What Are the Dangers of Isometric Exercises?

Isometric exercises are often incorporated into fitness programs, group exercise classes and therapeutic rehabilitation programs. While isometrics can be effective for building strength, caution should be taken to ensure that the exercises are appropriate for you, and that you are performing them correctly. Also take into consideration whether isometric exercises, which are done without joint movement, will help you meet your training goals.

Isometric Exercise

The word isometric is taken from the Greek roots iso, meaning equal or the same, and metric, meaning measure. Isometric contractions involve constant tension in the muscle with no joint movement or change in muscle length. A yoga plank held in static position is an example of an isometric exercise. While isometric exercises are often incorporated into fitness routines, the bulk of training is done with dynamic exercises that move joints through their full range of motion. Dynamic exercises allow the muscles to contract from their longest to their shortest length.

Isometrics and Hypertension

Isometric exercises are often not recommended for individuals with high blood pressure or heart disease, because the constant muscle tension places pressure on the arteries, causing a dramatic increase in blood pressure. However, a 2010 review of studies published in the "Journal of Clinical Hypertension" noted that isometric exercise can be beneficial for building strength in hypertensive individuals who are unable to perform dynamic exercises requiring full joint range of motion. While isometric exercise elicits a temporary hypertensive response, blood pressure quickly returns to resting values after the completion of exercise. The authors concluded that isometric exercise can be effective in lowering resting blood pressure, and that isometric exercise should be recommended as a training mode for hypertensive patients.

Isometrics and Joint Angle

While isometrics can be beneficial for increasing strength, bone density and lean muscle mass, the exercises have limitations in regard to effectiveness for functional movement. According to a 2005 study published in the "Journal of Sports Science," strength training with isometric contractions produces large gains in strength but adaptations are highly angle-specific. Training muscles isometrically over a range of joint angles may produce significant increases in strength compared to dynamic training. Edward R. Laskowski of the Mayo Clinic notes that while isometric training may increase strength, the mode is not effective for increasing speed or improving athletic performance.

Isometrics and Body Alignment

When performing isometric contractions, it is important to align your body to minimize stress on the joints. For example, in a yoga plank or side plank, your wrists and elbows should be aligned directly beneath your shoulders, with your arms perpendicular to the floor. In a static wall squat, your knees should be aligned directly over your ankles, with your lower legs perpendicular to the floor. To minimize stress to the rotator cuff, avoid prolonged isometric contractions of the arms at or above shoulder height. Isometric contractions of the muscles of the neck should be limited to eight to 10 seconds.