Study protocol for a multiarm, randomized controlled trial to determine the effectiveness of community-based frailty rehabilitation to improve physical function in older adults: The OPTIMAL Fitness Trial - Alexandra Papaioannou; Courtney Kennedy; Justin Lee; Patricia Hewston; Caitlin McArthur; Shyam Maharaj; Jonathan Adachi; Pauline Boulos; Raja Bobba; Alexander Rabinovich; Brian McKenna; Lisa Palubiski; et al. (PLoS ONE, 2026)