This 10K workout is a great indicator of marathon fitness

Marathon training is a long grind. It’s weeks of high mileage, strange workouts and plenty of sessions that might feel more about survival than progress. Some workouts move the needle, while others just maintain your aerobic fitness. When you are two to four weeks out, workouts should stop building fitness and start testing it. This 10K session does exactly that, putting both your speed and endurance under the microscope on tired legs.

Servus Calgary Marathon. Photo: Angela Burger
The workout

15–20 minutes easy warm-up + activation
5K at threshold effort
5 minutes very easy jog (a perfect time to practice race-day fuelling)
5K at goal marathon pace
15–20 minutes easy cool-down

This workout is effective because it simulates the reality of a marathon, requiring runners to run efficiently, despite already being fatigued. The opening 5K should be run at roughly your 10K race pace (your lactate threshold), or the fastest effort you can sustain without accumulating excessive fatigue. It should feel controlled but uncomfortable in the fourth or final kilometre.

For example, if your marathon goal is sub-3:30, you’re looking at roughly a 22-minute 5K at threshold pace, followed by a 24-minute 5K at marathon pace. That transition, from hard effort into a controlled marathon effort, is where the real test lies.

If you can hit the workout smoothly and feel in control throughout, it’s a strong indicator that your marathon (or half-marathon) goal is realistic. It should build confidence and reinforce your race-day plan. If you struggle to hold pace or fade on the second rep, that information is just as valuable. It may be a sign to adjust expectations, fine-tune pacing, and revisit your race strategy.

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