The key to a faster marathon is developing STAMINA
First, let's define stamina and how it differs from endurance.
Endurance -vs- Stamina
The terms “endurance” and “stamina” are often used interchangeably so let’s get it straight. Your endurance is your base aerobic fitness, or how well you can run at slow easy paces. Your stamina is your anaerobic fitness, or your ability to sustain faster paces. Aerobic means “with oxygen” and anaerobic means “without oxygen”.
Developing your endurance requires you to run aerobically, or slow enough you can breathe easy. During easy aerobic runs you are using about 99% fat-stores (and only ~1% glycogen) for energy.
The more you increase your effort, the more fat-stores your body burns for fuel until you max out this fat-burning energy system. This happens around 75% effort level, or about the point when your breathing begins to rapidly increase. That’s right, you max out your fat burning energy system around 75% effort level. Running harder than this effort level forces your body to tap into glycogen reserves for the extra energy needed to go faster.
However, your body doesn’t simply switch from using fat-stores to glycogen-stores. Instead it continues to go maxed-out on fat-stores and then adds glycogen as needed for the extra effort. For example; suppose you ran a little faster than a 75% effort level, say about 80%; your body will still be using the maximum flow of fat-stores for energy but will need to add more glycogen for the increasing effort.
Now here’s the important thing to know about fat-stores and glycogen-stores. Your body has an almost unlimited supply of fat-stores but a very limited supply of glycogen stored. Also, everything you do uses lots of fat-stores for energy AND some glycogen. However, you only use a tiny bit of glycogen during low effort activities so your body can easily keep enough in reserve to last all day long at lower effort levels. It’s only when you reach your maximum fat-store usage that your body needs a boost and begins to rapidly increase the flow of glycogen.
Your body is a like a hybrid car, here's how...
You can drive up to 75 mph on batteries alone (fat-stores) but if you want to go 80 mph you’ll need to add power from your gasoline engine (glycogen-stores). Now, suppose you want to go 85 mph; your batteries will still get you up to 75 mph but your gasoline engine will have to add even more power to get you up to 85 mph…using a lot more fuel. What if you want to get up to 95 or 100 mph? Yup, you’ll still be maxed-out on battery power and full-throttle on gasoline power too! But with only 1 gallon of fuel (glycogen) you’ll poop-out in no time.
Actually you never completely run out of glycogen because your body has a governor that won’t let that happen. As your glycogen stores begin to run below about 50% levels, your body goes into survival mode and starts restricting the flow of glycogen, making you want to slow down. If you keep pushing yourself until you run below about 25% fuel level, you’ll be overcome with fatigue and forced to walk. Anything below that would be a medical emergency but don’t worry about that, the pain you experience just trying to run at this low level will stop you from going there. You’ll be laid-out on the grass long before that happens.
Remember, your batteries (fat-stores) can last several hours up to 75 mph but since you only have 1 gallon of gasoline (glycogen), you have to be careful not to go too fast or you’ll burn through your gas too quickly. Anything below 75 mph means your gasoline engine is just idling…ready to quickly add power when needed. Yes, your gasoline engine is always running and burning a little bit of gas but your 1 gallon will last all day at an idle.
"During a race, you’ll obviously want to go harder than 75% effort level so the trick is to give it just enough extra gas to go faster, but not so much you run too low on fuel before the finish."
That's why it is essential to pace yourself in a race so you'll BONK at the finish line and not any sooner. The key is in developing a sense of how long you can hold your race pace. Ask yourself if your marathon race pace is 77%, 79%, 80%, 82% or 84% effort. What is the effort level (pace) you can sustain for the whole race before you run so low on glycogen that you have to stop running? That will be your true marathon race pace.
Remember, although a well trained runner can go for hours by staying below 75% effort level, she can only sustain a few minutes above 95% effort level. You simply have to develop a “sense of effort” to manage your paces. If you’re running a shorter race you can push it close to your maximum effort, but in a marathon you need to conserve your fuel. You have to find your tipping point so you don’t run low on fuel too soon or finish with too much fuel remaining.
Running FAST burns lots of glycogen, running SLOW burns only a tiny bit of glycogen
Now that you understand how your body fuels your run at different effort levels, let’s talk about developing efficiency. Most runners don’t know that you can actually train your energy system... even fewer know how.
