ACTN3 and hyperinsulinemic hypoglycemia, familial, 4: Several previous investigations have found that the ACTN3 XX genotype, which produces α-actinin-3 deficiency, may be deleterious to becoming a professional football player as the presence of XX players in professional football teams is lower than in control non-athlete populations [16], and they may be more prone to non-contact muscle-type injuries than RR football players [18,19].