Today the goal is to do nothing more than an easy walk and a three-minute initial assessment followed by an easy stretch series to help you mentally prepare for the month of exercise you have before you.
Outside or inside, it's your call. Or the weather's call. Take a 10- to 20-minute walk just to get your blood flowing. You don't even have to push yourself -- the point here is to start developing a habit and get yourself a little warmed up before performing your initial assessment.
Do 10 minutes if you're feeling especially crappy, 20 minutes if you have a moderate amount of energy.
The initial assessment determines a baseline score for lower-body, upper-body, and core strength that you can compare yourself to at the end of the challenge. All you need is a timer and somewhere you can record your scores (make a note in an app, or use old-school pen and paper).