1. 6/9/2016Dr. Sasho MacKenzie - HK 3761 Muscle Mechanics Related to Chapter 11 in the text http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter10/

2. 6/9/2016Dr. Sasho MacKenzie - HK 3762 peroneus longus peroneus brevis flexor halucis longus flexor digiturum longus triceps surea tibialis anterior tibialis posterior ext. hallucis longus ext. digitorum longus Preparation Hintermann Muscles crossing the ankle joint complex

3. 6/9/2016Dr. Sasho MacKenzie - HK 3763 muscle fascicle muscle fibre (cell) myofibril endomysium sacrolemma perimysium epimysium fascia Muscle Schematic Illustration

4. 6/9/2016Dr. Sasho MacKenzie - HK 3764 I - Band M Line A - Band Myofibril Z Line Huxley and Huxley, 1954

5. 6/9/2016Dr. Sasho MacKenzie - HK 3765 filament Z-line sarcomere A-band I- band Myofibril

6. 6/9/2016Dr. Sasho MacKenzie - HK 3766 Current paradigm to describe muscle contraction Hugh Huxley and Andrew Huxley published in 1954 two independent papers (which were basically identical) to describe the sliding of the thick and thin filaments past one another.  sliding filament theory Refinished in 1957 by A. Huxley  cross bridge theory Cross bridge theory

7. 6/9/2016Dr. Sasho MacKenzie - HK 3767 thick filament thin filament I-BandA-Band Cross bridge theory Z-lineZ-line

8. 6/9/2016Dr. Sasho MacKenzie - HK 3768 thick myofilament thin myofilament

9. 6/9/2016Dr. Sasho MacKenzie - HK 3769 I - Band M Line A - Band thick filaments Sliding filament model thin filaments 1m1m Z A I M Huxley and Huxley, 1954 Z Line

10. 6/9/2016Dr. Sasho MacKenzie - HK 37610 globular head tail portion myosin molecule thick myofilament Cross bridges

11. 6/9/2016Dr. Sasho MacKenzie - HK 37611 60 o 14.3 nm 43 nm Cross bridges

12. 6/9/2016Dr. Sasho MacKenzie - HK 37612 contraction rest cross-bridge thin filament thick filament sliding Cross bridge theory

13. 6/9/2016Dr. Sasho MacKenzie - HK 37613 Muscle Force Depends on Four Factors Sarcomere (muscle) length Velocity of muscle contraction Activation level Previous contraction history

14. 6/9/2016Dr. Sasho MacKenzie - HK 37614 Fact: Muscles at very long and very short lengths can not produce high forces Fact: Maximal force production of a muscle depends on its length Force-Length Relationship

15. 6/9/2016Dr. Sasho MacKenzie - HK 37615 100 75 50 25 0 ascending limb plateau region descending limb Force [%] Sarcomere length Force-Length Relationship

16. 6/9/2016Dr. Sasho MacKenzie - HK 37616 Force-Length Relationship 1.60  m 0.10  m 0.95  m Sarcomere = 1 z-line + 2 thin filament + 1 thick filament - overlaps

17. 6/9/2016Dr. Sasho MacKenzie - HK 37617 Force-Length Relationship

18. 6/9/2016Dr. Sasho MacKenzie - HK 37618 a b c 1.52.02.53.03.5 ab c 100 75 50 25 0 sarcomere length [  m] tension generated Force-Length Relationship

19. 6/9/2016Dr. Sasho MacKenzie - HK 37619 100 75 50 25 0 01.273.60 1 2 34 5 1.70 2.00 2.17 ascending limb plateau descending limb Force [%] [%] [%] Force-Length Relationship Sarcomere Length

20. 6/9/2016Dr. Sasho MacKenzie - HK 37620 Ascending limb: Point 2: Thin filaments overlap partially. A reduced number of cross-bridges can attach. Point 1:Complete overlap of thin filaments. No cross-bridges can attach. General: descending limbeasy to understand ascending limbmore difficult to understand Force-Length Relationship

21. 6/9/2016Dr. Sasho MacKenzie - HK 37621  Starting position in sprint  Knee angle in weight lifting  Design of weight lifting equipment  Design of bicycles Application of F-L Relationship

22. 6/9/2016Dr. Sasho MacKenzie - HK 37622

23. 6/9/2016Dr. Sasho MacKenzie - HK 37623 Velocity of Muscle Contraction muscle force velocity of muscle contraction eccentric concentric isometric –+ Why less force for faster concentric contractions? Why more force for eccentric contractions?

24. 6/9/2016Dr. Sasho MacKenzie - HK 37624 STFTForceVelocity VelocityPowerST FT Velocity Force/Power - Velocity ST = slow twitch FT = fast twitch

25. 6/9/2016Dr. Sasho MacKenzie - HK 37625

26. 6/9/2016Dr. Sasho MacKenzie - HK 37626 Activation Level It takes time for muscle to develop tension 1)Electrical signals must be sent from the brain (or spine) to activate muscles. The dynamics of muscle contraction once the signal reaches the muscle also takes time Even after activation is initiated, there is a delay in the force applied to the bones 2)At the start of a contraction, the sarcomeres will shorten but will not be able to generate their maximum force. The sarcomeres shorten because the tendons (and other elastic components of muscle) are stretched. The elastic components of muscles and tendons must be sufficiently stretched before the muscular force is transmitted to bone (Springs).

