Patanjali said it best. Yoga is the calming of the fluctuations of the mind. Anything that takes you on a journey of self-discovery to quiet the mind, give you clarity, and bring you peace becomes yoga.
If you have an activity that you love, you most likely practice or perform it regularly without fail, not because you force yourself, but because you simply love it. If this activity brings you peace and calms the mind, then this too can be yoga. Any action that you make to calm the mind becomes your yoga practice, on or off the mat.
You can see this in the focus and clarity of a runner, the fast and intense movements of an interval trainer, or perhaps in the quiet contemplation of a meditation. Whatever it might be for you, this is your practice and your practice and your yoga.
We often regard our mats as a sacred place where we meet our Self and calm the sensations and chatter between our ears. And while the mat is a sacred place and a safe place for these things to occur, taking your practice away from the mat can help you find this peace and calmness even after your yoga class has finished.