"Most runners don't run fast enough on hard days and too fast on easy days." - Coach Jim
Let’s take the hybrid car example again. As you know, the gasoline engine has to add power to go faster than 75 mph and this added power can make you go as fast as 100 mph at full throttle. But there’s a problem, this little gasoline engine overheats anytime you go above about 85 mph (lactate threshold). Its radiator isn’t very big so the engine accumulates heat quicker than it can be dissipated. Even if you still have plenty of gasoline, you’ll overheat and have to slow down so the radiator can catch up on cooling.
How is this the same as your energy system when you run?
Any time you run above about 85% effort level you begin to accumulate lactic acid faster than it can be cleared (the Cory Cycle). Depending how far above your 85% effort level you run will determine how quickly you become overwhelmed with lactic acid and are forced to slow down regardless of how much fuel you have remaining in the tank. Remember, it’s like overheating, not running out of gas.
Keep in mind that most runners can only sustain about 1 hour at their 85% effort level (lactate threshold) because at that intensity they will begin to run low on fuel AND they come close to overheating the engine the whole time. Going faster will run out of fuel sooner and overheat. Going slower will take longer to run out of fuel and won’t overheat.
Here’s the best part...
You can train your Lactate Threshold to go higher! That's right, you can actually run longer and faster at the same effort level as before without exceeding your lactate threshold (overheat). It’s like improving the cooling system of your engine by carefully cleaning it all the time.
How can you improve your lactate threshold (clean your cooling system)?
By now you know that most of your runs should be below your 75% effort level to improve your endurance (develop your aerobic energy system). But to improve on your STAMINA, or ability to sustain a faster pace for longer, you need to challenge your anaerobic energy system. Basically, you push your lactate threshold. Again, this is the point where you begin to accumulate lactic acid faster than your body can clear it. Remember, it’s like overheating.
Newer runners have a lactate threshold around 80% effort level while a highly trained runners threshold can be above 90% effort level, with most recreational runners somewhere around 85%. Regardless of your fitness level, in order to stimulate an improvement, all you need to do is work slightly above your lactate threshold. Read that again. If you do this on a routine basis your body will adapt by getting more efficient at using fat-stores for energy and better at conserving glycogen for harder efforts. Your lactate threshold will get higher.
More good news
You don’t need to push above this lactate threshold too often or for very long to stimulate adaptation. Although your lactate threshold is the pace you could hold for about an hour, you only need to exceed this effort level for 20-25 minutes, once a week for maximum benefit. Anything more has rapidly diminishing effect.
How to perform a lactate threshold run
Often called a Tempo Run, a lactate threshold run might look something like this. Start with a one-mile warm up, then run at 85%+ effort level for 5 minutes followed by a one-minute jogging rest, repeat 5 times for a total of 25 minutes. The idea is to force your energy system to exceed it’s capacity to clear lactate (overheat). Again, if you do this on a routine basis your body will adapt by getting better at it.
It’s critical that you actually exceed your threshold or there won’t be any significant improvement. So, you must know when you’re pushing above this effort level.
How can I know where my lactate threshold really is?
The easiest way to determine your own lactate threshold is to do a self-assessment run. Simply plan a 30-45 minute run at your hardest steady effort while wearing a heart rate monitor. When you’re done, look at the data to see what your average heart rate was during the middle 15-20 minutes. That is very likely your true lactate threshold, as measured by heart rate.
Now all you have to do is accumulate 20-25 minutes above this heart rate (effort level) once a week. Then after a few weeks, repeat the self-assessment to see any improvement. Again, for most runners it will be around 85% effort level.
As an alternative, the most accurate method to determine your lactate threshold is a lab test. These are often available at college labs or physical therapy centers but they can be costly; often more than $200 for a one-hour session. Basically, you run on a treadmill while wearing a heart rate monitor and respirator mask (to measure oxygen volume) and submit to blood sampling at various times during the test. Again, your results will show you what your heart rate is at your lactate threshold so you can target this number in training.
So, there you have it.
If you really want to improve your finish time in a marathon, you simply must improve your stamina by challenging your "lactate threshold" on a routine basis.