion).
It’s not surprising that injuries do occur, and recent research reports that up to 75% of runners experience an injury every year. So what’s the best way to prevent these injuries? This is a question that has been researched and debated for decades, even before recreational running became popular in the 1970s. To give yourself the best chance of preventing injuries, you first need to understand the factors that contribute to injuries. We can broadly group these into 2 factors:
1. Extrinsic factors- these are generally external to the individual or more environmental.
2. Intrinsic factors- relating to the individual.
We will discuss each of the extrinsic factors here, with the next report outlining all of the intrinsic factors that contribute to injury.
1. Extrinsic Factors
a. Weekly volume
Consistent loading is essential to help the body become conditioned to the physical and functional demands of running and therefore prevent injury over the long term. While regular loading is required, this needs to be carefully balanced with ensuring you don’t overload your body with too many weekly kilometers. Running causes an accumulated strain on the body, and those stressors need to be managed. One of the main reasons for runners sustaining an injury is due to increasing their running volume and/or intensity too soon. Volume increases should be incorporated gradually over time, especially if you are starting out. Recovery days, where you rest or cross-train (cycle, swim, strength train) are vital in allowing your body to adapt to changes in volume. Good quality sleep and diet are also imperative to allow your body to recover and adapt.
Tip: Do not increase your volume by more than 10% per week, which is a rule you can also apply to your weekly long runs if you are training for a half or full marathon. If you are starting out, do not run on consecutive days. Good recovery days are essential in preventing injuries.
b. Training Characteristics
These include duration, frequency, intensity and the surface you run on. This will depend on what you are training for and how experienced you are as a runner. In general, sudden changes in duration, frequency or intensity will all increase the risk of injury. Interval/threshold training sessions should not exceed 45min excluding warm up/cool down, and these should not exceed twice per week. Again, it’s important to have adequate recovery between your harder sessions, and do not perform hard sessions on consecutive days.
It is also important to mix up your running surfaces. Remember, the concrete of a cycling track is harder on your body than the bitumen/tar of a sealed road. This again is harder than a gravel track, which is firmer than grass. While there is evidence that your leg muscles will either stiffen or relax to attenuate forces transmitted from the terrain, it is a good idea to run at least half your miles on softer surfaces.
Tip: The total volume of your harder sessions (threshold, interval and repetition) should not exceed about 25-30% of your total weekly volume. Mix up your running surfaces as much as you can, running at least half of your miles on softer surfaces.
The shoes you wear are very important in your ability to stave off injury. This may seem obvious, but it’s vital you run in shoes designed for running, as opposed to cross trainers or more casual sneakers, as they have more support and cushioning for transmitting ground reaction forces. It is also good to rotate your running shoes regularly – ie. have at least 2 pairs which you can alternate on different days. Make sure you replace your shoes as they are required, and the volume you get for each pair will vary with brands and the type of running shoe. It is usually somewhere between 600-1000km’s. This will be less for lightweight / racing shoes. Another guide for determining when it is time to replace your runners is by the way your legs feel after a run…. undue muscle or joint soreness may mean the absorption characteristics are wearing thin.
It is also important to ensure the motion control profile of the shoe is appropriate for your foot. Some retailers offer video or force plate analysis, but our opinion is that such technical analysis is best left to health professionals, such as Podiatrists or Physiotherapists. About 80% of the population are over-pronators, and up to 5% are supinators, so only 15% of runners have a neutral foot. Having the incorrect motion control in the shoe for your foot will increase your injury risk.
Tip: Have at least 2 pairs of running shoes to rotate. Do not run in shoes past their use by date, and have your foot biomechanics tested by a health professional before choosing the right shoe.
We hope you have found this information useful. Using these guidelines relating to the extrinsic risk factors for running will go a long way in reducing your risk of injury.
If you need further clarification or guidance with any of these factors, simply schedule in a time with one of our physiotherapists who will be able to assist you accordingly.