Muscle Strength Therapy

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Muscle Strength Therapy

Passive range of motion – clinician performs the movement
Active assisted range of motion – clinicians assisted movement
Active range of motion – patients performs movements

The use of the overload principle for increasing strength for rehabilitation is the same as that used for conditioning (see Sports Medicine chapter).

Three types of exercise:
Isometric – when muscle contracts without movement of the joint – muscle is contracted with the body part against a fixed resistance – used initially after injury or if muscle too weak – exercise is held for 5-6 seconds followed by a rest of 10-20 seconds – done 10 to 20 times several times a day. Less effective than other forms of strengthening.
Isotonic – when muscle contracts and joint moves through range against a constant resistance or weight. Two types – (1) Concentric – muscle fibres shorten during contraction – the muscle’s insertion moves away from the origin. (2) Eccentric – muscle fibres lengthen – the muscle’s insertion moves away from the origin.
Isokinetic – uses devices at fixed speed with variable resistance – eg Cybex®, KinCom®.

Advantages and disadvantages of methods of exercise :
Advantages of isometrics:
• used early in rehabilitation without causing further joint irritation, because there is no joint motion
• increases static muscle strength
• helps retard atrophy
• assists in decreasing swelling (the muscles act as a muscular pump and assist in fluid removal)
• prevents neural dissociation through muscular contractions, which stimulate the mechanoreceptors system in the joint capsule and surrounding ligaments
• maintains neural association
• can be performed anywhere
• no special equipment needed
• can be performed in short periods of time
• has approximately a 20° physiological overflow through the range of motion

Disadvantages of isometrics :
• muscular strength increases are fairly specific to the joint angle where the exercises are performed (~20° physiological overflow)
• subject to physiological influences
• difficult to provide patient motivation
• no contribution to muscular endurance
• no improvement in functional force control accuracy
• no eccentric work provided
• creates ischaemic responses in muscles and subsequent pain

Advantages of isotonics :
• some can be relatively inexpensive
• readily available
• provides motivation by achievement (can lift more weight)
• can be progressively increased in varying increments for the overload principle
• work takes place through the ROM
• work occurs at speeds greater then 0°/sec
• has a concentric and eccentric component
• can improve muscular endurance (greater than 10-15 repetitions)
• can affect the neurophysiological system
• can be objectively documented
• various components of the program can be manipulated to maintain workload (reps, sets, weights)
• increase in muscular strength in few repetitions (1-8/10

Disadvantages of isotonics :
• maximally loads a muscle only at its weakness point in the ROM
• is not safe if someone has pain during the ROM because the patient must still support the weight
• if performed too soon, ballistically, can cause a reactive traumatic synovitis
• once the weight starts moving, there is a momentum factor with the weight
• does not develop rapid force (quickness)
• does not develop accuracy at functional speeds
• difficult to exercise at fast functional velocities (without susceptibility for injury)
• does not provide reciprocal concentric exercise
• not usually performed in a diagonal or functional plane
• difficult to develop an aerobic training response
• muscular eccentric isotonics causes delayed onset muscle soreness (DOMS)
• unable to spread workload evenly over entire ROM

Advantages of isokinetics :
• accommodating resistance allows maximal dynamic loading of a muscle throughout the ROM
• provides maximal resistance through the velocity spectrum
• inherent safety factor, due to accommodating resistance, therefore minimal risk to patient
• minimal post-exercise soreness with concentric isokinetic contractions
• validity of equipment
• reliability of equipment
• reproducability of testing
• isokinetic dynamometers and recording systems, computer, etc
• exercise through velocity spectrum
• specificity of movements
• helps force development of quickness (time rate of torque development)
• develops force control accuracy
• decreases reciprocal innervation time of agonist/antagonist contraction
• efficiency of muscular contraction
• accommodation to pain
• accommodation to fatigue
• joint nourishment
• decreased joint compressive forces at high speeds and length of time compression is placed on joint surface
• physiological overflow
• provides feedback to patients with recorders, computers etc
• neurophysiological “pattern” for functional speeds and movements
• objective supervision of submaximal and maximal programs and progressions

Disadvantages of isokinetics :
• cost of some equipment
• eccentric loading stimulus to the muscles causes DOMS
• lack of personnel trained in use or interpretation of isokinetic testing and rehabilitation
• the sensitivity of the equipment and recording devices in testing larger muscle masses such as hip, trunk
• availability of the equipment
• inconvenience of switching the equipment attachments for various joints and ease of various set ups
• time consuming if more than one joint is exercised/assessed
• some artificial parameters until the limb actually moves to reach the velocity of the dynamometer or decelerates

Methods of overloading:
• increase the weight that is used
• increased the number of repetitions or the number of sets of repetitions
• increased frequency (number of times per week)
• increase the speed
• shorter rest interval between session

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