1. Variable Resistance – Implication for Swimming Training
Type of Muscle Contraction
Static
Dynamic
Angle of Pull – Invention of Isokinetic machine
Swimming – Training for optimum muscle power and strength improvement
By Jackson Pui Man Wai, Ph.D.

3. First-Class lever
第一型槓桿

4. Second-Class lever
第二型槓桿

5. Third-Class lever
第三型槓桿

6. 40 kg x 1 m = 40 kgm
20 kg x 2 m = 40 kgm
(20+5) kg x 1.6 m = 40 kgm

7. Muscle Angle of Pull - Tension Relationship
Source: Fox, Bower, and Foss. The Physiological Basis of Physical Education and Athletics.

8. Muscle Angle of Pull - Tension Relationship
Source: Fox, Bower, and Foss. The Physiological Basis of Physical Education and Athletics.

9. Effect of Angle of Pull on Muscle tension
Experimental setting LF LW

10. Effect of Angle of Pull on Muscle tension
Realistic setting LF LW

11. Energy of muscle force converts to energy of acceleration
Open System
Energy of muscle force converts to energy of acceleration
F = ma
 a = F/m
 a  F,
Thus  F   a

12. Closed system
Energy cannot be dissipated by acceleration, energy of acceleration is absorbed as energy of resistance.
F = ma = mR (constant V)
R  F thus  F   R

13. Isokinetic Knee Extension and Flexion
~117°
~147°
Torque curves of quadriceps and hamstring muscle groups of normal subjects performed at 22.5°·s-1

22. CYBEX II Isokinetic Device
Shoulder Adduction and Abduction

24. THE END