Strategies for recovery from a trip in early and late swing during human walking

Abstract

The movement strategies and the underlying organization of the muscular responses for recovery from a tripping perturbation applied in early and late swing during walking were studied in humans. The latencies of the reflex response (60-140 ms) suggested that polysynaptic pathways are involved. The most common movement outcome was an elevating strategy of the swing limb in response to the early swing perturbation and a lowering strategy in response to the late swing perturbation. The elevating strategy comprised a flexor component of the swing limb and an extensor component of the stance limb. There was a temporal sequencing of the swing limb biceps femoris prior to the swing limb rectus femoris response to remove the limb from the obstacle prior to accelerating the limb over the obstacle. The extensor response of the stance limb generated an early heel-off to increase the height of the body. Thus, the lower limb joints collaborated to increase the height of the centre of mass and provide extra time to extend the swing limb in preparation for the landing. Flexion of the swing limb would be dangerous in response to the late swing perturbation as the swing limb is approaching the ground and the body mass has passed forward of the stance foot. Instead, a lowering strategy was accomplished by inhibitory responses of the swing limb vastus lateralis and/or excitatory responses of the swing limb biceps femoris. Both these responses resulted in a rapid lowering of the limb to the ground with a flat foot or forefoot landing and a shortening of the step length. Thus, in response to the late swing perturbation, the same recovery strategy was achieved by different patterns of muscle activation. These results demonstrate that the recovery strategies provided a functionally appropriate response for overcoming the obstacle and maintaining the ongoing locomotion.

Mechanically induced stumbling during human treadmill walking

“…This is in agreement with the flexor component of the swing limb in response to perturbations in early swing (~ 20% of the swing phase) as described by Eng et al (1994) as part of the so-called 'elevating strategy' .…”

“…A lengthened swing phase ( -80 ms) was also reported by Dietz et al, (1986) after applying a momentary resistance of 80 ms above the ankle joint at the onset of the swing phase in walking humans. For perturbations in early swing, Eng et al (1994) de scribed a mean swing phase prolongation of 97 mst and they also showed an example of a swing phase which was increased by about 180 ms (their Fig. 5).…”

“…3A) in the BF after perturbations in early swing, which were caused by obsta cles (height: 8 cm) on a walkway. The RF responses described by Eng et al (1994) occurred with a mean latency of 115 ms (their Fig. 3A).…”

“…Ghori and Luckwill (1989) found responses in the RF with a mean latency of 82 ms after a resistance applied during swing on a treadmill. Eng et al (1994) described mean response latencies of about 75 ms (their Fig. 3A) in the BF after perturbations in early swing, which were caused by obsta cles (height: 8 cm) on a walkway.…”

“…To achieve this, in a few studies obstacles were unexpectedly raised above the surface of a walkway to 12 A.M. Schillings et al / Journal o f Neuroscience Methods 67 (1996) 11-17 perturb the walking pattern in the swing phase (Grabiner et ah, 1993;Eng et aL, 1994). These perturbations were caused at a given specific position on the walkway.…”