Sub 2:25 Marathon Alternator

Workout - Sub 2:25 Marathon Alternator

• 10min @ 6'00''/km
• 10 lots of:
  • 1.0km @ 3'13''/km
  • 1.0km @ 3'35''/km
• 10min @ 6'00''/km

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This covers the essentials of “MY FAVOURITE MARATHON SESSION: TRAINING FOR A SUB 2:25 MARATHON” from The Welsh Runner. We’ve broken down the main ideas so you can run this session. For the complete picture, see the full video.

Key points

• The session alternates between fast and easy kilometers. You push at half-marathon pace, then recover at something just under marathon pace.
• Your average pace across the entire run should hit your target marathon pace (say, 5:30 mi or 8:52 km).
• Fast segments come in at roughly 5:10 mi (3:13 km). Easy segments at about 5:43–5:50 mi (3:33–3:35 km).
• The main block is about 21 km (roughly 13 mi) of alternations. You do a 5 km warm-up first, then easy running until you reach 18–20 mi total.
• No need to fuel during the run. The fast surges build up lactate, then the easier stretches clear it.

Workout example

1. 5 km easy warm-up.
2. Repeat for ~21 km (roughly 13 mi):
   • Fast km at half-marathon pace (~5:10/mi or 3:13/km).
   • Easy km at ~5:45–5:50/mi (≈3:33–3:35/km).
3. Cool-down: continue at an easy pace until total distance reaches 18–20 mi (29–32 km).

Adjust the reps or total mileage to where you are in training. Use the Pacing app to dial this in.

Try this run this week. Use the Pacing app to track your splits and adjust the paces for your own goal.

References

• MY FAVOURITE MARATHON SESSION: TRAINING FOR A SUB 2:25 MARATHON - YouTube (YouTube Video)