Exercise ...

the little grey cells. Reading size

I've been thinking too much about this challenge. Exercise? I usually only walk and sometimes stretch. Exercise? One gets exercised and strain emotions. Military exercises. Exercise book. Musical exercises . . . so my train of thought went.

Then I went on a futile hunt for my music exercise books . . . I haven't looked in the right place yet; must have put them somewhere 'safe'.

But these items I did find: A chart of yogic stretches; a GCE 'O' level music exam paper from 1966; cryptic crossword puzzles are a good brain exercise; Change-ringing used to be more commonly referred to as The Exercise; exercise your mind learning a language, too, though it doesn't have to Biblical Greek.