title: Electromyography of wrist and finger flexor muscles in olive baboons (Papio anubis).
abstract: Some non-human primates use digitigrade hand postures when walking slowly on the ground. As a component of an extended limb, a digitigrade posture can help minimize wrist joint moments thereby requiring little force production directly from wrist flexors (and/or from the assistance of finger flexors) to maintain limb posture. As a consequence, less active muscle volume would be required from these anti-gravity muscles and overall metabolic costs associated with locomotion could be reduced. To investigate whether the use of digitigrade hand postures during walking in primates entails minimal use of anti-gravity muscles, this study examined electromyography (EMG) patterns in both the wrist and finger flexor muscles in facultatively digitigrade olive baboons (Papio anubis) across a range of speeds. The results demonstrate that baboons can adopt a digitigrade hand posture when standing and moving at slow speeds without requiring substantial EMG activity from distal anti-gravity muscles. Higher speed locomotion, however, entails increasing EMG activity and is accompanied by a dynamic shift to a more palmigrade-like limb posture. Thus, the ability to adopt a digitigrade hand posture by monkeys is an adaptation for ground living, but it was never co-opted for fast locomotion. Rather, digitigrady in primates appears to be related to energetic efficiency for walking long distances.
authors.affiliation: Department of Anatomical Sciences, Stony Brook University, Stony Brook, NY 11794-8081, USA. Biren.Patel@stonybrook.edu
authors.forename: Biren A
authors.initials: BA
authors.lastname: Patel
authors.forename: Susan G
authors.initials: SG
authors.lastname: Larson
authors.forename: Jack T
authors.initials: JT
authors.lastname: Stern
mesh_terms: D000818:Animals; D004576:Electromyography; D005260:Female; D005385:Fingers / Q000033:anatomy & histology / Q000502:physiology*; D006225:Hand / Q000033:anatomy & histology / Q000502:physiology; D008297:Male; D018482:Muscle, Skeletal / Q000502:physiology*; D048530:Papio anubis / Q000033:anatomy & histology / Q000502:physiology*; D011187:Posture; D016138:Walking; D014953:Wrist / Q000033:anatomy & histology / Q000502:physiology*