Therapeutic Techniques to Increase Muscle Strength

1. Therapeutic Techniques to Increase Muscle Strength PT 154: Therapeutic Exercises III Ms. Mary Grace M. Jordan, PTRP December 1, 2009

2. As physical therapists… “…one of the major goal of physiotherapy in neurological rehabilitation is the optimization of functional motor performance..”

3. Major impairments limiting motor performance • Muscle weakness or paralysis • Soft tissue contracture • Lack of endurance • Physical fitness

4. Muscle Strength • The ability of contractile tissue to produce tension and a resultant force based on the demands placed upon the muscle. Functional Strength… “The ability of the neuromuscular system to produce, reduce, or control forces, contemplated or imposed, during functional activities, in a smooth, coordinated manner.”

5. Learning objectives… • Discuss muscular weakness, disuse weakness, and paralysis • Review the principles of strength training • Discuss the following: • Strength training regimes • Isotonic vs. Isometric vs. Isokinetic exercises • Open chain vs. Close chain exercises • Complications of strength training • Considerations in force gradation

6. Learning objectives… • Discuss concepts of resistance training, PNF, and Task-oriented approach to increase strength of neurologic and developmental conditions • Discuss evidence of technique effectiveness

7. Physiologic factors which affect strength STRUCTURAL • Cross-sectional area • Density of muscle fibers per unit cross-sectional area • Efficiency of mechanical leverage across joints FUNCTIONAL • Number, type, and frequency of motor units recruited during a contraction • Initial length • Efficient cooperation between synergic muscles

8. Strength is therefore… A function of the properties of muscle and depends on intact neurological function. (Buchner and De Lateur, 1991)

9. Skilled motor performance requires that… • Each muscle involved in the action has to generate peak force at the length appropriate to the action • Force has to be graded and timed so synergic muscle activity is controlled for task and context

10. Skilled motor performance requires that… • Force has to be sustained over a sufficient period of time • Peak forces must be generated fast enough to meet environmental and task demands

11. Can strength impairments be reliably measured in a patient with a CNS lesion?

12. Assumptions… • Measuring strength was not appropriate • Primary impairment affecting functional performance was not weakness but spasticity • Strength training in the CNS patient was considered contraindicated, since it was believed that strength training would increase tone problems (Bobath, 1978; Davies, 1985)

13. Recent research says… • Paresis is an important factor in impaired functional performance as spasticity. • Strength can be measured in 3 ways: • Isometrically • Isotonically • Isokinetically ***Alternative: dynamometers

14. Muscle weakness and paralysis… • Results in loss of movement or stability of a particular joint • Creates a state of muscular imbalance which affects all the groups concerned in the production of coordinated movements “CONTRACTION is the only means by which muscle power can be maintained or increased…”

15. Muscle weakness and paralysis… “…any lesion or habit which prevents or limits contraction will result in muscle wasting” • Paralysis • complete loss of ability to contract • Paresis • partial loss or a muscle may be merely weak or sub-normal

16. Muscle weakness and paralysis… • Causes • Lesions affecting the Anterior Horn Cells • Lesions affecting the Motor Pathways • Lesions affecting the Muscle Tissue • Reduced endurance due to decline in physical activity.

17. Disuse Weakness… • A minimum level of strength is necessary for the performance of everyday motor task. • Strength requirements of people fluctuate over their lifetimes, and even from day to day. • The neuromuscular system is capable of accommodating to these fluctuations.

18. Disuse Weakness… A patient may not use his muscles because… • He cannot • He does not need to • He will not

19. How will you know if its TRUE weakness or APPARENT weakness?

20. Hence…

21. Strength training …is necessary after stroke to improve the force generating capacity and efficiency of weak muscles and to improve functional motor performance.

22. Treatment of impaired strength • Focus on generating force to move a body segment or alternatively, generating force to resist a movement. • Use of PRE • Use of Isokinetic equipments • Eccentric vs. Concentric strength training • Task-specific circuit training

23. Principles of Strength Training • Overload (resisted work) • Progression • Specificity • Reversibility

24. Strength training regimes • Static, Dynamic, and Isokinetic • Progressive resistance exercises • Use of manual resistance • Use of light weights • Use of isokinetic training systems

25. Strengthening regimes

26. What to use? • Isotonic vs. Isometric vs. Isokinetic • Open chain vs. Close chain exercises

27. Therapeutic techniques to increase muscle strength • Resistance exercises • Proprioceptive Neuromuscular Facilitation • Motor Re-learning Program / Task-oriented approach

28. Kinetic chain exercises… • Are given to strengthen lower limb extensor muscles using body weight (i.e. step-ups, modified squat to stand, heel raise, leg press) • Take advantage of the specificity principle as muscles are exercised concentrically and eccentrically in a movement pattern that shares the dynamic characteristics of commonly performed motor actions (i.e. sit-to-stand, bending down to pick objects, stair negotiation).

29. Eccentric vs. Concentric exercise… • Voluntary eccentric contractions produce greater muscle force than concentric muscle contraction. • Eccentric exercise has greater mechanical efficiency and has lesser metabolic energy cost than concentric exercise.

