Little short of calling us scaredy cats, the author says that training dwarf and semidwarf apple trees isn't as difficult as we might think. And, as for pruning, he adds, the main difficulty is not enough of it.
Cott, A. E.
"Dwarf Apple Trees: Planting and Pruning,"
Iowa Farm Science: Vol. 16
, Article 5.
Available at: https://lib.dr.iastate.edu/farmscience/vol16/iss10/5