Many endurance athletes understand they should taper before races to give themselves adequate rest, but few understand why tapering is important and what happens to the body during this period.
Tapering was first recognised in the 1970s as having physiological benefit, and research has continued to offer further knowledge into why performance tends to improve if done properly.
# greater availability of glycogen (energy source)
# greater density of red blood cells
# more blood plasma
# higher enzyme activity
# improved neuromuscular co-ordination
# higher levels of norepinephrine (boosting heart rate, force of muscle contraction and enhanced mental awareness)
If you're a high-volume endurance athlete, your tapering phase should show gradual volume reduction over a three-four week period in terms of mileage, and letting quality work steadily comprise a higher fraction of the distance which remains.
Tapering shouldn't just be reserved for races, but incorporated on a monthly basis to your training plan. If you taper for the last five to seven days of each month, you'll find you'll make substantial gains in performance.
Smyth, B. and Lawlor, A. (2021). Longer Disciplined Tapers Improve Marathon Performance for Recreational Runners. Front. Sports. Act. Living. 3: 735220