Search

Background: During training, service members routinely walk with heavy body borne loads for long periods of time. These loads alter knee biomechanics and may produce jerky knee motions that reportedly increase joint loading and risk of musculoskeletal injury. Yet, it is unknown if service members use jerky knee motions during prolong walking with body borne load.Research Question: To quantify the effects of body borne load and duration of walking on the jerkiness of sagittal and frontal plane knee motion.Methods: Eighteen participants had angular jerk of knee motion quantified while they walked (1.3 m/s) for 60-min with three body borne loads (0, 15, and 30 kg). Peak and cost of angular jerk for sagittal and frontal plane knee motion was quantified and submitted to a repeated measures linear model to test the main effects and interaction of load (0, 15, and 30 kg) and time (0, 15, 30, 45, and 60 min).Results: Body borne load increased peak and cost of angular jerk for sagittal plane knee motion up to 35 % and 110 %, respectively, and frontal plane knee motion up to 20 % and 51 %, respectively (all p<0.001), while jerk cost of frontal plane knee motion (p=0.001) increased 31 % after walking 45 min.Significance: Body borne load produced large (between 20 % and 110 %), incremental increases in angular jerk for both sagittal and frontal plane knee motion; whereas, duration of walking led to a 31 % increase in jerkiness of frontal plane knee motion. Service members who often walking for long periods of time with heavy body borne loads may have greater risk of developing musculoskeletal injury and disease due to large increases in jerky knee motions. [ABSTRACT FROM AUTHOR]

This study determined if sustained walking with body borne load increases tibial compression, and whether increases in tibial compression are related to vertical GRFs. Thirteen participants had tibial compression and vertical GRF measures quantified while walking at 1.3 m/s for 60 min with body borne load. Each tibial compression (maximum and impulse) and GRF measure (peak, impulse, impact peak and loading rate) were submitted to a RM ANOVA to test the main effect and interaction between load (0, 15, and 30 kg) and time (minute 0, 30 and 60), and correlation analyses determined the relation between tibial compression and vertical GRF measures for each load and time. Each tibial compression and GRF measure increased with the addition of body borne load (all: p < 0.001). Time impacted impact peak (p = 0.034) and loading rate (p = 0.017), but no other GRF or tibial compression measure (p > 0.05). Although both tibial compression and vertical GRFs increased with load, vertical GRF measures exhibited negligible to weak (r: −0.37 to 0.35), and weak to moderate (r: −0.62 to 0.59) relation with maximum and impulse of tibial compression with each body borne load. At each time point, GRF measures exhibited negligible to weak (r: −0.39 to 0.27), and weak to moderate (r: −0.53 to 0.65) relation with maximum and impulse of tibial compression, respectively. Walking with body borne load increased tibial compression, and may place compressive forces on the tibia that lead to stress fracture. But, increases in tibial compression may not stem from concurrent increases in vertical GRFs. [ABSTRACT FROM AUTHOR]