Isometric exercise is producing muscular force without any movement. The muscle contracts hard, but it stays the same length and the joint angle doesn't change. Planks, wall sits, dead hangs, pushing against an immovable object: all isometrics. If you're straining and nothing is moving, you're doing one.
Why it matters
Two reasons, and the second one surprises people. First, isometrics build strength at the exact position you hold, with very little joint stress and almost no soreness, which makes them a favorite for rehab and for sticking points in big lifts. Second, the heart health angle. Large reviews of exercise trials have found isometric training (wall sits and handgrip work in particular) among the most effective exercise modes studied for lowering resting blood pressure. A wall sit competing with cardio on that front? Few people see that coming. If you have high blood pressure, loop in your doctor before leaning on any single protocol.
How to use it in training
Start simple. Wall sits: 4 holds of 30 to 60 seconds, twice or three times a week. Planks: 3 holds of 20 to 45 seconds, stopping when your hips start to sag. Breathe the whole time. Holding your breath during a hard isometric spikes blood pressure in the moment, which defeats the point.
Lifters can add pause work too. A 3-second pause at the bottom of a squat or bench press builds strength right where reps usually die.
Related terms
Go deeper
We broke down the blood pressure studies in detail: Isometric exercise and blood pressure.