“How do they know the load limits on bridges? They drive bigger and bigger trucks over until it breaks, then they weigh the last truck and rebuild the bridge.”
— Bill Watterson, Calvin and Hobbes
The authors of a recent paper in the Journal of Sports and Orthopedic Physical Therapy [October 2020] included this humorous quote of the famous comic strip philosophers as the introduction to their clinical commentary on the subject of the relationship between training workload in runners and the development of injuries.
As I’ve noted in earlier installments [ Training-Error Injuries, Too Much, Too Soon, Too Fast; revisited], it has long been conventional wisdom that so-called “training errors” are the primary cause of injuries in long-distance runners. This term is generally defined as running “too much, too fast, too soon,” which leads to a breakdown of some physical structure (muscle, tendon, ligament, joint), with “too much” – which refers to the number of miles per week – being considered the most culpable.
Paquette et al, however, challenge this assumption and argue that running distance should not be considered the sole, or even the most important, metric when trying to determine the most effective ways to help runners avoid injury. In effect, they argue that evaluating the distance a runner trains each week to determine what the “safe” load would be for a particular individual would be as accurate as Calvin and Hobbes’ method for assessing the load limit of a bridge. They reason that this is because there are so many other factors that can be responsible for leading to injury. They include in this category:
- Daily stress (family relationships, financial, sleep quality)
- Self-perceived exertion
While the authors believe these factors, as well as overall distance, can contribute to the development of injuries, they are more inclined to consider biomechanical influences as the most important to evaluate and modify as necessary. These include:
- Running surface
- Internal structural abnormalities (muscle/joint stiffness/laxity, weakness)
- Movement pattern asymmetries
- Ground reaction forces
The paper notes that there are now many more sophisticated, accurate tools a coach or therapist can access to more objectively evaluate each individual for these biomechanical factors with the goal of being able to effectively design a specific training program for that runner that will help avoid the overload that will result in an injury.
The problem with this, of course, is its practicality. The time and costs involved would most likely make this sort of assessment available to high-level scholastic or professional athletes for the most part, not the average, every day runner. Even with that, the authors note that “…even with the best monitoring approaches, differences in an individual runner’s tissue load capacity will always make injury prediction elusive.”
So where does that leave us “average Joe” runners in our efforts to avoid injuries? Do we go back to using the simple approach of just avoiding those “training errors” and hoping for the best? To some extent, I would say that it is not a bad idea to adhere to that principle, but perhaps more important is to follow the age-old advice of “listening to your body.” Undue soreness the day after a workout, more significant sharp pain in a localized region, or a feeling of overall, increased fatigue or low-grade illness should be the things to look out for and respected as signs that perhaps you need to back off a bit in your training, which would include such things as intensity, frequency, and yes, distance.