SEHS Topic 4.2.2- 4.2.5 Joint and Movement Type

Outline the types of different muscle contractions

• Types: isotonic, isometric, isokinetic, concentric, eccentric

• An isotonic contraction is any contraction is which a muscle shortens to overcome resistance.

• When a muscle shortens, at least one joint moves, and body movement occurs. The resistance can come from lifting a weight, pulling up your body, or from some other object such as when you lift a bag of groceries.

• An isotonic contraction involves two phases. • The concentric phase occurs when

muscle is shortened in an upward movement. • The eccentric phase occurs when the

muscle is lengthened in a downward movement.

• 1. A concentric muscle contraction is a type of muscle activation that increases tension on a muscle as it shortens.

• Concentric contractions are the most common types of muscle activation athletes perform in a gym when lifting weights

Muscle Contraction Types Cont’d: Eccentric

• An eccentric muscle contraction is a type of muscle activation that increases tension on a muscle as it lengthens. Eccentric contractions typically occur when a muscle opposes a stronger force, which causes the muscle to lengthen as it contracts.

• Common exercises that cause an eccentric contraction include lowering weights and the downward motion of squats, going down stairs, running downhill, push ups or pull ups.

Isometric Contraction

• Isometric muscle contractions do not involve any movement. An isometric contraction occurs when your muscles push against a fixed resistance and no joint or body movement occurs. Even though there is no movement, your muscles are still working and contracting.

Cont’d• Isometric Examples• You can do isometric exercises in two different ways:

By trying to move something that is too heavy for you to move or by holding static exercise poses. The second method includes plank holds, squat holds, side planks, abdominal holds, lunge holds and any other motionless exercise. Rather than counting repetitions, isometric exercises involve holding the position for a given amount of time, such as 30 seconds.

• Isometric exercises do not significantly build strength but they can maintain strength, which is why they are sometimes used in a rehabilitative setting.

• Ex. If someone suffers from arthritis and it is painful to perform range of motion exercises, isometric exercises may help maintain strength in the joint muscles without causing more pain

Isokinetic Contraction• An isokinetic contraction is a specific type of

concentric muscle contraction that occurs when the muscle contracts and shortens at the same speed throughout the entire range of motion.

• To produce one, special equipment is usually needed to gauge the speed of the contraction and keep it steady regardless of the force being exerted.

• This allows the muscle to maintain maximum force throughout the entire movement.

Cont’d

• Isokinetic exercises are also used in therapeutic settings. • Using a dynamometer to control the contraction, isokinetic

exercise helps build strength in stroke victims or people who have limited used of their muscles. An isokinetic contraction is a dynamic contraction but the speed of the entire movement is controlled by the machine.

• This control prevents injury and also measures areas of strength and weakness in muscles.

• Any exercise involving the contraction of muscles can be isokinetic if the dynamometer is being used

What is a dynamometer?

• A dynamometer or "dyno" for short, is a device for measuring force, torque, or power.

• In the medical terminology, hand-held dynamometers are used for routine screening of grip and hand strength, and the initial and ongoing evaluation of patients with hand trauma or dysfunction.

• They are also used to measure grip strength in patients where compromise of the cervical nerve roots or peripheral nerves is suspected

Cont’d

Agonistic and Antagonistic Muscles

• Most muscles work in pairs, and when a muscle works it needs to have an agonist and an antagonist.

• Antagonistic pairs are located in opposite sides of a joint or bone.

• An "antagonist" is a classification used to describe a muscle that acts in opposition to the specific movement generated by the agonist and is responsible for returning a limb to its initial position

Cont’d

Explain the concept of reciprocal inhibition• When the central nervous system sends a message

to the agonist muscle (muscle causing movement) to contract, the tension in the antagonist muscle (muscle opposing movement) is inhibited by impulses from motor neurons, and thus must simultaneously relax.

Analyze movements in relation to joint action and muscle contraction

• Ex. During the upward movementr of a bicep curl the joint action is: ____________

• Ans.: Flexion• While the biceps contracts concentrically, the

tricep contracts eccentrically.

• Analyze the exercises on the following slide for both.

• 1. 2.

• 3. 4.

Explain delayed onset muscle soreness (DOMS) in relation to concentric and eccentric muscle contraction

Cont’d• DOMS is primarily a function of eccentric muscle

contractions. • It is associated with muscle damage on a structural

level (microtears) and the inflammation response that follows.