Effect of Wind Tunnel Velocity on the Dynamics of Human Walking

The effect of air resistance has been studied in the past in building design and crosswalk width, as well as in sports activities (such as cycling and running). Most of these studies focused on the design rather than on the... [ view full abstract ]

The effect of air resistance has been studied in the past in building design and crosswalk width, as well as in sports activities (such as cycling and running). Most of these studies focused on the design rather than on the biomechanics of muscular joint. At our knowledge, there are no studies that have estimated the muscular power of lower limb joint during locomotion activities when human body was subjected to a controlled laminar wind. The purpose of this work is to present a preliminary work to study the effect of a controlled laminar wind on the joint moment and power of a lower limb joint during walking level activity. One specific subject participates in this study. The subsonic blow down wind tunnel Price-Païdoussis at the Laboratory of Applied Research in Active Controls, Avionics and AeroServoElasticity LARCASE was used to generate the flow needed for the testing of the subject’s behavior. Twenty-six (26) spherical reflective markers were affixed unilaterally onto the subject's left side and their 3D trajectories were tracked by five optoelectronic cameras (Vicon 460, Oxford metrics) at 120 Hz. Simultaneously, the ground reactions forces and moments were recorded using an AMTI force platform at 120 Hz. The segment inertial characteristics (mass, center of mass and inertia tensor) of each of the foot, shank and thigh were estimated using the De Leva statistical anthropometric table. A 3D inverse dynamics model based on wrench formalism and quaternion algebra was used to estimate the reaction forces and muscular moments at the left ankle, knee and hip joints. The muscular moments at each joint were normalized with respect to the body-weight. The generated wind-tunnel velocity, measured at the level of subject's center of mass, varied from 0, 5, 10, 15 to 22 m/s. For each velocity, five trials of 10 sec of walking were recorded. In the sagittal plane, the flexion/extension moments at the hip and knee joint, decreased respectively by 116% and 72% at heel strike with respect to the natural walking (0 m/s), whereas in the frontal plane, the hip and knee abduction/ adduction joint moments increased dramatically at mid-stance by 63% and 1571%, respectively. In the transverse plane, the internal/external joint moments increased by about 283% and 186% for the hip and knee, respectively at mid-stance. It is concluded from this study, that the control of gait is transferred gradually from the sagittal plane at natural cadence (0 m/s) to the frontal and transverse planes at 22 m/s. During gait, muscles that control outer planes (frontal and transverse) have as objective the stability of the human body, whereas at 22 m/s the objective of these muscles is now to produce the necessary energy to propel the body in the forward direction. This will load excessively the muscles that control the gait in these outer planes. It is expected then that the power of this muscles will be very high.