Introduction to the Chapter

What is biomechanics? Where did it come from, and why should I care?

Biomechanics is a hybrid scientific discipline that helps explain the movement potential of living or once living organisms. The bio in biomechanics refers to the necessity of understanding the basic biology of the organism being studied. If that organism is a person, that biological and anatomical knowledge provides a basic blueprint of the human machine and its capabilities. Such knowledge allows for a better understanding of how internal and external forces can be used to accurately predict the movement and/or injury potential of the person at any given time or in any situation they may find themselves.

The mechanics portion of biomechanics refers to the static and dynamic branches of engineering mechanics that provide the equations and formulas to accurately analyze both moving and nonmoving mechanical systems. If we look at the human musculoskeletal system as a machine composed of simple machines (levers, pulleys, etc.) that is powered by chemical factories (muscles) with information regarding how these talk to one another (nervous system), then you have the human machine that we all live in.

Learning Objectives

After completing this chapter, students should be able to do the following:

• Define biomechanics
• List the main areas of biomechanical research
• List the goals of biomechanics
• Name the “fathers of biomechanics” and the three areas in which they contributed to the field of biomechanics
• Point out examples of applied biomechanics in everyday life situations

What Is Biomechanics?

Biomechanics is a hybrid science that uses information from musculoskeletal anatomy, mechanical physics, and advanced motion technologies to help us better understand how and why we move.

Movement is basic to our survival, and gaining a deeper understanding of what it takes to move safely and efficiently is necessary for anyone, but especially for those interested in becoming human motion specialists like those studying exercise science, physical education, physical therapy, athletic training, coaching, occupational therapy, or a host of other human performance–related disciplines.

What makes biomechanics unique is that it models the human or other movement system as something that can be better understood when viewing it through the lens of basic mechanical physics. That does not mean that biomechanics is “just” physics hidden behind a curtain of human examples and applications. Biomechanics is much more than that. It is method of objectively seeing, discovering, and predicting a wide spectrum of human and animal movement in a way not done through any of the other science courses typically offered to students.

The Goals of Biomechanics

The goals of biomechanics are to increase or maintain people’s movement ability while at the same time working to decrease the likelihood and severity of movement-related injury. At times those goals conflict as pushing a body to its movement limits makes it more likely to suffer injury. That is a conundrum faced by biomechanists: how to help improve or maintain performance while also keeping the person safe from injury.

When working with athletes the goal may be to help the athlete running faster, lift heavier weights, or improve their ability to strike a ball with better accuracy and consistency while working to keep them healthy enough to train and compete at very high levels of performance. For those rehabbing from an injury, how quickly and effectively can the rehab proceed without resulting in further injury or other performance setbacks? It is a never-ending balancing act to push the boundaries of human performance while attempting to keep the person from being injured.

Equipment advances in speed skiing provide a real-world example of how working to improve performance can also increase the likelihood of severe injury for participants if something should go wrong.

The extremely aerodynamically efficient skin suits worn by speed skiers help them to reach speeds of greater than 245 km/hr as they rocket down the slope. Any mistake at that speed can result in severe injury. They are moving so fast that if they fall the heat generated from friction as they slide down the mountain trying to slow down in their very slippery suits often results in second- and third-degree burns, not to mention the bumps, bruises, and possible broken bones they are likely to suffer from a crash at such speeds.

Where Does Biomechanics Fit in the Area of Movement Sciences?

Under the umbrella term of kinesiology there are many subspecialties that merit study for students working toward degrees in human movement–related fields. Where does biomechanics fit in, and how is it related to areas such as exercise physiology and motor behavior? In many cases biomechanics acts as a bridge between the more biological-focused courses and those that are more related to the mechanics of movement. Figure 1.1 illustrates the bridge biomechanics provides that links many of the subspecialties of kinesiology and shows its important role in tying them together.

Where Did Biomechanics Come From?

From our earliest known human records, such as cave paintings dating back over 40,000 years, to the ancient records of virtually every civilization around the world, art and literature are full of images of human, animal, and cosmic motion. Motion is one of the basic tenants of life as we know it. It allows us to explore our environment and provides us with the means to survive. It is so basic that it is one of the very first indicators of life, a baby kicking within its mother’s womb, as well as a measure used to determine the death of an individual, when they can no longer breath.

