Biomechanics

Summary

Biomechanics is the study of the application of mechanical forces to a living organism. It investigates the effects of the relationship between the body and forces applied either from outside or within. In humans, biomechanists study the movements made by the body, how they are performed, and whether the forces produced by the muscles are optimal for the intended result or purpose. Biomechanics integrates the study of anatomy and physiology with physics, mathematics, and engineering principles. It may be considered a subdiscipline of kinesiology as well as a scientific branch of sports medicine.

Definition and Basic Principles

Biomechanics is a science that closely examines the forces acting on a living system, such as a body, and the effects that are produced by these forces. External forces can be quantified using sophisticated measuring tools and devices. Internal forces can be measured using implanted devices or from model calculations. Forces on a body can result in movement or biological changes to the anatomical tissue. Biomechanical research quantifies the movement of different body parts and the factors that may influence the movement, such as equipment, body alignment, or weight distribution. Research also studies the biological effects of the forces that may affect growth and development or lead to injury. Two distinct branches of mechanics are statics and dynamics. Statics studies systems that are in a constant state of motion or constant state of rest, and dynamics studies systems that are in motion, subject to acceleration or deceleration. A moving body may be described using kinematics or kinetics. Kinematics studies and describes the motion of a body with respect to a specific pattern and speed, which translate into coordination of a display. Kinetics studies the forces associated with a motion, those causing it and resulting from it. Biomechanics combines kinetics and kinematics as they apply to the theory of mechanics and physiology to study the structure and function of living organisms.

Background and History

Biomechanics has a long history even though the actual term and field of study concerned with mechanical analysis of living organisms was not internationally accepted and recognized until the early 1970s. Definitions provided by early biomechanics specialists James G. Hay in 1971 and Herbert Hatze in 1974 are still accepted. Hatze stated, “Biomechanics is the science which studies structures and functions of biological systems using the knowledge and methods of mechanics.”

Highlights throughout history have provided insight into the development of this scientific discipline. The ancient Greek philosopher Aristotle was the first to introduce the term “mechanics,” writing about the movement of living beings around 322 BCE. He developed a theory of running techniques and suggested that people could run faster by swinging their arms. In the 1500s, Leonardo da Vinci proposed that the human body is subject to the law of mechanics, and he contributed significantly to the development of anatomy as a modern science. Italian scientist Giovanni Alfonso Borelli, a student of Galileo, is often considered the father of biomechanics. In the mid-1600s, he developed mathematical models to describe anatomy and human movement mechanically. In the late 1600s, English physician and mathematician Sir Isaac Newton formulated mechanical principles and Newtonian laws of motion (inertia, acceleration, and reaction) that became the foundation of biomechanics.

British physiologist A. V. Hill, the 1923 winner of the Nobel Prize in Physiology or Medicine, conducted research to formulate mechanical and structural theories for muscle action. In the 1930s, American anatomy professor Herbert Elftman was able to quantify the internal forces in muscles and joints and developed the force plate to quantify ground reaction. A significant breakthrough in the understanding of muscle action was made by British physiologist Andrew F. Huxley in 1953, when he described his filament theory to explain muscle shortening. Russian physiologist Nicolas Bernstein published a paper in 1967 describing theories for motor coordination and control following his work studying locomotion patterns of children and adults in the Soviet Union.

How It Works

The study of human movement is multifaceted, and biomechanics applies mechanical principles to the study of the structure and function of living things. Biomechanics is considered a relatively new field of applied science, and the research being done is of considerable interest to many other disciplines, including zoology, orthopedics, dentistry, physical education, forensics, cardiology, and a host of other medical specialties. Biomechanical analysis for each particular application is very specific; however, the basic principles are the same.

Newton's Laws of Motion. The development of scientific models reduces all things to their basic level to provide an understanding of how things work. This also allows scientists to predict how things will behave in response to forces and stimuli and ultimately to influence this behavior.

Newton's laws describe the conservation of energy and the state of equilibrium. Equilibrium results when the sum of forces is zero and no change occurs, and conservation of energy explains that energy cannot be created or destroyed, only converted from one form to another. Motion occurs in two ways, linear motion in a particular direction or rotational movement around an axis. Biomechanics explores and quantifies the movement and production of force used or required to produce a desired objective.

