I'm an endurance cyclist, and I take 5g on ride days (4/week). I started based on this study (https://www.tandfonline.com/doi/full/10.1080/15502783.2023.2...). In short, it does have some benefits for endurance sports by enhancing surges in intensity such as climbing or the finishing kick. I've noticed some muscle mass increase, including my upper body, but nothing I would consider dramatic. I can't say I've experienced any mental effects, though I haven't taken an IQ test in decades, so who am I to say?