Stop Training Like a Miler: Why Marathon Success Needs a Diesel Engine, Not a Ferrari

You’ve seen it on the track, and maybe you’ve even done it yourself. A runner, deep into a marathon block, absolutely burying themselves in a gruelling session of 400m or 800m repeats, flat out, hands on knees, gasping for air. It looks impressive. It feels like hard work. But if you’re training for a half or full marathon, running at paces and intensities more suitable to a 1500m or 3000m runner is a dangerous trap. We all love the feeling of running fast, but in the world of long-distance running, specificity trumps "sexy sessions".

I had a perfect example of this recently. I was working with a talented client who was embarking on a sub-3 hour marathon goal, last year. They came to me with a strong background in middle-distance running, throughout their teens and early 20's and a few weeks into the programme, they reached out with a query: “Why are there no VO2 max intervals in my plan?” The truth? They never made it into the plan. Because of this athlete's background, their speed and speed-endurance were already highly developed. Also they were building towards the marathon. What they desperately needed was to develop their aerobic system massively, not double down on the fast, lung-busting intervals they were already comfortable with.

To run a fast marathon, you don't need to get better at racing at a high percentage of your VO2 max. You need to primarily raise the floor, not the ceiling.

The Science of the Diesel Engine

When you run distances from the half marathon upwards, the demands on your body change completely compared to a 1500m or 5K race. Peer-reviewed exercise physiology clearly tells us that endurance performance is heavily dictated by your fractional utilisation: how high a percentage of your VO2 max you can sustain without crossing your lactate threshold.

Renowned coach Pete Pfitzinger, in his landmark book Advanced Marathoning, hammers home the point that marathon success relies primarily on aerobic capacity and lactate threshold. His plans focus heavily on long runs, medium-long runs, and sustained threshold blocks. VO2 max work is treated purely as the icing on the cake and is used sparingly.

Similarly, Dr Jack Daniels, the mastermind behind the VDOT system, emphasises that while VO2 max intervals (I-pace) may have their place for some, the marathon engine is built on Easy (E-pace) and Threshold (T-pace) running. Spending too much time in the red zone leaves you too fatigued to execute the specific, sustained work that actually moves the needle for marathoners.

The bottom line is this: for the marathon, and to a similar but slightly lesser extent the half marathon, you need to be that diesel engine cruiser, really efficient at close to threshold pace, which unsurprisingly comes at training at those intensities.

The "Speed Gap" vs PUTTING YOURSELF "IN THE BIN"

Does this mean endurance runners should never run fast? Absolutely not. But how we run fast matters. Instead of racking up massive volumes of lactate-inducing track intervals, faster running for the endurance athlete should focus on biomechanical efficiency. Coach and physiologist Steve Magness often talks about developing the "speed gap". This concept involves improving your absolute raw speed (the ceiling) through very short, highly explosive efforts like 8 to 10 second hill sprints or fast strides with full recovery.

By pushing up your absolute max speed without accumulating fatigue, your marathon race pace suddenly represents a much smaller fraction of your maximum output. You become a more efficient, smoother runner, without the crushing fatigue that comes from 6 x 800m at 3K pace.

Leave the Track Spikes to the Milers

If you want to run a great half or full marathon, you have to let go of the idea that a session is only beneficial if it leaves you sprawled on the track. The “sexy” sessions might look great on Strava, but they don't build the specific physiological adaptations you need to thrive at mile 20. They also come with higher relative injury risk.

Embrace the sustained, controlled efforts at or below your lactate threshold. Build the aerobic floor. Work on your pure biomechanical speed through short, sharp strides. But above all, remember what you are actually training for.

Do the right training, for the right distance. Your cruiser diesel engine will thank you on race day.

NEED HELP to build THAT diesel engine?

If you are looking to take your long distance running to the next level, whether that is targeting a new half marathon PB, stepping up to the full marathon, or just maximising your own ability - having the right guidance makes all the difference. I offer 1-to-1 coaching and dedicated marathon mentorship programmes designed around your specific needs, goals, and physiology.

Get in touch today through the website to arrange a no-obligation free chat, and let's talk about how I can get you to that next start line with the rightly developed running engine for your needs.