3 C H A P T E R The Biomechanics of Resistance Exercise Everett Harman
Chapter Outline The musculoskeletal system Human strength and power Sources of resistance to muscle contraction Joint biomechanics: concerns in lifting Movement analysis and exercise prescription
Muscle Pulling Force Manifested As a Pushing Force
Muscle Pulling Force Manifested As a Pulling Force
Changes in Mechanical Advantage: Knee Extension and Flexion
Changes in Mechanical Advantage: Elbow Flexion
Changes in Mechanical Advantage: During Weightlifting
M ost of the skeletal muscles operate at a considerable mechanical disadvantage. Thus, during sports and other physical activities, forces in the muscles and tendons are much higher than those exerted by the hands or feet on external objects or the ground.
W hen a weight is held in a static position or when it is moved at a constant velocity, it exerts constant resistance, only in the downward direction. However, upward or lateral acceleration of the weight requires additional force.
Supporting the Vertebral Column During Lifting: The Fluid Ball
R esistance training is quite safe compared with other sports and fitness activities. Prudence can keep injuries to a minimum. Basic safety principles include good lifting form, appropriate resistance, accommodation to injuries, balance, and variety.
S pecificity is a major consideration when designing an exercise program to improve performance in a particular sport activity. The sport movement must be analyzed qualitatively or quantitatively to determine the specific joint movements that contribute to the whole-body movement. Exercises that use similar joint movements are then emphasized in the resistance training program.