NSM marathon block: how long should the long run be for a sub-3 attempt?
I’ve been running NSM for the past 6 months, averaging around 7 to 8 hours per week and 70 to 80km.
My current half marathon time is 1:26:30 from March 2026, and I’m aiming for a sub-3 marathon in October. Training has been consistent, I still have a few kg to lose, and I’m planning to start the 15-week marathon block in the next 4 weeks.
I also have another half marathon in the next 4 weeks as a progress check. I’ll be targeting sub-1:26, and hopefully closer to or under 1:25.
For context, I’ve previously run a 3:06 marathon, where I went through halfway in 1:28 and then blew up. I’ve also run a couple of 3:2x marathons off the bike in sub-9:30 Ironmans.
Current ST pace is roughly:
- 4:00/km for 3 to 4 minute reps
- 4:05 to 4:10/km for 6 to 7 minute reps
- 4:15 to 4:25/km for 10 to 11 minute reps
- 5:40 to 5:50/km for easy running and long runs
I’ve been looking at the marathon plan in the book, and my main concern is the duration of the long run.
James’ longest run was 2 hours 25 minutes, but that covered 33km. At my current easy/long run pace, I’m covering about 21km in 2 hours. Adding another 25 minutes would only get me to around 25km total.
My concern is that this doesn’t seem long enough to properly prepare for a marathon, especially when aiming for sub-3.
For other sub-3 runners who have used NSM, what did you do in this situation?
Did you:
- keep the long run capped around 2:25?
- extend it closer to 3 hours, which would be around 32km for me?
- increase the pace of the long run, even though that feels counterintuitive?
- do something else entirely?
Curious to hear what has worked for others. I’d like to get this sorted before starting the final marathon block.