The Physics of Fitness

How Will This Course Benefit You?

In this course “The Physics of Fitness”, you will be introduced to the dozens of biomechanical principles that benefit/influence the efficiency, productivity and safety involved in all resistance exercises. These biomechanical principles fall into three categories—“classical mechanics” (physics), musculoskeletal and neurological.

Resistance exercise involves the loading of a person’s muscles, using free weights, cables (pulleys), bodyweight and/or some type of exercise “machine”.

Exercise machines typically provide resistance either by way of a weighted lever arm, a weighted sled that slides along guide rods, a weight stack attached to a cable which is pulled by a circular or oblong cam, or an elastic exercise band.

Each of these produce a different and specific direction of resistance, which is then applied to a person’s limb(s).

A person’s limbs are essentially “levers”.

For example, a person’s forearm is a lever which has:

  1. A pivot point (the elbow)
  2. A “force” (a muscle which is attached on one end to the forearm, and on the other end to the upper arm and shoulder, crossing the elbow joint in between).
  3. A source of resistance is then held in the hand, which is connected to the end of a forearm that is of a specific length. The weight in one’s hand is a specific distance from where the elbow joint is, and also a specific distance from the point where the biceps (or triceps) attaches to the forearm.

All of these factors influence the amount of load that is placed on the biceps or triceps, when the elbow is bending or extending.

Resistance exercise, therefore, involves the laws of physics—“classical mechanics”.

The angle of a person’s limb (e.g., the forearm) in relation to the direction of resistance (gravity) influences whether the muscle is receiving more or less magnification of the load.

This magnification of load is quantifiable (measurable), and has a profound effect on whether an exercise is optimally productive and optimally safe—or not.

Further, the angle from which a muscle is able to pull on its corresponding limb also influences the amount of force a muscle must produce in order to move a given weight.

For example, in the case of the biceps, if the elbow is bent at 90 degrees, the biceps is able to pull on the forearm perpendicularly, which requires “less” force.

But if the elbow is straight, the biceps must pull on the forearm from an angle that is mostly parallel to it, which requires much “more” force—all other factors being equal.

Further, the direction of resistance an exercise provides determines which muscle is loaded—because of a principle called “opposite position loading”.

This is simple physics—the greatest percentage of the load always falls on the muscle that is directly opposite the direction of resistance.

The direction of resistance, or the position of the body relative to the direction of resistance, also influences “alignment”.

If the direction of anatomical movement, and the direction of resistance, and the origin and insertion of a target muscle on are all the same plane (on the same pathway or trajectory), the target muscle will receive the highest percentage of the weight being used.

But if there is misalignment, then the load to the target muscle is reduced by a percentage that is equal to the degree of misalignment.

That reduction to the target muscle is then shifted to other (often much weaker) muscles.

This results in a loss of benefit to the target muscle, and a potential injury risk to the non-target muscles that are possibly overwhelmed by that misdirected resistance.

The direction of resistance also influences the “resistance curve”—the sequence of increases and decreases of resistance that naturally occurs as a lever (i.e., a limb, like a forearm, etc.) travels through an arc (a range of motion), and interacts with gravity at different angles.

Specifically, the resistance to a muscle is increased when that limb is more perpendicular with resistance, and it is decreased when that limb is more parallel with resistance.

Most skeletal muscles have a “strength curve” that causes them to have more strength potential when the muscle is elongated (outstretched) and less when it is shortened (contracted).

Therefore, matching the resistance curve of an exercise with the strength curve of a muscle, greatly improves the productivity of an exercise, and decreases the potential injury risk that the exercise causes.

The direction of resistance, or the position of one’s body relative to the direction of resistance, also influences exercise “efficiency”.

This is a ratio between the amount of weight being used versus the amount of load experienced by a target muscle.

This can be measured as a percentage from zero to 100%.

For example, Parallel Bar Dips loads the Triceps with a significantly lesser percentage of the load, as compared with Supine Dumbbell Triceps Extensions (“skull crushers”).

This is because the forearm is mostly vertical during Parallel Bar Dips. It never comes close to being horizontal / perpendicular with gravity.

However, the Supine Dumbbell Triceps Extensions allows the forearms to go through that horizontal position.

Specifically, Parallel Dips only load the Triceps with about 11% of the weight being used (usually bodyweight), while Supine Dumbbell Triceps Extensions load the Triceps with 100% of the available load.

The difference is significant. The first exercise provides significantly less load to the triceps at a much higher energy cost, while the second exercise provides significantly more load to the triceps at a much lower energy cost.

A person who understands this principle can get more benefit with less effort, simply by selecting exercises more wisely.

Apart from the above noted physics-related factors, there are also anatomical issues.  These relate to the direction of movement for each skeletal muscle and each joint.

Most muscles produce one, primary, ideal direction of skeletal (limb) movement, which is defined by the muscle origin and insertion of each muscle, the direction of a muscle’s fibers, and the design of the joint that moves when that muscle contracts and elongates.

Exercises that produce the “correct” (ideal) anatomical movement are more productive for muscular development, and cause little or no risk of joint injury.

Conversely, exercises that move their corresponding limb in a direction other than the “correct” (ideal, most natural) direction, compromise the muscular development benefit, and increase the risk of joint injury.

