ABSTRACT
In.devising.these.exercises,.one.of.the.criteria.has.been.that.they.should.not.require. any.invasive.techniques..This.imposes.some.serious.limitations,.but.also.ensures.a. reasonable.level.of.safety.and.therefore.reduces.the.difficulties.with.getting.acceptance.from.the.Human.Ethics.Committee..Unfortunately,.some.of.them.require.rather. expensive.equipment,.but.there.are.several.that.can.be.carried.out.fairly.simply.
