Training for the Half Marathon

What the half marathon asks of you

A half marathon is run at a hard, steady effort close to threshold, the pace you can hold for about an hour, and you hold it for an hour and a half or more. Threshold work is the main quality piece of a half block because it is the training that most resembles the race effort, and a runner with a time goal who skips it is missing the main piece. It is not all that matters. You also need a long run that builds the endurance to hold the effort and enough easy running to recover from the quality.

Pick the block and the goal

Twelve weeks is a good block for a runner who already has a base, and 16 weeks if you need more build. A newer runner first spends 4, 6 or 8 weeks on baseline easy running, going from three or four days a week up to five or six.

Set the goal from short races and not from a wish. A recent 5K gives a first read: a 19:15 5K points to about 1:28:30 for the half. Run two or three more 5Ks over the two months of the build, and in the specific block, the last month and a half, move your half-marathon pace up or down by how you feel after workouts plus your data. Do not start the build at goal pace. See the guide on race goal-setting.

Choose a cool, established race with easy logistics. Under 15 C (59 F) is workable and 10 to 12 C (50 to 54 F) or cooler is better, with low humidity checked against past years.

Easy running and the long run

Most of your running is easy: a pace where you can hold a conversation, with the effort kept down so the quality days stay good. Mix truly easy runs, a long run and at least one hard day, and let weeks differ from one another.

The long run is still needed, but it need not be a marathoner's. An experienced half-marathon runner builds to 14 to 16 miles, and a runner already at 20 kilometers can peak with one run of 24 to 25 kilometers. Run it at a conversational pace, 90 seconds to 2.5 minutes per mile slower than half-marathon pace, and keep it within the three-hour limit for a long run.

Once the long runs are comfortable, add goal pace to some of them, but not all: 1 mile at goal pace in a 13 to 14 mile run, then 1.5 miles the next time, then 2 miles. A long run with pace work counts as a hard session. See the guide on the long run.

Threshold first, then half-marathon pace

After the baseline weeks, run 4 to 6 weeks of threshold work, then move to half-marathon-pace work. Threshold sessions look like 6 x 5 minutes, 30 minutes continuous or 3 x 10 minutes. The top weeks reach 40 to 45 minutes of threshold, and you do not start there. Break a 45-minute session into 3 x 15 minutes with 1 to 2 minutes of float recovery. If a threshold workout is too hard, cut its pace or its length by 5 or 10 percent. See the guide on tempo and threshold runs.

A runner who does all of their running easy, such as easy runs at 10:00 a mile with a goal pace of 8:30, is training too far below race pace. Add threshold intervals that start at 5 minutes on and 3 minutes of recovery, and build from there. Add hills in the build, and keep VO2 max work small until the last quarter of the block.

The race-specific phase runs from about 8 weeks out to 2 weeks out. The pace work is short and in pieces: half-marathon pace in pieces of 2 to 3 miles, for example 3 to 4 x 2 miles with short rest in the last 4 to 6 weeks, no more than once a week because each one is a hard session, with speed work at 5K pace. The aim is to find the pace, hold it, leave it and find it again. Add nothing new in these weeks. See the guide on race-specific preparation.

If you are new to running

A walker is a runner. You can run the whole half marathon in run-walk intervals, anywhere from 5 minutes running with 30 seconds walking to 10 minutes running with 1 minute walking. Practice the intervals in training and use the same ones in the race. If your heart rate climbs far above zone 2 within minutes of starting, 5-and-1, 10-and-1 or 2-and-1 intervals let it come down, and the running pieces lengthen as your aerobic capacity builds. See the guide on starting to run.

Fuel and shoes

A half marathon takes most runners well over an hour, so practice your race fueling on long runs. Past 90 minutes, take the first gel at 60 to 75 minutes and one about every 30 minutes after that, or every 35 to 40 minutes if your stomach is touchy. Eat well the night before, and you do not need a giant pasta plate. See the guide on carbohydrate during exercise.

Train in a daily trainer and race in a racing shoe, even if you finish near two hours. Try a new shoe on a short run before you race in it.

The taper

Taper for two weeks. Keep your run days and one or two workouts a week, and make the workouts smaller. See the guide on tapering.

Race day

Warm up with 10 to 20 minutes of easy running, dynamic stretching, and strides or two 2-minute pickups at about 80 percent effort. The shorter the race, the longer the warm-up.

Pace is the half marathon's main decision. Chris McClung sets it before the race from recent races and how goal-pace workouts felt. He has experienced runners start 10 to 15 seconds a mile slower than target and newer runners 20 to 30 seconds slower, reach target over the first two or three miles, hold it to about mile 10 and close over the last 5K. The first kilometer runs about 15 seconds per kilometer fast from nerves and the crowd, so stay out of danger and settle within the first couple of kilometers. The hardest stretch is 16 to 20 kilometers, and breaking it into single kilometers makes it manageable. In heat, run on effort and not on pace: in the mid-70s F with 85 to 90 percent humidity, add 20 to 30 seconds a mile. The guide on race-day pacing goes deeper.

Related guides

For the marathon, see marathon training. For the shorter races, see 5K and 10K training. For how a plan is arranged, see periodization.