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Couch to 5K
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4th run, breathing getting better but legs feel like a heavy weight..any suggestions?


I started c25k last week and completed the 4th session last night. I haven't found any easy yet, but my breathing has certainly started to improve. After sessions 1 and 2 I found it impossible to catch my breath and couldn't get a full lungfull of air. Sessions 3 and 4 were different, I felt like I was breathing cleanly, easily and I almost (almost!) enjoyed the feeling. My issue seems to be that my legs are just dead weights. I feel like after the second or third running interval my legs give up and I physically cannot go any faster than probably a fast walking pace (but jogging).

I am also dieting and tend to cut out all carbs, except fruit and veg. I wonder if its that im not eating enough or that I need to eat carbs before I run? Or is it that everyone has this and its just a part of getting fit?! If anyone has experienced the same, or has any suggestions I would much appreciate it!


10 Replies

I am not a nutritionist. So take anything I say as just opinion.

I'm not a fan of carb reduction diets, I think they are a bit faddy and it is very difficult to enter a ketonic state without being very extreme in what you remove from your diet.

When you exercise at a high level ie run fast you burn up your glycogen stores, when you exercise at a more moderate level you will burn fat instead. Glycogen runs out quite quickly and if your not fueling your body with essential carbs you are doing yourself a disfavour.

My advice. Eat carbs!! especially on exercise days. You should favour complex carbs like oats, wild rice and dried pasta though over quick hits like fruit.

And run more slowly :)


Well done you are doing great.

Hydration is crucial. Drink a minimum of 2 litres of fluid per day.

This guide may help healthunlocked.com/couchto5...……………...not-healthy

If you are eating a broad diet of nutritious food then you don't need to change your diet.

Exercises on your rest days, such as squats, will help. nhs.uk/Livewell/strength-an...


I checked IannodaTruffe 's first link, and whilst it looks a bit broken, it works OK.


Hiya Ksjo and welcome to our little community. You've come to the right place to get you through C25K. Post often, and ask for help and encouragement, and we can cheer you over the finish line.

I'm pleased that your breathing is improving. As for your heavy legs, well I think that you answered your own question. If this is your first real activity for some time, then you can only be expected to run at a very slow pace... just doing a running motion, even at a 'slightly-faster-than-walking' pace qualifies as a run, so jut go at this speed. If that gets you through each session, then that is OK. You'll have the rest of your running life to get faster.

My biggest concern is the 'cutting out all carbs' diet that you're on. We have some very good nutrition experts on this forum who may be along soon, but your body is going to need some fuel for running. W1 of C25K may burn 200 calories, and of course that is not much. So don't go mad, but have a banana, or a piece of toast with a poached egg about 1 hour before you go running. Of course your diet is expecting to burn off stored fat in place of burning carbohydrates, but I think that you are just going to get tired and have a low mood. Try to eat a balanced diet, drink plenty of water, have smaller portions and don't snack. That will help.


Hi ksjo, well done for starting the c25k plan. You started last week, and have done your 4th session. That would put you on Week 2 Run1 of the Nhs healthunlocked C25k plan. The program is designed to get you running from scratch, and you only need to do a gentle, light jog for all of the run intervals , then walk to recover a bit inbetween run intervals. If you try to run too quickly you will find it really hard to catch your breath.

It sounds like you are already finding the breathing a bit easier. Slow down the running and try to keep at a steady pace...

As the Lannodatruffe, MarkyD and pinkaardvark have said, good nutrition and drinking plenty of water will give you the energy you need. Making the right food choices, and steering clear of empty calories will help.

Good luck with Wk 2 Run2 Slow down and let us know how you get on😊xx


For half hour runs, you shouldn't need to change your diet at all (that is, if you have a well balanced diet to begin with of course). The calorie defecit produced is just not enough to justify eating more carbs, and I agree with some of the comments that I would not recommend any diets that focus on cutting things out. Instead, focus on adding more nutrition to your diet and just watching your portions


We can all identify with heavy legs! It will improve however! It's tiredness that causes it. Running is hard work but as you do a little bit more each session you will gradually feel better. Go nice and steady.

I lost quite a lot of weight but to do it I still ate carbs and still do. I think it's the body building fraternity that have caused folks to consider them as baddies. Lots of fruits and veg are carbs! Unrefined carbs are good, such as your spuds and sweet potatoes. If you have fewer of the refined carbs you'll be fine. I eat all the food groups but just moderately and always healthily. Just by cutting out any junk foods you will feel more alive very quickly

Good luck!


I found I had to increase carbs the first few weeks of the program, with the walk run walk intervals, otherwise I was overwhelmingly fatigued (and I'm an eat a bag of donuts at a sitting type of girl).


Wow, thanks all. This is all really useful info and much appreciated.

I think I'm just expecting more than I should. My mind is really focused, but my body is struggling to deliver! My partner is doing it with me and he originally graduated from c2k5 3 or 4 years ago, going on to run 7/8k's fairly regularly. He hasn't done any exercise since we met 2.5 years ago though so wanted to get back into it. His general fitness is much higher than mine seemingly and he is barely breaking a sweat! Lovely to have a running buddy, but I suppose I'm expecting I should be at the same level as him and that's totally unrealistic.

Re my diet, I don't usually eat a lot of refined carbs during the week anyway even when not dieting. I've got a super slow metabolism so i don't need to eat a lot to put on weight, dieting then usually means I have to go to 1000cal a day to make a jot of difference. I'm probably not eating enough. No breakfast, 200cal lunch and chicken and salad (no dressing etc) for dinner! Its not enough I know.

I'm doing 30-40 squats a day now and using the stairs at work etc so my rest days are still more active than they would have been. They are getting much easier too, can do 20 in a set and repeat later in the day.

I will take on board the advice re pace. I am being hard on myself.

Thank you all so much again, this is such a wonderfully supportive group.


Slow and steady.... it is not possible to run TOO slow I don't think :)

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