Biomechanics: Muscle Actions, Force & Movement
Biomechanics applies mechanical principles to human movement. In training, it gives us a language for describing how forces act on the body, how joints move, how muscles produce or control motion, and how technique changes the demands of an exercise or sport skill.
Key Takeaways
- Biomechanics examines motion, force, leverage, balance, and load.
- Muscle actions can be described as concentric, eccentric, or isometric.
- Range of motion is task- and person-specific; “more” is not automatically better.
- Technique affects how load is distributed, but biomechanics alone does not guarantee injury prevention.
Movement Mechanics
Human movement results from internal forces, such as muscular tension, interacting with external forces, such as gravity, ground reaction forces, water resistance, equipment, and contact with other objects. Biomechanical analysis asks what moved, around which joint, under what load, and with what result.
Levers are especially useful for understanding exercise. Bones act as lever arms, joints act as axes of rotation, and muscles apply force through their tendon attachments. Changing body position or where a load is held can change the torque at a joint even if the external weight stays the same.
Three Common Muscle Actions
- Concentric: the active muscle-tendon unit shortens while producing force, such as rising from the bottom of a biceps curl.
- Eccentric: the active muscle-tendon unit lengthens while controlling force, such as lowering the weight in a curl or controlling landing.
- Isometric: force is produced with little or no visible change in joint angle, such as holding a plank position.
Most athletic movements combine all three. Running, for example, requires muscles to absorb and control forces, stabilize joints, and then contribute to propulsion.
Range of Motion
Range of motion describes how far a joint or body segment moves during a task. Appropriate range depends on the individual, exercise, load, training goal, and sport. Training through a well-controlled range can be useful, but forcing a range that cannot be controlled is not automatically beneficial.
Compression, Distraction, and Load
Compression pushes structures toward one another; distraction pulls them apart. Both can occur normally during exercise. Biomechanics helps describe where forces are directed, while physiology and tissue capacity help explain how the body responds.
Training also produces neural adaptations. Early improvements in a new strength exercise can occur before major muscle hypertrophy because the athlete becomes more skilled at coordinating and recruiting the muscles required for the task.
What About “Trigger Points”?
People can experience localized tender or sensitive areas in muscle and surrounding tissues. The mechanisms behind pain and referred symptoms are complex, so a tender spot should not automatically be treated as proof that one specific tissue is the cause of pain elsewhere.
For Class
After reading, you should be able to:
- Define biomechanics in the context of exercise and sport.
- Differentiate concentric, eccentric, and isometric actions.
- Explain how lever length and load position can change joint torque.
- Discuss range of motion and technique without assuming one movement pattern fits everyone.
Used in College Coursework
This article is used as instructional material in Health and Wellness Studies coursework at Binghamton University. It is designed to support class discussion and application rather than replace individualized exercise, medical, or rehabilitation guidance.
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About the Author
Matthew Francis Gawors, MBA, is an instructor in Health and Wellness Studies at Binghamton University and a USATF Level 2 coach, personal trainer, wellness coach, triathlon coach, and running specialty professional. This article is part of the HWS Health & Performance Education Series.
