How to Train for Your First Marathon or Half Marathon: A Realistic Guide
Training for your first marathon is equal parts exciting and daunting. When I signed up for my first one, I had no idea what I was getting into. I overtrained, underfuelled, ignored niggles, and arrived at the start line with a dodgy knee and a lot of anxiety. I still finished, but the experience taught me that smart training matters far more than hard training. Here is what I wish someone had told me before I started.
Half Marathon or Marathon: Which Should You Do First?
If you have never raced beyond 10K, start with a half marathon. It is a serious challenge that requires proper training, but the 12 to 16 week build-up is manageable alongside a normal life. A marathon demands 16 to 20 weeks of dedicated training, with long runs that consume your entire Saturday morning. Get a half marathon under your belt first, learn how your body responds to distance training, then decide if the full 26.2 miles is for you.
Choosing a Training Plan
A good half marathon plan runs 12 to 16 weeks with 3 to 4 runs per week. A marathon plan runs 16 to 20 weeks with 4 to 5 runs per week. Most plans follow a similar structure: easy runs during the week, a tempo or interval session midweek, and a long run at the weekend that gradually increases in distance.
For beginners, I recommend plans from Hal Higdon (free online), the Garmin Coach feature (if you have a Garmin watch), or the Nike Run Club app. All three offer structured, progressive plans that adapt to your current fitness. Avoid any plan that has you running hard every day — recovery is where fitness is actually built.
The Runs That Actually Matter
The Long Run
This is the cornerstone of distance training. Your weekly long run teaches your body to burn fat as fuel, strengthens connective tissue, and builds the mental resilience to keep going when your legs want to stop. Build gradually — increase distance by no more than 10% per week, and include a cutback week every 3 to 4 weeks where you reduce volume by 20 to 30%. For a marathon, your longest training run should reach 20 to 22 miles. For a half, 10 to 12 miles is sufficient.
Easy Runs
Most of your running — 80% of your weekly mileage — should be at an easy, conversational pace. This feels counterintuitive when you are training for a race, but easy running builds your aerobic base without accumulating excessive fatigue. If you cannot hold a conversation, you are running too hard. Slow down. Seriously.
One Quality Session Per Week
This could be a tempo run (20 to 40 minutes at a comfortably hard pace), intervals (repeated efforts of 400m to 1600m with recovery), or a progression run (starting easy and finishing at marathon pace). One quality session per week is enough to build speed and lactate threshold without breaking you down.
Common Mistakes That Derail Training
- Running too fast on easy days: This is the number one mistake. Easy runs should feel genuinely easy. Your ego will resist this, but your body will thank you.
- Skipping the taper: The final 2 to 3 weeks before race day should involve a significant reduction in training volume. You are not losing fitness — you are allowing your body to absorb weeks of accumulated training.
- Ignoring niggles: A mild ache that persists for more than a few days deserves attention. Two rest days now prevents two months of injury later.
- Not practising nutrition: If you plan to use gels on race day, use them in training first. Your stomach needs to be trained just like your legs.
- Doing too much too soon: The excitement of a new goal leads to overtraining. Stick to the plan, even when you feel great and want to do more.
Race Day Advice
Nothing new on race day. Wear shoes you have trained in. Eat the breakfast you always eat. Use the gels you have practised with. Start slower than you think you should — the first 5K should feel almost too easy. The race really starts at mile 18 for a marathon and mile 10 for a half, and you need to have energy in reserve for those final miles.
Your first distance race is not about time. It is about finishing, soaking in the atmosphere, and proving to yourself that you can do something you once thought impossible. The PBs come later. For now, just enjoy the journey from training to finish line.
