The 10% Rule: Does it hold True?

Running related injuries

Amongst runners it is widely accepted and known that the volume of training for a runner should be increased gradually over time. The aim of increasing a runner’s loads gradually over time being to reduce the risk of overuse running related injuries, while building greater running fitness through the increased training workload.

Overuse injury rates are high for runners with reported annual incidence rates varying between 30 and 79% (1). It has been estimated that 60% of running related injuries can be attributed to training errors, that is getting volume increases or workloads wrong (2). One of the classic culprits of erroneous workloads being the trap that so many runners fall into; doing too much too soon.

The 10% rule

Amongst runners of all levels the ‘10% rule’ for weekly mileage increases is often prescribed by coaches and followed by runners, as a way of trying to gain fitness and reduce the associated injury risk.

The 10% Rule: Does it hold True? Click To Tweet

The ’10% rule’  implies that weekly training load increases should not exceed 10% per week. This is done in the hope that by increasing training gradually (ie by no more than 10% per week) injury risk will be reduced.

Typically runners think of the weekly increases in terms of running volume (miles or kilometres) covered. Following the 10% rule each week the mileage should be increased by 10% of the preceding week’s total mileage/volume.

For example:

• a 30km training week would be followed by a 10% increase of 3kms to make weekly total of a 33km training week.
• This would then be followed by a 36.3km training week, a 3.6km increase on the prior week’s volume.

Does scientific evidence support the 10% rule?

As widely adopted, espoused, and ingrained in run training programs as the 10% rule is, it is interesting to note that there is very little supporting scientific evidence underpinning the 10% rule and its effectiveness in aiding runners to reduce injuries.

Let’s take a closer look at the results of the relatively small amount of research that has been done looking at whether the 10% rule is a useful tool in assisting runners to reduce injury onset, while improving running fitness.

Surprisingly very little research has been performed looking at the merit of the 10% rule for training load increases and injury risk minimisation for runners.

In a study of 486 novice runners, a standard 8 week training program was compared against a 10% graded 13 week training program, for the risk of sustaining a running related injury (1).

Researchers found that there were no differences in injury prevalence between the graded 10% weekly increases training program (21%), and the standard training program (20%) groups.

They further concluded that when preparing for a 4-mile run it does not matter how you get there (either fast or slow) as the risk of sustaining an injury based on their findings appeared to be the same.

While this conclusion could be drawn from the findings of their study which showed no difference between a gradual build with a 10% training program and a standard training program, how you increase your running training loads really does matter. How you increase your running training loads does in fact  influence both the risk and rate of developing a running related injury, as outlined below.

What happens with greater than 10% weekly training load increases?

An example of how training load increases influence injury risk can be highlighted by the work of Nielsen et al (4) who showed that novice runners who had a greater than 30% increases in weekly training volume were more likely to sustain injuries than those who had smaller (22%) increases in training volume. They concluded that in novice runners, some individuals may tolerate weekly progressions around 20-25%, at least for short periods of time.

In team sports Gabbett et al (5) found that when training load increased from <10% per week  to > 15% per week the likelihood of sustaining an injury increased from 7.5% to approximately 21%. This represents a large increase in injury risk. In fact Gabbett et al reported that the likelihood of injury was as high as 38% when the weekly training load increase was 50%.

Instances when the 10% rule is limited in application

There are several instances where using the 10% rule to guide weekly training load increases is limited in application.

These instances are outlined below:

1. When coming back from injury (the injured athlete who cannot absorb 10% weekly increases)

In a recent paper (5) Gabbett outlines the concept of the ‘floor and ceiling’ with regards to an athlete’s physical capacity and their ability to absorb training load increases.

The ‘floor of safety’ represents an athlete’s current training load and their ability to remain uninjured and absorbing the training load.

The ‘ceiling of safety’ represents an athlete’s desired future physical capacity and the associated training loads that both develop this capacity and that can be absorbed with the associated higher training workload.

See the below figure taken from Gabbett’s paper: The training—injury prevention paradox: should athletes be training smarter and harder? To see an illustration of this floor and the ceiling concept:

If you have been injured, for example in a moonboot for six weeks, or you have been unable to train for a period of time (for example 12 weeks), than you will have become deconditioned with a concomitant reduction in your physical capacity, as a result or removing the training load and stimulus.

In essence the athlete’s capacity has fallen below the ‘floor of safety’ into what Gabbett has described as being the ‘basement’, the point where training loads have been below a training load that would confer an injury free state.

To learn more about the concepts of the basement, floor and ceiling of safety tune into a podcast recorded with the paper’s author Dr Tim Gabbett by clicking HERE>> Dr Tim Gabbett: Expert Edition The Physical Performance Show.

So applying the 10% rule to weekly training load increases for the injured athlete may prove to be too much too soon, and may result in subsequent injury (new injury or a return of symptoms associated with the initial injury).

2. When coming back from injury (the injured athlete who can absorb >10% weekly increases)

Conversely and as depicted in the above figure for the same deconditioned returning from injury athlete, applying the 10% rule for weekly training load increases may actually delay the athlete getting back to full capacity by prolonging rehabilitation time frames. In such an instance applying the 10% rule for weekly training load increases may prove to be too conservative of weekly increase. For example the injured athlete may have been able to safely absorb let’s say 15% or even greater weekly increases.

