Not a big gym guy? No worries. When it comes to a simple workout, your best option is the humble pushup. They were good enough for your dad, even your grandfather, and for good reason. A barometer of personal fitness, pushups test your body's core strength, engaging muscle groups in your abs, hips, legs and of course, chest and arms. The goal should be about 40, but those (especially in the beginning, can be broken into four sets of ten). Now drop and give us 20.
Lower your body until your upper arms are parallel to the floor, then push yourself up.