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Your guide to training for a half marathon in 12 weeks

April 06 2022 6 min read

Move over 10K! Half marathons are becoming the most popular distance amongst runners across the country.

The marathon’s little brother, the half, has taken the country by storm. Runners are hungrier for longer distances, more gruelling training regimes and a greater mental endurance. Many people who are a certain distance through their fitness journey think that a 10K is now longer challenging enough, hence the need for a longer race. Just because the distance is halved doesn’t mean your achievement should be, a half marathon is still a marathon after all.

Whatever your motivation to run may be, there is one important factor that will underline your success - your training regime. We would always advise that you should have developed a solid base of cardiovascular work before signing up for a half marathon. While it is possible to go from couch potato to marathon runner in a few months, it will put immense strain on your body and could lead to injury.

Nevertheless, if you have been pounding the pavement for 20 minutes at least two times a week for a good couple of months, you should be ready to begin marathon training. If you feel like you are up for the challenge but would like some extra guidance, arrange a session with one of our personal trainers to get you started.

Additionally, we have put together a handy 12-week breakdown of training to help you cross the finish line.


If you haven’t already, sign up for the half marathon. It means that you’ll have plenty of motivation (and probably fear) to begin training. You should aim to run around 8 miles in your first two weeks, which could be split into sections of 2-3 miles across three days.

As the distances you are running aren’t that gruelling, you should be eating only slightly more than your usual calorie intake. Make sure you are getting a balanced diet mainly consisting of protein. Opt for meals such as tuna steak, with broccoli, and carrot and sweet potato mash.


Increase your run by 0.5 miles each session and aim to run at a comfortable pace that you could hold a conversation in. You want to keep pushing yourself but you don’t want to risk working too hard and causing an injury. Remember to keep drinking plenty of water throughout the day to make up for the fluids you are sweating out in training.

It’s important to always start the day with a high carbohydrate breakfast such as porridge, as this will provide you with slow releasing energy throughout the day. Add some flavour with a touch of cinnamon, a spoonful of honey or some fruit.


This is the halfway point of your training and where it really steps up a gear. While you should continue with your running, by sticking to around 10 miles a week, it’s also important that you start your strength training. You rely on your leg and arm muscles to propel you to the finish line which is why it’s crucial to build up your muscles. Start to integrate weights into your routines either through specific training, such as circuit training or Body Pump or using weight machines in the gym.

As you are expending more energy by increasing your runs, you should also be upping your calorie intake. You still want to be eating large amounts of protein but should increase the amount of carbohydrates you consume. Eat meals such as wholegrain (brown) pasta with lean mince, tomatoes, mushrooms, kidney beans, spinach, peppers and olives to make sure you have enough fuel and nutrients to keep you going.


We understand it’s hard to keep yourself motivated to keep doing the same things. If you’re struggling with the idea of running every day then implement some cross training into your route. Switching running for another high intensity cardio activity such as cycling or using the elliptical trainer isn’t cheating, it will in fact benefit you even more as you will develop different muscles to the ones used in running.


You probably feel like a pro runner by now, as each training session really feels like you are one step closer towards your goal. Stick to your usual running sessions three times a week but now dedicate one day to doing a really long run. To begin with, try and run for 10 miles during your long run and then move it to 12. Most people choose to do this on a Sunday as it takes quite a bit of time and you can have a large portion of roast dinner, with extra potatoes and yorkshire puddings, as a reward.


With two weeks of training to go this is where it really counts. Aim to keep running 4 miles a few times a week and stretch your long run out to 12 miles. Ensure that you have enough recovery time in between your long run and your half marathon, you don’t want to be running on overworked, tired legs.

Now is the time where you should be loading up on carbohydrates to gather enough energy for next week. Aim to still eat plenty of protein but make sure that around 70% of your diet is carbs. Wholegrain pasta, brown rice and potatoes are great sources of energy. Meals such as turkey chili, with brown rice and loads of vegetables will provide you with enough energy without slowing you down.


You’d imagine that the final week of training would be your most challenging yet, but you’re wrong! The final week of training should give your body a chance to rest. While you should still complete your 4 mile runs a few times a week, try not to overdo it - it would be a disaster if you had trained for all this time only to get an injury in the final week.

You should still be eating a high-calorie, protein-rich diet to fuel yourself up for the big day, but avoid red meats as they take longer to digest. A meal such as chicken stir fry, with egg noodles, nuts and plenty of vegetables thrown in is a great choice for a last week dinner idea. If you take only one thing from this today, make sure you eat before you race. Aim to eat a high-carbohydrate breakfast such as peanut butter and banana on wholegrain toast 2-4 hours before you are due to start and drink plenty of water to maintain a good level of hydration.

Hopefully, this advice will be enough to get you through your training. A half marathon does take a huge amount of effort, but it is a fantastic achievement which you definitely won’t regret.