Hyperextendable butterflyer knees

I've known for a long time that good butterfly swimmers have some physical advantages (I almost called them adaptations) for this most strenuous of strokes.  But I never knew how advantageous one particular aspect of their physique was until I read this article:

Elite swimmer dolphin kick analysis

The elite swimmer being analyzed is Thiago Pereira.

Here's what caught my interest:


"At least in this trial, Thiago´s maximal knee flexion was 112 degrees. Interestingly, in a sample of 19 international level swimmers Arellano (2002) reported an average angle of 113 degrees. His maximal hip flexion was 148 degrees."

OK, so 90 degrees of knee flexion is essentially a perfectly straight leg.  His knees (and apparently many other top flite swimmers) hyperextend 22 degrees.  *Shudder*.    Another piece of information indicating that elite athletes are not anything like the vast majority of us average persons.