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RESISTANCE EXERCISE • Definition • Resistance exercise is active exercise in which muscle contraction is resisted by an outside force. This outside force may be manual or mechanical.
Goals and indications of resistive exercises A. Increase muscle strength Strength refers to the force out put of a contracting muscle and is directly related to the amount of tension of contracting muscle. In order to increase the strength of a muscle, the muscle must be loaded or resisted so that the increasing level of tension will develop due to hypertrophy and recruitment of muscle fibers . B. Increase muscular endurance: Endurance is the ability of the muscle to perform low intensity repitative exercises over a prolonged period of time Muscular endurance is improved by performing exercises against mild resistance for many repetitions.
• Increase power • Power is defined as work per unit of time (Force x distance/time) • The rate at which a muscle contracts and develop force throughout the range of motion and relationship of speed and force are factors that affect power. • There is no question that strength, endurance and power are all related and can be improved with resistance exercises.
Physiological Adaptations to Resistive Exercise • Regular resistive exercise is associated with several positive adaptations which is dosage dependant. These changes include:
• Muscle • Increase of the cross sectional area of the muscle due to – increase myofibril per muscle fiber – fibers splitting – increase number of muscle fiber • Increase protein content of the muscle fiber. • Increase energy source necessary to fuel muscle contraction and increase levels of ATP, and creatine phosphate. • Increase neural activation, motor unit recruitment, and firing rate of each unit.
• Connective tissue • Resistive exercise may alter tendon and ligament structure make them larger, stronger and more resistance to injury. • Increase tensile strength of tendon and ligament
• • Bone Improve and maintain bone density. Cardiovascular system Increase cardiac output Increase stroke volume Increase maximal oxygen consumption Decrease heart rate Decreased or unchanged systolic and diastolic blood pressure.
Overload Principle: • the foundation of training to increase muscular strength and endurance is the overload principle which states that “In order to increase strength or endurance a load that exceeds the metabolic capacity of the muscle must be used to induce adaptive changes in muscle that lead to increasing strength and endurance”
• Types of resistance exercise Resistance Exercise Isometric Isotonic Isokinetic
Isometric Resisted Exercise • Isometric resisted exercise is a static contraction of muscle against external resistance without appreciable change in its length or joint motion. • Advantage • Isometric exercise is valuable when joint motion is uncomfortable or contraindicated, during immobilization. • Isometric exercise is effective when weakness exist at a specific point in the ROM. • Easy to understand. • Disadvantage • Isometric strength is specific to the joint angle (joint angle dependent).
Isotonic Resisted Exercise • Isotonic resisted exercise is dynamic exercise that is carried out against resistance as a muscle lengthens or shortens through the available range of motion. • CONCENTRIC CONTRACTION occurs when active muscle undergoes shortening while overcoming external resistance. • ECCENTRIC CONTRACTION occurs when active muscle undergoes lengthening while being overcome by an external resistance. • Eccentric contraction performed against supramaximal resistance generates greater force production than concentric contraction.
Mode of Resistance Application (manual-mechanical) • Manual Resisted Exercise • Manual resistance exercise is active resisted exercise in which the resistance force is applied by therapist to either a dynamic or isometric contraction. • Advantage • The resistance can be varied with changes in strength production throughout the range. • When joint motion is allowed, manual resisted exercise offer an easy inexpensive method of strengthening muscle. • Specific or individual muscle could be strengthened. • Disadvantage • The amount of resistance depend on therapist condition. • The resistance can not be measured so the treatment results can not be documented. • Effort and time consuming as therapist can treat only one patient at a time.
Mechanical Resistance Exercise • Mechanical resisted exercise is active resisted exercise in which the resistance provided by equipments to either a isotonic or isometric muscle contraction. – A variety of mechanical equipment are available ranging from simple to complex, small to large, and expensive to inexpensive. The choice between them depend on the patients need and ability, goal of the exercise and availability of the apparatus. • • Free weights Weight machine Exercise bicycle Pulley system
• Advantage • Objective quantitative documentation of the patient progress. • The level of resistance not limited by therapist strength. • Add a variety to the exercise. • Safe time and effort of therapist. • Disadvantage • The resistance can not be varied throughout the range of motion. Amount of resistance is fixed all over the range. • Need space and may be expensive.
The exercise dosage can be increases by: • • 1 - Changing the relationship to gravity 2 - Increase lever arm (hand placement) 3 - Increase repetition of exercise 4 - Increase duration of exercise 5 - Increase amount of resistance (mild- moderate- maximum) 6 - Speed Be sure not to proceed to a more difficult exercise before the patient perform the lower graduation first, otherwise overwork and fatigue occur
Isokinetic Resistive Exercise • Isokinetic exercise is a form of active exercise in which a muscle or group of muscles contracts against a controlled accommodating resistance which is moving at a constant angular velocity. • The isokinetic exercise are performed with a specialized apparatus that provides variable resistance to a movement, so that no matter how much effort is exerted, the movement takes place at a constant speed. – The isokinetic device are computerized training and testing device that provide maximum resistance through the entire ROM. – The device provide multi-angle isometric resistance, resisted concentric and eccentric exercise.
Advantage • Ability to fully activate more muscle fiber for longer period because the machine accommodate the resistance according to the changing ability throughout the ROM. • Allow training at a variety of speeds • Provide objective documentation • The isokinetic device provides many strengthening protocols to chose from according to the patient condition and the goal of exercise. For example (isometric conditioning, isokinetic conditioning, eccentric & eccentric conditioning and open & closed chain conditioning)
Disadvantage • The device is expensive • Require trained personnel for setting up the patient training program.
Precaution with Resisted Exercise • The use of valsalva maneuver should be avoided during resistive training especially by a patient with cardiopulmonary disease, recent abdominal, intervertebral disc, or eye surgery. • During resistive training especially with eccentric contraction and increase exercise dose minor lesions of the muscle and inflammation occur resulting in delayed onset muscle soreness(DOMS). If this occur, start with warming up period and decrease exercise dose.
Contraindication of Resisted Exercise • Acute inflammation of the musculoskeletal system • Pain • Infection. • Recent fracture or non-united fracture