This is such a simple but satisfying trope, it always elevates the stakes and makes room for interesting plotlines
I'm kinda sad only few battle shounen series (i.e., HxH/FMA/JJK) have made use of it with actual major developments. The big three use sparingly and poorly, other series don't...
Blah blah another chapter of 'Ippo is at his physical peak'
Just focus on the other characters Morikawa, you're not giving us Ippo back for at least another 5 years