Use Newton’s Laws of Physics to Work Out Smarter

If you’ve ever seen an episode (or 10) of “The Big Bang Theory,” then you know this popular TV show is a comedy about very intelligent people working as research professors in subjects like particle physics.

While the characters in “The Big Bang Theory” make it seem like you need to spend years studying physics to understand the topic, if you are a fitness fanatic or even if you only manage to make it to the gym once a month, you are already a practicing physicist.

No matter how much you work out, you may already be as smart as Dr. Sheldon Cooper, the uber-nerdy character played by actor Jim Parsons. There are three simple laws, along with some important concepts, that can help you understand how you practice physics every time you work out. Knowing these simple principles and how to apply them can help you harness your inner geek to make your workouts even more impactful.

Newton’s Laws of Physics:

Inertia: Otherwise known as momentum, this law states that a body at rest stays at rest unless acted on by an outside force. A weight, or any piece of equipment, remains in a static, stationary position until your muscles contract to generate the force required to move the weight (more on that in a moment).
A force is the product of a mass and its acceleration as explained by the formula: F = ma, in which the mass is that of the object being moved and acceleration occurs when that object transitions from a state of rest to a state of motion. Applied to fitness, this rule tells us that when your muscles move (or accelerate) against a mass, they produce force. In general, the heavier the mass being moved, the more muscle force required to accelerate it from a state of rest.
For every action, there is an equal and opposite reaction: When applied to exercise science, this becomes the SAID principle: Specific Adaptations to Imposed Demands. In other words, the body will adapt (reaction) to the method in which it is trained (action). When training on machines where the range of motion is dictated by the machine, the body does not have to account for the constant force of gravity and will react by becoming strong specifically for that machine. But the body may be weak when placed in an environment where it has to stabilize a resistive force against the constant pull of gravity. This is why it’s a good idea to vary your workouts between machines and free weights on a regular basis. Using machines can help you become stronger; using free weights can help you integrate that strength between a number of different muscles.

Besides these three laws, it is important to understand some other basic principles of physics:

A calorie is a measure of unit of energy. It is the amount of energy required to heat 1 liter of water by 1 degree centigrade. If you eat a piece of food with 100 calories, it is providing 100 units of energy, which your body will either burn or store (as fat) to be used at a later date. (It takes about 100 calories to walk or run 1 mile.)
Velocity is the rate at which an object travels a specific distance in a certain time period— distance x time and is quantified as meters per second (m/s).
Acceleration is the rate at which an object increases in velocity with every additional second and is expressed as meters per second, per second (m/s ² ).
Work is the amount of force required to move an object a certain distance, described by the equation W = Fd, and is measured in newtons x meters. If a piece of equipment provides you information on joules, it is telling you the exact amount of work you are doing.
Power is the velocity of force production, or is the amount of work performed in a specific amount of time and can be expressed by the equation of either Power = Force x Velocity or P = Work/Time. The faster you can apply a force to move an object, then the greater amount of power you can generate, which is measured in watts, which is joules per second (J/s).

Why do the laws of physics matter to my workout?

Here’s why this information is important: If the “desired reaction” described above is a change to your body, it first requires taking specific actions (Newton’s third law). Want to improve aerobic efficiency to shave minutes off a race? Then you’ll have to perform an appropriate volume of running—the action—to initiate the desired change(s) in your body—the reaction.

Strength training is a function of the second law of physics. Moving a heavy mass with minimal acceleration will produce one type of strength. This can be observed in the sport of powerlifting, in which athletes compete to lift the most weight in the barbell deadlift, barbell squat and barbell bench press. Rapidly accelerating a mass generates a significant amount of power, which can be seen in the barbell snatch and barbell clean-and-jerk performed in the sport of Olympic weightlifting.

Keep in mind that muscles are programmed to contract by the nervous system. Doing the same weights for the same reps at the same tempo is like using an old flip phone from the early 2000s, which is hardly efficient in this modern age of smartphones. Training the muscles to increase their overall force output will then, according to the laws of physics, help you maximize the return on your time invested in exercising.

Thus, to get the greatest benefits from your workouts, it is important to do a variety of different types of exercise so that your body is exposed to a variety of different forces.

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