When Should You Start Training For A Half Marathon?

Setting your goals high and aiming to complete your first half marathon is a big step. Realizing that you’re committing to a race that is more than twice the distance of a 10K is a herring feat. After your goal lust comes back down to a manageable level it’s time to put this goal in a realistic, achievable frame of time to crush it. One of the first questions that most first time half marathon runners ask is, when should I start training for a half marathon?

When Should I Start Training For a Half Marathon?

Depending on your current fitness level and weekly running volume, you can be ready to run a half marathon in as little as 12 weeks for a first time half marathon race. If your fitness level is below average and your running volume is less than 10 miles a week, you might be looking at a time frame of 15 to 24 weeks.

Fitness Assessment

The first thing you should do is have a physical exam performed by a registered medical profession as to whether or not you’re physically able to run a half marathon. After your doctor gives you the ok, it time to assess your current physical capabilities before selecting a half marathon training plan.

The answer to when you should start training for a half marathon depends primarily on two indicators:

• Current fitness level
• Weekly volume of running

Current fitness level

The best indicator of your current fitness level is NOT you. If you even feel the slightest inkling about your physical fitness level not being up to par, please have a physical fitness exam performed by a medically licensed professional. Your current physical fitness levels take into account your blood pressure, weight, and many other medical indications that can be caught through an exam and blood work.

If you are having trouble running at least one mile, I suggest starting with a free training plan that I designed: How to run one mile when you’re out of shape. After you’re able to successfully run one mile without stopping you can move onto a 12-15 week training plan.

Weekly volume of running

Your weekly volume of running is a good indicator of how far and how long you can run for. When you have a consistent larger weekly volume of running, you’re going to be able to run for longer amounts of time and for further distances. These weekly miles are referred to as your running base volume.  When you’re first starting out you have a zero base of running volume because you haven’t been running which conditions the body to run further and further each week. Each week that you run you is increasing your body’s ability to run aerobically (with air) for longer periods of time. When you’re first building your running base, you will become winded and out of breath quickly since your body’s capacity to run more efficiently hasn’t been increased.

When your building your running base, you are expanding capillary growth around your muscle’s cellular structure which aids in more efficient oxygen delivery.

Building a strong running base can be done by starting to run 3-4 times a week at an easy pace for the distance of 1-2 miles. Each week you want to gradually stack on more miles so that you can run for at least 3 miles without stopping. This could take anywhere from 3-6 weeks to get to this a weekly running volume greater than 10 miles a week. Base training runs should be done at an easy, conversational pace.

How long will it take me to train for a half marathon?

The length of time depends primarily on your weekly running volume. I would use these guidelines as to how many weeks it will take you to train for your first half marathon:

Your weekly running volume is below 10 miles or you have never really “run” before

This is also the time frame to use if you might be obese (30% above your ideal weight). It will take you an additional 6 – 12 weeks to lose weight and build a running base. For more information on building a running base check out this post: What are base miles. As a running coach, I can’t stress this enough, when you run with the extra weight you are amplifying the impact of your body weight with each step. A runner that is in relatively good shape that is not overweight already has an impact of 2-3 times his body weight with each step. When you add the extra weight, it causes more undue stress on your legs and joints that could lead to injury quickly.

If you eat nutritiously should naturally lose anywhere from 1/2 a pound to a pound during your half marathon training. You need to be careful to not overcompensate with extra calories. When you start training more often you’re going to get hungry. Eating a cheeseburger with fries every day out of justification for your hard training won’t cut it. In fact, you might even gain weight during your half marathon training. Read more below on weight gain and weight loss during training. Total training time for a half marathon will be between 15 and 24+ weeks.

Your weekly running volume is greater than 10 miles and you can run a 5K (3.1 miles) without stopping

This is the ideal sweet spot to train for a half marathon. You don’t necessarily have to be able to run 3.1 miles without stopping, however you should be able to complete a 5k (3.1 miles) within 45 minutes so you can finish a half marathon within 4 hours. Total training time for a half marathon will be 12 weeks.

Your weekly running volume is between 10 and 20 miles and you can run up to 6 miles in one session

You’re already logging long-distance runs in excess of 6 miles so your training schedule window is about 8 weeks.

Your weekly running volume is between 20 and 30 miles and you can run up to 10 miles in one session

You can run a distance of 10 miles in one training session. Your training schedule window is about 4-6 weeks.

How long will it take to train for a half marathon?

Walking a Half Marathon

If you’re severely obese you might consider walking a half marathon, but only after you lose some of your weight and get within a 20% range of your ideal weight. I’ve written a detailed post about walking a half marathon in under 4 hours with pacing charts.

Depending on what your goal is, you may simply want to attempt to walk the half marathon instead of running it. Although you will be walking, you still need to be able to walk the entire length of the race, which is 13.1 miles (21.1 km). Race cut-off time is an important factor in walking a half marathon. Most runners won’t have a problem finishing a half marathon within the Race cut-off times because they are moving at a faster pace.

Walk/Run, Run/Walk, or Run a Half Marathon

Using a run/walk interval method of training is highly encouraged for a first time half marathoner. When you use this method of training you are greatly reducing the risk of injury because you’re giving your legs time to rest in between run intervals. A walk/run and run/walk are essentially the same. However, a walk/run is more heavily walking versus running and with the run/walk, you are more concentrated on running.

Determining your half marathon start date

Below are tables that show you the training start date depending on when your race date is. Saturday was used for the race day since most races are on Saturdays. There are some races on Sunday, so just adjust the day by one, since you will still more than likely start your training on a Monday. Data tables for 8, 10, 12, and 15 weeks have been created below for easy reference.

Should I be gaining weight during half marathon training?

When you start to train for your half marathon,  you will naturally shed some weight. What I see time and time again with runners is what I refer to as “overcompensation calories.” We go out for runs that can last hours and then we want to eat a big cheeseburger with fries. What I would be wary of is the device on our wrist that is calculating how many calories we’ve burned during a particular workout. Check out this post I wrote that shows you three unconventional ways you might be gaining weight. Your smartwatch’s data might be one of the biggest culprits behind your eating habits and excess weight gain.

For a compiled detailed list of the best-running watches for half marathon training check out:

Best Half Marathon Training Watches

Should I be losing weight during half marathon training?

It’s ok if you’re losing some weight when you start running more miles and burning more calories. The reason why it might not be the best time to intentionally lose weight is because of all of the new training tasks that you are taking on. Your body will be working harder than it normally would during your training cycle, so intentionally cutting out calories could lead to undue stress, lack of nutrition, and inadequate muscle repair and recovery.

Normal weight loss during a half marathon training plan should be no more than 1 pound a week.

What is considered a healthy diet?

Reference: U.S. DEPARTMENT OF AGRICULTURE, Dietary guidelines

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