I have noticed a little more stamina in my workouts, along with taking a pre-workout. Overall, I feel a little more energetic. I love everything about this product, MK 677. I was skeptical at first, but after taking 1 capsule for the first few days and then 2 ever since, weights in the gym feel lighter! I added this to my stack of pre-workout pills, and I feel like Superman. Not to mention my sex drive is through the roof! Great stuff!!! Great company and great customer service. Everything is great, and I am really impressed. I am going to recommend this to my buddy.