Ideally, we're supposed to fit in at least 30 minutes of moderate exercise on most, if not all, days of the week. In reality, sometimes that's just not physically possible, especially when you're jam-packed -- from long work hours to social obligations to day-to-day tasks.

That being said, with a little clever multi-tasking, you can still squeeze in some quick exercises that take virtually no additional time and with no equipment needed. Just do these better-than-nothing exercises for the days when you just don't have time to hit the gym:

When walking...

Up the intensity by increasing your pace, tightening your glutes and abs and pumping your arms as you walk for the extra calorie burn.

While working at the computer...

Take a three-minute break every hour. Get out of your chair and use your desk to do 15 inclined pushups -- if you have a tendency to slouch at the computer, this is especially helpful in strengthening your chest and upper back -- and walk around to get the blood moving.

When climbing the stairs...

So you're taking the stairs instead of the elevator? Great! Now work your legs and butt a little harder -- hold onto the railing and take two steps at a time.

While waiting in line...

Squeeze your abdominal muscles and draw your belly button in like you're trying to zip up a pair of too-tight jeans. This move engages the transverse abdominals which helps sculpt your middle.

When cleaning the dishes...

Use cleaning time to do calf raises -- lift up on your toes and hold for 10 seconds, lower, then repeat. This will strengthen and tone your calf muscles.