As a physical therapist, I've seen firsthand how running can be both exhilarating and challenging for the body. Whether you're a seasoned marathoner or a casual jogger, the thrill of running often overshadows the complex and intense physical processes that occur with each stride. While it might feel like your heart and lungs are working overtime, there's so much more happening beneath the surface.

Your body is an incredible machine, designed to handle the demands of running. But let's not forget: every step you take is a mechanical feat, with forces acting on your muscles, bones, and joints in ways you might not fully appreciate. Let's break down what's happening to your body when you hit the pavement, trail, or track.

The Forces at Play: What Happens to Your Body with Every Step

When you run, your body deals with forces that can be 2.5 to 3 times your body weight with every step. Think about that for a second. If you stand on one leg, you're balancing 100% of your body weight. Now, imagine adding 150% more weight and hoisting that load on one leg with each stride. This is essentially what your bones, tendons, muscles, cartilage, and ligaments are dealing with every time your foot hits the ground.

It's a common misconception that distance running is a small amount of stress spread over a long period. In reality, running is a large force acting on your body for an extended period. Not only are you absorbing significant vertical forces with every step, but your body is also managing braking and acceleration forces — amounting to 40–50% of your body weight — as you move forward. Additionally, lateral forces (about 15% of your body weight) act on your body with every effort.

These forces are relentless, hitting your body from all angles. It's no wonder that running feels so hard at times — it's essentially a full-body workout that pushes your musculoskeletal system to its limits.

The Body's Active Response to Running

Think of a rubber ball being thrown off a roof. As the ball accelerates toward the ground, it flattens slightly on impact and then bounces back. This is an example of a passive system responding to a load. Now, imagine you're in mid-stride, and gravity is pulling you back to earth. Unlike the rubber ball, your body isn't passive. It's a complex, dynamic system made up of parts that work together to absorb and react to forces in real time.

Your body doesn't just passively absorb these forces — it actively adjusts. This happens through three essential systems that control movement: your joints, muscles, and nervous system. These components work together to respond to the stresses of running, ensuring that your body can move efficiently and effectively.

The Three Essential Systems for Running

1. Joint Structures: The Body's Framework Your joints are the mechanical parts of your body that provide structure and allow for movement. Think of them like hinges on a door. The bones form the structure, and they connect to other bones via joints, which are lined with cartilage. This cartilage acts as a cushion and lubricant, allowing for smooth movement. Ligaments connect the bones and keep everything in place.

However, joints on their own don't move. They are like the hinges on a door — completely dependent on external forces to move. That's where your muscles come into play.

2. Muscles: The Workhorses of Movement Your muscles provide the force needed to move the joints. Muscles don't just move joints — they also stabilize them, preventing excessive movement or strain. Think of your muscles as the engine behind every movement you make when running. They contract to generate the force needed to move, and they coordinate with each other to ensure smooth, controlled motion.

3. The Brain: The Master Controller Your brain and nervous system act as the control center, orchestrating every movement. The brain sends signals to your muscles, telling them how much force to generate and when. It's not just an on/off switch. Your brain fine-tunes every action, adjusting the amount of force based on the conditions. Whether you're running uphill, downhill, or on uneven terrain, your brain constantly adjusts to ensure efficient movement.

Coordination: How Your Body Responds to Running

With each stride, these three systems — the joints, muscles, and nervous system — are in constant communication. When you hit the ground, your joints sense the compression and movement caused by the impact. They send signals to your neuromuscular system, triggering your brain to engage the necessary muscles to generate just the right amount of force. Your muscles then contract, pulling on the joints to create movement.

But it doesn't stop there. There's a feedback loop between your muscles and your brain. As your muscles sense changes in length or tension, they send signals back to the brain, ensuring that you don't overstretch or strain them. Meanwhile, your joints continue to relay information about how much force is needed as they move through their range of motion.

This constant communication acts as a system of checks and balances to make sure everything is running smoothly. If done correctly, your body produces a net mechanical force that counters the impact of each stride, allowing you to keep running efficiently.

The Complexity of Running: It's Not Just One Step

All of this coordination — muscle contractions, joint movements, and neural feedback — happens in an instant with every step. But running isn't just about taking a single stride; it's about sustaining this complex process over thousands of strides during a run. Each step you take requires precise timing, control, and adjustment to ensure that your body can handle the repeated forces and stresses of running.

Programming Quality Movement: The Key to Running Efficiently

When you run, your body is running a program over and over again with each stride you take. The three systems we just discussed — your joints, muscles, and brain — each have specific inputs and outputs that determine the quality of your stride. Unfortunately, many runners focus heavily on volume, trying to log more miles each week. While increasing your mileage might build endurance, it also increases the mechanical load on your body. If your movement quality is lacking, this added stress can lead to injury or compromised performance.

It's not just about running more; it's about running better. So, how do we improve the quality of our movement while running?

Ask Yourself Two Key Questions:

1. Is your movement safe? What kind of movement skills and body awareness are you bringing to your runs? Are you able to maintain good form, or are you setting yourself up for injury?

