In reply to helix:
No medical knowledge but have some very recent experience of ruptured long head bicep tendon:
1) Me (age 56, sport climbing into high 7s). Full rupture of long head bicep tendon in July. Had about 3 weeks off while getting it diagnosed and going to a physio with climbing expertise. Operation not recommended and was given go ahead to climb, maybe not going full in on hard projecting straight away. Within a 2 or 3 of weeks I was climbing pretty much without thinking about it, got some decent routes in the mid 7s done and then had a good trip to Chulilla where I was climbing very close to what i had been on a trip early in the year. I honestly don't feel there's been any impact on climbing, just a not particularly obvious popeye on my arm (my biceps being pretty weedy 😄).
2) in one of those weird coincidences my regular climbing partner (56, sport climbing low 8s) ruptured his second long head bicep tendon (other done years ago) a few weeks after mine. His expensive private surgeon was even more positive on the outcome, said he could climb straight away and should expect little or no impact on strength. He had been suffering from some shoulder pain prior the injury, particularly on the crux undercut move of his long term 8b project - on coming back he definitely felt better and managed to tick it early Autumn. With bigger muscles than me the popeye effect is significantly more noticeable, otherwise absolutely no impact on his climbing.