Cardio must be done, but done correctly. By that I mean only for a short period of time, but with great intensity. Banish the 30-45 minute sessions and replace them with 15-20 minutes. Do HIIT CARDIO (High Intensity Interval Training). This involves alternating periods of all out intense effort with a much slower pace.
Base your intensity on a verbal conversation sliding scale of 1-10. (Not Maximum heart rate!)
Number 1 being a slow walk with minimal effort and exertion.
Number 5 being a power walk where you can carry on a conversation without heavy breathing and feeling like your lungs will explode.
Number 10 being an all out sprint/run at 100% maximum effort.
Example: A 15-minute session would be seconds at pace #5 and a .30 second sprint one at level 10 and then repeat this cycle for 15 minutes. GREAT WORKOUT. No warm-up necessary because you should be performing cardio work after weight training.
So when is the best time for cardio and how should I do it? The answer is any time! The most important thing is that you just do it. If you want to get the maximum benefits possible from every minute you invest in your workouts, and then you should consider getting up early and doing cardio before you eat your first meal - even if you're not a "morning person." Early morning aerobic exercise on an empty stomach has three major advantages over exercising later in the day:
The primary benefit you'll get from early morning cardio sessions is what I call the "afterburn" effect. When you do a cardio session in the morning, you not only burn fat during the session, but you also continue to burn fat at an accelerated rate after the workout. Why? Because an intense session of interval style cardiovascular exercise can keep your metabolism elevated up to 24 hours after the session is over.
If you do cardio at night, you will still burn fat during the session, so you definitely benefit from it. However, nighttime cardio fails to take advantage of the "afterburn" effect because your metabolism drops like a ton of bricks as soon as you go to sleep. While you sleep, your metabolic rate is slower than any other time of the day.
Perry Nickelston, DC, SFMA
Move Smarter...Move Better...Perform Great!