Overview of Muscle Contractions
Although we typically think of lifting weights as the only method to contract and train muscles, there are in fact three different types of muscle contractions all producing strength and mass: isotonic, isokinetic and isometric. An isotonic contraction is when the force is greater than the resistance and movement occurs. There are two phases of an isotonic contraction--concentric phase (the muscle shortens) and eccentric phase (the muscle lengthens). An isokinetic contraction is a muscle contraction that occurs at a constant velocity. An isometric contraction is a type of muscular activity in which there is tension in the muscle but there is no movement. The resistance is equal to or greater than the force of the muscle, thereby inhibiting movement.
A study involving 98 adult subjects ranging in ages 19 to 61 years showed a marked increase of up to 20 percent in muscle strength with as little as seven minutes of isometric training each day. Understanding the physiology, proper guidelines, and exercise technique of isometric training can greatly improve the quality of your workout thereby achieving greater results.
The Physiology
The term "isometric" combine "iso," meaning same, and "metric," meaning distance. Isometrics by definition are performed in static positions without visible movement or change in the distance of the angle of a joint. Strength increases only at that specific angle of the joint. Isometric contractions recruit muscle fibers that are often neglected in some dynamic exercises (isotonic contraction). Strength increases quickly due to the intramuscular pressure obstructing much of the circulation to the muscle. This lack of oxygen to the working muscle then stimulates the synthesis of actin and myosin (muscle filaments) within the sarcomere of the muscle.
The Guidelines
Resistance in isometric exercises come from different applications. You can use your own body weight, such as in holding a yoga pose. You can use a structural object such as pushing against a door frame. When using free weights or weight machines, you can hold a weight in a fixed position for a period of time.
When performing isometrics, instead of counting to a specific number of repetitions like you do in isotonic training, you will hold the position for a period of time. When using your own body weight or pushing against an inanimate object, you can typically hold the position for 30 to 60 seconds. When holding a weight in a fixed position, the weight should be heavy enough to hold for only 6 to 10 seconds.
The Exercises
Choose a variety of exercises that will train the entire body.
Chair Pose (Legs)
Positioning: From a standing position, inhale and raise the arms overhead with the arms shoulder width apart. Exhale as you bend your knees, squatting as though you are going to sit into a chair. Keep your back flat, extending your chest toward the sky in an upright position as much as possible.
Holding: Keep lifting your rib cage and breathing fully into the chest. Keep your knees behind your toes.
Breathing: Breathe deeply for five breaths.
Modifications: If you have difficulty keeping your back straight, lower your arms parallel to the floor.
Plank (Upper Body and Core)
Positioning: Place your palms on the floor and jump your legs back. Your hands should be directly under your shoulders.
Holding: Keep your back straight, like a plank, and your midsection strong and stable.
Breathing: Exhale as you jump back. Breathe deeply into the pose for five breaths.
Modifications: Drop your knees to the floor. Instead of jumping back, you may step back one foot at a time.
V-Sit (Core)
Positioning: From a seated position, balance on your sitting bones. Raise your legs to where your body is in a "V" seated position. Your arms are extended in front of the body parallel to the floor.
Holding: Continue to bring heat from the center and let it proceed to the extremities. Lift your lower back in and up. Keep lifting out of your rib cage.
Breathing: Hold for five breaths.
Advancement: To feel a deeper stretch in the hamstrings, grab the big toe or the ankles.
Modifications: If you have a back injury or are a beginner, you can bend the knees and hold onto the hamstrings or the back of the knees.
References
- Muscle Strength Training And Weight Loss From A Combined Isometric Exercise And Dietary Program. Journal of Applied Research, March, 2007.
- Comparison Between Isometric And Isotonic Contractions In Guinea-Pig Taenia Coli Under Anoxia. The Japanese Journal of Pharmacology. Vol.24 , No.2, 1974
- Fitness Made Fun
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