Tapering works mainly through an exponential volume reduction with intensity maintained, and shorter, disciplined tapers (roughly 1-3 weeks) outperform longer or less disciplined ones — though almost none of this evidence is triathlon-specific
Interpretation
Bosquet et al.'s meta-analysis of 27 studies found a 2-week taper produced a moderate improvement (ES 0.59), with the best results from an exponential (not linear) 41-60% volume cut while maintaining both intensity and frequency. Wang et al.'s more recent meta-analysis found the 8-14 day window outperformed both shorter and longer tapers, in a sample that — importantly — contained no triathletes at all. Smyth and Lawlor's large observational dataset of 158,117 marathoners found a strict 3-week taper saved a median of 2.6% versus a relaxed 1-week taper, with a larger benefit for women specifically, while a 4-week taper showed no significant benefit over shorter ones.
Practical implication
Recommend an exponential volume reduction (not a linear one) with maintained intensity, in the roughly 1-3 week range, while being explicit that essentially none of the underlying taper research was conducted in Ironman or long-course triathletes — it's extrapolated from single-sport endurance research.
Sources
3 sources, independently verified.
A 2-week taper produced a moderate performance improvement (effect size 0.59±0.33); the best-performing taper design cut volume by 41-60% using an exponential (not linear) reduction (ES 0.72±0.36), while keeping both training intensity (ES 0.33±0.14) and frequency (ES 0.35±0.17) largely maintained — all differences significant at p<0.001. The core evidence for 'cut volume hard, keep intensity' tapering.
An 8-14 day taper produced the largest performance improvement (SMD -1.47) of any duration tested, clearly ahead of 15-21 days and ≥22 days; maintained intensity (SMD -0.55) and maintained frequency (SMD -0.53) both helped, while reduced intensity or frequency did not reach significance. Important caveat flagged in the TriForward article: no triathletes were in this sample, so direct application to Ironman tapering is an extrapolation.
A strict 3-week taper was associated with a median time saving of 5min 32s (2.6%) over a relaxed 1-week taper, though only 64% of runners in the dataset actually used a disciplined 2-3 week taper. Women showed a larger benefit from tapers of 3 weeks or less (strict 3-week 3.19% vs 2.38% for men); the benefit of a 4-week taper was not significant for either sex. A large observational dataset, not a controlled trial.