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Principles of Exercise Prescription in Rehabilitation

Principles of Exercise Prescription in Rehabilitation. Exercise Science. Focus:. Exercise training principles in rehabilitation Resistance training rehabilitation Flexibility Rehabilitation Proprioception Rehabilitation Progression / Functional Progression Safe design of exercise program.

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Principles of Exercise Prescription in Rehabilitation

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  1. Principles of Exercise Prescription in Rehabilitation Exercise Science

  2. Focus: • Exercise training principles in rehabilitation • Resistance training rehabilitation • Flexibility Rehabilitation • Proprioception Rehabilitation • Progression / Functional Progression • Safe design of exercise program

  3. Focus: • Skeletal System Adaptation to Decreased Use / Immobilisation • Muscle • Bone • Tendon • Ligament • Cartilage • Clinical Implications

  4. Aerobic Energy System Anaerobic Circulatory Function Cardiorespiratory System Heart Function Respiratory Function ROM Physical Fitness Flexibility Joint Tissue Muscular Neuromuscular System Neural Fat Mass Body Composition Fat-free Mass

  5. Goals of Rehabilitation Develop, improve, restore +/or maintain: • Strength • Endurance • Cardiovascular fitness • Mobility • Flexibility • Stability • Co-ordination, balance and functional skills

  6. Principles of Training • related to morphological changes • incorporation of exercise that replicates the desired functional activities

  7. Bedrest Casting Spinal Cord Injury Skeletal System Adaptation to Reduced Use - Spectrum of Disuse Convertino et al, 1997 Reduced Activity

  8. Adaptation to Reduced Use • Hindlimb suspension • Immobilisation • Spinal Cord Transection (will not be discussed) Experimental Models

  9. Considerations for these models • Usually performed on healthy, uninjured tissues • Structural and mechanical properties of the injured tissue will be further compromised (viz. Stages of healing) • Surrounding tissues are also immoblised (need to consider this too!)

  10. Skeletal Muscle Adaptation to immobilisation/decreased use • Muscle Mass • Muscle mass  total amount of contractile material in the muscle • Tension production • Force  muscle fiber CSA • Fiber Type • Protein Synthesis • Sarcomere length & number • Motor unit activity

  11. Hindlimbsuspension (animal model) • Suspending animals in a horizontal position by a sling or by the tail, with hindlimbs in the air • Model of decreased use, lower motor neuron intact, low muscle tension production • Spaceflight Thomason and Booth, 1990

  12. Hindlimb suspension (animal model)

  13. Unilateral lower limb suspension (human model) • Sling suspension on one leg and subject ambulates with crutches • Allows for freely movable joints but removes loadbearing • Similar to hindlimb suspension in rats Tesch et al, 1991

  14. Hindlimb Suspension (animal model) Plantaris and Soleus muscles : • Muscle mass  rapidly, next 30 days the rate of  becomes slower  then plateaued • Contractile tension  by 50% • More pronounced in soleus Only soleus (slow twitch fiber) : • showed  muscle speed • Evidence:  in contraction and half-relaxation time and  in Vmax

  15. Why slow twitch fiber? • Fiber type distribution corresponds to the normal level of use • Primary function: constant firing to sustain postural control in everyday activity • (Fast twitch fibers are recruited for maximal contractions of short duration)

  16. Summary • Muscle Mass  • Fiber Size  • Tension production  • Fiber Type  • Protein Synthesis • Sarcomere length & number • Motor unit activity (EMG) •  fiber CSA •  muscle mass • Selective atrophy of slow twitch muscles •  muscle force generating capacity • Slow-to-fast fiber type conversion (if the disuse is extreme enough)

  17. Why is there a  in muscle mass? • Fiber size relates to no. of myofibrils • myofibrils is made up of 70% protein  muscle force related to total amount of myofibrillar protein • Protein synthesis and degradation occur within the cell  Protein Turnover • Regulation of muscle mass represents balance between protein synthesis and degradation

  18. Sarcomere Length and number • Muscles immobilised in shortened position   in number of sarcomeres • Little or no change in sarcomere length • Muscle adjusted sarcomere number to reset Lo to immobilisation length  maximise the sliding and cross-bridging potential • Result of the muscle protecting itself from overstretching sarcomere

  19. Consequences of this change • Muscles become stiffer • More resistant to passive stretch • Less energy is absorbed before failure • Shift of length tension ratio to the left • Sarcomere changes take place at myotendinous junction

