Sudden loss of endurance / distance

Hi all,

Bit of a long post but just giving all the details, would be interested to hear any peoples thoughts on what is happening here.

I have been running for around a year and have slowly increased my stamina and distance over that time. I only run on a treadmill in the gym, and always run at a 12kmh. 2 weeks ago I was at the point where I the maximum distance I could run was 20k in 1 hour 40 minutes. I would do this distance once a week and on 2 or 3 other days a week would just run 10km or 12km or do some interval training and sprints

I was at the point where I could happily run 10km in 50 minutes without really breaking a sweat, and by the end my heart rate would be around 155bpm. Usually the first 30 minutes or so my heart rate rises to around 145bpm right away and then sits there.

However the last week, I have tried to run 3 times and each time within 10 minutes my heart rate is in the 150's and by 30 minutes is in the 160's and by the time I get to 9km I am absolutely done for, have not been able to even reach 10km, let alone any further.

My resting heart rate is between 39-42bpm. I have always had low blood pressure, usually around 110/70, though this week I have had it taken twice (at the doctors) and it has been 96/62 which although low, they say that is fine.

I have not changed my diet or my routine in anyway. I am generally very fit and over the last year have reduced my weight from 190lbs to 150lbs which I have been for a couple of months. I recently had a full 360 health assessment through my job now which gave me a clean bill of health and stated I was very fit, and had a body fat % of around 11%.

I have had a search around the net for information regarding why this might be but have got no where, so am curious if anyone here may have an insight as to why all of a sudden my stamina has plummeted and my max distance has halved ?

Any advise welcome, thanks for taking the time to read all this.



  • You could just need a rest and to take it easy for a week or so, even if you don't feel tiered if your body is it wont let you do it no matter how hard you try.  If your stressing about hitting the speed each time you run now you'll find it harder, try jogging 5 mins and if you feel ok increse the speed every 3 / 5 mins untill you hit your normal pace.  It'll come back when your not even trying- I keep getting injured, if I relax and jogg my speed brings its self back with the help of a few sprint sessions. If I get p* and try to push each one nothing happens and I get slower.

    Don't give up running is done with the mind not the legs!

  • Sounds sensible, will give it a go and see what happens. I don't feel tired or run down, but like you say maybe its as much psychological as anything.

    I was planning on starting to run outdoors and do a half marathon later this year, so hopefully this will get resolved. Maybe its just a temporary thing and next time it will be fine, I don't know. Will be going on Friday afternoon so shall see then. Just wondered if this was something that runners commonly went through, as I don't actually know any other runners to talk about it with.

  • Sounds like you need a bit of a rest! Or at least not worry too much about hitting the numbers for a week or so. As Kiss This said, you're body will not do what you want if it needs a rest. Try not to worry about it too much and just relax for a week then see what happens image
  • Jason, you could just need a rest. You could have a viral infection and your body is fighting that, in which case you need a rest... If you rest for a couple of weeks (no running/equivalent exercise, or only very light) and still have the same problem then it may be worth going back to your GP for another check-up.

  • JeremyGJeremyG ✭✭✭
    Get outside and slow up a bit. I have to use a treadmill a lot due to working offshore and sometimes I have the same feeling. Running outside is so much more fun so you don't notice time/pace etc. also could be a virus but also I would say if your body fat % is right it is low so you may need to be eating more to sustain your running. First thing to try as suggested is to take a break and see if this improves things
  • They said my body fat was low, but was fine and expected for someone running over 50km a week.

    Well I guess I still have things to learn about running image

    I worked all night Thursday, went to bed 8am Friday morning, slept for 4 hours then got up and went to the gym and ran 15k without any problems. Rested all day Saturday, went to the gym Sunday morning and struggled to run just 8k. Just not used to having these backward steps, over the last year I have just improved no matter how much I trained, I guess my body finally said enough image

    Will have a couple of days off and then see what happens Wednesday.

  • My suggestion is similar to the others, have a more restful week, not a no running week but a less running and slower week.  I always think having a drop back week every 4th week or so helps.  If your resting heart rate has increased it is a good indication of over training

  • I am experiencing something very similar. I was training and racing very well about two weeks ago since then my performance seems to have fallen off a cliff! I'm going to have an easier week and see how things go. I'm over 50 now and think I can still train like a teenager is the problem.  



  • waycatwaycat ✭✭✭

    I am so pleased to see this thread as I am going through very much the same thing right now.  

    I really feel as if I've lost my running mojo at the moment.

    I have battled through the hard runs, but it does get very disheartening when I feel as if I'm a beginner all over again and pretty much starting out.

    Ah well, I guess after reading everyone's advice on this, I can take a couple of days rest and not feel too guilty about it, or worry and fret over losing my fitness.

    Thanks to Jason for starting this!

  • I often have off weeks/fortnights, especially during marathon buildup. It is nearly always due to not running enough miles at an easy aerobic pace.

    You would be far better off running some of your mileage at 10 or 11 and maybe 15-20% a little quicker at 13 or 14.

    Whenever you feel a slump like you are experiencing now, cut both your speed and total distance until you feel the zing come backimage

    Running all your miles at the same speed can zap you for some reason. Always best to mix it up a little.

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