Seven Principles. Seven basic principles of biomechanics serve as the building blocks for analysis. These can be applied or modified to describe the reaction of forces to any living organism.

1. The lower the center of mass, the larger the base of support; the closer the center of mass to the base of support and the greater the mass, the more stability increases.
2. The production of maximum force requires the use of all possible joint movements that contribute to the task's objective.
3. The production of maximum velocity requires the use of joints in order, from largest to smallest.
4. The greater the applied impulse, the greater increase in velocity.
5. Movement usually occurs in the direction opposite that of the applied force.
6. Angular motion is produced by the application of force acting at some distance from an axis, that is, by torque.
7. Angular momentum is constant when an athlete or object is free in the air.

Static and dynamic forces play key roles in the complex biochemical and biophysical processes that underlie cell function. The mechanical behavior of individual cells is of interest for many different biologic processes. Single-cell mechanics, including growth, cell division, active motion, and contractile mechanisms, can be quite dynamic and provide insight into mechanisms of stress and damage of structures. Cell mechanics can be involved in processes that lie at the root of many diseases and may provide opportunities as focal points for therapeutic interventions.

Applications and Products

Biomechanics studies and quantifies the movement of all living things, from the cellular level to body systems and entire bodies, human and animal. There are many scientific and health disciplines, as well as industries that have applications developed from this knowledge. Research is ongoing in many areas to effectively develop treatment options for clinicians and better products and applications for industry.

Dentistry. Biomechanical principles are relevant in orthodontic and dental science to provide solutions to restore dental health, resolve jaw pain, and manage cosmetic and orthodontic issues. The design of dental implants must incorporate an analysis of load bearing and stress transfer while maintaining the integrity of surrounding tissue and comfortable function for the patient. This work has lead to the development of new materials in dental practices such as reinforced composites rather than metal frameworks.

Forensics. The field of forensic biomechanical analysis has been used to determine mechanisms of injury after traumatic events such as explosions in military situations. This understanding of how parts of the body behave in these events can be used to develop mitigation strategies that will reduce injuries. Accident and injury reconstruction using biomechanics is an emerging field with industrial and legal applications.

Biomechanical Modeling. Biomechanical modeling is a tremendous research field, and it has potential uses across many health care applications. Modeling has resulted in recommendations for prosthetic design and modifications of existing devices. Deformable breast models have demonstrated capabilities for breast cancer diagnosis and treatment. Tremendous growth is occurring in many medical fields that are exploring the biomechanical relationships between organs and supporting structures. These models can assist with planning surgical and treatment interventions and reconstruction and determining optimal loading and boundary constraints during clinical procedures.

Materials. Materials used for medical and surgical procedures in humans and animals are being evaluated and some are being changed as biomechanical science is demonstrating that different materials, procedures, and techniques may be better for reducing complications and improving long-term patient health. Evaluation of the physical relationship between the body and foreign implements can quantify the stresses and forces on the body, allowing for more accurate prediction of patient outcomes and determination of which treatments should be redesigned.

Predictability. Medical professionals are particularly interested in the predictive value that biomechanical profiling can provide for their patients. An example is the unpredictability of expansion and rupture of an abdominal aortic aneurysm. Major progress has been made in determining aortic wall stress using finite element analysis. Improvements in biomechanical computational methodology and advances in imaging and processing technology have provided increased predictive ability for this life-threatening event.

As the need for accurate and efficient evaluation grows, so does the research and development of effective biomechanical tools. Capturing real-time, real-world data, such as with gait analysis and range of motion features, provides immediate opportunities for applications. This real-time data can quantify an injury and over time provide information about the extent that the injury has improved. High-tech devices can translate real-world situations and two-dimensional images into a three-dimensional framework for analysis. Devices, imaging, and modeling tools and software are making tremendous strides and becoming the heart of a highly competitive industry aimed at simplifying the process of analysis and making it less invasive.

