Constant Stride Research Articles

Toward stimulating the central generator of stepping

Normal subjects were asked to walk at five different speeds while adopting four defined postures. Normal walking was used as a control. The lower limbs were either medially or laterally rotated about 30°, while the trunk was either inclined about 15° forward or backward. These postures were not fixed with splints but were voluntarily maintained during walking. Regressions were calculated which helped to determine changes in gait from control at equal velocities and stride durations. Maximum velocity decreased significantly in all cases except when the trunk was inclined forward. This decrease of velocity was due to decrease of stride length; stride frequency increased significantly. For lateral and medial rotations of the lower limbs, stance and double support phases increased while swing time decreased; no changes occurred in these phases of stride for the trunk postures. The test postures were selected as they were expected to stimulate receptors in the hip to transmit sensory feedback that could drive the stepping pattern generators. Since at a constant velocity stride frequency increased and swing decreased, it is suggested that medial and lateral rotations of the lower limbs about the hip joint are effective in exciting the appropriate hip joint receptors to transmit sensory feedback that can drive the generator circuit.

Gallop velocity and limb contact variables of quarter horses

High-speed cinematography was used to examine the relationship between velocity and linear and temporal ground contact variables of the equine transverse gallop gait. The stride characteristics of four Quarter horse fillies were used as a model. Horses were approximately thirty months of age and had been raised and trained similarly. Horses were filmed by two cameras simultaneously (243 frames/second) while galloping under the standardized conditions of a specially constructed 1.5m-wide track. Horses were all ridden with the same saddle and bridle by one person. Kinematic variables determined for sixty-two strides included stride length, step lengths and stride frequency as well as contact and non-contact periods of single limbs and combinations of limbs. Galloping velocity (10.0 to 15.0 m/sec) was strongly influenced by stride frequency (2.16 to 3.04 sec −1 ) and to a lesser extent by stride length (4.41 to 5.56 m). Stride length and stride frequency were independent. Variations in velocity were not associated with any detectable variations in absolute or relative distances between successive limb impacts. Increases in stride length at constant stride frequency were accomplished by increasing the distance between fore limb impacts and also the distance between fore leading limb impact and the subsequent hind trailing limb impact. Decreases in stride duration with increased galloping velocity occurred at the expense of hind trailing limb unipedal contact, fore leading limb unipedal contact and the airborne phase duration.

Kinematics of swimming of penguins at the Detroit Zoo

Kinematic parameters were examined in a study of the swimming abilities of seven species of penguins housed at the Detroit Zoo. Penguins produce thrust over both halves of the wing stroke cycle, as observed in fishes using the caudal or pectoral fins for locomotion, but not in other birds in level forward flight. Unpowered gliding phases between wing strokes were observed in all species at swimming speeds less than 1.25 m/sec, while Emperor, King and Adelie penguins interpose gliding phases over a broad range of speeds. Videotape records reveal that length‐specific speed is correlated with increases in wingbeat frequency and, for most of the species examined, stride length. These findings are in contrast to those reported for other, flying birds, which maintain a relatively constant wingbeat frequency but vary stride length with forward speed, and for most fishes, which vary speed with tailbeat frequency but maintain a constant stride length. The results are somewhat comparable to those reported for Cymatogaster, a fish which uses the pectoral fins for locomotion. Drag coefficients of three gliding Emperor penguins were 2.1, 3.0 and 3.0 × 10‐−3 at Reynolds numbers of 1.25, 1.62 and 1.76 × 106, respectively.