Perhaps the most often misunderstood concept of training is aerobic endurance versus speed. Because it’s often difficult to “feel” aerobic endurance, it’s easy to think that not being able to kick the last 800 meters of a race or not being able to race faster at shorter distances is due to a lack of speed. This is why so many runners turn to the track for lung-busting 400’s to help them get faster.
This difficulty stems from the fact that what you feel doesn’t always correlate with what is happening physiologically in your body. For example, the heavy, cement-like feeling in your arms and legs at the end of a 5K isn’t a sign of muscle weakness or that you need to spend time in the gym. Rather, this feeling is caused by the release of hydrogen ions when racing beyond your anaerobic threshold, which creates an acidic environment in the muscles and impairs muscle contraction. This is why runners are better served hitting the roads for a tempo run than they are hitting the weight room if they want to avoid fading at the end of a race.
Unfortunately, you may be focused on the wrong weakness and thereby not maximizing your training time or your workout effectiveness.
How much speed do you need?
If you can already run far faster than your goal race pace, the problem isn’t your speed. You need to focus more on improving your aerobic endurance and lactate threshold.
From a training standpoint, speed is rarely the limiting factor in how fast you can race, even for a distance as “short” as the 5K. Let’s look at this idea in more depth as the great coach Arthur Lydiard once did when he popularized training 800 and 1500 meter runners with a steady diet of 100 mile weeks.
If you want to run 20 minutes for the 5K, you need to average 6:25 pace per mile. Technically, that means the fastest pace you need to be able to run is 6:20 per mile. If you’re a 21-minute 5k runner or a 3:25 marathoner (roughly the equivalent of a 21-minute 5K runner), I have little doubt you can run a 6:20 mile; you’re probably capable of running a mile close to 6 minutes. Thus, the problem isn’t that you don’t have enough speed to run a 20-minute 5K, it’s that you lack the endurance to run three 6:25 miles without stopping.
Therefore, when you’re examining your training and identifying your strengths and weaknesses, the most obvious areas of improvement are going to come from improving your aerobic endurance and lactate threshold. If you can already run far faster than your goal race pace, the problem isn’t your speed.
Aerobic capacity and lactate threshold, what running coaches refer to as “strength” work, are the backbone of your ability to sustain a fast pace for a long period of time. In short, the higher your aerobic capacity, the longer you can run near your maximum speed.
All runners want to open up the stride and close hard the last 400 meters of race. Not only does it feel great to pass droves of competitors, but finishing strong helps motivate you for the next race. However, actual speed has little to do with how fast a runner can finish the last 400 or 800 meters of race.
As discussed above, most runners already have the absolute speed necessary to fly through the finishing shoot. A 20-minute 5K runner is probably already doing multiple 400 meter repeats at about 5:30 pace (60 seconds faster than race pace). However, finishing the last 400 meters of a 5K at 5:30 pace is probably next to impossible for that same runner. Again, the ability to kick and finish fast is not limited by absolute speed. Rather, the limiting factors are the ability to run fast when tired or to hit the last 800 meters in a less oxygen deprived state.
Therefore, if you’re a runner who is trying to improve your finishing speed or you tend to fade during the last mile, your training time would be better spent improving your aerobic capacity, not necessarily your absolute speed. Tempo runs and cruise intervals are going to address your late race “speed” weaknesses better than a steady diet of 400 meter repeats.
What role does speed play?
Certainly, speed is a component of a well balanced training plan and it’s important to include speed workouts to improve your running efficiency and V02max. If you completely neglect speed altogether, or any energy system for that matter, your performance will suffer.
Perhaps the biggest role speed plays is that it helps improve your running economy and efficiency. In unscientific terms, speedwork helps you run goal race pace with less effort.
However, there is a limit to how much you can develop your absolute speed. At some point, your body approaches its natural talent point and working to improve speed provides diminishing returns. Luckily, improving your aerobic capacity is virtually limitless.
Therefore, once you’re able to run about 20-30 seconds faster than your goal 5K pace for a full mile, you’ve probably developed enough speed to comfortably race your goal pace. The focus in your training should then be turned to improving your aerobic capacity and lactate threshold, which will help you develop the physiological fitness to race faster and maintain a top end speed for longer.
So, the next time you’re analyzing your training and looking to identify the areas you need to improve the most, ask yourself whether it’s really your speed that is holding you back or if you actually need to get stronger aerobically.
Originally published January 2014