5K Running : Does it hurt to run the day before a 5k race

A question that a lot of casual parkrunners are asking is “Does it hurt to run (or more properly ‘train’)  the day before a 5k?”

The simple answer is “YES IT DOES HURT” and you will hear advice from people to the contrary but they are pretty much wrong.

But it is a bit more complicated than a simple yes/no.

First of all if you are asking that question then you CANNOT BE A SERIOUS ATHLETE who follows high-level training plans and maybe who is also coached. Because you must surely already know the answer and how it applies to your personal physiology.

Many training plans WILL have you doing some very light exercise the day before a 5k race but they do not apply to most of us and are really about detailed fine tuning to make small differences for most casual athletes around vasodilation and plasma volumes. Like much of the advice on the net, that you read, it can often be based on deep sports science but the derived benefit may apply to marginal gains for elite athletes.

So let’s turn the question around. If you run tomorrow then when will you get the NET exercise benefit? Well the answer to that is in about 10 days to 2 weeks time (based on increased fitness LESS increased fatigue). So it follows that running the day before a 5k race will not help make you fitter for the following day. It can’t help. It might NOT HURT TOO MUCH but IT MIGHT HURT (if too quick). It’s not worth the risk.

Taking it to the extreme. If you did a VO2 session the day before a race I reckon you would be many tens of seconds off your 5k PB the next day.

Some would even say that you should be careful with any exercise the day before; for example I would not even do stretching the day before – full adaptation will probably not have taken place in 24 hours.

Temper the information in that previous paragraph, however, with your ‘freshness’. Exercise in the 10 days to 2 weeks prior to your race (taper) is designed to keep you ‘race ready’.  So by exercising LESS you WILL PROBABLY BE getting less fit BUT you are benefitting OVERALL because your FATIGUE is falling off MUCH MORE quickly. This is tapering.

Tapering is quite tricky to do perfectly, for most of us it’s just easier to avoid running the day before a 5K RACE (remember this is the5krunner.com NOT themarathonrunner.com and NOT the 100m-sprinter.com)

But then again if you are running a 5k but not bothered about a PB or anything like that then sure DO GO FOR A RUN the day before. But here you are just doing a race as part of training. The 5k you are doing IS NOT A RACE (either against the clock or someone else).

So if you, as a casual parkrunner, are racing tomorrow then DO NOT RUN TODAY. At all. I would even extend that to 2 or 3 OR EVEN 4 days before a ‘proper’ race (after an extended training period where I’m heading for a PB). My example is me today. I just did my 5k. I’m a ‘good’ runner and not an elite runner. I got a PB but it was just a course PB and 20 seconds off what I could have done on a good day on that course and the conditions were perfect today. Today is Saturday and I last ran on Tuesday but had a pretty serious 20 minute bike ride (personal TT) on Wednesday. So I had not properly recovered and it probably made around about 1% difference to my time. You have to DO A LOT OF TRAINING to improve by 1% but to knock 1% off your PB maybe all you have to do is not run for 2-3 days. Think about it. Run smart.

The same applies if you are a youngster. You still need that day off before going for a PB. The older you get the more recovery you need.

As I’ve already alluded to, a ‘proper’ pre-race taper (ie reduced exercise) will last about 2 weeks. But it’s hard to do that if you are doing lots of ‘races’ where you are trying to combine PBs with getting stronger. Also a ‘proper’ taper WILL have you doing SOME exercise leading up to the days before a race and this exercise MAINTAINS your fitness (week stops it falling too much) as your fatigue levels also fall.

If you want to look some more into this then google the terms: ‘adaptation’ and ‘compensation’. Here’s a diagram that probably won’t help at all ! But it does show that there CAN BE a negative effect the day after RELATIVELY HARD training. You will find many similar diagrams on the net.

Super Compensation
Super Compensation

This one is probably a bit clearer regarding recovery:


There are a few forums that link to this post and dispute what I am saying.  Fine!! Keep training hard the day before a race then 🙂 I’m just trying to help ! You could also look at tapering on brianmac.co.uk (if you still don’t believe me, he is referred to by British Cycling…errr they’re quite good right?) or elsewhere on this site.  You will also hear advice from people like the very well respected and quoted coach, Hal Higdon, who recommend 4 days rest before a 5K race.

Still think I’m wrong?

Good luck. Run smart.

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4 thoughts on “5K Running : Does it hurt to run the day before a 5k race

  1. Totally wrong and incorrect. I run a lot of races, and have over 35 years, now at 50, I train and race. Now, the day before a race, it is important to “blow out the pipes” -to run and easy slow 50 mins! If you run 30 mins, it can be pointless, and is not enough to dilate the vessels, you are better off just not running at all, rest up. When I do nothing rest up, it is the same as running 2-35 mins day before no change in results, how I feel, recovery, etc. Over 15 years of doing it this way now, a trick is to do the 50 minute run, easy, day before the race, early enough in the day mind you, and the pipes (vessels) are blown up, and you’re ready to rock the next day-I feel real strong out of the gate, and really ready at the beginning, it is a real advantage over the other runners, and when I pass good runners, I feel bad, cause I’m so ready with that run the day before. So, if race is Saturday, I take off the Thursday before! and run the 50 minute run the day before [much data on this distance the day before, and many elites do this].

    1. vaso dilation?

      there is no one correct taper for everyone apparently. there are a few taper variants. you sound like a friend of mine and how they react to day-before exercise. My preferred method is also to do a super easy run the day before with one minute at about 10% slower than race pace and, like you, I would totally rest the day before that.
      For less experienced runners there IS a much greater risk of over-cooking it the day before and then that can have quite a big negative impact vs the slight positive impact that doing it properly might have had.

  2. You may or may not be correct. However the way you communicate your message makes you an asshole.

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