How long you hold a lunge depends on your goal. If you want better performance and explosive energy in your lower body, push up and out of the lunge position quickly with no pause at the bottom of the range of motion. If you are trying to build muscle and strength in the lower body, hold the lunge position longer, two to three seconds is good. The longer you hold the lunge, the more fatigued the muscles will become. The movement part of the lunge exercise requires balance and coordination so if that is your goal, do more reps.