Ever wonder how your body performs everyday actions like walking, running, or even picking up a cup of tea? It all comes down to an amazing field called biomechanics—the study of the physics behind human body movement. Biomechanics combines principles from physics and biology to understand how muscles, bones, tendons, and ligaments work together to create movement. Whether you’re an athlete striving for peak performance or simply handling daily tasks, biomechanics is key to how you move, maintain balance, and build strength.
In this blog, we’ll explore how biomechanics governs human movement and dive into the physics that make it all possible. From Newton’s laws of motion to the mechanical wonders of our joints and muscles, we’ll break down the science behind each step and motion.
Newton’s Laws and Human Movement
If you’ve ever learned about physics in school, you’ve probably heard of Newton’s laws of motion, which are foundational to understanding biomechanics. Let’s look at how each law plays a role in our everyday movements.
First Law (Law of Inertia): This law explains that an object will stay at rest or continue moving at a constant speed unless an external force acts upon it. In terms of biomechanics, it explains why we need to exert effort to initiate movement. For instance, when you’re sitting on the couch, your body remains still until your muscles generate enough force to stand up.
Second Law (Force and Acceleration): This is the famous F=maF = maF=ma (Force = mass × acceleration) formula. It’s crucial to understand how much force we need to apply to move different parts of our bodies. For example, if you want to sprint, your muscles need to generate a higher force compared to walking, as you’re trying to accelerate your entire body faster.
Third Law (Action and Reaction): For every action, there’s an equal and opposite reaction. When you take a step, your foot pushes against the ground, and in return, the ground pushes back with equal force, propelling you forward. This is why surfaces like sand, which provide less resistance, make it harder to walk compared to firm ground.
The Role of Muscles and Joints in Movement
Our body functions like a highly efficient machine where muscles and joints serve as motors and hinges. But what happens mechanically when you, say, lift your arm?
Muscles work through contraction, pulling on tendons (which attach muscle to bone) to create movement at the joints. Joints, on the other hand, act like pivot points, where bones rotate or slide to allow movement.
For example, think about lifting a dumbbell. The biceps muscle contracts to bend the elbow while the triceps muscle relaxes. This action occurs at a hinge joint (like the elbow) that permits flexion and extension. The amount of force generated by your muscles determines how much weight you can lift, which ties back to Newton’s second law.
Torque and Leverage in the Human Body
Torque is a key concept in biomechanics, especially in movements that involve rotation, like throwing a ball or twisting your torso. Torque is the rotational equivalent of force, and it’s what allows our joints to turn.
Consider your arm as a lever system. When you bend your arm at the elbow, the distance from the elbow to your hand acts as the lever arm. The longer the lever arm, the more torque you can generate, but it also means you’ll need more force from your muscles to maintain control. This is why carrying heavy objects feels harder when your arms are extended compared to when they’re closer to your body.
Leverage also comes into play in sports. Athletes often use biomechanics to fine-tune their movements, increasing efficiency and minimizing the risk of injury. For instance, a professional pitcher in baseball or cricket generates maximum torque at the shoulder to throw the ball at high speeds.
Biomechanics of Walking and Running
Walking and running are among the most fundamental human movements, but they’re surprisingly complex from a biomechanical standpoint. Each step you take involves a series of gait cycles, which include both a stance phase (when your foot is on the ground) and a swing phase (when your foot moves forward).
In walking, your body maintains a relatively low centre of mass and uses less energy. Running, on the other hand, requires much greater force, and the body works like a spring to store and release energy. Elastic energy is stored in tendons and muscles, like the Achilles tendon, which helps propel you forward when running.
Case Study: Biomechanics in Rehabilitation
Imagine you’ve sprained your ankle. Understanding the biomechanics of how the ankle joint works can help a physical therapist create a rehab plan. The ankle is a hinge joint, much like the elbow, that allows for dorsiflexion (raising the foot) and plantarflexion (pointing the toes). By analyzing the way your ankle moves and the forces involved, the therapist can tailor exercises to strengthen your muscles and improve your range of motion without causing further injury.
In athletes, biomechanics is also essential in injury prevention. Gait analysis—a technique that examines the way a person walks or runs—can reveal inefficiencies or imbalances that might lead to overuse injuries. By correcting these movements through proper training, athletes can enhance performance and avoid long-term issues.
Everyday Biomechanics: Sitting and Lifting
You don’t have to be a professional athlete to benefit from understanding biomechanics. Consider something as simple as lifting a heavy object. Many of us have heard the advice, “lift with your legs, not your back,” but do you know why that’s important?
Using your back to lift heavy objects can put significant strain on the lower spine, potentially causing injury. By engaging your leg muscles and keeping your back straight, you distribute the force more efficiently across stronger muscle groups, like your quadriceps and glutes. This not only makes the lift easier but reduces the risk of strain or injury.
Similarly, even sitting requires biomechanical awareness. Poor posture while sitting can place undue stress on your spine, leading to discomfort or long-term issues like spinal disc degeneration. Making sure your chair provides support for your lower back and keeping your feet flat on the floor can promote proper posture and alignment.
Conclusion
The physics of human movement goes beyond theoretical equations; it offers valuable insights into everything from athletic performance to daily physical activities. By diving into biomechanics, we can optimize our movements, prevent injuries, and improve our overall well-being.
Next time you go for a run, lift a box, or simply walk down the street, think about the amazing physics working behind the scenes to keep you moving efficiently!
Author’s Note
I’ve always found the human body to be one of the most fascinating machines. By combining biology and physics, biomechanics helps us understand how we can move better and live healthier lives. I hope this blog sparked your curiosity about the science that governs our every move!
G.C., Ecosociosphere contributor.
References and Further Reading
- Introduction to Biomechanics
- 1. Life Science | Resources for Teaching Elementary School Science | The National Academies Press. https://nap.nationalacademies.org/read/4966/chapter/5#14
- Pulled Hamstring Muscle: Causes & Treatment For Hamstring Strains. https://www.knee-pain-explained.com/pulled-hamstring.html
- Man and machine – fluid boundaries? – December 24, 2023. https://orthexo.de/en/man-and-machine-fluid-boundaries/
- Shoulder Dislocation: What You Need to Know – Campbell Clinic. https://www.campbellclinic.com/shoulder-dislocation/
