Physical Education · Ch 8 — Fundamentals of Kinesiology and Biomechanics in Sports
Definitions of Biomechanics
Definitions of Biomechanics
The standard definitions of biomechanics that a Class 11 Physical Education student should know all stress the application of mechanics to living bodies and to the forces acting on them.
Standard definitions
- Hatze (1974): biomechanics is "studying the movement of living things using the science of mechanics."
- "The area of study wherein knowledge and methods of mechanics are applied to the structure and function of the living human system."
- James G. Hay: "Biomechanics is the science concerned with the internal and external forces acting on a human body and the effects produced by these forces."
Why these forces matter
Hay's definition is the most useful for sport because it names the two kinds of force the rest of the unit keeps returning to:
- Internal forces — generated inside the body, chiefly by the muscles pulling on the bones.
- External forces — acting from outside, such as gravity, friction and air or water resistance.
As a glimpse of how real the "effects produced by these forces" are, the textbook gives a biomechanical load calculation: a person who weighs 80 kg, is 186 cm tall and bends about 45 degrees forward to lift a 10 kg load at a reaching distance of 30 cm places a strain of roughly 255 kg on the discs of the lumbar region — which is exactly why safe lifting technique matters.
Internal and external forces working together
Every sporting movement results from internal and external forces acting at the same time, never one alone. Take a vertical jump: the internal force comes from the quadriceps, glutes and calf muscles contracting to extend the hip, knee and ankle, while the external forces are gravity, pulling the body back down the instant the feet leave the floor, and the ground reaction force, the floor pushing back up during take-off. The height of the jump depends on how effectively the internal muscular force overcomes these external forces in the brief time available before take-off — a direct real-world illustration of Hay's definition.