3. When performing with a large training base behind you (the uninjured athlete who cannot absorb >10% weekly increases)

An athlete with high chronic training load will likely tolerate much smaller increases in training load from week to week.

If an athlete is at their relative ceiling of training load than adding 10% weekly increases to already high chronic loads may not be tolerated. Rather the weekly training load increases might need to be more like 0.1% weekly load increases, as even less than 10% may prove to be too large of weekly increase.

4. Any runner’s week to week program increases

One of the major limitations I see with using the 10% rule to guide weekly training load increases is that applying the 10% rule based on weekly volume or ‘mileage’ fails to take into account the ‘internal’ load of the given training.

That is volume is only one part of the loading equation for a runner or athlete. Volume, or distance run is merely the work done-or in science terms the ‘external load’.

The problem with focusing solely on the external load is that it does not take into account the intensity or perception of effort of the given training session or run.

A 5 kilometre run for runner ‘A’ is different in load to a 5 kilometre run for runner ‘B’, who may have less physical capacity and have run the distance at the same intensity as runner ‘A’ and hence exerted themselves more.

The best way to take into account perception of effort and intensity of training loads is to calculate the training session in terms of loading units.

An example of this for runners being to multiply the number of minutes run by the intensity of the session (based on a perception of effort scale whereby 0 = nothing at all and 10 = maximal exertion).

For example a 5km run that took 25 minutes and was rated as an 8/10 for effort by a runner would look like this:

25 x 8= 200 units

Now with these known training units a runner can best manage weekly training loads by using the acute: chronic workload ratio as first defined by Gabett (5).

When using the acute to chronic workload ratio research indicates that scores of 0.8-1.3 represent the ‘safe zone’ of loading with the lowest risk of injury (4-5%). The ratio is a score of a new week of training’s units divided by the average of the preceding four weeks of training loads.

When there exists a sudden ‘spike’ in training loads there exists an increase in the risk of injury. Gabbett found that a ratio greater than 1.3 (but less than 1.75) yielded a 7-10% risk of injury, and a ratio of > 1.75 yielded a 15-20% risk of injury (5).

It should be noted however that not all training load ‘spikes’ should be avoided (3). Some athletes can tolerate acute to chronic workload ratios much greater than 1.5. Such athletes tend to have large chronic training bases, and as a result they can tolerate what Gabbett terms training ‘shock blocks’ (click HERE>> to learn more).

Shock blocks are planned weeks of spiked training loads that are designed to heavily fatigue an athlete and result in super-compensation fitness gains. In these instances the large and chronic training base tends to be protective against injury for the athlete.

Alternately other athletes may get injured with an acute to chronic workload ratio much lower than 1.5. Just because an athlete is at risk of injury does not mean they will develop an injury; as Gabbett outlines (5) ‘risk does not equal rate’.

Summary

The 10% rule of weekly training increases can certainly be used by runner’s as an objective method to track weekly training increases in an attempt to minimise injury risk.

It is in my opinion a far better method of tracking training load changes and increases than ‘flying blind’ with no strategy to increase loads, improve performance, and attempt to manage injury risk.

However it should be noted that the 10% rule actually lacks scientific evidence to support its use as guide to weekly training load increases.

Gabbett concludes that ‘there might be something in the 10% rule but there is not a lot of research around it’ HERE>>.

Hence limiting training load increases to 10% per week is at best a ‘guideline’ rather than a ‘code’ or hard and fast ‘rule’.

Happy running.

Physio With a Finish Line™,

Brad Beer (APAM)

APA Titled Sports & Exercise Physiotherapist (APAM)
B.Physio/ B. Ex. Sc
Author ‘You CAN Run Pain Free!’
Founder POGO Physio
Host The Physical Performance Show

Featured in the Top 50 Physical Therapy Blog

References

1. Buist, I., Bredeweg, S. W., Mechelen, W. van, P., K. A., Pepping, G.-J., & Diercks, R. L. (2008). No Effect of a Graded Training Program on the Number of Running-Related Injuries in Novice Runners: A Randomized Controlled Trial. The American Journal of Sports Medicine, 36(1), 33–39. https://doi.org/10.1177/0363546507307505
2. Hreljac, A. (2005). Etiology, Prevention, and Early Intervention of Overuse Injuries in Runners: a Biomechanical Perspective. Physical Medicine and Rehabilitation Clinics of North America, 16(3), 651–667.doi:10.1016/j.pmr.2005.02.002
3. Gabbett TJ. Debunking the myths about training load, injury and performance: empirical evidence, hot topics and recommendations for practitioners. Br J Sports Med Published Online First: 26 October 2018. doi: 10.1136/bjsports-2018-099784
4. Nielsen RO, Cederholm P, Buist I, Sørensen H, Lind M, Rasmussen S. Can GPS be used to detect deleterious progression in training volume among runners? J Strength Cond Res. 2013 Jun;27(6):1471-8. doi: 10.1519/JSC.0b013e3182711e3c
5. Gabbett TJ. The training—injury prevention paradox: should athletes be training smarter and harder?. Br J Sports Med 2016;50:273-280.