These are some of the things I use to build strength when I'm not at the gym or park. They're really easy to just do for 5 minutes at a time, and don't make you sweat usually. The round things are The Perfect Pushup V2. Great for stronger triceps, chest, and back, all without the wrist strain of normal pushups. Those 2 black handle things are also normally for pushups, but I use them more for practicing planks and tricep dips. Then there's the gripper, good for forearms and hand strength. And last is a jump rope. Haven't used it too much because it's still snowing, but it's a great cardio exercise that also develops coordination.