One of the questions I’m asked often at the gym is whether to do cardio before or after weight training. A lot of people assume they should do cardio first to warm up, and believe they’re burning more calories because they have a higher energy level at the beginning of their workout. However, this isn’t the case, and in this post I’ll attempt to explain why.
The truth is that doing cardio before you lift weights could be detrimental depending on your goals. If you goal is to lose weight, which to be honest is the goal of the majority of people in the gym, you should be doing cardio at the end of your workout. The reason It’s more beneficial to do cardio after you lift boils down to the way your body uses what you eat for fuel.
When you consume carbohydrates, your body stores it as glycogen in the liver as fuel prior to being converted to fat if it goes unused. This stored form of carbohydrate must be used as fuel first before our body switches over to using less efficient forms of fuel (fat) for energy. Studies show that it can take up to 30 minutes of cardio to burn off the stored carbohydrate before your body even switches to using fat.That’s the key here, because we want to burn off those stores as quickly as possible to maximize our fat-fuel usage.
Also, carbohydrate is the main fuel source for weight lifting because of its high energy yield for intense exercise over short duration. That’s why bodybuilders ‘carb load’, to increase the amount of high energy fuel at their disposal for intense bouts of heavy lifting.
This is also why low-carb diets target fat loss because without sufficient intake of carbohydrate, your energy levels are lowered but fat becomes the primary fuel source from the get-go. That’s why it’s so common to hear that the ‘fat burning zone’ is a moderate exercise level (3-6 METS) because anything above that won’t use fat for the fuel. So if you burned off the majority of those carbohydrate stores through your weight training, you’ll be in that fat burning zone sooner when you hit the treadmill.
To sum everything up, here’s two scenarios and you chose which you prefer:
Cardio BEFORE Weight Training
Run for 30 minutes and feel great having high energy the entire time. If it takes 30 minutes to use your stores, you’ve now depleted your high yield energy source prior to starting weight lifting, and have not touched your stored fat yet. Switch up to weight training, and feel that your energy levels are diminished, lifting lower weight than normal and report greater fatigue sooner, and will likely burn less calories.
Cardio AFTER Weight Training
Lift weights for 30 minutes at a high intensity and have high energy, and burn off the majority of your carbohydrate stores. Switch over to the treadmill for 30 minutes, and you may burn through the remaining stores in the first 5-10 minutes. This leaves you to burn fat for the remaining duration and although you may feel tired your body will still be able to sustain a moderate jog for an extended period of time, and you’ll have burned more fat calories by the end of your workout.