Tapering
Evidence: strong
One of the best-quantified practices in the sport: a ~2-3% gain from cutting volume ~40-60% over about two weeks while holding intensity. It costs nothing.
A taper is the planned reduction in training before a race that allows accumulated fatigue to clear while fitness is retained, so that performance rises. It is one of the best-quantified practices in endurance training. A meta-analysis of 27 studies found an optimal taper produces a performance gain of roughly 2 to 3%, with an overall effect size of about 0.59 (Bosquet et al. 2007). That figure is the gain from a well-executed taper under study conditions, so it is a best case rather than a guaranteed return; a poorly judged taper yields less.
The parameters are unusually well defined for a training practice (Bosquet et al. 2007; Mujika 2010):
- Duration around two weeks. This carries the largest effect among the variables studied.
- Reduce volume by roughly 40 to 60%, progressively. Cutting volume is what drives the benefit.
- Maintain intensity. Keeping fast running in the taper matters; reducing it does not help.
- Maintain frequency. Keep running often; cut how much, not how many times.
The mechanism is the practical face of supercompensation: hard training suppresses performance through fatigue, and removing most of the volume while holding intensity lets the underlying fitness surface. A 2 to 3% gain is large in racing terms, on a par with what super-shoes or the best legal supplements offer, and unlike those it costs nothing.
Distinct from the race taper is the in-training deload week, which is widely practised but, unlike tapering, has thin trial support. See deload and rest.
A worked example
A two-week marathon taper
Take a peak week of 100 km. Two weeks out, drop to roughly 70 km; the final week, roughly 50 to 55 km, with the steepest cut in the last few days. Keep the weekly quality session, but shorter: a few race-pace kilometres rather than a long threshold block. Keep running most days, just less each day. The legs feel fresher and slightly restless by race day; resist the urge to add a hard “confidence” session, which only adds fatigue.
The numbers follow the evidence above: volume down by about 40 to 60%, intensity and frequency held. The most common taper mistakes are cutting too little, so fatigue never clears, or cutting intensity as well as volume, which lets fitness slip just when it should be surfacing.