  20. Effect of immobilisation on muscle tissue in varying lengths • Lieber, 1992 • Dog quadriceps model - RF, VL & VM • RF - two joint mm, 50% slow fibers • VL - knee extensor, 20% slow fibers • VM - knee extensor, 50% slow fibers • 10/52 immobilisation with external fixator

  21. Immobilisation model (Lieber, 1992) •  in both fast and slow fiber area   force-generating capacity • Slow fibers atrophy: VM > VL > RF • Fast fibers atrophy: VM = VL > RF • Connective tissue: VM = VL > RF

  22. Immobilisation model (Lieber, 1992) • Immobilisation length influences the atrophic response • VM & RF started off with same % of slow fibers • RF less rigidly immobilised (2 joint) • Initial % slow muscle fiber  indication of use  good predictor of relative degree of atrophy

  23. Electrical Activity (measured by EMG)  motor neuron excitability  ability to activate motor units during maximal contractions  in muscle strength

  24. Immobilised muscle  no electrical activity no tension production no motion

  25. Summary • Fiber Size • Muscle Mass • Tension production • Fiber Type • Protein Synthesis  • Sarcomere length & number  • Motor unit activity (EMG)  • Increase protein degradation •  in sarcomere number • Position specific • Impaired activation of motor units • Time specific

  26. So….What does it mean?

  27. Practical Implications • Avoidance of prolonged immobilisation • Selective training of muscle groups most seriously affected • Utilise a gradual, progressive overload starting at low intensities

  28. Human muscles?? Most vulnerable: • Function as anti-gravity muscle • Cross a single joint • Large proportion of slow fibers

  29. Fits all the description Predominantly Fast • Soleus • Vastus medialis • Vastus lateralis Antigravity, predominately slow, cross multiple joints • Tibialis anterior • EDL • Biceps • Longissimus • Erector Spinae • Gastrocnemius • Rectus Femoris Human Muscles

  30. PracticalImplications • Reconsideration of the evaluation of muscle strength (tested at different points of ROM to determine if the muscle is positionally weak or weak throughout the ROM) • Exercise intervention: Restoration of normal length-tension relationship at appropriate range

  31. Resistance Training

  32. Resistance Training - Goals • Strength • Fmax at a specified speed • Endurance • ability of the muscle to perform till fatigue • Power • Force x velocity

  33. Mode of Training

  34. Different types of exercise equipment • Free weights • Elastic resistance devices • Pulley system • Variable resistance equipment

  35. Progression

  36. Progression • Force / Resistance • Reduction in WB  Full WB • Movement direction: Secondary links and planes  Primary links and planes • Isolated muscle / joint  multiplane / multijoint exercises

  37. Progression • Support: Double support  single support  double non-support  single non-support stable surface  unstable / irregular surfaces • Speed: Slow  Fast; Consistent  acceleration - deceleration

  38. Resistance Training Progression Isometric • Pain free position  lengthened position Isotonic • Concentric: Stress-free position  stressful position • Eccentric: Slow velocity  high velocity; low resistance  high resistance

  39. Resistance Training Progression Isokinetic • Stress free position  stressful position • Submaximal resistance  maximal resistance • slow velocity  high velocity

  40. Muscle Endurance Progression • Local muscle endurance • takes longer than muscle strength • speed specific • Cardiovascular endurance

  41. Flexibility

  42. Flexibility Rehabilitation • Static  Dynamic flexibility • Sports specific muscle flexibility and ROM • Progressive velocity flexibility program • muscle stretches at higher velocity over time • movement simulation • integration into functional activities / sports

  43. Progressive Velocity Flexibility Program • Static stretching • Slow short-end range stretching • Slow full-range stretching • Fast short-end range stretching • Fast full-range stretching

  44. Bone

  45. Effect of Disuse on Bone Mass (Bloomfield, 1997) • Structural change lags behind muscle (Because of slow turnover of bone tissue) •  urine and fecal Ca2+ 1/52 bedrest, peak at 5/52 - 7/52 (~ 50% of negative Ca2+ balance) • Combination of  intestinal absorption and  bone mineral density •  Bone resorption or  formation of new bone or both

  46. Changes in Bone Mass • Loss depends on the location, use patterns, bone composition, prior status of the bone • Lower extremity > upper limb • Lx, NOF, tibia, calcaneus** >> radius • Trabecular bone > cortical bone

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