The art of extrapolation: defining a consistent time goal

Covering 21.0975 km, the half-marathon is a flagship distance. An exciting active endurance challenge that requires surgical pacing precision. To succeed, defining your time goal shouldn't be left to chance; it must rely on reliable physiological indicators (MAS, race history, endurance index).

• The time-reserve trap: Many runners make the mistake of starting faster than their target pace, thinking they are building up a 'time cushion' for the end of the race. Physiologically, this strategy is suicidal: the lactic acid produced by this early over-exertion will catch up with you after the 15th kilometre. Absolute consistency (even pacing), or even a slight negative split (running the second half faster), remains the absolute key to personal bests.

• Safety prerequisite: Although the half-marathon is an ideal transitional distance, our coaches recommend that you can run continuously for at least 1 hour without stopping before starting a specific training plan.

Three reliable methods to estimate your finish time

1. Estimation based on MAS (Maximal Aerobic Speed)

As a general rule, a trained runner with a good endurance index is able to maintain between 80% and 85% of their MAS over a half-marathon. This percentage varies depending on weekly training volume: a runner less accustomed to long distances will likely hover around 75% to 78% of their MAS on race day.

2. Projection from a reference time (The 2.2 method)

If you have a recent 10 km time, multiply your time (in minutes) by a coefficient of 2.2 to estimate your theoretical half-marathon performance. Example: for a reference of 50 minutes over 10 km, the calculation gives 50 x 2.2 = 110 minutes, representing a target goal of 1h 50m. This coefficient can be refined based on your profile: it drops to 2.1 for endurance runners, and rises to 2.3 for beginners.

3. The limiting factor: the endurance index

While MAS indicates your engine's raw power, the endurance index determines your fuel tank's capacity. Two runners with the exact same MAS of 16 km/h can achieve very different times (for example, 1h 38m vs 1h 47m) depending on their ability to sustain a high percentage of this MAS over time. It is this specific parameter that the KIPRUN PACER app develops through specific pace training blocks.

Target Pace & Split Times Chart (AS21)

To lock into the right rhythm from the first kilometre and avoid an over-fast start, memorise your intermediate split times:

• 1h 30m Goal (Sub-1h30): Pace of 14.1 km/h (4'15 min/km). Key splits: 5 km in 21'15 | 10 km in 42'30 | 15 km in 1h 03'45.

• 1h 40m Goal (Sub-1h40): Pace of 12.7 km/h (4'44 min/km). Key splits: 5 km in 23'40 | 10 km in 47'20 | 15 km in 1h 11'00.

• 1h 50m Goal (Sub-1h50): Pace of 11.5 km/h (5'13 min/km). Key splits: 5 km in 26'05 | 10 km in 52'10 | 15 km in 1h 18'15.

• 2h 00m Goal (Sub-2h00): Pace of 10.5 km/h (5'41 min/km). Key splits: 5 km in 28'25 | 10 km in 56'50 | 15 km in 1h 25'15.