Physical fitness! There are a lot of fads and trends in this area. Both calisthenics and power lifting with some conditioning strike me as solid fitness routes to take. Personally I lean towards calisthenics because there is less equipment required, and I have a slight fear of injury from doing something wrong with the power lifting. Anyways, Hybrid Calisthenics is a site by Hampton, a friendly fitness YouTuber. His YouTube channel is great and to the point. His site here is also useful. The general idea behind this fitness program is to perform Pull-ups, Push-ups, Squats, Bridges, Twists and now Leg Raises. Each of these movements comes with a bunch of easier and more difficult variations. So, you choose a variation for each of these categories of movements and perform the listed number of repetitions. If you can't perform the repetitions, you choose an easier variation of the same movement until you can. The plan, then, is that you do these exercises, increase repetitions until you can handle the next more difficult variation of any particular movement, and you just keep trying to progress. The basic idea here I believe is taken from the book Convict Conditioning, but Hampton is a much friendlier guy who keeps all of the progressions realistic.