3 Signs It’s Time for an Endurance Athlete to Rest

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By Jason Koop,
Head Coach of CTS Ultrarunning

Open up any training program from any running publication and you will inevitably see the following training structure:

3 weeks ‘on’

1 week ‘off’

In normal training nomenclature this means you train hard for three weeks, take one week easy, and then repeat that cycle. Did you ever stop to think why this structure emerged in the first place? The roots of this training philosophy emerged more from convenience (4 weeks is about a month) and tradition than from physiology. Despite the lack of logic, static training programs abound with this even and cyclical flow of hard and easy weeks.

It does not have to be this way. Training cycles do not have to fit the 3 weeks on, 1 week of paradigm regardless of athlete, time of year or training focus. Rather than the calendar driving when to go hard and when to go easy, it makes more sense for your training to dictate the hard to easy workflow. The latter choice, while more difficult to execute, will result in maximizing your effort and time so that you push when you can, rest when you can’t and reap more rewards along the way.

I’ve developed a 3-point checklist I work through with every athlete when determining when to apply rest. It’s based on physiology, practice and, if available, wearable devices that can track things like sleep and Heart Rate Variability.

Training means your performance will deteriorate before you get better

To start out with, we all need to understand that fundamentally, training makes your performance deteriorate in the short term (days and weeks) before you get better in the long term (weeks and months). You have to train hard enough such that your body says ‘dang, this is hard. I better build up some more physiological stuff if I want to keep doing this and not die’. Without a difficult enough training stress and then the requisite recovery, you won’t improve.  You have to have both, not simply one or the other.

In this sense, training can look like a good stock market chart with ‘improvement’ on the Y axis and time on the X axis. The general trend over long periods of time will be upwards, but it is certainly not trending up every single week.

The take home message here is that you can’t set PRs every week. If you are, congratulations! You are either new to the sport and/or your training is too easy and will stagnate at some point.  Even if you have a moderate amount of training background, you should fully expect your performance in some way to get moderately worse before you apply rest and you see further improvements.

Performance declines

Your first and most powerful indicator that you need rest is when your daily performance starts to decline past a certain threshold. If you are doing regular intervals and harder runs, you will have some basis of performance to benchmark week to week. By comparing the Normalized Graded Pace or Graded Average Pace for the intervals of your weekly hard runs, you can see if they are getting better, worse or staying the same. When your performance drops off by 3-8% on more than two out of the last three workouts, it’s time to give yourself a rest phase.

Any performance drop of less than 3% is within normal day to day variation. I would not even consider those a drop in performance, just noise in the measurement, so you can continue to train. Similarly, any one day where your performance drops by 3-8% should be anticipated and I would not think twice about continuing to train.

But, stack two out of three workouts in a row where you can see a marked decline in performance and that is good an indicator that you have enough cumulative fatigue to warrant a rest phase. It’s the sweet spot between enough stress that your body will adapt and not so much that it will take an undue time to recover.

When you feel worse for 3 days in a row

Similar to how you can measure performance decline to indicate when you need to rest, you can also use how you feel day to day as an indicator of overall fatigue. Simply put, if you feel progressively worse for three days in a row while running, it’s time to take some recovery. And, just like one difficult training day should not take you off of your training too much, one day where you feel worse than you did before should not deter you either.

So how bad do you have to feel to warrant it a ‘worse’ day? Unlike hard workouts where you will have consistent and quantifiable benchmarks to compare against, feeling ‘worse’ for three days is a row is going to be subjective. If you are tracking your Rate of Perceived Exertion (which you should), this could mean that it is a point or two higher for a normal EnduranceRun effort. Or, you can scroll back through your training comments (which you should also be keeping track of) and look for how you described each workout. If your comments indicate that you are ‘sluggish’, ‘flat’ or any similar vocabulary, these are merely written descriptors that you are feeling run down. In any case, don’t try to find hard and fast metrics. If you simply feel worse during your runs for a few days in a row, that’s enough of an indicator that you can bring some needed recovery into the mix.

When the training phase gets long

In absence of measurable performance declines or simply feeling bad, you still should take a recovery phase every so often. But, if your training is on fire and you feel good day in and day out and you keep seeing improvements week to week, is there even a need to apply some recovery? The answer is yes.

It might be tempting to keep extending training phases in the absence of feeling fatigued or seeing a performance decline. But, even in these circumstances, a rest phase reset should occur every so often. While there is no exact science as to when to cap off a training block, particularly when everything seems to be going swimmingly, I will still only let training phases run on for 6 weeks at a time, at the very maximum, before applying rest. The 6-week maximum timeframe is based a bit on experience as well as science.  When researchers look at the time it takes for training to make an impact on performance, the general timeframe is 4 to 6 weeks. Meaning, when you do a hard workout or series of hard workouts, it takes your body 4-6 weeks for that work to manifest into some meaningful improvement in performance and/or physiology. So, incorporating rest near the end of this timeframe allows you to take advantage of your body’s natural build and break down processes.

What about monitoring Heart Rate Variability, Resting Heart Rate and Sleep Cycles?

More recently, various tools that measure physiological and lifestyle variables have become popular among athletes trying to gain an edge on their performance. Wearable technology like the Whoop strap and Oura ring have emerged with a promise to tell when you are fatigued, if your sleep is compromised, when you should take a nap and even when you might be getting Coronavirus. I have seen and used these tools for decades, dating all the way back to taking a waking pulse with my fingers, no hardware and algorithms required.

While any of these new devices can add value to the training process, it’s important to keep context in mind and not let the data tail wag the performance dog. Performance, or lack thereof, will still be your best indicator of when to apply rest. Information from wearables adds detail to the picture. They should ever so slightly nudge you to ‘yes’ I need to rest, not drive the process.

Don’t be afraid to rest early

Finally, realize that this workflow is reliant on subjective measures and judgment calls (‘how do you feel?’, etc.).  You are not going to get a perfect answer and sometimes you will slightly over or underestimate how long you can continue to train without rest. If you are starting to slice that hair too thin, it’s best to err on the side of rest. Your body can only handle so much stress over long periods of time. So, if you slightly undershoot the length of the current training phase you are going to give your body the ability to extend the next one. It will all come out in the wash as long as you are being reasonable phase to phase, working hard when you can and backing off when you reach one of the three thresholds described above.


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