2. Is your movement efficient? Could you rewire your running form to make each stride easier and reduce the risk of breaking down as you tire during a long run?

An efficient movement program can improve not only your performance but also the long-term health of your joints. By focusing on movement quality, you can rewire your brain and body to run more efficiently and safely. Just as you can adjust the number of miles you run, you can also improve the quality of those miles. Your brain learns through movement awareness, refining how much force you need to apply, when, and where to apply it.

Dynamic Plasticity: Your Brain's Ability to Adapt

One of the most remarkable aspects of our body is neural plasticity — our brain's ability to learn, adapt, and change over time. Every time you practice something new, whether it's learning to swim or refining your running form, your brain makes new connections from one nerve cell to another. The more you practice, the stronger these connections become. This is the foundation of motor learning and why "practice makes perfect."

Your nerves and brain adapt dynamically to different running conditions. For example, running on asphalt, grass, or a rocky trail presents different challenges, and your body automatically adjusts muscle actions and timing to accommodate the terrain. The same principle applies when you change shoes or modify your pace. Your nervous system is constantly making adjustments behind the scenes to optimize your performance.

This ability to adapt means that your body can learn to run better. By incorporating a neural plasticity-based training program, you can train your body to run with more control, improving both your durability and performance over time. The key is to give your body the right inputs to rewire your movement patterns, allowing you to move more efficiently.

Moving with Precision and Force

You may have heard some coaches say that runners naturally find their most efficient running form over time. While this might be true to an extent, most runners are operating under Plan B — the body's way of compensating for its limitations in mobility, stability, strength, and power. Plan B can certainly get you through your weekly mileage, but it's not optimal. It's the result of your body compensating for existing issues rather than operating at its peak potential.

Plan A, on the other hand, is your optimal form — the way your body is designed to move when everything is functioning properly. If your running form feels awkward or inefficient, it doesn't have to stay that way. Through deliberate practice, you can retrain your body to move more efficiently. The goal is to recover your Plan A form by addressing any deficiencies in mobility, strength, or coordination.

Injury and pain can throw a wrench in this process. Trying to push through an injury by running more miles will only exacerbate the problem. If you have back pain, knee pain, or another injury, it's time to fix the root cause. Loading your body with 35–55 miles a week while carrying unresolved issues will lead to injury cycles that prevent you from achieving consistency in your training. Instead of pushing harder, focus on improving movement quality to break the cycle of injury.

Building a Strong Foundation for Better Running

There's another common problem I see with runners: poor coordination. When runners tell me they can't jump, what they're saying is that they cannot coordinate their bodies well enough to deliver force down to the ground. This is crucial because running is essentially about driving force into the ground to propel yourself forward.

Research has shown that runners who can generate more force in a shorter period of time run faster. This means that no matter what level of runner you are, you can train and improve your ability to deliver force, improving both speed and durability.

To move with precision and force, you need a balance of mobility and stability. Mobility allows you to move without restriction, while stability helps you control your movements throughout each mile. By developing these skills, you can reduce the stress per stride, ensuring that your body moves in the most efficient way possible.

Improving Movement Quality for Better Performance

So how do you improve your movement quality as a runner? By focusing on the specific skills that make running more efficient and powerful:

  • Mobility: You need enough mobility to move fluidly without restriction. Tight hips, ankles, or hamstrings can limit your ability to move efficiently, increasing the strain on your joints.
  • Stability: Stability allows you to control your movements and maintain balance, reducing the risk of injury. Stable hips, knees, and ankles keep your body aligned and moving smoothly.
  • Force Generation: A stronger "spring" in your step leads to better performance. By improving your ability to drive force into the ground, you can increase your stride length and speed.

Developing these skills will help you move better, making you more durable as a runner. Durability leads to consistent training, and consistency is key to improving as a runner.

If you're struggling with mobility, stability, or coordination, consider joining my weekly runner's prehab email program. Each week, I send targeted mobility and stability drills designed specifically for runners to help you improve your movement quality, reduce the risk of injury, and boost your performance.

Final Thoughts: Running is a Full-Body Orchestration

Running is often seen as a simple, natural movement, but it's a highly coordinated and demanding task for your body. Every step you take is a carefully orchestrated dance between your muscles, joints, and brain. Together, these systems work to keep you moving forward while absorbing and reacting to the significant forces that act on your body.

The next time you head out for a run, take a moment to appreciate the incredible complexity of what's happening inside your body. From the impact of your foot hitting the ground to the way your muscles generate force and your brain coordinates it all, running is a full-body experience that requires strength, coordination, and resilience.

By understanding the mechanics of running and how your body responds to stress, you can make informed decisions about your training, recovery, and injury prevention. Remember, running isn't just about your heart and lungs — it's about the incredible system that supports every step you take.

Running is much more than just putting one foot in front of the other. It's about programming your body to move efficiently, precisely, and with force. By improving your mobility, stability, and neural coordination, you can enhance your performance and reduce your risk of injury. Don't settle for Plan B — take control of your running form and aim for your optimal Plan A. Your body will thank you, and you'll enjoy running more than ever before.

~Dr. Abby