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Is marathon training harder than Ironman training? Study says: Yes

"In spite of Ironman athletes' superior training time and total or weekly training load... the preparation of a 42K showed to be harder" says Spanish scientists after completing comprehensive research

Lisa Bentley wins the 2008 Ironman Canada.

Sure, Ironman triathletes train a whole lot more than runners training for a marathon (or for an ultra, for that matter). But do they actually train harder–or dare we say, smarter–than a runner preparing for a mere 42.2K run?

RELATED: Triathlete goes sub-2:40 to break course marathon record at Ironman Championships

According to a new study conducted in Spain with experienced runners and Ironman triathletes, no, they don’t. Training for a marathon is actually much harder, even though the Ironman includes a full marathon along with a 3.8-kilometre swim and 180 bike ride.

Although only 30 athletes were involved–15 marathon runners (we’ll refer to them as “42K” below) and 15 Ironman triathletes (let’s call these subjects “IM”)–the study used a meticulous design. The athletes were matched for age, weight, height, fitness (VO2max), training experience and even race performances (as a percentage of the winning time). Exercise tests were performed to determine and set training zones before participants began a dedicated training program.

Participants were then followed for 16 weeks leading up to their goal race and their activities were measured and quantified. In order to assess the relative training load for all athletes, researchers used a metric called the Objective Load Scale (or “ECO,” the acronym for the term in Spanish), which gives a score based on the type, duration and intensity of any given activity. This allows different types of activities to be objectively measured and compared.


Not surprisingly, the Ironman athletes trained significantly more than marathoners when it came to total training time (206.7 hours for IM vs. 84.3 for 42K), weekly training time (12.9 hours per week for IM vs. 5.2 for 42K), total training load (13,347.1 ECO for IM vs. 8,416.1ECOs for 42K) and weekly training load (834.1 ECOs for IM vs. 526 for 42K).

However, when ratios were used to compare how that time and training was actually spent in relation to that measured during competition (11:45 for IM vs. 3:06 for 42K), the marathoners came out on top.

Training load per training hour was significantly higher for marathoners (99.3 ECOs for 42K vs. 65.8 for IM). This translates to about 1.5 ECOs in 42K training vs. 1 ECO per minute for IM. Additionally, the average weekly training load per every minute spent in competition was significantly higher for 42K (2.9 vs. 1.2), as well as the training time invested per every minute in competition (1.7 vs. 1.1, 42K vs. IM). Basically, this means that marathoners invest a greater proportion of both time and training load, relative to the time spent competing. Said another way, triathletes don’t spend as much time training or train as hard given the demands of their event.

Equally interesting were some of the insights garnered about how the athletes trained. For simplicity, all the athletes in the study trained in three zones: above (i.e. slower than) lactate threshold; below (i.e. faster than) threshold or somewhere in between. This can conveniently be simplified to easy, hard and medium training.

Findings showed that there was no difference between the triathletes and the runners in terms of the percentage of time or the percentage of training load spent above threshold (i.e. easy). Differences, however, emerged regarding the percentage of time and of training load spent in the medium and hard zones. Notably, triathletes spent more time in the medium zone while runners spent more time in the hard zone. This supports the long-standing coaching wisdom that hard days need to be hard and easy days, easy; rather than wasting time in the middle.

The findings also showed that those who spent the most time training in the easy zone performed better while the opposite was true when training in the medium zone. In runners, but not triathletes, the more time training in the hard zone predicted better performance.