REF-784 · Muñoz et al., 2014 · International Journal of Sports Physiology and Performance, Vol. · Paper · PubMed
Training-Intensity Distribution During an Ironman Season: Relationship With Competition Performance
Nine triathletes followed the same periodised programme for 18 weeks toward the same Ironman, with training controlled by heart rate in three zones set from gas-exchange (run, bike) and lactate (swim) thresholds. Most training time was in zone 1 (68%), while the race itself was mostly ridden and run in zone 2 (59%). More total training time and more zone-1 time went with faster race times, and a larger share of training in zone 2 went strongly with slower race times.
Participants
n=9 triathletes (abstract: "Nine triathletes") who completed the same programme aiming at the same Ironman event. Age, sex, training history and finish times are not given in the abstract.
Protocol
One periodisation model for all athletes, 18 wk, training controlled by heart rate in every session.
Thresholds: ramp tests in running and cycling with gas-exchange analysis for the aerobic (AeT) and anaerobic threshold (AnT); a graded lactate test in swimming.
Three zones: zone 1 below AeT (low), zone 2 between AeT and AnT (moderate), zone 3 above AnT (high).
Training and the race were both quantified as cumulative time in each zone and correlated with race performance time.
Key Results
| Measure | Value |
|---|---|
| Training time in zone 1 | 68% ± 14% |
| Race time in zone 2 | 59% ± 22% |
| Total training time vs race time | r = -.69 (more training, faster) |
| Zone-1 training time vs race time | r = -.92 (more zone 1, faster) |
| Total zone-2 training time vs race time | r = .53 (more zone 2, slower) |
| % of training time in zone 2 vs race time | r = .94 (bigger zone-2 share, slower) |
The authors conclude that athletes race mainly in zone 2 but perform better with more training in zone 1, and that a high amount of cycling training in zone 2 may contribute to poorer overall performance. The abstract gives no sport-by-sport numbers, so the cycling-specific part of that conclusion cannot be checked here.
Practical Application
In nine triathletes monitored through an 18-week Ironman build, the ones who trained more in total and more below the aerobic threshold raced faster (r = -.69 and -.92 with race time), and a larger share of training between the thresholds went with a slower race (r = .94) — even though the race itself was spent mostly in that middle zone (59%). Training at Ironman race intensity is not the way to get fast at it: keep most of the hours easy, below the first threshold, and do not let the week drift into the middle zone.
Race intensity is a zone-2 effort by heart rate for these athletes; being able to hold it comes, on this evidence, from easy volume, not from rehearsing it every day.
Inference, not tested here: total hours and zone-1 hours rise together in a programme like this, so the two correlations cannot be separated — part of the "zone 1" effect may simply be volume.
Inference, not tested here: for a half-distance race the same logic is plausible but it is an interpolation between this Ironman evidence and short-course data, and should be labelled as such.
Limitations
n=9, one programme, one race: correlations with very small n are unstable, and with a shared programme the spread in distribution between athletes was limited.
Observational: no athlete was assigned a distribution, so cause cannot be inferred.
Zones by heart rate, which drifts over long sessions; time in zone by heart rate is not the same as time in zone by power or pace.
The abstract gives no per-sport breakdown, no finish times and no athlete characteristics.
Written from the abstract and record metadata only (full text not read).
How this entry was checked and changed
Why this level
observational, n=9, correlations only