Ask Pete: What’s the Difference Between 5K, 10K, and Half Marathon Training?
Runners make a mistake when they base all their training on the length of a target race: here's what you need to be your best at every distance.
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What are the main differences between 5K, 10K, and half marathon training? – Pascal
Okay, this needs to be our little secret, given that my last book, Fast 5K, speaks directly to 5K training: There is almost no difference between 5K and 10K training, and there’s only a smidge of difference between what you need for the 5K and the half marathon.
Runners make a mistake when they base their training on the length of a target race, thinking that a 5K requires a much smaller volume of training than a half-marathon—you know, because it’s a much shorter race. Instead, runners should plan their training based on the muscle-fiber, energy-system, and nervous-system requirements of each race, which coincidentally happen to be very similar for all three distances.
- Energy systems: For a 5K race, about 90–95% of the energy you use will be produced aerobically. For the 10K, it’s about 92–97%. For the half marathon, about 98–99%. In other words, all three races depend almost entirely on aerobic energy.
- Muscle fibers: For all three races, you’ll use 100% of your slow-twitch muscle fibers. For all three, you’ll also need between 50–85% of your intermediate fibers. You’ll recruit significantly more of your fast-twitch fibers (about 50%) for the 5K than the half marathon (about 5–10%), but due to these fibers’ anaerobic nature and the intense force required to recruit them, it takes the same type of workout to train a small percentage as a larger one. Bottom line: You use most of the same fibers for all three races, and when you don’t, you use the same workouts to train the fibers you do use.
- Nervous system: Your nervous system is responsible for the contraction and relaxation of your muscle fibers, and it’s also responsible for coordinating these contractions in multiple muscles across multiple joints in order to produce the most efficient stride and expenditure of energy possible. As your running speed changes, the way your nervous system utilizes muscles also changes—for instance, at slower paces your quadriceps and calves make a large contribution to propelling you forward, while at the fastest paces it’s your glutes and hamstrings that carry the load. By including a significant volume of training at varied paces—as you do when training for both 5K and half marathon—you ensure that your nervous system will become efficient at recruiting the full range of muscle fibers and energy systems required for all three races.
Having said all that, there is one training adjustment you’ll need to make when targeting a half marathon versus a 5K. You’ll need to lengthen your weekly long run at least a couple (at most a few) times in your build-up to the race. This isn’t so much a physiological adjustment as it is a psychological one. You’ll want to prepare your brain—that worrywart behind the curtain—for the extended effort that accompanies a half marathon race. By going longer at a normal distance pace, you convince your brain that it’s safe to go longer at half-marathon pace.
Finally, understand that your program isn’t a bank account. You aren’t depositing mileage and workouts into an account until you’ve saved enough for a 5K race—or with a larger deposit, a half marathon. Instead, your program should be designed to stimulate adaptations in your body that allow you to race better. You’re building your running body the way Detroit builds a car, by assembling the pieces of a machine that’s ready to perform. Build a better running machine, and you’ll run a better 5K, 10K, and half marathon.
Pete’s freebee training tip:
There’s a simple rule I always follow when deciding how to prepare for an upcoming race: Never run a workout if you don’t know what it does. When I landed my first high school head-coaching job in track and field, I only really knew the thinking behind four workouts: distance runs, repetitions at race pace, hill repeats, and (oddly enough) technique drills. So that’s what I had my athletes train. And we won league. My bag of workouts has grown a lot since then, but the principle remains the same. When you know why you’re running a workout, you’ll do it correctly and improve. When you don’t, you risk injury, excessive fatigue, and a significant chance that, at best, you won’t improve, and, at worst, you’ll regress.