I can't answer your question scientifically (like you are probably looking for to use for your studies), only from experience. I'm slightly overweight with moderate strength and play front row. Our team does a lot of conditioning. I've had times where I get driven back in the scrum, but am able to recover much quicker than our opponents and run passed the gasping opposition to support where applicable. We also had a casual player (just for practices to stay in shape) who was a good looking, fast, ripped, in-the-prime-of-his-life male snap a leg completely because he wasn't really driving hard and let the other player dictate play. It also goes much further than physicality.
PE GCSE by any chance?
