Question: How fast should I run my long run? Should I shoot for a specific pace?
Answer: Unfortunately, there isn’t a single “best” pace that works equally well for all runners; it depends on your current fitness, your running goals and overall training program, and what you mean by “long.”
Let’s first agree on what constitutes “long.” A key point to remember: It’s not length in miles that makes a run long, it’s length in minutes. New runners, for example, go long simply by running more than typical week-day runs. Experienced runners log up to 50 percent more than their usual daily running time on weekly long runs (with runners who train less than five times a week sometimes doing more than that). Competitive runners need to exceed 90 minutes—the point at which they begin to accrue many of the most sought-after benefits of long runs.
With that in mind, let’s discuss pace—or more accurately, effort. Your effort level determines which muscle fibers and energy systems you’ll train during your run. The longer you run, the more muscle fibers you’ll train; as fibers run out of carbohydrate energy, other fibers are recruited to replace them. But beware: The faster your long run pace, the longer it takes your body to recover, which may eclipse other essential training time. So it’s important to choose an effort-level (and length) that fits snugly into your overall training program and best serves your racing goals.
—Pete Magill is a coach and author of Speed Runner: 4 Weeks to Your Fastest Leg Speed in Any Sport
GAUGE YOUR EFFORT
All of these paces will get you benefits from a long run; which one you choose depends on your goals and current fitness level.
Low effort (jogging or easy running, 3 or more minutes/mile slower than 5K pace): This effort only activates about 35–65 percent of your slow-twitch (endurance) fibers, but it’s great for teaching your body to burn fat as fuel. At this effort level, you’ll use up to 75 percent fat to fuel your run, making it good for ultra runners.
Medium-easy effort (2-3 minutes/mile slower than 5K pace): You’ll activate 75–80 percent of slow-twitch fibers and more than 10 percent of intermediate (strength and speed) fibers, triggering an increase in those fibers’ carbohydrate fuel stores and aerobic-energy production. This is a good effort level for 10K, cross-country, half marathon, and marathon runners.
Fast effort: In this version of the long run, you interrupt medium-easy effort with periods of tempo or goal-marathon-race-pace effort. You train more than 50 percent of intermediate fibers, and your body learns to burn lactate (a carbohydrate energy source that’s produced within your muscle fibers at more intense efforts). Another version of this includes “fast-finish” runs, where you increase your pace over the final 30-90 minutes, finishing at near maximal effort. Runners getting ready for a marathon should include a few of these runs.