I've bought multiple bottles of AMP and have tested them back to back on identical rides with and without application
The only benefit I see is that you end up massaging your legs pre ride as you apply the product- this makes me feel a little more "ready" to ride - but I don't last longer in intervals and in hard rides can still cramp as often as without using the product
So- to me it's an expensive massage cream
I started using AMP Human a few months ago during races and harder training sessions and have continued to use it because I feel like it really works. It's not a miracle worker, so bad legs still do exist, but they're much further between, and when you have good legs, they're REALLY good.
I used to only use it during races and larger training rides because the old formula was slimy and hard to wash off and, overall, was not enjoyable to apply or wash off. The Next Gen formula is a game changer though. It applies as well as any lotion I've ever used, and doesn't feel gross on my legs. I'll for sure start using it during all of my work outs now.