A triathlete swims in a tiny above-ground pool on her rooftop, her waist attached to the wall with resistance bands, while a baseball player bats into a car tire and a boxer throws his punches into a bag of rice hanging from a mango tree. In cash-strapped Cuba, famed for its resourcefulness as well as its sporting prowess, professional athletes are inventing ways to work out and practice despite the closure of common training grounds due to the coronavirus pandemic.