Alright lads , I had a bit of a niggle about 3 weeks ago so decided to take a week of . Now I have been back running for 3 weeks and I am struggling to even get to 3 km . I could do about 10 km before that. Anyone have any advice ?
That sounds very strange. Not really enough information to even guess at what is going on though. What was the niggle? How exactly are you struggling, what is stopping you? Pain, tiredness, can't breathe fast enough, muscles won't work properly, your head not in it? Do you have any other signs of being ill, like cold symptoms?
In no healthy individual will a week's rest result in a 70% reduction in performance, so something else must be going on.
EDIT: If it's related to this thread:
https://www.paras.uk/threads/shin-splints.264/ and the answer to the above is "pain in my shins", then you need to stop again immediately. Shin splints cases can range from mild, normal and solved by a short rest, to really quite serious and requiring medical intervention before you do permanent damage. If you've rested for a week, restarted and your pain and performance is getting that much worse, then you should probably suck it up and phone your GP for a physio assessment. Explain you have already done the "rest-restart" advice and it is unsolved, and you are applying for the Army so this is, in effect, work related. Nobody will be able to accurately diagnose or suggest remedies to the problem without seeing you in person, because there is a large range of potential causes for shin splints and they all require a personal assessment. That is likely to be difficult at the moment due to COVID, but there it is.
The basic issue with shin splints is an irritated, inflamed or injured muscle, which is putting stress on the tendons that attach that muscle to the bone. Mild irritation often disappears with rest. If it's on the more serious end of the spectrum, it can be damaging the tendon. Tendon damage is serious and difficult to repair. Your GP might ask you to do a couple of self-assessment exercises to see if this likely. Don't freak out - statistically this probably isn't you. But you should be aware that "shin splints", while usually mild, can also progress to a serious problem. Don't think it's only ever a simple niggle.
Rest periods to recover properly from shin splints are usually longer than people think - certainly weeks and sometimes months. You also need to identify what is causing the problem. Often it's overuse (too much too quickly), but sometimes it's an underlying biomechanical issue (how your specific muscles and bones are aligned), which then needs to be addressed through physio exercises.