Each skeletal muscle and joint is explained in this course, ensuring that the student understands how to select the most productive exercises, and avoid the exercises that provide a compromised benefit and pose a higher risk of injury.

In addition to the above described mechanical and anatomical factors, there are also neurological and physiological factors that play a role in the degree of productivity of certain exercises.

“Active insufficiency” occurs when a muscle is over-shortened (during an exercise), causing the actin filaments of the muscle to overlap.  This leads to muscle weakening (even cramping), which is counter-productive when the objective is to optimize the effectiveness of an exercise.

Knowing the anatomical positions that cause this to occur, allows a person to avoid exercises that require those positions, and favor exercises that avoid those positions, thus avoiding active insufficiency.

Muscle contraction occurs by way of system known as “innervation”—nerve impulses that are sent to specific muscles by the Central Nervous System (CNS).

These nerve impulses are similar to “on” and “off” switches. Some nerve impulses cause a muscle to “fire” (i.e., to contract), while others cause it to shut off (i.e., to relax), and each can occur in varying degrees.

Thus, it is wise to avoid exercises that limit muscle innervation—exercises which cause a target muscle to unintentionally receive a “relax” signal, precisely when you’re trying to maximize its engagement.

This course explains how to select exercises that allow optimal target muscle innervation (contraction), without interference by the CNS.

“Passive Insufficiency” occurs when the muscle that is on the opposite side of a target muscle is over-stretched, during an exercise.  When this happens, the CNS “weakens” the contractile ability of the target muscle, in order to protect the opposing muscle from being injured.

Needless to say, this would be counter-productive when the objective is optimal muscle stimulation of the target muscle. Understanding the circumstances during which this situation occurs, allows a person to avoid exercises that cause it.

“Reciprocal Innervation” is a situation in which the CNS “shuts off” (partially or entirely) an antagonist muscle (i.e., a muscle that is opposite the muscle that is working), while the agonist muscle is loaded.

For example, when a person performs a Barbell Curl, the Central Nervous System innervates the biceps to fully “fire”, while simultaneously sending a “relaxation synapse” to the triceps, causing it to relax.

This process prevents the interference of a muscle that is intended to work, which would be caused if its opposing (i.e., “antagonist”) muscle were allowed to simultaneously contract.

Any time a muscle is activated, its antagonist muscle is being “shut off”—either entirely or partially, depending on the circumstances.

Unfortunately, many traditional compound exercises involve opposing muscles, which means that some of the target muscles involved in those exercises are compromised.

Despite the amount of effort required during some compound exercises, one or more of the muscles which are meant to be prioritized during the exercise, are actually being “weakened” by way of reciprocal innervation.

They are being sent a partial relaxation “signal” by the Central Nervous System, because the opposing muscle is being activated simultaneously.

This course explains how and when this happens, and how to select exercises most wisely, in the pursuit of optimum muscle stimulation and development.

Fitness and muscle building myths are prolific.

During the time that weight lifting, bodybuilding and the pursuit of physical fitness has been evolving (the past 100 years, approximately), many people have arrived at some bizarre conclusions and false beliefs about which exercises are good or bad, or what result certain exercises produce.

The commercialization of the fitness industry has made matters even more confusing for consumers, and also for Personal Trainers. It’s often difficult to know what is correct.

But having sufficient knowledge of the biomechanical principles that are in play during resistance exercise allows a person to clearly see what is truth and what is fiction.

This course—“The Physics of Fitness”—exposes why false beliefs about resistance training are inaccurate, and reveals the facts that allow you to recognize which exercises that are maximally productive, efficient and safe—and which are not.

If you are in the business of helping clients improve their physical condition, or you simply want to optimize the benefits you achieve from your own workouts, this course is essential.

The difference between knowing these bio-mechanical principles and not knowing them, is the difference between getting fantastic results with the least amount of wasted effort and risk of injury, versus getting compromised benefits using more effort than is necessary, and a high probability of injury.

In essence, having this knowledge gives you a tremendous advantage, in regards to maximizing the benefits of resistance exercise.

Not having this knowledge is simply irresponsible, if you’re a Personal Trainer.

Not having this knowledge translates to not being able to deliver optimal results to your clients, while causing them to work harder than they need to, and exposing them to a higher risk of injury than is necessary.

A Personal Trainer should be as respectable as a licensed Physical Therapist, at the very least.

This requires scientific knowledge of the subject—not simply “in the trenches” experience, a willingness to promote the current trends, and an ability to be an enthusiastic supporter.

The information provided by this course separates those who are serious about being an outstanding professional trainer, and those who either don’t care enough to do the job right, or are satisfied just being an exercise companion, masquerading as a trainer.

These biomechanical principles apply to everyone, of all ages, of both genders, and for all goals.

The laws of physics are universal—they behave the same way all the time, regardless of whether a person is using resistance exercise for Powerlifting, for Football, for Golf, for Bodybuilding, for Pole Vaulting, or simply for general fitness.

All of our bodies have the same design—the same skeletal structure, the same muscular attachments and the same muscular function.

Therefore, the same rules about which resistance exercises are more efficient and more safe, apply to everyone.

This is why it is so important to know what these rules are!

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