As with most things in fitness... It depends. There is a difference between that end of the day tired, or the beginning of the day tired, that simply goes with life and if you waited to be fully energized you may never go. BUT you also have to ask yourself WHY you're tired. Lack of sleep (the most obvious) but your nutrition may be zapping your strength as well. What are you eating during the day? Too much sugar and fats? Or maybe you're not eating enough food all together? But often it's just a busy life and to THAT, I say.... GO ANYWAY. Working out can actually increase energy, focus and confidence which will make it easier to tackle your day.

BUT if your tired feels like sheer, can't-catch-your-breath exhaustion, whether by over-training, or over-life-ing take the day off and don't feel guilty. Stress, and body chemistry works against you when you train in an an exhausted state, not to mention, dangerous.

By Heather FreyFounder of SmashFit.com, Fitness expert for the TV show "Miami Mom's" on NBC Miami Nonstop, PT, Writer/Blogger, Fitness Model, National Figure Competitor