Guidance on stay at home regulations that came into effect on 5 January 2021.
Stay at Home
To minimise the risk of spreading the virus, you must stay at home as much as possible. By law, in a level 4 area, you can only leave your home (or garden) for an essential purpose.
There is a list of examples of reasonable excuses below. Although you can leave home for these purposes, you should stay as close to home as possible. Shop on-line or use local shops and services wherever you can. Travel no further than you need to reach to a safe, non-crowded place to exercise in a socially distanced way. To minimise the risk of spread of coronavirus it is crucial that we all avoid unnecessary travel.
Examples of reasonable excuses to go out:
local outdoor recreation, sport or exercise, walking, cycling, golf, or running that starts and finishes at the same place (which can be up to 5 miles from the boundary of your local authority area) as long as you abide by the rules on meeting other households
The list is more comprehensive, I have picked the exercise one. Other reasons include essential shopping, banking, healthcare, charity help, care work, legal proceedings, animal welfare.
I honestly, honestly fail to see the blurryness. You're being told what you can lawfully do to leave the house (and the rules on exercise in particular, of interest to us here on this forum, are particularly well defined) and you are being
asked to do it as little as possible.