Isometric exercises, also known as static strength training involves the holding and the controlling of the muscle being worked.
Isometrics is a key component in many sports training workouts. Whichever part of the body you are working you would hold that muscle at a certain level of tension for a specific amount of time. With the proper breathing methods it is an extremely efficient workout.
A couple of examples of isometric exercises are the plank bridge and the side bridge.
In a plank bridge you want to begin by lying face down on the mat. With your elbows bent and forearms on the mat, lift yourself up to form a bridge so that you are on your toes and forearms. Keep a flat back and don’t allow your hips to drop. Hold this for 10-30 seconds, or longer if you can and then repeat 2-3 times.
The side bridge is very similar only you are on your side. Press up with your forearm so that only your forearm and side of the foot are touching the mat. Hold for 10-30 seconds, or longer if you can and then repeat 2-3 times.