Concentric Contractions

In the concentric, or shortening phase of a lift, your ability to generate peak force in less time improves. A combination of both heavy resistance and resistance training with lighter resistance can be used to build strength and power during the concentric phase. The curl phase when performing an arm curl and the standing phase when performing a squat are both concentric strength building movements. This is sometimes referred to as the positive portion of the repetition.

Eccentric Phase

This is sometimes called the negative portion of a repetition or the lengthening phase. This occurs when the muscles stretch to accommodate resistance. An example of this would be lowering the bar when performing the bench press or lowering in to the squat position when performing squats. This can allow for greater increases in micro trauma to your muscle fibers, which can produce greater increases in muscle growth.

In isometric exercise your muscles don’t expand or contract, which makes it sound easy — until you try hold a position with the resistance pulling against you for 60 seconds. Isometric exercise involves keeping certain muscles tensed for a period of time.

Both eccentric and concentric actions occur in conventional resistance exercise, but each has slightly different effects. Both can help you achieve increases in strength and muscle mass while burning fat. Focusing on one type of training may help you achieve specific goals. But on the Total Body Board you can add variety to your workout by mixing it up a little, for example, once you can do a 12-rep set of leg extensions easily, try alternating concentric and eccentric sets. You can add isometrics to any exercise by pausing at the top of the move for a few beats.