Walking 45 mins is OK if you take food and liquid with you.
CLKD Yes, that is the case when somebody does not have an underlying condition.
However, I believe that Oldsheep has ME, the fatigue is very different to just being weary
The fatigue / knackernedness that exists in ME is like the fatigue caused by MS. It is overwhelming, when it's bad people can not get out of bed, even having a shower is too tiring and has to be taken in stages, constantly having to sit down to rest. It is possible to exercise but it has to be balanced with constant rest.
When I was first diagnosed with MS the GP at that time knew nothing about MS fatigue and was of the "just get on with it" school. I had a word with my MS nurse, GP got a letter from my then consultant. GP apologised saying "I now know about MS fatigue, I hadn't realised"