http://AskTheTrainer.com/lunge-exercise.html Personal Trainer Mike Behnken, MS, NASM-CPT-PES, CSCS Lunges are the safest and most effective exercise for lower body. You can perform lunges with only body weight to get a tremendous leg workout. You can hold dumbbells, kettlebells, bags of rice, cans of soup or any form of resistance you have handy to increase the difficulty. This is the walking lunge which can help you improve your balance and coordination as well as leg strength. If you Lunge far forward enough to where your front heel is directly under your knee you will keep your patellofemoral joint from being overstressed. This correct form will also allow you to work your glutes and hamstrings along with your quads in an optimal muscle recruitment pattern. Lunges are not the best exercise for your quads, so why perform them as a quads exercise? If you take a short lunge and your center of gravity moves forward you will put undue stress on your knee and be asking for future knee problems. http://AskTheTrainer.com/posture-problems.html