Have you ever watched someone walk? Not just seen them stroll past, but actually taken the time to focus on how they perform one of the most basic types of human movement? If you have, you likely noticed that each person has a unique movement style. That movement style is more specific to that person than their fingerprints. It is so individually specific that it can be used to uniquely identify them from any other person on earth. How a person walks is an outward expression of all of the physical and emotional experiences they have experienced during their lives. It’s their movement signature that cannot be faked or reproduced by anyone else. Biomechanical analysis of gait confirms the unique aspects of this and a wide variety of human and animal movement patterns. Yes, there are similarities between how individuals perform different movement tasks, and we are all governed by the same physical laws of movement, but we each place our own special stamp on the types of movement we use to navigate our world. Biomechanics can help us identify the similarities and differences that makes each one of us special from a movement standpoint.

All of us have experienced and observed motion throughout our lives, but few have truly understood what motion is. How does motion start, what causes it to change, and what are the ranges of motion for humans, animals, and other objects that we encounter every day? To begin to answer those questions we will apply the science of biomechanics. This text is designed to provide a brief glimpse into the biomechanics of motion and help you to better understand you, those around you, and the world in which we live!

The “Fathers” of Biomechanics

It wasn’t until the late 1960s and early 1970s that the term biomechanics began to be widely used to describe this area of motion science that views all bodies in motion as mechanical systems governed by the principles of mechanical physics. Prior to that time descriptors such as movement studies, exercise science, kinesiology, and others served as umbrella terms under which the mechanics of motion was housed. As more students studying movement sciences gained access to computers it became possible for a much larger group to learn and conduct research related to movement based on the mechanical properties of a body. It was the right time for this area of study to establish its own academic identity, and after much discussion the term biomechanics (bio for living or once living and mechanics for the branch of physics related to mechanical motion) emerged as the term to be applied to this unique area of motion study. Today’s students of biomechanics have at their fingertips technology and resources that the early biomechanists (the correct term for someone who practices biomechanics) couldn’t even dream of. The hand and manual calculator-based results of the analysis of human gait reported in the seminal work by Braune and Fischer took over a decade to complete and required the invention of a suite of specialized equipment to biomechanically analyze the walking patterns of a handful of study participants. Now the calculations and the special tools needed to perform that level of gait analysis are available to almost every student who takes a biomechanics class.

There were three men who standout in the history of biomechanics for their contributions to the three main areas of biomechanics (anatomy, physics, and instrumentation) that deserve a little special attention. The men are Giovanni Borelli, Sir Isaac Newton, and Eadweard Muybridge. Of the three, only Sir Isaac Newton is widely recognized for his genius, but the other two hold special places of honor in the field of biomechanics. Each is considered a “father” of modern biomechanics for their significant contributions to this field of science.

Ironically, it is almost a certainty that none of the fathers of biomechanics ever heard the word biomechanics spoken or saw it in written in text, nor could they have realized that their life’s work would significantly contribute to the eventual creation of the field of biomechanics, yet they will be forever tied to its inception.

Anatomy

Giovanni Alphonso Borelli (1608–1679)

Giovanni Borelli was born in Naples, Italy, and lived his whole life in the that Mediterranean country. He is remembered as a Renaissance Italian physiologist, physicist, and mathematician (https:\\en.wikipedia.org/wiki/ Giovanni_Alfonso_Borelli). But in the field of biomechanics we remember him as a “bone collector” whose posthumous text de Motu Animalium or On the Movement of Animals marked the first widely referenced text on the anatomical/mechanical characteristics of the human body.

Borelli conducted his research into the mechanical properties of the human body during a time when such study was strictly prohibited by the Catholic Church. If found guilty of performing such work a person could be excommunicated from the Church, resulting in a loss of any hope of attaining heaven during the afterlife. That threat was more than enough to keep most from exploring how the interval functions of the body worked. But not Borelli. He secretly acquired human specimens that he dissected and carefully documented the musculoskeletal structure and function of their bodies. His work led to a couple of chapters inserted toward the end of the de Motu Animalium that were followed by multiple chapters dealing with anatomical information on other forms of animals. The book itself was published after his death by his son so that Giovanni wouldn’t be in peril of being found out by the Church and denied his chance for eternal bliss. Whether he truly believed the Church teachings or was concerned with its possible punishments, he took no chance.

To ensure his contributions to biomechanics are not forgotten, the highest individual award in the area of biomechanics presented by the American Society of Biomechanics is the “Borelli award.”

