Given the fine balance between work, family, and social activities, it's a challenge to try to fit exercise in their somewhere. Most people are fooled into thinking that it doesn't count unless you're breaking a serious sweat, but even the baby steps towards getting fit are important. In fact, short spurts of exercise can be enough to effect weight loss, muscle growth, and your overall well-being.
Here are a couple ways to stay trim without trying too hard:
Sit at your desk and lift a foot about eight inches off the ground. Hold your leg, bent, up for a count of 20. Pulse your knee up 20 times. Finish the set and perform the same exercise on the other leg. Repeat several times. It's great for shaping your quads and slimming thighs.
Another at-your-desk toner: Wrap your right foot around your left ankle, and stand up, balancing on one lag for at least 30 seconds. Pulse and hold on the ball of your left foot for 20 counts. Then switch.
I think it's great to emphasize working out can be done in small spurts. For example, when I go to the grocery store, I park at the far end of the parking lot and use a shopping basket (good arm workout). I'm doing the leg exercise you suggested and it also tightens your core area.