How effective is isometric exercise?

At what. It's not clear what your goal is. They are good for muscle stabilization and in the rehabilitation setting. But to be honest, these types of static contractions, don't allow for a muscle to work through it's range of motion. It won't likely help with building size and strength. It may help with decreasing blood pressure and maintaining some degree of strength.
R U ready. Any exercize result depends on what you put into it strength gains only occur at the angle you use in the exercise. During an exercise, blood flow to the muscle stops, blood pressure rises, and less blood flows back to the heart. This could be dangerous if you have heart problems.

Related Questions

How effective is isometric exercise for fitness?

Has its limits. Isometric exercise, like weight lifting, etc. Can definitely build muscles, which helps capabilities/fitness, but is limited because it does not help cardiovascular health, and during the exercise, blood pressure can be greatly increased. This can be very disastrous in people who are vulnerable, like those with aneurisms. Read more...

How effective is isotonic vs isometric exercise?

Isotonic/isometric. Both are effective, just different. It is easier to do isometric. True isotonic is more challenging. Read more...
Balanced approach. Isotonic is what most people think of when they think of exercise. Isometric works the muscle without moving. In other words its like trying to lift an object that you can't move. They both have pluses and minuses. A balanced approach to exercise is the best approach. Read more...