Muscle contraction is essential in muscle building because it activates muscle fibers and generates force to allow your body to move. In weightlifting and bodybuilding, they involve two main phases of muscle contraction – eccentric and concentric.  * During the eccentric phase, your muscle lengthens and strengthens while consuming less energy. * In the concentric phase, your body muscle contracts a consuming force greater than what’s added.  To trigger muscle build-up, you must spend more time in the eccentric phase. For instance, during a squat, your body going down performs eccentric forces, and going up means concentric muscle force. To integrate this technique into your routine, you can either slow down your time during the eccentric phase or incorporate variations in your exercise where you focus on lengthening your muscles.