Beast Within is one of my favorite Ultimas and the one I’ve probably been using the longest, I’m actually listening to it right now 
Anyways to add to what @Meng123 posted:
I personally prefer to listen to it after a workout for a recovery focus and use Beast Unleashed before and/or during a workout for the energy burst.
I have experienced faster recovery so that I can workout the same muscle group more often per week. Just recently, I went a month off of subs and noticed by the second week that my recovery was slowing down and it was getting harder to workout the same group more frequently.
I don’t know if the healing is as intense as paragon since (I believe?) that they made new physical shifting discoveries between releasing BW and Paragon. But it still gets the job done anyways!
I have experienced faster muscle growth and breaking my plateau that I was stuck in for years. I’ll be making a more detailed journal post soon about my physical progress over the past 10 months.
Some other things:
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I used Beast Within in a combo with my custom that also contained Serum X and Physical Shifting: Sexiness, both that also help in this area, it has been a very powerful combo for me.
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I recommend to try listening to the supercharger track with the guided meditation and then after listen to the Ultima and try to do similar visualizations as the guided meditation. This will sometimes give me a surge of energy and excitement and I think makes the effects of the Ultima more profound.
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Working out now gives me such satisfaction while running these Ultimas, they’ve defiantly brought life again to my once stale, “get it over with” exercises.