Trying to get the most bang for your buck in your workout? Check your heart-rate! I love a 30-45 min workout mid-week to insure that I get my workout in even when time is crunched. You already know the answer: HIIT (High Intensity Interval Training). Keeping your hear-rate up is key but knowing when you've blown it out and when you're just (mentally) dragging is tough. Swing by your favorite exercise shop and grab a heart-rate monitor or right now, go to amazon.com!
Here's the math for hitting the sweet spot while training: Your age-220
That sum x .60 (60 %)
x . 70 (70%)
x . 85 (85%)
Last but not least, crank it up to 95% for the final stretch!
This is my personal training goal 47-220= 173
173 x .60=104
173 x .70=121
173 x .85=149
173 x .95= 164
happy calculating-