In this post, we explore why your body resists change after injury, and how to guide it toward recovery.
At a glance
- Recovery and positive change don’t happen by chance—your body resists change due to biological inertia.
- Newton’s First Law applies: “An object at rest stays at rest…” — the body stays in its current state unless acted on by an external force.
- Entropy causes decline over time: muscles weaken, joints stiffen, healing slows if no action is taken.
- External forces that drive recovery include:
- Movement and exercise
- Targeted rehabilitation
- Adequate nutrition and hydration
- Rest and sleep
- Mindset and consistency
- Small, consistent actions disrupt inertia and counter entropy, gradually building momentum toward healing.
- Recovery is intentional: deliberate effort and consistent action are what reverse the tide of pain and injury.
Introduction
I always wondered why the body doesn’t simply return to its previous state after injury.
Why do we have to work so hard to make progress?
The answer to this question comes from an unlikely source: Sir Isaac Newton.
Newton may not have been thinking about pain and injury when he wrote his First Law of Motion in 1687, but the principle applies remarkably well to the human body.
Newton’s First Law of Motion states that “an object at rest stays at rest, and an object in motion stays in motion, unless acted upon by an outside force.”
In many ways, our bodies follow the same rule. When we’re in pain, recovering from injury, or stuck in unhealthy patterns, we tend to stay in that state unless something disrupts the cycle.
Understanding this concept — and its partner, entropy — can reshape the way you think about healing and regaining strength.
Inertia in physics (and why it matters to you)
In physics, inertia explains why a moving car keeps going until the brakes are applied, or why you lurch forward when the vehicle suddenly stops. Objects resist changes to their state of motion.
Your body has its own form of inertia. When pain and injury strikes, inertia can be the very thing that keeps you stuck in a cycle of stiffness, weakness, and avoidance.
Biological inertia
The body likes stability — scientists call this homeostasis. After an injury, your body adapts to protect itself: muscles tighten, movement patterns shift, and you avoid positions or activities that cause pain. Over time, these adaptations can become your new normal.
Unless you introduce an external force — like targeted exercise — your body will remain in that state. Inertia, in this sense, explains why doing nothing won’t stimulate change.
Entropy: The drift toward disorder
But inertia isn’t the only principle at work here. Enter entropy: the natural tendency for systems to move toward disorder over time.
In the body, entropy looks like this:
- Muscles weaken when they’re not used.
- Joints stiffen when immobilised.
- Healing slows without energy and effort devoted to it.
If inertia explains why the body resists change, entropy explains why the body actually declines without intervention. Doing nothing doesn’t just maintain the status quo — it allows entropy to take over.
External forces: How change happens
The good news is that just as inertia and entropy push us toward stagnation and decline, external forces can push us back toward growth and healing. These forces include:
- Movement and exercise: Improves mobility and circulation.
- Targeted rehab: Restores strength and reduces compensations.
- Nutrition and hydration: Provide the raw materials for repair.
- Rest and sleep: Give the body time to heal and reorganize.
- Mindset and consistency: Keep you moving forward even when progress feels slow.
Every small, intentional action becomes a “force” that shifts your trajectory away from entropy and toward recovery.
Building positive momentum
The benefit of inertia is that once movement begins, it tends to continue. In recovery, the hardest part is the first step — getting moving again after injury or pain. Once that step is taken, each action compounds: movement reduces stiffness, strength returns, pain decreases, and confidence grows.
This creates a feedback loop where the very forces that made it hard to start, now work in your favour. Inertia, once an obstacle, becomes a friend.
Summary
Newton’s First Law teaches us that nothing changes without a force. The human body is no different. Inertia keeps us in the state we’re in, while entropy slowly pulls us toward decline. But with deliberate effort — movement, training, nutrition, rest — we can reverse the tide.
So if you’re struggling with pain or injury, don’t wait for things to improve on their own—take control and make the first step toward your recovery.