How Not to Slow Down During a Half Marathon

Frustrated that you keep slowing down during a half marathon? Read this article to learn how to improve your half marathon time!

Slowing down in a half marathon is a common complaint amongst recreational runners. After all, racing 13.1 miles (21.1km) is challenging – that’s a long time to hold onto a demanding pace. Many culprits can cause slowing down in a half marathon: inadequate training, poor nutrition, an inappropriate pacing strategy, a negative mindset, and more. This article will guide you through how to improve your half marathon time – including how to finish a half marathon feeling strong, not struggling. 

How to improve half marathon time

There is not one universal solution for how to stop slowing down in a half marathon. Many factors in training and on race day impact your finish time, including training volume, types of workouts, nutrition strategy, pacing strategy, and mindset. You may need to change just one of these – or many – to improve your half marathon time. 

Increase training volume

The half marathon is almost entirely aerobic. Therefore, your training volume has a direct impact on your performance. A 2020 study published in the Scandinavian Journal of Medicine and Science in Sports found that runners who ran over 20 miles (32 km) per week finished faster and experienced less decline in their pace during a half marathon.  

 If you often experience slowing down during a half marathon, you may benefit from increasing your training volume – whether you run 15 miles per week or 40 miles per week. (With the caveat: as long as you can recover and complete your workouts.) Increases in weekly mileage do not have to be significant; even 5-10 miles per week more, stacked over the several weeks of a training cycle, can be beneficial. (Read this article to learn how to safely increase your running mileage.)

Half marathon speed workouts

In addition to long runs, one of the most effective training practices to improve half marathon time is to incorporate half marathon pace workouts in your training. Why? Race pace workouts prepare you for the unique metabolic, mechanical, and psychological demands of race day. Even your running economy (the amount of oxygen you use at any speed) will improve if you familiarize yourself with goal pace in training. If you train your body to hold race pace – and train your mind to tolerate it when it becomes uncomfortable – you are less likely to slow down on race day.

Half marathon speed workouts typically involve extended portions at your goal race pace. Depending on your training, you may do workouts that involve 4 to 8 miles at half marathon pace (either continuously or broken up into 1-2 mile intervals). (This article contains some examples of half marathon speed workouts.) 

Your training will not comprise of just half marathon pace workouts. You will still do easy runs, including easy-paced long runs. If you try to run every run at half marathon pace, you will likely overwork yourself before race day. Additionally, workouts at faster than half marathon pace (such as 5K or 10K pace intervals) will also improve your fitness. Aim to include one half marathon pace workout most weeks in the final 6-8 weeks before your race. 

Nail your nutrition and hydration

Whether you are running a 1:30 hour or 2:30 hour race, a race day nutritional strategy will help you avoid slowing down in the half marathon. During a half marathon, your body uses carbohydrates to produce energy – and carbohydrates allow for more output per liter of oxygen than fat. If you do not consume enough carbohydrates before or during to support the demands of the race, you could slow down in the later miles. 

The brain protectively lowers exercise intensity if it senses low carbohydrate availability. Low glycogen levels can occur in the half marathon due to the combination of higher intensity (above aerobic/first threshold) and duration. If you maintain adequate levels of blood glucose during the race, your muscles oxidize higher amounts of carbohydrates for energy – even later in the race. Your brain will also sense the carbs and know that it doesn’t have to slow you down to protect against the damaging effects of low muscle glycogen. 

A performance-enhancing nutrition strategy for a half marathon will include a pre-race breakfast, intra-run nutrition, and hydration. If you hope to finish in less than two hours, take 30-60 grams of carbohydrates per hour. For finish times greater than two hours, you could benefit from 60-90 grams/hr. Hydration needs are dependent on sweat rate, but most runners find they need at least 10-16 oz of fluid per hour to race their best. You can also experiment with caffeine to see if that helps you avoid slowing down during a half marathon. 

For more information, reference the following articles:

Improve your mental resilience

Slowing down in a half marathon can happen to the fittest of runners if they are not psychologically prepared for the discomfort. A half marathon race starts off relatively comfortably. However, by the time you reach mile 8-9, the distance demands a lot more focus to stay on pace. You will experience muscle discomfort and mental fatigue in the final miles. Every runner wants to slow down – but those who do not slow down can keep pushing because they worked on their mindset in training. 

Mental resilience is a trained quality. If you want to be able to improve your half marathon time, you need to work on your ability to tolerate discomfort in training. Do not expect to magically be able to push through on race day. Instead, incorporate mindset training into your entire half marathon build.

Certain training approaches can train you to psychologically tolerate physical discomfort better. Longer goal pace workouts and fast finish long runs will expose you to how race pace feels when you are tired. You can practice mantras, cues, and other mindset techniques during these workouts. If you experience race day nerves, a shorter distance tune-up race will help you practice how to cope with nerves. 

Strategize your half marathon pacing

For most recreational runners, half-marathon pace is above their first/aerobic threshold and under their second/lactate threshold (or “zone 3” on a five-zone scale). This pace feels truly moderate for the first half of the race – and that means it’s all too easy to start out too hard. If you start even 15-30 seconds per mile too fast, you risk starting out above your second threshold – at a place where your physiology is less stable and you fatigue more rapidly. 

You can improve your half marathon time and avoid slowing down by being deliberate about your half marathon pacing strategy. At about 30-45 minutes before the race, warm up with 5-10 minutes of light jogging. Once the race starts, use the first mile to build into goal pace or goal pace plus 10-15 seconds per mile (depending on the course). Check your watch at the first half mile mark (or first half km mark) to ensure you haven’t gone too fast – and if you have, rein the effort in immediately. By mile 2 to 3, you want to settle into goal pace – not faster. 

From there, you want to aim for a consistent pace as much as possible. On a hilly course, you may need to anticipate slower paces on uphills (and faster paces on the downhills). Once you reach mile 11-12, if you feel like you can speed up, do it! 

Additional strategies for race day

In my years of coaching, I have observed some small yet effective race day strategies help runners improve their half marathon time. These strategies should be done in conjunction with the above training advice. 

Race day strategies include:

  • Find a way to relax before the race: listen to favorite music, audiobooks, etc. 
  • Avoid social media in the hours before the race.
  • Carry your own handheld bottle during the race so you can easily drink to thirst. 
  • When you want to slow down, check your running form and cadence. Fixing your form and quickening back up your cadence will combat late-race declines in running economy.
  • Smile at volunteers and spectators – this releases dopamine and lowers your perception of effort in the race. 

Running a half marathon at a speed you’re proud of

The half marathon is a challenging distance. If you slow down during a half marathon, do not judge yourself negatively for it—it’s an experience that happens to most runners! If you slow down in a half marathon, let that be a learning experience. 

Download a half marathon training plan to prepare for your next race! 

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