You’re a few minutes into some form of aerobic exercise like running, cycling, swimming.
You’re going along fine and then suddenly you start to feel the pinch. Your muscles get tired and heavy, and your heart and lungs feel like they’re maxed out.
For me, I know the precise point where this happens on my common running routes. I’ll be jogging along, feeling ok and then I get to that block where I start feeling pretty average.
You’ve only just begun but you’re already questioning why you started – and how on earth you’re going to finish.
What’s going on here?
Is it something we should worry about and maybe stop exercising? Or is there no cause for concern?
Well, there’s actually a very good reason for this.
An understanding of this reason can really help us get through this uncomfortable phase. Not to mention prevent us from unnecessarily discontinuing in the mistaken belief there’s something wrong.
So here’s what’s happening – from our body’s perspective.
Before exercise – our body coasts along comfortably
Before we start exercising, our body is going about its business in a sedentary state.
We’ll be sitting at the office desk, in the car, on the sofa or maybe we’ll be a little more active as we potter about.
But the point is, compared with what’s to come, it’s a low workload that demands minimal energy.
When the workload is low, our body can easily meet this energy demand. It can do it without raising a sweat, literally, which is a good indicator of how hard we’re working, along with things like a low heart rate and respiratory rate.
When our body successfully balances energy supply and demand, we’re in what’s called steady-state. And when we’re not exercising, we’re in a comparatively low and slow steady state.
First few minutes of exercise – our body is slow to get going
When we start exercising, we suddenly change gears from being sedentary to physically active.
This causes a dramatic shift in the overall workload.
Our body’s steady-state gets blown apart because the sudden increase in energy demand exceeds our ability to supply it.
It’s not that our body can’t meet the demand, it’s just that it takes our body a bit longer to spool up.
It just can’t instantaneously meet the demand of our sudden decision to exercise.
So during this roughly two-minute lag time, steady-state is lost and we go into a state of oxygen debt because we’re using it up faster than we supply it.
But it’s not the end of the world.
Our body has a solution to that – albeit a temporary fix.
Rather than producing energy aerobically (“with oxygen”) as is the case in steady-state, our body is forced to use a different way to generate energy called anaerobic (“without oxygen”) metabolism.
This solves the energy issue and keeps us moving but it’s only a temporary fix because a by-product of this process is lactic acid. And it’s this lactic acid that’s responsible for the fatigue and muscle burn that makes us slow down or stop.
So in answer to our issue – what’s happening when we feel that pinch is a build-up of lactic acid, which is caused by a temporary lag in our body’s ability to supply energy aerobically.
Remainder of exercise – our body catches up
When we continue exercising, our body has the time it needs to catch up.
It’s starts supplying energy at the required rate and therefore restores steady-state.
Although it’s a steady-state at a higher level compared with when we were resting.
We return to producing energy via aerobic metabolism, which allows our body to come out of oxygen debt and return to the relative comfort of exercising in this perfectly balanced state.
At some point we may increase the workload by moving faster or going up a hill, for instance. When this happens we may create another imbalance between energy supply and demand, and force our body back into an anaerobic state.
But that’s what fatigue is all about. It’s our body’s signal for us to slow down and get back into steady-state. Of course, at some point, that fatigue will rightly spell a good reason to pull the pin. However, that fatigue is for a different reason than the initial pinch we felt.
Besides, that fatigue is earned unlike that initial discomfort.
How to work with this normal response to exercise
- Don’t get turned off exercise: Now that you’re armed with an understanding of what’s happening and why, you needn’t shy away from exercise. Don’t avoid it or discontinue under the mistaken belief it’ll remain that hard for the entire duration or that it’s a sign of your own poor fitness. That initial pinch is a completely normal physiological response that’s common to every human body.
- Warm-up. You’ve heard it before but maybe haven’t appreciated this reason for it. If you start slowly and gradually build up the intensity, your body is better able keep up with its energy supply. This can enable you to remain in a steady-state and avoid the uncomfortable symptoms of going too hard, too early.
- Press on. If you’re like me and can’t help yourself from starting like a bull at a gate then just know it’s going to hit you suddenly but will pass just as quickly. Slow down a little during this phase to you’ll help your body regain the upper hand so that you can continue more comfortably.
- Listen to your body. Get to understand what your body is telling you and why. It’s all communication and feedback. Make it less personal and more physiological. It’s not you. It’s just a sign of having upped the intensity a little too much. So back it off a little and see how you feel. Simply start experimenting and listening to your body as you go. You’ll gradually build a closer relationship with your body and before too long, you’ll be on the same page and working together.