30. Studies showed that… • Utilizing both concentric and eccentric muscle contractions in strength training has been shown to produce better gains in strength than concentric contractions alone. (Hakkinen and Komi, 1981)

31. Quick stretch… • Concentric activation of weak muscles may be facilitated by the enhanced muscle spindle activity occurring as a result of the rapid switching from eccentric to concentric muscle activity. • If an eccentric contraction immediately precedes a concentric contraction, concentric phase generates more force due to the effect of the stretch-shortening cycle.

32. Elastic band resistance exercise… • An inexpensive and simple means of exercising which can be carried out by patients on their own. • Provides variable resistance throughout the range of movement • There is some difficulty controlling the exact amount of resistance • Recommended as a means of increasing ms. Strength, preserving or inc. jt. range and ms. extensibility, and encouraging unsupervised exercise.

33. PNF • An approach to therapeutic exercise that combines functionally based diagonal patterns of movement with techniques of neuromuscular facilitation to evoke motor response and improve neuromuscular control and function.

34. PNF techniques • Repeated contractions • Dynamic reversals of antagonists • Stabilizing reversals • Rhythmic stabilization • Combination of isotonics • Repeated stretch from beginning of range • Repeated stretch throughout the range

35. Motor Re-learning Program • Task-oriented approach to improve motor control focusing on re-learning of daily activities. • 4 steps • Analysis of task • Practice of missing components • Practice of task • Transference of learning

36. What time / phase should you start implementing strengthening exercises?

37. What do you need to consider in grading the force that you will apply to your patient?

38. Resistance exercises • Any form of active exercise in which a dynamic or static muscle contraction is resisted by an outside force, applied either manually or mechanically. • Take note: • Warm-up • Placement of resistance • Direction of resistance • Stabilization • Intensity/Amount of resistance • Number of repetitions and sets; rest intervals • Monitor patient’s response • Cool-down

39. Eliciting activity in very weak muscles • Grade 2-3 • Partial body weight resistance • Resistance through a small range of movement • Lifting small weights through a limited range • Elastic band exercises • Concentric and eccentric exercise on an isokinetic dynamometer

40. Eliciting activity in very weak muscles • Grade 0-1 • More studies are needed to explore training of severely weakened or paralyzed muscles • In theory, since lower levels of muscle activation are required for the same force effect in eccentric compared to concentric exercise, attempts at eccentric contraction may enable an individual with very weak muscles to improve activation.

41. Resistance exercises • Precautions • Valsalva maneuver • High-risk patients • Coronary artery disease • Myocardial infarction • Cerebrovascular disorders • Hypertension • S ubstitute motions • Overwork weakness

42. Complications to strength training • Spasticity • Incomplete innervation • Muscle substitution • Effect of drugs on exercise • Effects of length changes on muscle

43. How to prescribe strengthening exercises?

44. Basic considerations… • Dosage can be increased by increasing the number of repetitions, the number of sets, and the resistance provided. • Muscles should be exercised to the point of fatigue but not pain in order to obtain some change. • Patients should be warned that they may experience a small degree of delayed muscle soreness.

45. Basic considerations… • Strength training utilizes resistance from body weight, free weights, elastic bands, isokinetic dynamometry, exercise machines, treadmill walking. • Strength training can be carried out under supervision, independently and in group circuit training classes.

46. Basic considerations… • The exercise should be specific as possible to the functional actions being trained to ensure carryover. • In the case of patients with very weak muscles, any type of exercise which results in generation of some force can be practiced. • Strength training is carried out with sub-maximal loads (as a general rule 10 repetitions at 50-80% of maximal possible 1RM load with a goal of 3 sets)

47. Is there evidence on the effectiveness of the techniques?

48. Studies… • Research now is documenting the contribution of impaired strength to functional limitations in patients with CNS lesions. • Led to a growing awareness of the need to examine and document weakness in the patient with CNS pathology. • Training programs appear to be effective in improving strength; the degree to which they affect other primary impairments is not clear.

49. Studies reported… The following changes after periods of strength training and physical conditioning: • Increases in muscle strength, improved postural stability, and reduction of falls in the elderly. (Aniansson et al 1980, Aniasson and Gustafsson 1981, Sauvage et al 1992, Fiatarone et al 1990,1994, Judge et al. 1993, Tinetti et al. 1994, Campbell et al. 1997, Gardner et al. 2000) • Increases in muscle strength after stroke (Sunderland et al. 1992, Engardt et al. 1995, Sharp and Brouwer 1997, Sherrington and Lord 1997, Brown and Kautz 1998, Duncan et al. 1998, Teixeira-Salmela et al. 1999, 2000, Weiss et al. 2000)

50. Studies reported… • Improvement in gait performance (Nakamura et al, 1985, Bohannon and Andrews 1990, Nugent et al 1994, Lindmark and Hamrin 1995, Sharp and Brouwer 1997, Krebs et al. 1998, Teixeira-Salmela et al. 1999, 2000, Weiss et al. 2000) • Improvements in the ability to balance (Hamrin et al. 1982, Weiss et al. 2000) • Improvements in stair climbing (Bohannon and Walsh 1991)