San Marino, all good, sir. I'm patient (most of the time). If you have any more info on GW's effects please share when you have the opportunity.
Finally some free time
I will try to keep it short (as always). Sorry in advance, if it isn't.
Regarding the muscle fiber types: there are in general two types: slow twitch and fast twitch. Logically, a powerlifter aims for fast twitch while a sprinter is looking forward to slow twitch. You don't have only one type the composition in your body is mixed. So you can have for example slow twitch in your legs while having fast twitch in arms or chest.
Your genomes decide, how the composition is. It gives a bandwith in which you also have influence. If you would train like a sprinter for years, your body (resp. legs) will have more slow twitch fibers than actually as a powerlifter.
But I have to start earlier...
In one of the studies made, the researchers found out, that there is a correlation between a PPARdelta like GW-501516 and the muscle fiber composition, indeed. The PPARdelta substances influences the fatoxidation. As you probably know, the slow twitch fibers are the biggest energy "waster" in the body (only focussed on the muscle types). And this same type also stands for higher endurance and longer contraction times.
In one of the meant studies, the researchers modified the mice genetically, that they produce PPARdelta like GW-501516 itself in the muscle (no joke). In a comparison with normal laboratory mice while a high fat diet over 97 days, the researchers found out, that the modified mice gained only 1/3 of the bodyweight, which the control group gained.
Furthermore, the researchers were surprised, that the same mice (the modified mice) had a genetically change of their muscle fibre type. The red type nearly doubled.
The same mice were able, to raise their endurance of about 92%, which also speaks for a higher amount of slow twitch muscle type (don't fix on these 92%. With very high probability this numer cannot be transferred on humans. There are a lot of factors which speak agains such a transfer).
As you see, the muscle fibers could change - and the powerlifter is (probably) not amused haha. But keep in mind: when exercising, you can push the above mentioned bandwith in several directions.
Firstly, as long as you still train with low reps, your affected muscle won't change withing days. This is a process, which takes a longer period of time. Don't be afraid of loosing your big trained legs to Bolt-like legs. This won't happen.
Secondly, if you are an endurance athlete and taking GW-501516 you will notice the real boost of that substance. Your fiber types are already opimized (training and/or genetics) and the GW pushes you more in the endurance way.
Thirdly, this mentioned study only talks about PPARdelta generally, and not about GW-501516. Nevertheless, the probability is there, that GW will affect the muscle composition. This sounds probably dramatic and bad, but it isn't. How much of you guys couldn't do any heavy squats while taking GW? I'm very sure, none of you. Keyfactors are: training, dosage, intake length.
As a final word of my personal side: if you are worried, you will lose your well trained legs or pecs or whatever, that won't happen - not regarding to this mentioned "muscle fiber change"-story above.
There are so many things about PPARdelta, which a lot of people barely know (bio-clock story, COX-2 story, AMPK story, etc. etc.). Therefore: ALWAYS RESEARCH WELL BEFORE USING RESEARCH CHEMICALS.
Enjoy the weekend.
san