Stress has a reputation as a bad thing. We typically think of work, family or life stress, but we’re going to discuss stress in terms of strength and conditioning, fitness and physical rehab. Stress still gets a bad rep in this setting. We hear phrases like, “squatting past your toes stresses your knees” or “deadlifting stresses your back”. We think of stress as a bad thing, but it’s really important to understand what stress actually means.
There is a mathematical formula for calculating stress in a physical sense. Stress equals force divided by surface area. Stress increases when the force increases and/or the surface area impacted decreases. Inversely, stress decreases when the force decreases and/or the surface area increases. An easy example is to think lying on a bed of nails. While pointed, our entire body weight (or force) is spread over a large surface of nails, versus if we were to try and lay on one single nail it would surely puncture our skin. With specific exercises, we can bias certain tissues more in order to achieve our goals.
While we cannot truly quantity stress in a clinical training/rehab setting, the concept can be taken further to help maximize rehab and performance with a few added qualifiers.
#1: Stress needs context:
Stress is just stress- it is not inherently good or bad. A 100lbs dumbbell needs context to mean anything. A 100lbs single-arm bicep curl probably is a lot of weight. Squatting 100lbs? Probably not a lot. But even that needs further context. For a patient recovering from ACL reconstruction surgery, squatting 100lbs is a big milestone, whereas for a powerlifter a 100lbs squat is probably a warm-up. Which leads to the next point…
#2: Stress is relative:
What’s probably more important than the actual stress is our ability to handle or tolerate that stress. That 100lbs squat for the ACL patient is a lot because they’ve just experienced a traumatic injury requiring surgery, and they need time to build their strength back. For that powerlifter, a 100lbs squat is not a lot of weight because they’re used to squatting 500lbs+. But even for both individuals, their ability to tolerate stress is going to fluctuate daily based on many factors- sleep, nutrition, hydration, work/family/life matters, etc…
#3: The human body is adaptive:
It’s important to remember we are not machines; we are living, human beings, and our bodies show remarkable ability to adapt. When we workout, we apply a stress to our body, and our body responds to that stimulus by getting bigger and stronger. When we stop working out for a period of time, our body responds by deconditioning. However, when we are exposed to stress greater than what we can tolerate, that is when pain and injury can occur. So we need to find a stressor that is enough of a stimulus for adaptation, but not too much that it leads to injury; aka the Goldilocks zone.
#4: Stress can be good, and is needed:
Because of the negative connotations we have with the word “stress” maybe we just need to rename our terms. Working out does stress our muscles, but we just don’t think of it as stress in the same context. So maybe “load” is a better word. In a training/rehab setting, we need to progressively load our joints, muscles, tendons and ligaments within that Goldilocks zone because our body adapts to the loads that are placed upon it.
It’s not fair to say “that exercise causes stress” because it lacks context; but that is also kind of the point if we want to get stronger. We want to stress ourselves. We need to apply stress to our muscles/tendons/ligaments/bones at an appropriate amount to build capacity and return from an injury. But too much stress, more than what we can tolerate, can be bad. Good strength training and injury rehabilitation means progressively applying more stress or load to a person so that they adapt and are able to handle the demands of their sport or activity.