Difference Between Isometric & Dynamic Exercises
The fundamentals behind most of the common resistance-training exercises are dynamic and isometric principles. These two types of resistance exercises are performed very differently and have different purposes. Dynamic exercises are most common for strength and athletic goals, while isometric exercises are most often used for physical rehabilitation.
Isometric exercises involve contracting a muscle for a prescribed amount of time. There is usually no noticeable change in the muscle length during isometric contractions, and the joints do not move. Examples of isometric exercises include standing with your hands against a wall, pushing on it for 10 seconds at a time or holding a plank for 30 seconds. These types of exercises are not the most effective for strength gains, but they are helpful if you are injured or have a condition that could be aggravated by movement.
Dynamic exercises involve concentric and eccentric contractions. For example, when you perform a biceps curl, the action of curling the weight up is the concentric motion. Concentric contractions occur as a muscle shortens and generates force against a load to move it. The eccentric portion occurs when the weight is lowered back down and the muscle lengthens. To perform the concentric and eccentric movements of dynamic exercises, the muscle must be able to generate enough force to overcome the resistance to move the weight.
Isometric exercises are often used in physical therapy because they require no joint movement and pose minimal risk. They can also be performed by people who have been immobilized. Dynamic exercises, common to resistance-training programs to gain strength and build muscle, require mobility and can pose injury risk when performed improperly. A 1984 study in the "Journal of Applied Physiology" compared the effects isometric and dynamic training and found that muscles adapt differently to each. Dynamic exercises increased muscle velocity in participants while isometric exercises improved maximal power.
Always consult a doctor before beginning any type of exercise program. Dynamic and isometric exercises aren't for everyone, so make sure that your fitness program aligns with your health goals and doctor recommendations. If you have high blood pressure or heart problems, for example, you should not perform isometric exercises because they can significantly elevate blood pressure. If you have any questions about how to perform an exercise, ask a fitness professional.
- MayoClinic.com: Are Isometric Exercises a Good Way to Build Strength?
- Journal of Sports Science: Effects of Dynamic Resistance Training on Fascicle Length and Isometric Strength; LM Alegre et al.
- International Encyclopedia of Ergonomics and Human Factors, Volume 1; Waldemar Karwowski
- Journal of Applied Physiology; Isometric or Dynamic Training: Differential Effects on Mechanical Properties of a Human Muscle; J. Duchateau and K. Hainaut
- Serious Strength Training; Tudor Bompa, Mauro Di Pasquale and Lorenzo Cornacchia
- Fitness and Health; Brian J. Sharkey and Steven E. Gaskill
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