1. Muscle Mechanics Chapter 17 KINE 3301 Biomechanics of Human Movement

2. Instrumentation used to study muscle force- velocity and force-length relationship.

3. Length changes to an individual sarcomere during an isometric contraction. The sarcomere directly underneath the end-plate will be the first to develop tension which causes the sarcomeres to the right and left to lengthen.

4. Sarcomere Force – Length Relationship

5. Force – Length in Normal Joint Range of Motion

6. Force – Velocity Relationship (P + a) V = b (Po – P)

7. Efficiency of Eccentric & Concentric Exericse Bernard Abbott, Brenda Bigland-Ritchie, JJ Woods Loiselle D S et al. J Appl Physiol 2010;108:1465-1471 ©2010 by American Physiological Society

8. DOMS – Damage to Muscle Following Eccentric Contractions

9. Stretch – Shorten Cycle 1.Stored elastic energy (tendon, cross-bridge, and titin). 2.Eccentric phase elicits a stretch reflex. 3.Eccentric phase pre-loads the muscle, so the concentric phase begins at a higher force. 4.Two joint muscles (rectus femoris, gastrocnemius) transfers energy and allows the muscle to work at a lower velocity and a higher force. The stretch – shorten cycle is defined as an eccentric contraction followed by an immediate concentric contraction. Additional work is performed during the concentric phase of a stretch – shorten cycle. This extra work is attributed to:

10. Stretch – Shorten Cycle The area under the force – length curve is equal to the work done.

11. Effects of Increasing the velocity of stretch on the concentric work done for the concentric phase. © 1974 by American Physiological Society Adapted from: Cavagna and Citterio. J Appl Physiol 1974; 239:1-14.

13. Three Component Muscle Model Describes the mechanical response of muscle. Contractile Component (CC) models active cross-bridges. Dashpot models muscle viscosity. Series Elastic Component (SEC) models elastic structures in series (tendon, passive cross- bridges, titin). The SEC explains extra work done in stretch-shorten and EMD. Parallel Elastic Component (PEC) models passive elastic structures (passive cross- bridges, connective tissue: endomysium, perimysium, epimysium, titin, desmin.