Seen as we are in winter and I know it is a big ask to get out running or power walking, especially if it is bucketing down but go find a nice warm indoor pool and get your tone on....
Here is a guide to some different level workouts you could try.. I find this funny.. I now longer care whether anyone is joining me as I am motivating myself to re train some of my fitness thought processes and its wicked!
and in case I need proof..
Muhammad Ali in training underwater in a Miami swimming pool (1961)