Fig. 5. Composite measures of variability in loading pattern, shown for the cranial and caudal midshaft surfaces of both bones during outdoor (grey) and treadmill (black) locomotion. (A) Participation ratio (PR) and (B) Distance to Individual Mean (DIM) are measures of two-dimensional spread, and (C) percentage of footfalls that land in the expected loading zone indicates how consistently individual footfalls land within the expected range of TSO and FTSR. For both measures of 2D spread (A,B), outdoor footfalls are more variable than those of treadmill locomotion, but not all comparisons are significant because of low degrees of freedom (^*significant difference, P<0.05). (C) For both bones the percentage of footfalls landing in the expected loading zone is not significantly different between outdoor and treadmill conditions. Values shown are means ± s.e.m.