Normalised mean OD of mATPase activities and their relationships to the fibre types. A: Mean OD standardised to Z scores of mATPase activity after acid (pH 4.42, acATPase) and alkaline (pH 10.35, alATPase) preincubations of the MyHC-based fibre types. Values are pooled means of the 814 fibres analysed in the two skeletal muscles (PM and FD). Vertical bars represent the 0.95 confidence intervals. B, C: Fibre-to-fibre relationship between OD of the immunostaining and mATPase activities in different subsets of hybrid fibres. Relationship between the BAF8 MAb (anti MyHC I) and acATPase staining of all I+IIA hybrid fibres analysed in the FD (n = 23 fibres) (B). Relationship between the SC71 MAb (anti MyHC IIA and IIX) and alATPase staining of all IIAX hybrid fibres identified in the PM (n = 48 fibres) (C). r: Pearson coefficient of correlation; #: p < 0.001 level of significance.