I previously blogged on a new tool called the acute:chronic workload ratio (ACWR) and its use in helping to reduce injury risk. The basic idea is that keeping your training load in the ‘sweet spot’ over time not ramping up too quickly, but maintaining a fairly steady workload) will reduce your injury risk. Your workload over the previous week is called the ‘acute’ workload, while the average weekly workload over the previous four weeks is the ‘chronic’ workload. Dividing the acute workload by the chronic workload gives you the ACWR. Keep the ACWR in the sweet spot of 0.8 to 1.3, and injury risk the following week will be low. If it rises above 1.5, the injury risk the following week increases 2-4 times! Ideally we want to develop a high chronic load over time.

I received some interesting feedback from local athletes and coaches, but one discussion with running coach Will Rodgers, of Running Lane, led to a question that needed more digging to get an answer: How does this model fit in with tapering?

Tapering is the practice of reducing training before a race to give energy for the main performance. If you Google this term you will see there is much variation in suggested levels of taper and will also see there are some that do not advocate any taper. With such variation, I decided to message the author of the ACWR, Dr. Tim Gabbett, who responded quickly with a very detailed answer. I will give him credit here as I have e-mailed research authors before with very mixed level/quality of response. His answer was that there is little research looking at how workload affects both injury and performance. Most of the research has been on injury or performance. He felt that from an injury standpoint the ACWR did provide some guidance on taper, and that an ACWR of less than 0.50 would yield a significant injury risk. But on the flip side, greater tapers lead to greater performance gains.

The question then becomes: Are we tapering for injury prevention or performance?

How your answer the question, and how you choose to taper, then, will depend on your individual situation and goals:

• Athletes’ first race returning from injury
  • If you have had an injury, have rehabilitated it well, and this is your first race back, then using a taper within the sweet spot of the ACWR is probably wise. That means not tapering more than 20% in any one week.
  • If you look at a novice training program such as one listed on halhigdon.com, their first taper week is actually in the 15-20% range so I think this level of taper is quite conservative.
  • Once you have a couple of races under the belt, and have increased your chronic workload without any adverse issues, you could then consider larger tapers which would give a bigger performance boost.

• Athletes who have been performing pain-free for an extended period (e.g. one year or more):
  • Over this time, if you have been working on a good program of increased mileage, strength training, etc., you will have developed a higher chronic load which will make you more resilient to injury.
  • Therefore, you will likely be safer in trying to do a larger taper to increase performance.
  • A systematic review¹ from 2007 looked at the evidence around tapering and performance. Once all of the papers were considered the optimum taper was thought to be 41-60% over a two week period, with no change to intensity and sessions.

• Elite-level athletes:
  • For elite athletes whose goal is maximum performance at specific events (e.g., the Olympics), the risk/reward balance is tilted in favor of accepting a higher injury risk in order to achieve peak performance for specific, special events. In this case, a more dramatic taper may be selected in order to maximize race-day performance
  • A recent paper² considered the tapering strategies of elite British runners in the marathon, 10k, 5k, 3k, 1500m, 800m. The marathon runners had a median taper of two-weeks, whereas the long-distance runners (5-10k) tapered for 6 days. The marathon runners tapered 47% for continuous running, and 36 for interval running, whereas the long distance runners tapered 29% for continuous running and 33 for interval running. Both the marathon and long distance runners increased the intensity of their interval sessions during the taper. Using the data from all of the elite runners of all the distance they came up with a formula that could be used to predict tapering. I have included the formula along with a practical example in the tab below. BUT! Since this was developed for elite-level athletes, it may not be appropriate to apply the formula to us mere mortals for whom the increased injury risk that comes along with a more agressive taper probably outweighs any potential performance enhancement.

As you can see, there is a balance between the science and the art of tapering, which is why you want to work with a rehab professional and coach who has a grasp of both! On that note, let’s consider one other aspect; how to best train before the taper. Another study³ used mathematical modelling to find that 20% increase in training load in the 28 days prior to taper increased the performance after taper. This suggests that to get the optimal effect of taper, you need an increase in load before. If your training plan plateaus for a few weeks before taper it may make the taper less effective. Another paper⁴ stressed the danger of training too much leading up to the taper. This is called ‘functional over-reach’ and it can negatively affect the optimization of the taper, potentially increasing injury risk.

The relationship between our regular training and taper is important and not fully understood. However, using the science and experience we have, as well as utilizing sensible pain guidelines, we can make finding a better taper strategy less of a guesswork process.

References:

1. Bosquet L, Montpetit J, Arvisais D, Mujika I. Effects of tapering on performance: a meta-analysis. Med Sci Sports Exerc. 2007;39(8):1358-65.
2. Spilsbury KL, Fudge BW, Ingham SA, Faulkner SH, Nimmo MA. Tapering strategies in elite British endurance runners. Eur J Sport Sci. 2015;15(5):367-73.
3. Thomas L, Busso T. A theoretical study of taper characteristics to optimize performance. Med Sci Sports Exerc. 2005;37(9):1615-21.
4. Aubry A, Hausswirth C, Louis J, Coutts AJ, Le meur Y. Functional overreaching: the key to peak performance during the taper?. Med Sci Sports Exerc. 2014;46(9):1769-77.

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