Wednesday, October 17, 2018

Why Sprinting Burns More Fat Than Jogging

Ask people why they started jogging and most will say to lose weight, or perhaps just to "to get in shape."  To that end joggers spend hours and hours every week slogging at a steady pace, burning up miles and, hopefully, fat.

Do these people look happy to you? Photo by samchills.

But long distance runners, or those who just jog a lot, also end up burning lean muscle mass.  They lose fat, sure, but no one would point to a long distance runner and say, "There's a person in great shape."  They usually just look...drained.

When you jog, you're doing an aerobic exercise.  That means you're using glucose (from carbohydrates) and oxygen to generate energy.  The glucose in your muscles gets used up first, followed by the glycogen your body has stored up.  An adult can store around 1,800 to 2,00 calories worth of glycogen, enough to fuel 90 to 120 minutes of sustained exercise.  After that, you "hit the wall" - and that's the point at which your body finally starts converting fat into energy.

And now you know what the liver is for.

When you sprint, your body doesn't rely on oxygen to generate energy - the rapid switch from resting  to sprinting doesn't give it time.  In this type of anaerobic exercise, you'll rapidly deplete the ATP (adenosine triphosphate) in your muscles, which is enough to give you energy for 10 - 30 seconds.  When you stop sprinting, your metabolism increases as the body tries to draw in enough oxygen to begin recover its resting state. 

This post-exercise oxygen recovery (EPOC) phase can last for between 24 - 48 hours after your sprint - and it's the reason why sprinting is better for burning fat than jogging is.  Your body is working to repair the damage it incurred sprinting and to recover the depleted glucose and ATP you used up. And because sprinting is an anaerobic activity, you'll also build muscle in your recovery period.

In one study, participants were assigned to either a steady-state cardio group or a high intensity interval training (HIIT) group.  The results showed that the HIIT group burned three times more body fat than the steady-state group.  Another study found that sprint intervals decreased body fat in women by 8%.

To get the benefits of sprint interval training, you need to run, not jog.  Keep your pace to around 90% of whatever you feel your max is, and if you're not sure what you're max is, then test yourself once and see where you limits are.

It's a dramatic difference - you have to force your body to adapt to the rapid change of sprinting, and jogging isn't going to cut it.  Your sprint time should be around 30 seconds or less, depending on your fitness level, and your recovery time between sprints can vary from full minute to just 30 seconds.  Keep that up for around 15 minutes, and you'll have finished a workout that you'll feel for the rest of the day.

If you don't know how to get started with sprint interval training, you should check out Sprinterval.  It's a six-week sprint interval training program that starts easy but ramps up the intensity over the course of the program.  Before you try Sprinterval you should be able to jog continuously for at least 30 minutes (meaning you can complete a 5k without stopping), and of course, you should always consult a doctor before you start any exercise regiment.

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