If there is one concept that is crucial to injury prevention for runners, it is mechanical stress — and knowing how to quantify it is particularly important.
The human body is made up of various tissues including cartilage, bone, muscle and more. During physical effort such as running, these tissues are put under strain by different types of forces — tension, compression and torsion.
These various forces exerted on the human body during physical activity can be described as mechanical stress.
Measuring mechanical stress means quantifying the stress experienced by tissues, with the aim of drawing the right conclusions and preventing the risk of injury.
The level of stress applied and the areas affected will vary depending on the physical activity performed. It is easy to imagine that the Achilles tendon, for example, will not be loaded in the same way during a running session as during a swimming training session.
Different sports involve different levels of stress. Cycling, for example, has a low and quantifiable level of mechanical stress.
In contrast, running shows signs of significant stress. It tends to vary according to several factors, in particular speed, which will increase the force applied.
To get a sense of the amount of mechanical stress accumulated on a daily basis, you would need to analyse the stress level generated by each daily task, in order to build an overall picture of the total mechanical stress reached.
This is why when a person remains inactive during a rest day or a period following an injury, stress levels will obviously be low or even non-existent. Staying in rest mode for too long can weaken the body and make it more vulnerable to injury.
Conversely, for someone who engages in regular and intensive sport, the amount of accumulated stress will place that person in a risk zone and increase the likelihood of injury.
The body therefore sends signals once its maximum capacity to adapt to mechanical stress is reached — such as pain, morning stiffness or swelling.
The ideal approach is to "minimally stress" the body in order to build tolerance without exceeding the so-called maximum threshold. By staying within this range, the body adapts to stress and can increase its tolerance. Structures strengthen, allowing training intensity to increase without risking injury.
To summarise, quantifying mechanical stress is a preventive measure when no injury is present. However, pain can exist without the maximum capacity having been exceeded. This may therefore point to an injury that needs to be assessed by a healthcare professional.
The body has a remarkable and unique capacity for adaptation, with constant ongoing evolution. It is important not to overlook the fact that fatigue, stress, fear and similar factors can influence the body's tolerance threshold and tend to make it more vulnerable.
Equally, a state of happiness or well-being tends to have a positive impact on the body and on recovery from injury. Which goes to show just how closely body and mind are connected!
