Quantitative electromyography and muscle function of the hind limb during quadrupedal running in the lizard Sceloporus clarki

Although the hind limb usually is considered to pro vide the propulsive force in lizard locomotion, no study to date has analyzed motor or kinematic patterns of the lizard hind limb during running for more than one stride for a single individual. Quantitative electromyography and kinematic data are used to describe the motor pat terns of 11 muscles of the hind limb used during quadru pedal running in the lizard Sceloporus clarki. Basic kine matic patterns of hind-limb and axial movements are de scribed briefly, and motor patterns are quantified by averaging electromyographical patterns from nine cons ecutive strides during which the lizard was running at 0.83 rn/s. Kinematics and muscle functions are discus sed in light of hypotheses presented in the literature. Many functional hypotheses based on gross observatio nal studies are not supported by quantitative electromyo graphical and kinematic data. These preliminary results indicate that axial bending, limb retraction, crural exten sion, and plantar flexion of the foot have important syn ergistic contributions to generating force during the limb cycle. Thus, extensive kinematic and electromyographi cal studies are needed to probe the functional details of hind-limb locomotion in sprawling vertebrates.