It seems that too much of a good thing (ie pronation or supination) slows down the peroneus. A slower contraction time as the foot moves from midstance to terminal stance (when the peroneus longus contracts to assist in descending the 1st ray) appears to biomechanical consuquences…
“RESULTS: Participants with pronated or supinated foot structures had slower peroneus longus reaction times than participants with neutral feet (P = .01 and P = .04, respectively). We found no differences for the tibialis anterior or gluteus medius.
CONCLUSIONS: Foot structure influenced peroneus longus reaction time. Further research is required to establish the consequences of slower peroneal reaction times in pronated and supinated foot structures. Researchers investigating lower limb muscle reaction time should control for foot structure because it may influence results.”
J Athl Train. 2013 May-Jun;48(3):326-30. doi: 10.4085/1062-6050-48.2.15. Epub 2013 Feb 20.
Foot structure and muscle reaction time to a simulated ankle sprain.
Denyer JR1, Hewitt NL, Mitchell AC.