The negative split is one of my favorite distance running techniques that is sure to help you cut seconds and minutes off of your race times. A negative split is defined as running a later portion or a race at a faster pace than an earlier portion of the race. In essence, you start out slow and speed up as you go, each split is successively less than the one before it (negative). But why would you want to do that and how will that make you faster? Let's start at the beginning.
When I began running, I, like many others, believed that you should start fast when you are fresh and slow down as you wear out and become tired. Some call this 'banking time'. You are running faster than your goal at the beginning in an effort to bank enough time so that you can run slower later in the race. There is a fundamental flaw to this line of thinking and it has to do with your physiology (fancy word for body science). As you might already know our muscles get energy during running from glycogen (carbohydrates) and fat stores in your body. Glycogen is limited in quantity, and even a well trained athlete will not last long running above 85% of their max heart rate. They will be running anaerobically and burning a great deal of glycogen and producing lactic acid in their muscles at a rate faster than it can be removed. Lactic acid stops your muscles from converting fat into energy. This will cause you to slow way down or even walk. Your goal is to use your fat reserves, which are much greater in quantity and will keep you going longer.
The negative split running strategy coupled with the right aerobic training you can teach your body to use more fat and less glycogen which will allow you to run for much longer periods of time while burning fat and without running out of glycogen or generating large amounts of lactic acid.
So what can you do about it? First focus your training to be aerobic, in the 60-75% of your maximum heart rate range for at least 30 minutes. Yes that means running slower when training; it seems counter intuitive but it works. And the next time you race, instead of going out at full speed and fading in the later miles, start out at a pace a few seconds per mile (10-15) slower than your goal pace for the first few miles, and slowly pick up the pace running each mile a few seconds faster than the last. During the second half of the race you should be cruising at a bit faster than your goal pace and if everything goes correctly your second half will be faster than your first half and you will meet your goal.
Negative Split Works!
The first time I attempted to run a negative split it took almost 4 minutes off of my previous half marathon time where I went out at 6:59 at the start and slowed greatly at the end. This time I started off at a 7:20 - 7:24 min/mile pace for the first 3 miles and had tons of energy during the second half of the race and passed several people. I finished with an overall pace of about 7:09 min/mile.
You know the feeling when you're pushing really hard, maybe running up a long hill or kicking it in for the last quarter mile of a race? The muscles in your legs slowly turn to stone. It takes several minutes post-hill or post-race for them to feel normal again.
This stone-like sensation is caused by a buildup of lactic acid in your muscles. Lactic acid is a byproduct of the chemical reaction that pulls sugar (glucose = fuel) from your blood and burns it for energy. The amount of lactic acid produced depends on how hard your muscles are working.
There are several "zones" that your body will normally go through during a workout: aerobic and anaerobic. These zones correlate to your heart rate, which increases as your muscles work harder. Each of us have a maximum heart rate, MHR, which is the maximum number of times your heart can beat per minute (generally, this number does not increase or decrease with fitness level, but may change with age). If your heart rate is 70% of your MHR, or less, you are in the aerobic zone. Conversely, if your heart rate is above 70%, you are in the anaerobic zone.
The aerobic zone is also called the "fat-burning" zone because your body is using oxygen to turn stored fat into energy. There are many positives to training and running in the aerobic zone: energy production does not produce large amounts of lactic acid, so your muscles do not tire as quickly; energy production from fat is very efficient; and the more you train in the aerobic zone, the better your body will become at converting fat to energy!
When you are in the anaerobic zone, your body is demanding energy now! It burns the sugars in your bloodstream in the absence of oxygen, creating lactic acid. If you are in the lower end of the anaerobic zone, the amount of lactic acid produced is small enough that it can be dissipated by your bloodstream. However, when your legs are pumping, propelling you up that hill, the lactic acid builds up in your muscles quicker than it can be removed, hence the stonelike feeling. As your body works to dissipate the lactic acid, your legs will feel better, but you'll be left with much less energy for the rest of your run, and for that next hill!
So what can you do? Refuel! Getting that glucose in your blood back up to a reasonable level as quickly as possible is very important, especially if you are part-way through a long race. So eat some sugar!
Of course there are many practical options available, from GU energy gels that contain caffeine for that extra kick to Clif Shot Bloks which taste like delicious fruit chews. But what about something a little more fun? Maybe a handfull of Starburst(R) Jelly Beans or Candy Corn? After all, what could have more sugar than Candy Corn! If you compare the nutrition facts and look at the top ingredients, candy does provide a large amount of sugars, but specifically formulated energy gels and chews contain slightly more complex carbohydrates which will fuel your body for longer and may actually be easier to digest; they also contain amounts of potassium and sodium - other essentials that your body desperately needs during a tough run. My recommendation? Indulge sweet treats once in a while, but for general training needs, and especially on race day, stick to the products specifically formulated for athletes.