The bench press is a dynamic exercise involving joint movement. Isometric contractions involve muscular force, but typically don’t change the length of the muscle. Planks are one example. According to a review of studies published in the International Journal of Sports Medicine, isometric strength training can be an effective tool for boosting running, jumping and cycling performance.
To build muscle size, researchers recommend applying 70% to 75% of maximum voluntary contraction for 3 to 30 seconds per rep with muscle time under tension lasting 80 to 150 seconds throughout your workout. To build strength, isometric reps should last 1 to 5 seconds using 80% to 100% of maximum voluntary contraction with a total contraction time of 30 to 90 seconds per workout. Plan your isometric training program around 36 workouts.