Understanding Human Movement: A STEM Approach (Part 2 – Engineering & Math)

In a previous article, “Can a STEM Perspective Deepen Our Appreciation of Human Movement?,” we discussed how we can apply science and technology principles to better understand human movement.

In this follow-up article, we will look at human movement through the lens of engineering and mathematics.

Engineering Elastics

Many basic structural engineering principles directly apply to rehab professionals’ practice.

For example, the principle of elastics is frequently discussed within structural engineering. This principle describes to what extent deformation is proportional to the forces applied to a particular material. In rehabilitation, muscles are that particular material. Although we often say that athletes are “flexible,” muscles must actually have elasticity and extensibility, not flexibility.

A rubber band is often used to explain this engineering concept. The band elongates and develops potential energy, and then, when let go, releases kinetic energy. Human movement relies heavily on this principle.

Here’s what this looks like in action in the human body. The rectus femoris is a two-joint muscle across the hip. When a person kicks a soccer ball, the following movements occur:

1. The rectus femoris elongates as the hip moves into extension.
2. This elongation builds potential energy until the foot comes off the ground to initiate the swing phase.
3. The kinetic energy released in the system allows movement to carry the leg forward.
4. The twisting, created by the contralateral counter trunk rotation and reciprocating arm and leg swing that accompany the hip extension, creates tension throughout the anterior chain.

Elasticity in the entire system is needed to create efficient movement. To effectively measure hip range of motion (ROM), it’s important to take up all soft tissue slack three-dimensionally.⁵

When the body utilizes passive lengthening of muscle chains, as in elastics, the body moves more efficiently.

For example, when pitching a ball, the maximizing force development in the large muscles of the core and legs produces 51 to 55 percent of the kinetic energy that is transferred to the hand.² In the kinetic chain, the thoracolumbar fascia connects the lower limbs through the gluteus maximus muscle to the upper limbs through the latissimus dorsi.

Math & Dynamic Systems

Every treatment decision therapists make for patients has some basis in the dynamic systems theory—especially when applied to human movement.

Human movement is an incredibly complex system comprising many different dynamic systems all working at the same time, including:

• Musculoskeletal
• Neural
• Cognitive
• Environmental
• Hormonal
• Emotional³

When combined, the systems at work during sport are exponential and most likely infinite, making it difficult to capture these systems in a laboratory setting with the current technology available. Like an engine, the human system has different parts in different systems. There are some systems at work that clinicians simply cannot control, such as gender, hormonal, and environmental. When helping a patient, identify and manipulate modifiable factors whenever possible.

Conclusion

The STEM approach illustrates how many different disciplines are at work with regard to rehabilitative therapy, and taking a global view of these elements can be beneficial.

To learn more about dynamic integration of the kinetic chain and how to construct therapeutic hip exercise programs, check out my MedBridge courses, “Exercise Prescription for Hip & Pelvis Movement: Part 1” and “Exercise Prescription for Hip & Pelvis Movement: Part 2.”