How to Train for a Half Marathon: A Complete Guide for Sydney Runners

The half marathon — 21.1km — rewards structured preparation. Whether it's your first or you're chasing a personal best, here's what you need to train effectively and arrive at the start line healthy.

How Long Do You Need?

For first-time half marathon runners, 12–16 weeks is appropriate assuming you can already run continuously for 30 minutes. If starting from minimal base, extend to 20 weeks.

The Key Training Principles

The 80/20 rule: Approximately 80% of your running should be at an easy, conversational pace. 20% at moderate to hard effort. Most recreational runners train too hard on easy days and too easy on hard days — this blunts adaptation and increases injury risk.

The 10% rule: Don't increase weekly mileage by more than 10% per week. The most common cause of half marathon training injuries is too much too soon.

One long run per week: The cornerstone of half marathon training. Progressively build your long run from 10km to 17–19km over the training block, run at an easy pace — 60–90 seconds per km slower than goal race pace.

Sample Weekly Structure

• Monday: Rest or easy cross-training
• Tuesday: Easy run 45–60 min
• Wednesday: Interval or tempo session
• Thursday: Easy run 30–45 min
• Friday: Rest or easy cross-training
• Saturday: Long run
• Sunday: Rest or very easy recovery run

Injury Prevention

The most common half marathon training injuries are runner's knee, IT band syndrome, shin splints and plantar fasciitis — most occurring from load errors. If you develop any persistent pain during training, get it assessed early.

Race Week and Taper

Reduce weekly mileage by 30–40% in the final 2 weeks before the race. Some runners feel flat during taper — this is normal and doesn't mean you've lost fitness.

Injury Prevention During Half Marathon Training

Half marathon training is where most runners encounter their first significant overuse injuries. The combination of progressively increasing mileage, unfamiliar long run distances and the psychological pressure of an approaching race date creates conditions where load management mistakes are common and costly. A few prevention principles that are consistently underapplied:

Taper properly. Reducing volume by 20–30% in the 2–3 weeks before race day allows accumulated training fatigue to dissipate while preserving fitness. Many first-time half marathoners either undertaper (arriving at the start line fatigued) or overtaper (losing confidence and fitness). The goal is fresh legs on race day, not maximum training in the final weeks.

Don't trial anything new on race day. New shoes, new nutrition products, new socks and new pace strategies are all best trialled in training, weeks before the event. Race day is not the time to experiment.

Address asymmetries before they become injuries. Hip abductor weakness, ankle stiffness and single-leg stability deficits are all common precursors to half marathon training injuries. A single assessment mid-training can identify these before they become symptomatic.

Race Day Strategies

Pacing is the single most influential factor in half marathon performance for non-elite runners. Starting too fast — a near-universal mistake among first-timers — leads to glycogen depletion and significant slowdown in the second half. Negative splitting (running the second half faster than the first) or even pacing produces the best finishing times and experiences for most amateur runners.

A practical target: start the first 5 km at 10–15 seconds per kilometre slower than your goal pace. This feels conservative in the early stages — that is the point. The restraint in the first half buys the performance in the second.

For runners managing a niggle or recent injury during half marathon training, our sports chiropractic and exercise physiology teams at Elevate Health can assess and manage the complaint while keeping you on track for your race. Book at our Bella Vista or Earlwood clinic — no referral needed.

If you are experiencing injury during your half marathon preparation, our sports chiropractic and exercise physiology teams can assess the load and biomechanical factors contributing. For understanding the most common running injuries, see our article on the 8 most common running injuries. Our guide on why you get injured when you increase running covers the load management principles most relevant to event training.

Frequently Asked Questions

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

Most beginner programmes run 12–16 weeks. Runners with a solid base of 30–40 km per week can typically prepare in 10–12 weeks. The most important variable is not the programme duration but building the base consistently enough to handle the peak training load without injury.

How many kilometres per week should I run when training for a half marathon?

Peak weekly mileage for half marathon training typically ranges from 50–70 km for experienced runners. Beginners can complete a half marathon with a peak of 40–50 km. The rate of mileage increase — not the absolute volume — is the strongest predictor of injury risk. The acute:chronic workload ratio is a useful framework for managing this.

What is the most common half marathon training injury?

IT band syndrome, shin splints and patellofemoral pain are the most common running injuries in half marathon training — typically occurring when weekly mileage increases too rapidly or recovery is insufficient. Most are load-related and preventable with appropriate training progression.

References

1. Nielsen RO, et al. (2014). Training load and injury incidence in competitive marathon runners. International Journal of Sports Physiology and Performance, 9(2), 269–277.
2. Gabbett TJ. (2016). The training-injury prevention paradox. British Journal of Sports Medicine, 50(5), 273–280.
3. Lopes AD, et al. (2012). What are the main running-related musculoskeletal injuries? Sports Medicine, 42(10), 891–905.