*** many thanks to Neil Rooney for this blog post ***
Most people who partake in running or triathlon begin with a goal of just completing whatever race they want to do but soon after that race, if they have been bitten by the bug they'll want to run faster. The common method for increasing running speed is running faster and faster on each training session. However that method is incorrect and will lead to minor increments in running times, injury and poor health.
The correct way to get faster at endurance running is learning how to run slow first, this will speed you up long term and will help you avoid unnecessary injury. I should point out that endurance or distance running is anything further than 800m. Yes that's right 800m, so if you are training to run the mile or anything further you are training for endurance or at least you should be. The 5km race series or the run in a sprint triathlon (5km) is definitely an endurance feat and this should be addressed in training. Any run that is longer than a marathon (26.2 miles or 42.2km) is considered an ultra-distance race.
The line between endurance running and speed running can be drawn at the 800m line because of physiological measures. If you prepare correctly it is possible (just like David Rudisha demonstrated in the London Olympics 2012) to run 800m in an all-out sprint from start to finish. During this distance your body can rely predominantly on sugars as a fuel source from start to finish. This means you can run in an anaerobic (without using oxygen for fuel and solely relying on glycogen) state. Any distance further, let’s say 1 mile, you cannot run solely on sugars, at some point in that distance fats must be a fuel source. Which means you cannot go all out sprint from start to finish, you must pace yourself and you will have to use oxygen along with those fats. Therefore running in an aerobic state.
As I have mentioned before, all 3 of our energy systems are active all the time. However the dominance on one system will change dramatically depending on exercise. The line between burning glucose (sugar) as a primary fuel source and fats as a primary fuel source is called the lactate threshold. It is this key feature of physiology that you are trying to raise by training, the higher this lactate threshold becomes, the faster and longer you will be at distance running.
The lactate threshold is determined by the body’s ability to burn fat as a fuel source. By developing your muscles’ power stations (mitochondrial density) you can raise your lactate threshold. Raising your lactate threshold inevitably brings that number closer to your maximum heart rate (MHR) number. If you don't know your maximum heart rate it can be roughly calculated by subtracting your age from 220. MHR = 220 - Age. So lets say we take an individual who is just beginning running. Lets suppose her MHR is 180bpm (beats per minute) and at 120bpm she will reach lactate threshold. That means when exercising the heart rate up to 120bpm she will be relying 50% on fat and 50% on glucose as a fuel source. If she keeps the heart rate below 120bpm she is relying predominantly on fat as a fuel source and above 120bpm she is relying predominantly on glucose as a fuel source. Since distance running requires fat as a fuel source, you don't need a great deal of distance before fat is dominating sugar fuel source considerably. A nd the longer you run the more and more fat dominates as a fuel source. So in order to become faster you must be able to burn fat more quickly, remember fat yields more than twice the energy that glucose yields per gram.
The key question I suppose is "how do I train to burn fat and raise my lactate threshold?" This training needs to increase the muscles mitochondrial density and vascular pathways (see previous posts on the Run Sensible site). The more power stations and road ways the more energy you will have available. The only way to increase mitochondrial density is to train your body to burn fat. This can only be achieved by training just below your lactate threshold.
So our individual needs to run at a heart rate of 119bpm, for her long run. As the muscles develop and open new mitochondria the lactate threshold will slowly increase as will her speed and ability to run further. Now lets suppose after 6 weeks of training the lactate threshold is 125bpm (as a result of new blood vessels and increased mitochondria in the muscle cells), the individual will now be able to run at 124bpm and feel as comfortable as she did at the beginning when running at 119bpm. If at 6 weeks later the new lactate threshold is 130bpm she will feel comfortable running at 129bpm and so on! You get the message? Since the heart rate or bpm determine the effort and the effort determines the speed, the higher the heart rate (so long as you are under the lactate threshold) the faster you become at distance running.
An important note to remember. If you are all the time training above your lactate threshold you are training your body to burn sugar. If you train your body to burn sugar, guess what? Your body is going to crave sugar! It doesn't matter how strict you are on the Paleo diet, the Atkins diet or any other low carb diet, if you train your body to burn sugar by being above your lactate threshold, your day is going to be filled with thoughts of quick fix sugar foods and fizzy drinks. You can't cheat physiology, you just can't!
My suggestion to anybody doing any type of training from running, cycling, swimming, cross fit, weight lifting or spinning you should include a sub lactate threshold training session once a week to gain speed, reduce fat and prevent injury.