If you're short on time or motivation, you'll want movements like the kettlebell swing in your strength training routine that use multiple muscles at the same time. All you need is a kettlebell and some space to do it.
I counted up the muscles used in this exercise myself with a pen and paper. A modest estimation would suggest that this one exercise uses 15 of them, if not more, from the core to the shoulders to the glutes, and even the calves.
