بسم الله الرحمن الرحيم

1. بسم الله الرحمن الرحيم وبه نستعين

2. TYPES OF MUSCLE CONTRACTIONS PHTH 201

3. Types of Muscle Contractions • Isometric contraction: when the ms. does not shorten during contraction while tension is increasing. • Isotonic contraction: when the ms. shortens or lengthens while the tension on the ms. remains constant.

5. Types of Isotonic Contractions 2 Types: • Concentric: the muscle shortens, e.g. contraction of the biceps to produce elbow flexion. • Eccentric: muscle lengthen or is stretched while contracting, e.g. lowering a load on the ground.

6. Tension Variation • The tension in the muscle may vary in its length: Passive tension: tension developed in the ms. length is increased while is not stimulated ( i.e. concentric contraction). Total Tension: tension that a ms. develops when stimulated to contract isometrically.This tension also vary with the change of the initial length. Active tension: is the difference between the total tension and the passive tension at any length( the amount of tension) actually generated by the contractile process.

7. Tension Variation (cont.) • Tension increases with an increased length, but overstretch may lead to weakness of the muscle. • Rupture of the muscle occur when it is stretched to about 3 times its equilibrium length of the relaxed muscle cut from its bony attachment.

8. Types of Skeletal Fibers • Slow Oxidative or Type 1 Fibers: • In postural ms. as can maintain contractions for long periods. • Produces ATP with high efficiency. • Has a large number of mitochondria & mitochondrial enzymes. • Has aerobic energy transfer. • Is innervated by small motor neurons that activate small number of fibers • Fast Oxidative or Type II a Fibers: • Are moderately resistant to fatigue. • Have mytochondrias & considerable amount of myoglobin. • Red fibers. • Moderately well developed capacity for aerobic & anaerobic energy transfer. • Intermediate motor neuron, its activities are e.g; middle distance runnng, swimming,…

9. Types of Skeletal Fibers (cont.) Fast Glycolitc or Type IIb Fibers: • Rely on anaerobic glycolysis. • Become fatigued easily. • Few mitochondria. • Little myoglobin → white fibers. • Specialised in powerful, brief types of contractions. • Large motor neurons that activate large number of fibers for heavy loads. • Mixed with other muscle fibers as in limb muscles, eye and finger muscles.

10. Isometric Exercises • Isometric resistance is a static form of exercise that occur when the muscle contracts without an appreciable change in the length or the muscle or without joint motion. • No physical work is done by the force ( force x distance), but a great amount of tension and force out put are produced. • A muscle can generate greater tension with a max. isometric contraction, but not as much as with a max. eccentric contraction

11. Isometric Exercises (cont) i.e. • Eccentric cont. = max. tension • Isometric cont. = intermediate tension. • Isotonic cont. ( concentric) = minimum tension. i.e. to start a stregthening program: • Start by isotonic (concentric) harden by isometric then harden by eccentric . • If no contraction start by static then follow the same progression.

12. Rules and Principles of Isometric Exs. • Strength will increase if an isometric contraction is sustained against resistance for at least 6 seconds. Isometric resistance exs. will not improve m. endurance as effectively as dynamic exs. • During isometric training it is suffiscient to use an exercise load ( resistance) up to 60-80% of th m. force-devloping capacity in order to gain strength. • Since there is no joint mov. , strength will devlop only at th position in which the ex. is performed. • To develop strength throughout the ROM, resistance must be applied when the jt. is in several positions.

13. Rules and Principles of Isometric Exs.(cont.) 4.The length of a m. at the time of a contraction directly affects the amount of tension that can be produced at a specific point in the ROM.→ the amount of resistance will vary at different points in the range. 5. Resistance can be applied either manully or mechnically by having the pt. hold against a heavy load or push against an immovble object.

14. Rules and Principles of Isometric Exs.(cont.) 6. Muscle setting exercises are also a form of isometric exs. but are not performed against apreciable resistance. • Muscle setting exercises will be used to describe gentle static muscle contractions used to maintain mobility between muscle fibers and then decrease muscle spasm & pain. • Quadriceps settings and gluteal settings are common examples. • They are not performed against resistance and will not increase appreciably muscle strength. • Settings may retard atrophy in the evry early stage of rehab. of muscle or joint when jt. Immobilization is necessary.

15. Indications of Isometric contractions • Pain ( sever pain in joints e.g. arthritis); • Effusion of the knee.( static cont. of the knee). • Weakness of the m.( as 1st step in m. reeducation). • Immobilization in plaster cast or back splint. • Inflammation of the joint ( static contraction around the joint) to avoid weakness during theacute stage.

16. Practical Points • Position: suitable & comfortable. • Time of contraction equal time of relaxation( not less than 6 sec.) • Repetition, teach the pt. on the sound limb, then on the affected limb to be repeated 10 min. every hour. • Manual or mechanical ( Velcro weights or elastised material as Theraband) could be used gradually , beginning with high repetitions and low resistance the reverse. • Instruct the pt. not to hold his breath.

17. Contraindications to Isometric Exs. • Hypertension • Haert Disease

18. Isometric Regimens • Brief maximal isometric exercise (Hettinger & Muller): • Single isometric cont. of the muscle to be strengthened against a fixed resistance. • Hold for 5 -6 sec. , once a day, 5 – 6 days a week. • Brief Repetitive Isometric Exs. (BRIME): • Refinement of the previous study. • 5 – 10 brief but max. isometric contactions are performed against max. isometric contactins are performed against resistance 5 days per week.

19. Isometric Regimens in Rehabilitation & Conditioning • Early studies documented that isometric resistance exs. can be effective means of improving muscle strength. • Minimal effects in muscle endurance→ dynamic ( isotonic& isokinetic) exs. are more effective. • Multiple angle isometric exs. are necessary to improve strength throughout the ROM. • Resistance should be applied at least every 20° throughout the range. • 10 sets of 10 repetitions of 10 sec contraction every 10° in the ROM ( Davies).