Preparing for a 10K or a Half Marathon
Introduction
Running five kilometres and running twenty-one are different problems. The first is solved almost purely with consistency; the second demands structure, because the volume required is enough to injure you if you accumulate it badly.
The good news is that the structure is simple and fits into three session types.
Most people's limiter isn't fitness. It's the rate at which they increased volume.
Starting point and timelines
For a 10K: you need to be able to run about 5 km comfortably. From there, eight to ten weeks.
For a half marathon: you need to be able to run 8 to 10 km comfortably and to have been running regularly for some months. From there, twelve to sixteen weeks.
If you don't meet the starting point, the plan isn't "train harder": it's spending a few weeks building that base first. Skipping that step is the most common cause of injury in new runners.
The three sessions that matter
With three or four running days, everything organizes into three types:
1. The long run. The central session. Run at a comfortable pace — conversation possible — and lengthen it progressively. For a 10K, up to 12-14 km; for a half, up to 16-18 km. You don't need to run the full 21 in training.
2. The threshold session. Blocks at a sustainable but uncomfortable pace, where you can only manage short sentences. For example, 3 blocks of 8 minutes with 2 minutes of easy jogging between. It's the session that most improves the pace you can hold.
3. Intervals. Shorter, faster sets: 5 to 8 repetitions of 3 hard minutes with full recovery. They raise the ceiling.
The rest of the days, if you run, are easy miles: the boring part that builds the base.
Weekly structure
Three days (minimum viable):
- Day 1: easy run or intervals, alternating weeks.
- Day 2: threshold session.
- Day 3: long run.
Four days:
- Day 1: easy run.
- Day 2: threshold.
- Day 3: easy run.
- Day 4: long run.
Intervals come in every other week, or replace the threshold session in the final phase.
Increasing volume without getting injured
This is the part that decides whether you reach the race.
Increase gradually. The 10 % weekly rule is a useful heuristic, though its support is weaker than usually presented; what matters is the principle, not the exact number: sharp increases are the best predictor of overuse injury in runners.
Every three or four weeks, back off. A week with 25-30 % less volume lets the body absorb.
Lengthen the long run slowly. One or two kilometres per week, not five.
Count time, not just distance. If you run slowly, the same distance is more minutes of impact.
Strength doesn't compete, it helps
This is what most people omit and where the evidence is strongest.
Strength training improves running economy — you use less oxygen at the same pace — and is associated with better performance in distance runners, without needing to gain muscle mass.
Two weekly sessions suffice: squat or leg press, hip hinge, single-leg work, calves and core. Moderate to heavy loads, few reps. Do them on different days from hard running sessions, or the same day but afterward.
Race day
Pace. The classic error is starting too fast. The first kilometres feel easy and that feeling deceives. Go out at goal pace or slightly below.
Nothing new on race day. Not shoes, not breakfast, not a gel you haven't tested in training.
Fuelling. For a 10K you don't need to eat during the race. For a half lasting more than 75-90 minutes, taking carbohydrate during the run — gels or sports drink — is worthwhile, and you should have practised it in long runs.
Hydration. Drinking to thirst is a reasonable guide for these distances in temperate weather.
Common mistakes
Running every day at the same pace. Neither easy nor hard: the pattern that tires most and improves least.
Skipping the long run. It's the least replaceable session.
Increasing volume and adding intervals in the same week. Two increases at once.
Ignoring niggles. Shin, knee or Achilles pain that appears and recurs isn't run through: you adjust volume and get it checked if it persists.
Breaking in new shoes near race day. Any change of footwear needs weeks of adaptation.
Before you start
If you're over 40 and have been inactive for a long time, have cardiovascular risk factors, chest pain on exertion or a diagnosed condition, get a medical check before starting a plan at this volume. And if chest pain, dizziness or disproportionate breathlessness appear during training, stop and seek care.
Conclusion
A 10K or a half is prepared with three session types — long, threshold and intervals — plenty of easy miles, two strength sessions, and a prudent volume progression. What usually fails isn't the plan: it's the speed at which volume rises.
Before writing your plan, establish two numbers: how many kilometres you run per week today and what your current long run is. The whole plan follows from there, rising a little each week and backing off every fourth. If you don't know those two numbers, measuring them is your first job.
References
- Blagrove, R. C., Howatson, G., & Hayes, P. R. (2018). Effects of strength training on the physiological determinants of middle- and long-distance running performance: A systematic review. Sports Medicine, 48(5).
- Balsalobre-Fernández, C., Santos-Concejero, J., & Grivas, G. V. (2016). Effects of strength training on running economy in highly trained runners: A systematic review and meta-analysis. Journal of Strength and Conditioning Research, 30(8).
- Damsted, C., et al. (2018). Is there evidence for an association between changes in training load and running-related injuries? A systematic review. International Journal of Sports Physical Therapy, 13(6).
- Jeukendrup, A. E. (2014). A step towards personalized sports nutrition: Carbohydrate intake during exercise. Sports Medicine, 44(S1).
- Nielsen, R. O., et al. (2012). Training errors and running related injuries: A systematic review. International Journal of Sports Physical Therapy, 7(1).