What are Isometrics?
Isometrics can best be described as, “the continuous contraction of a muscle over a set amount of time where the actual length of the muscle remains unchanged”. Visualize holding a plank position or a push-up for example.
Basic Insight of Muscle Groups
Well first lets start with definitions of skeletal muscles and some of their functions.
- Type I fibers (Slow twitch): Strength and endurance of a muscle. So think body builder and marathon athletes. The postural muscles of the spine are also slow twitch.
- Type IIa fibers (Intermediate): An intermediate of slow and fast twitch fibers. Think track & field, 800m and the miler and the soccer athlete.
- Type IIb fibers (fast twitch): Speed of the muscle contraction. Boxer, sprinter, and power lifter.
All fiber types listed above are grouped together in segments called “motor units”. Each muscle has many motor units that can be activated to push off the balls of the feet during a running stride for example. However, for the purpose of this article it should be noted that not all motor units necessarily activate to perform a movement. As an athlete begins to apply more force to the ground to increase running speed, a larger demand is placed on the muscles, and more muscle fibers/motor units are recruited/activated.
Isometric Benefit
Unlike weight training there isn’t any repetitions performed during an isometric exercise such as holding a dumbbell with the elbow flexed at 90 degrees. Remember, isometric exercise is simply to apply force “without” any change in muscle length.
Each time you safely and “rationally” push a muscle group to maximum capacity, you promote the development of that group. Therefore increasing your metabolism and lean body mass. By forcing your muscles to hold a position such as a dumbbell in a curl position your body starts to recruit more and more motor units/muscle fibers, maybe even recruiting fibers that aren’t used much. The muscles that are activated can be forced to continuously work over time until maximum muscle activation and fatigue.
What’s your favorite isometric exercise?
