Seeing multiple 30–40 y/o rec soccer athletes re-injure grade I–II biceps femoris within 2–3 weeks despite pain-free 5/5 strength, symmetric hop tests, and a staged sprint build. Current plan is eccentrics (Nordics twice weekly), progressive high-speed running, and posterior-chain strength, but I’m considering adding isokinetic cutoffs (>90% symmetry at 60/180°/s) and a >95% max sprint tolerance — anyone seeing better durability with stricter RTP thresholds?