27. 6/9/2016Dr. Sasho MacKenzie - HK 37627

28. 6/9/2016Dr. Sasho MacKenzie - HK 37628 Previous Contraction History If a muscle is initially contracting isometrically and is then stretched…. ….the muscle will produce a greater isometric force at it’s new length. Also, a concentric contraction immediately following an eccentric contraction will be more forceful. This is known as the “force enhancement” phenomenon and has been repeated in hundreds of experiments. There are several theories behind this behaviour but none are globally excepted.

29. 6/9/2016Dr. Sasho MacKenzie - HK 37629 In 1994, two men attempted to set a world bungee jumping record by performing the highest double bungee jump in history off of Royal George Bridge. The bridge was located in Colorado and was suspended 300 m above the Arkansas River. John (69.2 kg) and Rory (90.1 kg) used a bungee cord (linear spring) that was 50 m long. John was physically tied to the bungee while Rory simply held onto John. The duo had meticulously planned their jump so that they would come to a stop just as they touched the water. Rory would let go of John allowing him to make his way back to the top and reel John back to safety. –Knowing that the 50 m long bungee cord had a stiffness (k) of 15, was their jump successful? In other words, did the pair come to rest just at the surface of the Arkansas River? (3) –The top of the bungee was fixed to the middle of the underside of a huge metal I-beam. Assuming that 250 KJ of the strain energy was lost as heat (not converted back into kinetic energy) and that the pair dropped in a perfectly vertical path, what happened to John after Rory was dropped into the water? Make sure to include John’s velocity at 300 m above the surface of the river. (3)

30. 6/9/2016Dr. Sasho MacKenzie - HK 37630 NEXT CLASS READ CHAPTER 5 AND Construct a flow chart depicting what the torque developed about a joint depends on.

31. 6/9/2016Dr. Sasho MacKenzie - HK 37631

32. 6/9/2016Dr. Sasho MacKenzie - HK 37632 Z Line M Line A Band thick filaments thin filaments titin I Band

33. 6/9/2016Dr. Sasho MacKenzie - HK 37633 globular head tail portion myosin molecule thick myofilament centre of filament

34. 6/9/2016Dr. Sasho MacKenzie - HK 37634 60 ° 14.3 nm 42.9 nm cross bridges on thick myofilament

35. 6/9/2016Dr. Sasho MacKenzie - HK 37635 actin chains tropomyosin actin globule troponin 38.5 mm thin myofilament

36. 6/9/2016Dr. Sasho MacKenzie - HK 37636 1 µm ZA I M Titin Sliding filament model: Cross-section area of thick filaments and thick-thin myofilaments overlap

37. 6/9/2016Dr. Sasho MacKenzie - HK 37637 1.0 0.5 0 00.20.40.60.81.0 Force / Power [normalized] Force Power Velocity [normalized ] Force/Power - Velocity

38. 6/9/2016Dr. Sasho MacKenzie - HK 37638 Sarcomere Length Maximum overlap of myosin and actin allows for a maximum amount of cross-bridge connection and hence force.

39. 6/9/2016Dr. Sasho MacKenzie - HK 37639 First experiments: Fenn and Marsh, 1935Fenn and Marsh, 1935 Hill, 1938 Found (“stumbled” onto) the Force-velocity relationship while working on heat production of isolated frog skeletal muscle.Hill, 1938 Found (“stumbled” onto) the Force-velocity relationship while working on heat production of isolated frog skeletal muscle. Force-Velocity Relationship

40. 6/9/2016Dr. Sasho MacKenzie - HK 37640 60 o 14.3 nm 43 nm 14.3 nm 43 nm model I model I model II model II model I model II

41. 6/9/2016Dr. Sasho MacKenzie - HK 37641 myosin filament actin filament A A1A1 B1B1 B2B2 M4M4 A4A4 M1M1M1M1  Huxley 1969; Huxley and Simmons, 1971 Cross bridge theory

42. 6/9/2016Dr. Sasho MacKenzie - HK 37642 Cross bridge theory

43. 6/9/2016Dr. Sasho MacKenzie - HK 37643

44. 6/9/2016Dr. Sasho MacKenzie - HK 37644 Knee Extension

45. 6/9/2016Dr. Sasho MacKenzie - HK 37645 0.00.51.01.52.0 2.5 [cm] 0 20 40 60 Length Force passive structures Force-Length AccumulatedForce-Length Active and passive structures[N]

46. 6/9/2016Dr. Sasho MacKenzie - HK 37646 100 75 50 25 0 03.60 1 2 34 5 ascending limb plateau region descending limb Force [%] Sarcomere length 1 z-line0.10  m 2 thin filament1.90  m 1 thick filament1.60  m total length 3.60  m no cross bridges can attach

47. 6/9/2016Dr. Sasho MacKenzie - HK 37647 100 75 50 25 0 03.60 1 2 34 5 2.17 ascending limb descending limb Force [%] Sarcomere length 1 z-line0.10  m 2 length thin filament1.90  m 1 thick filament no overlap0.17  m total length sarcomer2.17  m all cross bridges can attach

48. 6/9/2016Dr. Sasho MacKenzie - HK 37648 100 75 50 25 0 03.60 1 2 34 5 2.00 2.17 ascending limb descending limb Force [%] Sarcomere length 1 z-line0.10  m 2 thin filament1.90  m 1 thick filament no overlap0.00  m total length sarcomer2.00  m all cross bridges can attach