Biomechanics and Skill Acquisition
Biomechanics and Skill Acquisition
Biomechanics applies mechanical principles to human movement. Candidates must know Newton's three laws and apply them to sport (inertia, force equals mass times acceleration, action-reaction). Understand force, mass, weight, momentum (mass times velocity), impulse (force times time, equal to change in momentum), and work, power and energy relationships. Know levers: first, second and third class, with the body mostly using third-class levers (effort between fulcrum and load) favouring speed and range over force. Understand torque (force times perpendicular distance from axis) and how changing the moment arm alters rotation. Study projectile motion: angle, velocity, release height and gravity determine trajectory; optimal angle is less than 45 degrees when release height exceeds landing height. Understand centre of mass, base of support, stability and balance, plus angular momentum and conservation of angular momentum in spins and dives.
Traps
Confusing mass with weight; assuming a longer lever always increases force (it may increase torque while reducing speed); thinking 45 degrees is always optimal; ignoring air resistance; and muddling impulse (force over time) with force alone. Another trap is using the wrong lever class for a body segment.
Worked example
A gymnast tucks to spin faster. Reducing the radius of gyration reduces moment of inertia; because angular momentum is conserved, angular velocity rises. Rule of thumb: smaller radius, faster spin; larger radius, slower spin. For catching a ball, a player 'gives' with the hands to extend impact time, reducing the force for the same change in momentum (impulse-momentum relationship).
Rule of thumb
When asked how to increase stability, lower the centre of mass, widen the base of support, and align the centre of mass over the base.