At this point, Duracotus, reviving, sees his arms and
legs curling inwards (without incurring lasting damage — space travellers have a charmed life), which Kepler explains in this way:
This study shows that one way in which we can increase the emphasis on the medial hamstrings during several strength training exercises (including the
leg curl) is to rotate the foot
inwards, while rotating the foot outwards emphasises the lateral hamstrings.