Weight training may seem straightforward: pick up something heavy, move it around, get stronger. But beneath the surface, weight training is deeply rooted in physics. Understanding the basic principles of physics that govern how your muscles move and how forces are applied to your body can help you train more efficiently and maximize results. Let’s dive into the science of weight training and explore how physics powers your workouts.
1. Force: The Foundation of Weight Training
In physics, force is a push or pull exerted on an object. In weight training, every time you lift a dumbbell, squat with a barbell, or perform a push-up, you’re applying force to overcome the resistance of gravity.
The most basic formula from physics that applies here is Newton’s second law:
F = ma
Where F is force, m is mass, and a is acceleration. In weight training, the “mass” is the weight you’re lifting, and the “acceleration” is how fast you can move that weight. To increase the force your muscles need to produce, you can increase either the weight (mass) or the speed at which you move it (acceleration).
2. Gravity: The Constant Opponent
Gravity is one of the primary forces you’re battling during weight training. It pulls everything towards the earth, meaning every time you lift a weight, you’re working against gravity.
Lifting weights requires you to exert enough force to overcome the weight’s gravitational pull. The heavier the weight, the more force you need to exert. This is why weight training builds strength over time—your muscles adapt to exerting more force, helping you lift heavier weights.
3. Levers: How Your Body Moves Weights
Your body operates like a system of levers during weight training. In physics, a lever consists of:
• A fulcrum (the joint)
• A load (the weight or resistance you’re lifting)
• A force (your muscles contracting to move the load)There are three classes of levers in the human body, but most weight training exercises use the third-class lever, where the effort is applied between the fulcrum and the load. For example, when you perform a bicep curl:
• Fulcrum: Your elbow joint
• Load: The dumbbell
• Effort: Your bicep contracting to lift the dumbbell
Understanding this can help you adjust exercises for maximum effectiveness. By manipulating the length of the lever (such as changing your grip or arm position), you can make exercises easier or harder depending on your goals.
4. Torque: Rotational Force in Action
In weight training, torque plays a crucial role because most movements involve rotating your joints. Torque is the measure of the rotational force applied around a joint, and it’s calculated as:
T = r x F x sin x (theta)
Where T is torque, r is the length of the lever arm (distance from the joint to where the force is applied), F is the force exerted, and θ is the angle between the force and the lever arm.
To lift weights efficiently, you want to generate enough torque to move the load. The larger the lever arm (like having your arm fully extended), the more torque is required to lift the same weight. That’s why exercises like lateral raises feel much harder as your arms extend outward, even with light weights.
5. Work, Power, and Energy in Weightlifting
In physics, work is done when a force moves an object over a distance. The formula for work is:
W = Fd
Where W is work, F is force, and d is distance. Every time you move a weight through a range of motion (like squatting down and standing up), you’re doing work. The more weight you lift and the greater the distance you move it, the more work you perform.
Power in physics is the rate of doing work:
P = W/T
Where P is power, W is work, and t is time. In weight training, power refers to how quickly you can perform a movement. Power-based training involves moving weights rapidly, such as in Olympic lifts like the snatch or clean and jerk, where the goal is to generate as much force as possible in a short time.
6. Mechanical Advantage: Efficiency in Movement
Not all exercises are created equal in terms of mechanical advantage. Mechanical advantage is the ratio of the force produced by your muscles to the force required to move the load. When you have a high mechanical advantage, you can lift heavier weights more easily.
For example, in a deadlift, you have a greater mechanical advantage because your body is positioned in a way that allows for a more efficient force transfer from your muscles to the barbell. In contrast, a bicep curl has a lower mechanical advantage because of the long lever arm and the small muscle group involved.
Understanding mechanical advantage can help you tailor exercises to suit your goals. For example, compound movements like squats and deadlifts provide high mechanical advantage, allowing you to lift heavier and recruit more muscle groups.
7. Momentum: Friend or Foe?
Momentum is the quantity of motion an object has, and it’s calculated as:
p = mv
Where p is momentum, m is mass, and v is velocity. In weight training, you generate momentum when you lift weights quickly, which can either help or hinder your workout depending on your goals.
If you’re performing explosive exercises like kettlebell swings, momentum helps you move the weight efficiently. But if you’re doing controlled strength exercises, too much momentum can reduce control, intent, consistency, and overall benefit to the target movement. That’s why slow, controlled movements are often recommended for building muscle, you’re relying on your muscles to do the work, not momentum.
8. Progressive Overload: Applying Physics to Build Strength
Progressive overload is a fundamental principle of strength training that ties directly into physics. To build strength, you must continuously challenge your muscles with increasing amounts of force. This means progressively increasing the weight you lift, the number of reps, or the intensity of your workouts.
By applying more force over time, your muscles adapt to the increasing demands, growing stronger and more resilient. This concept aligns perfectly with Newton’s laws of motion, which state that an object will only accelerate if a force is applied to it.
Final Thoughts: Training Smarter with Physics
Weight training isn’t just about lifting heavier weights, it’s about understanding how your body interacts with forces, gravity, and mechanics. By applying basic principles of physics to your training, you can lift more efficiently and understand why you are. It will provide a foundation of knowledge that can help sift through trendy showboat exercises online and open the doors to the function of muscles and their actions as they relate to exercises that you do.
Whether you’re new to weight training or a seasoned pro, every lift is a physics experiment in motion. So, train smarter, not just harder, by leveraging the power of physics to take your workouts to the next level. If you wanna skip the nerd work, let our coaches do it for you! We love everything there is to know about these topics which admittedly everyone isn’t fascinated with, so let us take the guess work out of which exercises to do and why. Sign up for a free consultation today!
References:
1. Brown, Lee E., and Vance A. Ferrigno. Training for Speed, Agility, and Quickness. 3rd ed., Human Kinetics, 2014.
2. Faulkner, John. Principles and Methods of Strength Training. Routledge, 2018.
3. Newton, Robert U., and Gregory G. Haff. Strength and Power in Sport. 2nd ed., Blackwell Science, 2001.
4. Zatsiorsky, Vladimir M., and William J. Kraemer. Science and Practice of Strength Training. 2nd ed., Human Kinetics, 2006.
5. Israetel, Mike, et al. Scientific Principles of Strength Training. Renaissance Periodization, 2015.