Mechanical Stress Quantification : To not do too much, too fast

Running is a great way to improve cardiovascular fitness, all the while working all the major muscle groups in our core and lower body. However, being a high impact sport, running can lead to joint, muscular, and tendon overload injuries if your body is not progressively adapted to it. In fact, 80% of musculoskeletal injuries are due to training overload, i.e. abruptly going from no physical activity to an intense daily workout regimen. The goal of this blog post is to provide the tips and information you need on how to adapt your body to running and prevent overload injuries.

Mechanical Stress Quantification

Our bodies have a remarkable ability to adapt to new activities and situations. However, if someone who has never ran before decides to run 10km without prior training, chances are their body will not be happy afterwards and they are at risk of injury; their body was not given the chance to adapt to this new activity.

Adaptation occurs when the mechanical stress, or load, applied to the body (e.g. the impact on joints or muscular demand from running) does not surpass your body’s total capacity to adapt to such stress. Essentially, the goal is to find the sweet spot between not enough stress and too much stress, and progressively increase that stress to allow for continuous adaptation. The official term for this concept is mechanical stress quantification.

The graph above depicts what quantification of mechanical stress looks like. The red line portrays the maximal adaptation capacity, whereas the green line portrays the minimal amount of mechanical stress needed to create adaptation in our bodies. These thresholds vary from one individual to another, and also vary depending on the level of daily load applied.

When the level of daily load surpasses the red line, that is when injury is likely to occur and you might experience symptoms such as pain during running, pain after running, or morning stiffness. When the level of daily load is between the green and red line, you have achieved the sweet spot, and adaptation will occur, allowing you to progressively increase your load. Below the green line refers to the “rest area” when the level of load is not sufficient to create adaptation.

So how do we apply this to running? Here are a few tips:

• Start and finish your running sessions by a 5 minute walk, to allow your body to warm up and cool down
• One way to progressively adapt your body to running is alternating between 1 minute running and 1 minute walking. Try this for the first two weeks (starting with 6 total minutes, then increasing by 2 minutes each time you go out for a run). For the following weeks, progressively increase the running to walking ratio.
• Make sure you run 4-6 times per week to make sure your body gets that daily load it needs to adapt.
• Monitor your symptoms. If you experience pain during or after your run, or morning stiffness the day after, you might have surpassed your body’s maximum adaptation capacity and you should decrease your load.
• Increase your weekly training volume (i.e. total amount of minutes or distance running at about the same speed) by about 10% each week.

Remember, each individual is different and there is no one-size fits all training regimen. These are general guidelines to prevent injuries and you should do what feels right for you. Your physiotherapist can help you tailor an individualized training program to support you through your fitness goals, injury-free.