Arch height and maximum rearfoot eversion during jogging in 2 static neutral positions

Context: Clinically, lowering of the medial longitudinal arch is believed to be closely related to rearfoot eversion. However, the relationship between arch height and rearfoot eversion during gait is unclear. Objectives: (1) To examine the influence of 2 reference positions (weight-bearing neutral position [WBNP] and subtalar neutral position [STNP]) on maximum rearfoot eversion, tibial internal rotation, knee flexion, knee internal rotation, and dorsiflexion-plantar flexion of ankle joint measures during jogging and (2) to compare the relationships among static arch height, navicular drop, and the 2 maximum rearfoot eversion measures. Design: Crossover study. Setting: Gait laboratory. Patients or Other Participants: Thirty-three volunteers between 18 and 40 years of age. Intervention(s): Each participant stood on the treadmill in 2 static positions: WBNP and STNP. Kinematic data were obtained using a 10-camera motion analysis system (120 Hz) when participants jogged at 2.65 m/s on the treadmill in bare feet. Main Outcome Measure(s): Rearfoot and shank angular kinematics, navicular drop, and static arch height. Results: Maximum rearfoot eversion was greater (WBNP: 4.03°±2.58°, STNP: 10.91°±5.34°) when STNP was the static reference (P<.001). A strong correlation was seen between maximum STNP eversion and navicular drop (r= 0.842) but not between WBNP and navicular drop (r=0.216). Differences were noted in dorsiflexion and knee kinematics during gait between the static references; however, the effect sizes were low, and the mean differences were smaller than 2°, which was less than 5% of total excursion during gait. Conclusions: Using STNP rather than WBNP as the reference position affects estimates of frontal-plane rearfoot movement but not other ankle or knee motions in jogging.