It’s Just Physics

By Personal Fitness Trainer Amber Walz Seattle Athletic Club Downtown

Physics is the science of matter and energy, intertwined with facets of everything that makes up the physical world. Force is proportional to the mass of something multiplied by the acceleration (f=ma). Every exercise you do is going to relate to how much force needs to be applied to overcome the inertia of the mass in order to create acceleration.

Gravity is fundamental to understanding kinesthetic principles that govern our bodies. Gravity is pulling on our bodies relative to where the fulcrum (pivot point) is located; usually this is at a joint. As an example, when performing a deadlift the fulcrum is at the pelvis and gravity is acting at the longest length of the lever (your head), so you would need to determine how much force would be need to be exerted to move whatever the weight is, or adjust how close the weight in your arms is relative to the body. The use of mechanical levers is used advantageously in the gym in equipment design like pulley systems and can be used in seesaw type lever mechanics by manipulating the lever arm so that you can maneuver a heavier weight at the opposite side of the fulcrum. This can be seen in dollies and tools like wrenches.

The rate of gravity at terminal velocity in free fall is 9.8m/s2. This gives us an understanding of how fast a weight will fall toward the ground once we have lifted it, how this will increase or decrease the difficulty of an exercise dependent on what position we are doing it in, and if we jump, fall, or throw something, what distance it will cover, in what time and with what force. We encounter another force that effects movement and that is friction, of greatest relevance, air resistance. A good example of the effect of air resistance is when we are running. The mechanical advantage is if there is less surface area for the air to hit. In this way, if we bend our knees and elbows at 90 degrees, we reduce the amount of surface area affected by air resistance. So, the study of kinesthetic mechanics dictates our movement through the atmosphere and has to account for both gravity and friction.

Thermodynamics is the conversion of thermal energy to mechanical energy, or heat energy congruent with work input versus work output. Though the first law of thermodynamics states energy can neither be created nor destroyed, complete conservation of energy determining work output does not biologically equate. In other words, energy that should be accounted for degrades, a quantity defined as entropy. The human body has about a 25% efficiency rate with heat energy being of greatest loss. How much we intake should be calculated based on this principle with the understanding of unaccounted for loss through entropy. Heat is a measurement of energy and temperature is an average measurement of energy. Temperature is an important factor when you are working out that determines if it will take more energy when it’s cold to keep your body temperature at homeostasis, or loss of energy through sweat when it’s hot to keep your body temperature at homeostasis. The design of sports clothing is specific to thermal insulation, reduction of water absorption (wick away), and compression for added support in susceptible areas (compression socks/ tights/ sports bras).

If we are to better control our exercise experience, we can use physics to determine: how to best lift a weight to produce a specific goal, what food intake is needed for a specific workout, and how to best account for weather conditions and terrain. If you have any questions about how physics can be related to exercise contact Amber Walz.

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dead lift, fulcrum, gym, kinesthetic principles, pulley systems