Physics

Sir Isaac Newton

Sir Isaac Newton was born in England and gained worldwide prominence in a variety of scientific disciplines, including mathematics (inventor of calculus), physics (laws of motion and gravity), and astronomy (reflecting telescope). Because during his life two calendars were widely in use in Europe, his birthday is reported to be either on Christmas Day 1642 (Julian calendar) or January 4, 1643 (Gregorian Calendar), and death on March 20, 1726 (Julian calendar) or March 31, 1727 (Gregorian calendar). And no, that is not a typo in the year of his death; look it up if you don’t believe me!

Newton was credited with developing calculus during a forced break from his studies at Cambridge University due to a plague outbreak in England at the time. It was his study of the physical world and attempts to match his observations with the mathematics of his day that led him to develop a form of mathematics that helps us understand functions related to situations of continual change over time, such as most forms of human motion.

It was Newton’s ability to grasp the “big picture” and summarize it into understandable mathematical equations that lead to his laws of motion and gravity, which enable us to better understand motion in our world. His influence in the application of classic mechanical physics led to the term Newtonian physics—a way to express through formulas the thought processes used to study, understand, and predict the outcomes of most forms of mechanical systems in motion.

Instrumentation

Eadweard Muybridge (1830–1904)

Eadweard Muybridge was born in England but immigrated to the United States at the age of 20. At 30 he suffered a severe head injury and returned to England to recuperate. It was during that time he found his professional calling as a photographer. He returned to the United States and moved to San Francisco, where he set up shop as a photographer of natural wild landscapes.

Photographic technology at the time made it almost impossible to capture a clear, nonblurred image of any object that was moving. Always interested in advancing the art of photography and using it to enrich himself, he set about a series of experiments attempting to modify his cameras to capture short duration snapshots. By inventing a high-speed mechanical shutter mechanism that could be attached to the lens of his cameras he discovered a way to clearly capture images of animals during motion. He didn’t know it at the time, but that technical breakthrough might have saved his life!

It was around the time he invented the high-speed shutter mechanism that a personal issue looked to put an end to his work permanently. Having shot and killed his wife’s lover, Muybridge was put on trial for murder. A murder conviction would have likely resulted in him being hung. Lucky for him, he had made some rich and powerful friends as a photographer and inventor.

One such powerful friend was Leland Stanford (former governor of California and founder of Stanford University). Stanford was a regular client of Muybridge, having purchased many of Muybridge’s photographs. At the time, all artistic representations of a horse galloping showed at least one hoof in contact with the ground. It’s said that Stanford didn’t believe that to be the case but had no way to prove his suspicions. Legend has i, that Stanford made an open wager of $25,000 payable to any person who could prove that a horse when if full gallop would at some point have all of its hooves off the ground. Muybridge, being in desperate need of money to hire the right lawyers to have him acquitted of the murder charge, sought out Stanford and told him he had the technology to win his bet if Stanford could provide him with access to a horse and racetrack. Fortunately for Muybridge, Stanford agreed.

Muybridge was given access to one of Stanford’s racehorses and use of his race track in Palo Alto, California, starting in 1873. By carefully setting up 24 individual cameras, each spaced 1 foot apart with trip wires used to snap successive pictures as a horse raced by, Muybridge was able to successfully capture the silhouette of the horse and rider galloping down the track. Those images showed that a horse is completely airborne at some point during a full gallop (see Figure 1.2), providing the proof Stanford was looking for (Ball, 2013).

Regardless of whether there was a bet, Muybridge had earned enough money through his dealings with the rich and famous to afford the best legal defense in his murder trial. He was acquitted of murder and returned to his tinkering with cameras. Eventually he invented a way of sequentially projecting the snapshot images of moving objects at a high rate of speed. This resulted in the viewer believing that they were seeing actual motion and not a series of still images. He named his invention the zoopraxiscope (Figure 1.3).

The zoopraxiscope was the first motion picture projector and the predecessor of cinematography and the various forms videography used today.

More on the life and times of Eadweard Muybridge can be found in this video:

To ensure his contributions to biomechanics are not forgotten, the highest individual award in the area of biomechanics presented annually by the International Society of Biomechanics is called the “Muybridge award.”

Penn State Water Tower

Biomechanics was a relatively new label used in the area of human movement science when Dr. Richard Nelson founded the biomechanics laboratory in the Water Tower on the Penn State University campus in State College, Pennsylvania, in 1967. Nelson realized that a revolution in technology was starting that would allow for the human machine to be studied in ways never before possible. He, along with Drs. Dewey Morehouse and Peter Cavanaugh, created one of the most important early centers for the training of future biomechanists. Between the students who studied under the trio and the many visiting scholars that spent time in the tower over the years, a legacy was created that links many biomechanists across the world to this humble structure that is still producing outstanding contributors to the area of biomechanics.

