Biomechanical responses on specific load carriage and positive gradient walking: A pilot study

Normal load carriage is an inevitable part of military marching tasks. Military tasks are inextricably related to carrying huge loads irrespective of different terrain. Continuous carrying of heavy loads from level ground to uphill gradient may alter kinetic and kinematic responses. Such responses, in the long run, may cause the risk of injury. This study was designed to find out the effects of external load on kinetic and kinematic responses at specific loads and grades (+10°). Six healthy Indian soldiers mean (± standard error of mean [SEM]) age 30.5 ± 3.5 years, height 168.7 ± 2.8 cm, weight 73.8 ± 7.08 kg participated in this study, walking on treadmill (Deneb and Polak-speed-1625) at 3.5 kmph for 6 min at 10° inclination for two conditions, with no-load and 30 kg compact-load at controlled laboratory condition 25°C and 50% relative humidity (RH). Compressive, shearing, torque, joint reaction force, and erector-spine forces for kinetic and angular changes of neck, trunk, thigh, forearm, upper arm, and leg were analysed by biomechanical analysis software (Ergomaster 4.6). A paired t-test and repeated measures analysis of variance were applied to determine the significant effects of the load on dependent variables. Significant changes were found in kinetic (compressive, shearing, torque, joint reactive force, and erector spine force) and kinematic (neck and trunk) parameters with subsequent increments of loads. From this study, it was concluded that walking in uphill condition, compressive, shearing, torque, joint reactive force, and erector spine force was found to be increased by 2.58, 4.65, 4.06, 2.83, and 4.06 folds, the angular changes found in neck and trunk were 1.78 and 1.25 folds compared to no-load conditions, respectively. The exerted forces, namely compressive force 74.12%, shearing force 86%, joint reaction force almost 75%, and erector spine force 83.82%, were very close to the injury risk profile; only the change of torque was not much closer to the risk profile. Such findings could be used for recommending load carriage guidelines for future studies.