The Effects of Walking Speed on the Biomechanics of Backpack Load Carriage
Abstract
An analysis of the effects of 3 walking speeds (1.17, 1.33, and 1.50 m/s) on gait during backpack load carriage was performed on 16 male volunteers using a cinematographic system, force platform, tri-axial accelerometer, and 6 surface electrodes located over the trapezius, spinal erector, quadricep, hamstring, gastrocnemius and tibialis anterior muscles. Conclusions: (1) As load carriage speed increased: (a) there was greater knee flexion at heel-strike, probably reducing shock, (b) hip position at toe-off became more extended, as the rear leg pushed off to a greater degree and the front leg stretched further forward, (c) there was greater total arm swing, most of which was accounted for by increased arm swing in the rearward direction, (d) the minimum vertical position of the body center of mass declined, (e) there were greater upward and downward center of mass vertical velocities, necessitated by greater stride frequency and vertical center of mass range of motion, and (f) changes occurred in load carriage technique that kept several ground reaction forces lower than proportional to the increase in speed, (2) the greatest percentage of joint torque increase with load carriage speed increase occurred about the hip, and the least occurred about the ankle, indicating that muscles producing torque about the hip were most involved in increasing load carriage speed and those producing torque about the ankle were the least involved. The electrical activity data from the leg muscles supported the joint torque findings. Increase in load carriage speed was effected much more through increasing horizontal than vertical ground reaction force, (3) while amplitude of muscle activity tended to increase with speed, the patterns of muscle activity remained the same, and (4) eccentric tibialis anterior activity at heel-strike controlled the rate of plantarflexion to prevent the foot from slapping against the ground, and increased proportionally to speed.
Document Details
- Document Type
- Technical Report
- Publication Date
- May 01, 2000
- Accession Number
- ADA378381
Entities
People
- Clay Pandorf
- Everett Harman
- Ki H. Han
- Peter Frykman
Organizations
- United States Army Research Institute of Environmental Medicine