Climbing trees can be an excellent way to improve fitness. When one climbs up and down trees frequently they are building muscle in areas all over their body. The upper body such as the arms and shoulders benefit from pulling the individual upwards. The lower body benefits from pushing the individual toward the top. It is rewarding and fun.
Dedicating 30 minutes to working out every evening can actually go a long way. You can burn off a lot of the calories you consumed throughout the day by doing push ups and sit ups when you get home. You want to push yourself every time too, so that you get into shape as quickly as possible.