Examining Gait Adaptations in Loaded Foot Marches Using Instrumented Insoles Gait Adaptations in Loaded Foot Marches

Loaded foot marches (LFM) impose significant physical demands, altering gait and increasing the risk of musculoskeletal injuries in warfighters. Instrumented insoles offer a promising solution for rapidly screening and monitoring LFM gait changes in the field. The purpose of this study was to use instrumented insoles to examine acute and gait adaptation responses to a LFM and to assess the influence of physical fitness on gait responses. Fourteen participants (m = 9, age = 31.2 ± 7.3 years) with LFM experience completed the study. Physical fitness (PF) measures, including body composition, aerobic fitness, strength, and lower body power, were collected during a familiarization session. Instrumented insoles with inertial measurement units were worn during a 5-min unloaded walk followed by a 2-h LFM (20 kg ruck) at 1.34 m/s on a treadmill. Gait measures collected included cadence, ground contact time (GCT), double support time (DST), swing time variability, and asymmetry measures. Changes in gait measures were analyzed using paired t-tests and repeated measures ANOVAs. Bivariate correlations between PF and changes in gait measures were computed. Cadence (P = .048, d = 0.58), GCT (P < .001, d = 1.3), and DST (P < .001, d = 3.2) increased for the unloaded compared to LFM. Gait changes from unloaded to LFM showed cadence was correlated with absolute VO2max (r = 0.63, P = .022) and body mass (r = 0.56, P = .046); while GCT was correlated with absolute VO2max (r = -0.58, P = .038), body mass (r = -0.66, P = .015), and fat-free mass (r = -0.57, P = .040). During the 2-h LFM, cadence significantly decreased (P < .001, ηp2 = 0.608), while GCT (P < .001, ηp2 = 0.709) and DST (P = .003, ηp2 = 0.415) increased during the first hour, with no further changes observed in the second hour. Gait changes during the 2-h LFM were significantly associated with several PF measures, including body composition, lower-body strength, and power. The findings suggest participants exhibited consistent direction but variable magnitudes of gait changes during LFM, and changes were correlated with individual physical fitness and body composition. Instrumented insoles show potential for real-time screening and monitoring during LFMs, offering valuable insights into individual-level gait responses.