The Pyramid Set Principle has been around forever. It is based on the theory of progressive resistance. This is an excellent way to increase strength and increase muscle size. The way it works is really quite simple. With each successive set you increase the weight used for the exercise while decreasing the amount of repetitions.
An example would be during your next chest workout, while on the bench press warm up with 100lbs on the bar for 12 reps. You would then add 10lbs to each side of the bar for 10 reps. After that set is completed add another 10lbs to each side of the bar for 8 reps. This principle can be used for every muscle group and exercise. The dumbbell biceps curl would work like this; alternating curls with 10lbs for 12 reps, 12lb alternating curls for 10 reps and finish
with 15lb alternating dumbbell curls for 8 reps.
By increasing the weight with each succeeding set, you create a greater demand or workload on the muscle. The heavier weight causes the muscle to fatigue sooner causing few repetitions to be completed. This will cause hypertrophy or growth. This is a good thing! The more muscle you have on your body, the higher your resting metabolism will be (rate at which you burn calories at rest). It will also shape and sculpt your body to prevent the "Skinny Fat" looking body.
Give Pyramid Sets a try during your next workout and see the difference it will make in your strength and muscle gains.