Women in Biomechanics: Shaping the Future of Movement Analysis

Biomechanics is a newly recognized field of science, first defined in the English language during the mid to late 1800s. It is a hybrid term formed from the ancient Greek words bios (life) and mechanika (mechanics) to describe the study of living or once living creatures, their movement patterns/possibilities, and their underlying structural makeup. It wasn’t until the 1960s that the term began to be considered a subspecialty of kinesiology, similar to exercise physiology or motor development.

Women have played an increasingly important role in the areas of biomechanical research and education, with many contributing greatly to the biomechanical knowledge base of today. Two of the more widely recognized women in biomechanics are Drs. Jaquelin Perry and Jill McNitt-Gray.

In 1992 Perry published Gait Analysis: Normal and Pathological Function, a seminal work that was updated in 2010 and continues to be a widely used by those who study/treat lower extremity function. Perry was widely acknowledged as one of the leading researchers, scholars, and clinicians in the area of polio. She continued to be an active clinician almost until the day she died at the age of 94 in March of 2013.

McNitt-Gray is a professor at the University of Southern California, where she studies the mechanisms organisms use to control and distribute mechanical load during goal-directed multijoint movements involving external loading. A product of the Penn State Biomechanics program, she has been an extremely active researcher, educator, and scholar for more than 3 decades (USC Dornsife, n.d.).

Who Are Biomechanists Today and in the Future? (or, You Might Be a Biomechanist If . . .)

Some people have spent a lifetime of work and study to better understand how humans and animals move, are injured, and successfully return to activity. But you don’t have to go to school and earn degrees that say biomechanics to become a biomechanist. Anyone who is curious about and wonders at how they or other things move is a biomechanist.

An infant, amazed and fascinated by the sights and sounds of the environment in which they find themselves uses their senses to make sense of the world around them. They are a biomechanist. Eventually they will learn to move themselves, first by crawling, then, after many failed attempts, walking. Through trial and error, they learn to apply their understanding of motion to achieve their ultimate goal of controlled movement in the form of human locomotion. That is biomechanics. The junior high student trying to figure out how to gain control over their bodies again following a growth spurt is functioning as a biomechanist. The “invincible” young adult trying all kinds of different, and often dangerous, combinations of human and machine pairing, from bike riding to snowboarding, is a biomechanist. Older adults attempting to stay active and healthy while juggling careers and family demands are biomechanists. The elderly adapting to the reality of declining health and vitality by using canes and walkers to assist them as they move are continuing their lifelong application of the principles of biomechanics. Regardless if your career path leads to sports, health care, teaching, coaching, private industry, or almost any area involving performance or understanding human and/or animal movement, biomechanics will have value for you.

Summary

Biomechanics is a field of science that attempts to better understand the movement possibilities of living or once living organisms through the application of knowledge in the areas of anatomy, physics, and instrumentation. The application of biomechanics across a wide range of needs, from athletics to combatting neurodegenerative diseases, have helped individuals improve/maintain their movement ability while decreasing and/or reducing the severity of injuries sustained while attempting to reach their movement goals. We are all biomechanists!

Takeaways

• Biomechanics is a hybrid science that uses the knowledge of biology and musculoskeletal anatomy to predict the movement and injury potential of living or once living organisms.
• The main areas of biomechanical research are sports, daily life, and medicine.
• The goals of biomechanics are improving/maintaining function while limiting injury and improving recovery outcomes when injuries do occur.
• The “fathers of biomechanics” and their main area of expertise are Giovanni Borelli (anatomy), Sir Isaac Newton (physics), and Eadweard Muybridge (instrumentation).
• We are all biomechanists with our own movement goals and aspirations.

References

Ball, E. (2013). The inventor and the tycoon. Doubleday.

Braune, W., & Fishcher, O. (2011). The Human Gait. Springer Berlin, Heidelberg.

Perry, J. & Burnfield, J. M. (2010.) Gait analysis: normal and pathological function (2nd edition). Thorofare: SLACK Incorporated, 576.

USC Dorsnife. (n.d.). Jill McNitt-Gray. https://dornsife.usc.edu/labs/biomech/mcnitt-gray

Image Credits

Fig. 1.2: Source: https://commons.wikimedia.org/wiki/File:The_Horse_in_Motion.jpg.

Fig. 1.3: Source: https://artsandculture.google.com/asset/zoopraxiscope-disc-eadweard-muybridge/QgFEWJoEKUWqAQ.