Types of skeletal muscle actions - Part 1

Types of skeletal muscle actions - Part 1
Dr. Shirin Davarpanah Jazi, introduces, as part one of a two-part series, the difference in skeletal muscle actions. Shirin is a highly accomplished Karate expert, holding black belts in Shotokan and Shitoryu styles, while also being the first Iranian female to achieve international officiating status in 2002. Additionally, she has a PhD in Human Neuroscience and is a physiotherapist, specializing in human movement and fitness.

There are multiple types of skeletal muscle actions which are relevant for individuals involved in athletic activities:

Static (Isometric) Muscle Actions : In static muscle actions, tension is developed within the muscle without any corresponding movement, resulting in no change in muscle length. However, the external resistance surpasses the force produced by the muscle, resulting in no mechanical work (force x distance) due to the absence of displacement. Even though energy is expended, no actual movement occurs as a result.

Dynamic (Isotonic) Muscle Actions:

Concentric muscle actions entail the muscle generating sufficient force to overcome external resistance. This leads to muscle shortening and movement at the associated joint. In these actions, energy expenditure translates into positive mechanical work as both force production and displacement take place.

Eccentric muscle actions occur when the muscle lengthens while producing force. This happens because the external resistance moves in the opposite direction of the standard concentric (shortening) action. Eccentric muscle actions are associated with the production of a high force by the contractile elements and are crucial training stimuli. However, they can also lead to muscle damage and soreness. Thus, it is recommended to initially limit the use of eccentric contractions in exercise training. Furthermore, these contractions have clinical significance in the rehabilitation of tendinopathies.

Dynamic (Isokinetic) Muscle Actions: Isokinetic muscle actions are characterized by maintaining a constant velocity and typically require specialized computerized equipment, often found in a laboratory or clinical setting. This equipment maximizes resistance at various angles within the range of motion. Isokinetic contractions can be either concentric or eccentric. These contractions and associated devices prove invaluable for athletes as they enable the performance of exercises that closely mimic the speed and requirements of sport-specific activities.

In part two, Shirin will explain how these differences may affect the muscle mass you attain.


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