Pii: S0301-0082(98)00081-1
نویسندگان
چکیده
ÐStudies on the re ̄ex modulation of vertebrate locomotion have been conducted in many dierent laboratories and with many dierent preparations: for example, lamprey swimming, bird ̄ight, quadrupedal walking in cats and bipedal walking in humans. Emerging concepts are that re ̄exes are task-, phaseand context-dependent. To function usefully in a behaviour such as locomotion wherein initial conditions change from step to step, re ̄exes would have to show modulation. Papers are reviewed in which the study of dierent re ̄exes have been conducted during dierent behaviours, with an emphasis on experiments in humans. A framework is developed in which the modulation and ̄exibility of re ̄exes are demonstrated. Alterations in cutaneous, and muscle (stretch and load receptor) re ̄exes between sitting, standing and walking are discussed. Studies in which both electrical, mechanical and `natural' receptor activation have been conducted during walking are reviewed. Re ̄exes are shown to have important regulatory functions during human locomotion. A framework for discussion of re ̄ex function throughout the step cycle is developed. The function of a given re ̄ex pathway changes dynamically throughout the locomotor cycle. While all re ̄exes act in concert to a certain extent, generally cutaneous re ̄exes act to alter swing limb trajectory to avoid stumbling and falling. Stretch re ̄exes act to stabilize limb trajectory and assist force production during stance. Load receptor re ̄exes are shown to have an eect on both stance phase body weight support and step cycle timing. After neurotrauma or in disease, re ̄exes no longer function as during normal locomotion, but still have the potential to be clinically exploited in gait modi®cation regimens. # 1999 Elsevier Science Ltd. All rights reserved
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