Careers and Course Work

Careers in biomechanics can be dynamic and take many paths. Graduates with accredited degrees may pursue careers in laboratories in universities or in private corporations researching and developing ways of improving and maximizing human performance. Beyond research, careers in biomechanics can involve working in a medical capacity in sport medicine and rehabilitation. Biomechanics experts may also seek careers in coaching, athlete development, and education.

Consulting and legal practices are increasingly seeking individuals with biomechanics expertise who are able to analyze injuries and reconstruct accidents involving vehicles, consumer products, and the environment.

Biomechanical engineers commonly work in industry, developing new products and prototypes and evaluating their performance. Positions normally require a biomechanics degree in addition to mechanical engineering or biomedical engineering degrees.

According to the Occupational Outlook Handbook, there were 19,300 bioengineers and biomedical engineers (the category that includes biomechanical engineers) employed in 2020. The handbook projects that there will be 1,100 more jobs for bioengineers and biomedical engineers each year from 2020 to 2030, a job growth rate of about 6 percent.

Private corporations are employing individuals with biomechanical knowledge to perform employee fitness evaluations and to provide analyses of work environments and positions. Using these assessments, the biomechanics experts advise employers of any ergonomic changes or job modifications that will reduce the risk of workplace injury.

Individuals with a biomechanics background may chose to work in rehabilitation and prosthetic design. This is very challenging work, devising and modifying existing implements to maximize people's abilities and mobility. Most prosthetic devices are customized to meet the needs of the patient and to maximize the recipient's abilities. This is an ongoing process because over time the body and needs of a patient may change. This is particularly challenging in pediatrics, where adjustments become necessary as a child grows and develops.

Social Context and Future Prospects

Biomechanics has gone from a narrow focus on athletic performance to become a broad-based science, driving multibillion dollar industries to satisfy the needs of consumers who have become more knowledgeable about the relationship between science, health, and athletic performance. Funding for biomechanical research is increasingly available from national health promotion and injury prevention programs, governing bodies for sport, and business and industry. National athletic programs want to ensure that their athletes have the most advanced training methods, performance analysis methods, and equipment to maximize their athletes' performance at global competitions.

Much of the existing and developing technology is focused on increasingly automated and digitized systems to monitor and analyze movement and force. The physiological aspect of movement can be examined at a microscopic level, and instrumented athletic implements such as paddles or bicycle cranks allow real-time data to be collected during an event or performance. Force platforms are being reconfigured as starting blocks and diving platforms to measure reaction forces. These techniques for biomechanical performance analysis have led to revolutionary technique changes in many sports programs and rehabilitation methods.

Advances in biomechanical engineering have led to the development of innovations in equipment, playing surfaces, footwear, and clothing, allowing people to reduce injury and perform beyond previous expectations and records.

Computer modeling and virtual simulation training can provide athletes with realistic training opportunities, while their performance is analyzed and measured for improvement and injury prevention.

Bibliography

"Bioengineers and Biomedical Engineers." Occupational Outlook Handbook, Bureau of Labor Statistics, US Department of Labor, 1 Feb. 2021, www.bls.gov/ooh/architecture-and-engineering/biomedical-engineers.htm. Accessed 31 Mar. 2021.

Bronzino, Joseph D., and Donald R. Peterson. Biomechanics: Principles and Practices. Boca Raton: CRC, 2014. eBook Collection (EBSCOhost). Web. 25 Feb. 2015.

Hamill, Joseph, and Kathleen Knutzen. Biomechanical Basis of Human Movement. 4th ed. Philadelphia: Lippincott, 2015. Print.

Hatze, H. “The Meaning of the Term ‘Biomechanics.’” Journal of Biomechanics 7.2 (1974): 89–90. Print.

Hay, James G. The Biomechanics of Sports Techniques. 4th ed. Englewood Cliffs: Prentice, 1993. Print.

Kerr, Andrew. Introductory Biomechanics. London: Elsevier, 2010. Print.

Peterson, Donald, and Joseph Bronzino. Biomechanics: Principles and Applications. Boca Raton: CRC, 2008. Print.

Watkins, James. Introduction to Biomechanics of Sport and Exercise. London: Elsevier, 2007. Print.