Contributed by New Yorker/Gym-goer Jeremy S. (MizzFIT Guest Blogger)
I’m looking forward to our next workout and thanks for asking me to contribute. Here’s what’s on my mind today…
A few days ago, I was chatting with a gym acquaintance and inquired how his training was coming along. Despite a rigorous cardio routine of 3-5 miles a day and a weight training program involving various compound exercises (multi-joint movement that works several muscle groups at one time) he was not burning fat at a recognizable rate. Attempting to assess why his efforts were not paying off, I asked him two basic questions. When are you running and how fast are you running? His answers would determine whether he was running himself into a fat-burning pitfall.
Believe it or not, all cardio is not created equal. Running ‘fast’ is far less productive than running ‘slow’ when trying to burn fat. To maximize fat burning, you want to train at 60-70% of your maximum heart rate. The percent of fat calories burned in this zone are somewhere between 60-85%. In contrast, although a high intensity workout of 80-90% of your maximum heart rate has several significant benefits (i.e. increase the strength of your heart, build endurance, improve your cardiovascular and respiratory system) the percent of fat calories burned actually drops to just 15-30% from fat. Check this link for how to calculate your maximum heartrate.
When you run at a high intensity, you shock your body into self-protection mode. Your body is slower to burn fat because it believes it will need that all important ‘fuel’ source for later. Sure, you will lose weight and burn calories, but they will largely be from stored carbohydrates in the form of glycogen and muscle. A high intensity spin class is a great example of this phenomenon at work. Spinning, like all high intensity workouts is very beneficial, but frankly, you’re more likely to see ‘skinny fat’ body types than hard bodies sitting on those bikes. At a lower intensity, you actually trick the body into thinking it’s not working, and therefore it has no issue releasing fat. It’s also important to note, that even when cardio training at 60-70% of your maximum heart rate, it takes 15-25 minutes to use up stored glycogen before your body will begin releasing fat.
I realize it’s discouraging to hear that the first 15-25 minutes of your workout are merely a warm-up for the workout that actually yields results. But I have good news: a loophole! Your glycogen levels are naturely depleted at two specific times: 1) first thing in the morning before you eat and 2) after weight training. While you sleep, your levels of glycogen slowly decline to provide glucose for various bodily functions. Similarly while weight training, your muscles use glycogen for energy leading to its quick depletion. Right after these 2 events, your body is most primed to burn fat. This is EXACTLY when you should be starting your cardio workout if you’re aiming to maximize fat-burning.
Returning to my gym acquaintance, he responded that he hit the gym after work. He would start by sprinting those 3-5 miles at a 7-minute pace. After his cardio, he would hit the weights. Was he working hard? Absolutely. Was he experiencing the many benefits associated with weight training and cardio? Most definitely. Was he maximizing fat burning: Nope. My advice: 1) Figure out your fat burning heart rate 2) Purchase a heart rate monitor and use it while cardio training to get an accurate read on how your body feels at 60-70%. 3) Run after you weight train for at least 20 minutes, but no more than 45 minutes.