Insulating against injury

Certain anthropologists believe that a major reason for the success of the human over the millennia is their capacity to run and that in its evolution, the homo erectus has developed physical characteristics suited to running, particularly distance running. Such characteristics include shortened arms; prominent buttocks; lengthened Achilles tendons; short and parallel toes; and a foot arch that can flex to absorb initial contact and the associated ground-reaction forces, before quickly stiffening to optimise propulsion. These ancestors ran a lot, logging hours of practice on variable surfaces, in simple, or even no footwear, functioning optimally with the anatomical tools listed above.
When the best runners from today, or from years gone by, are assessed and their technique analysed, the following traits are identified: they exhibited a high cadence, minimal vertical displacement, shortened contact time with the ground, little or no breaking phase per step and energy-efficient movements.
In the last 15-20 years, distance running has been enjoying another global wave of popularity. RunningUSA.org highlights that 19 million people finished running events in 2013 up from 4.8 million in 1990. Also, of interest is that in 1990, 75 per cent of the finishers were male, whereas in 2013, 57 per cent were female. The US Center for Disease Control reports that 22 per cent of Americans who meet the Physical Activity Guidelines do so through running.
Unfortunately, and despite all this great energy, a large percentage of runners are getting injured. In 2007, Van Gent carried out a literature review of these injuries and found evidence that between 20 per cent and 80 per cent of runners will report suffering an injury every year. Van Poppel in 2015 found that 16-33 per cent of runners finishing events had injuries during their training protocols.
Interestingly, Videbaek (2015) reported that the novice runner has a 250 per cent higher risk of injury than the experienced runner. That’s a huge difference.
What makes some runners so much more insulated against injury than others? The research says: the capacity for adaptation is a huge ally, if we use it properly.
The body will adapt, if the applied stress is not greater than its capacity to cope and strengthen. The Envelope of Function (Dye, 2005), also known as the athletes’ uninjured load capacity, is a useful concept when it comes to understanding where you are on your physical fitness trajectory and helping you generate a realistic plan for durable gains.
The concept tries to empower the athlete by getting them to spend time considering what set of physical loads are currently ‘manageable’ without injury, and at what frequency one can tolerate these loads. This simple idea can give us confidence in our starting point, or where we are currently in terms of physical capacity. From there, we can increase tissue tolerance through adaptation and strengthening, if we are consistent in our training and progress in small increments. We are trying to optimise the size of our ‘manageable envelope’ and avoid training errors that would have us operating in the ‘excessive envelope’ and risking injury. The diagram above shows that I can run for one hour with a low risk of injury, but I should not try 1.5 hours yet, as I am not trained for it. I have selected a training session that involves too great an increase in terms of load or frequency, which will increase my risk of overwhelming my tissues and causing injury.
While working as a physiotherapist in Vancouver, Canada, I attended a running workshop, which was delivered by the brilliant Irish physiotherapist Jean Lewis (Dun Laoghaire Physiotherapy and Sports Injury Clinic). She was trained by the Canadian track and field physiotherapist, Blaise Dubois (therunningclinic.com). I really like the tips give when it comes to running and progressing our capacity:

• When starting a new exercise chapter, it is initially more important to be consistent than it is to progress;
• During your training runs, especially if you are starting or restarting after a period of not running, it is a good idea to work in some walking to your running sessions. Many of the training protocols designed for people starting a new chapter of running have these walk intervals worked in;
• Once confident and strong with your baseline level of load and training frequency, an increase in volume should not exceed 10 per cent per successful week. A successful week is a week where the athlete enjoyed each session with no pain between their runs or at the end of the week.
  The weekly long run should not exceed the longest run of the previous week by more than 10-15 minutes;
• If you are having a big training week, boosting volume and working on cardiovascular fitness can be done by adding a cross training activity such as cycling or water-based exercise, both mechanically less stressful;
• Be cautious and gradual when running on a new surface (hills, hard, cross-country, wet weather, slippery leaves etc.); and
  Quantify hill training by counting the number and length of your hills. Start low to ensure you are within your ‘manageable envelope’ and progress cautiously.

Training frequency
We do not know the optimal frequency at which one should train. Jean and Blaise make the interesting comment that runners tend to suffer injury to low and medium metabolism connective tissues (ie. tendon, bone, fascia), which are better-suited to less intense but repeated stresses. This raises the argument that weekly volume should be spread over as many running sessions as possible (eg. four to six sessions of running per week), rather than fewer, longer sessions. Four sessions per week may be wise, even if one to two of the runs are only 10-20 minutes. This programme of frequent running gives the body exposure to a healthy dose of mechanical stress, which drives unconscious learning of efficient mechanics and seems to be synonymous with injury-reduced running.