Ask your physician which forms of cross training are «OK» for you — different bone injuries come with different restrictions! (runningstrong.com)
The most form of cross cardio is probably the triathlon where you switch three forms of cardio in a given time frame (swimming, biking and running). (fitnessandpower.com)
Peep elite Crossfit athlete Noah Ohlsen's unique form of cross training in the instavid above! (dailyburn.com)