I currently direct the Human Biology Program at the University at Albany. My research focuses on human locomotor biomechanics, with particular interest in relating locomotor behavior to brain size and development and skeletal morphology in humans, nonhuman primates and other mammalian model organisms. My research contributes to a better understanding of the evolution and development of human locomotor function and the neurological, skeletal, physiological and adaptive implications of evolutionarily important changes in locomotor behavior (i.e., bipedal walking, endurance running).
Relative limb proportions can be used to discriminate among primates that use different locomotor... more Relative limb proportions can be used to discriminate among primates that use different locomotor behaviors, with humans having relatively longer lower extremities and suspensory and knuckle walking apes having relatively long forelimbs. Understanding the developmental and evolutionary origins of this differentiation is key to explaining human and hominoid locomotor evolution. This research tests the hypothesis that greater limb differentiation is associated with higher evolutionary autonomy for limb segment lengths. Humeral, ulnar, femoral and tibial lengths were measured for large samples of Homo, Pan, Gorilla, Pongo,Hylobates, Macaca, Cercopithecus, Ateles, and Alouatta. Species-specific phenotypic correlations, measures of evolvability and autonomy were obtained for each bone following mean-standardization for sex and population differences. In general the elements of animals showing greater limb differentiation tended to have greater autonomy, but this was not always the case f...
Broad allometric studies of the musculoskeletal system have frequently sought to explain how loco... more Broad allometric studies of the musculoskeletal system have frequently sought to explain how locomotor variables have been influenced by body mass. To examine animals that vary widely in body mass, these studies have included taxa that differ in their locomotor adaptations and phylogenetic relatedness. Because these sources of diversity could obscure the effects of body mass, this study was designed to test the effects of adaptive differences in limb proportions and phylogeny, as well as body mass, on locomotor kinematics and extensor muscle mechanical advantage. More specifically, two hypotheses were tested in a sample of closely related animals: (i) that, among animals with similar body mass, those with longer limb segments should adopt more extended limb postures to moderate the joint and midshaft bending moments that they experience, and (ii) that body mass will have similar influences on joint posture and joint moments in closely related and diverse mammalian samples. Three-dim...
Hydrogen sulfide is a colorless, noxious gas with the distinctive smell of rotten eggs. This comp... more Hydrogen sulfide is a colorless, noxious gas with the distinctive smell of rotten eggs. This compound is a powerful reducing agent that is encountered in a number of industrial processes. When hydrogen sulfide is present, it exposes workers to the potentially lethal effects of the rapid hypoxemia that results from exposure to this agent. The "warning sign" is the characteristic smell of rotten eggs; this smell should alert anyone in the area that a potentially serious risk exists. The immediate removal of the victim and administration of high-flow oxygen is essential. Neurologic sequelae may require anticonvulsants and care must be exercised to observe for cardiac, hepatic, and renal insufficiency. Depending on the concentration, hydrogen sulfide can rapidly overcome a potential victim.
Differences in rhythmicity (relative variance in cycle period) among mammal, fish, and lizard fee... more Differences in rhythmicity (relative variance in cycle period) among mammal, fish, and lizard feeding systems have been hypothesized to be associated with differences in their sensorimotor control systems. We tested this hypothesis by examining whether the locomotion of tachymetabolic tetrapods (birds and mammals) is more rhythmic than that of bradymetabolic tetrapods (lizards, alligators, turtles, salamanders). Species averages of intraindividual coefficients of variation in cycle period were compared while controlling for gait and substrate. Variance in locomotor cycle periods is significantly lower in tachymetabolic than in bradymetabolic animals for datasets that include treadmill locomotion, non-treadmill locomotion, or both. When phylogenetic relationships are taken into account the pooled analyses remain significant, whereas the non-treadmill and the treadmill analyses become nonsignificant. The co-occurrence of relatively high rhythmicity in both feeding and locomotor systems of tachymetabolic tetrapods suggests that the anatomical substrate of rhythmicity is in the motor control system, not in the musculoskeletal components.
Functional interpretation of limb bone cross-sectional geometry depends upon knowledge of the mag... more Functional interpretation of limb bone cross-sectional geometry depends upon knowledge of the magnitude and direction of habitual loading. Quantification of bone loading has only been possible using invasive, in vivo strain measurement and a non-invasive alternative ...
Patterns of diversity in gorilla cranial morphology REBECCA M. STUMPF. JOHN D. POLK. JOHN F. OATE... more Patterns of diversity in gorilla cranial morphology REBECCA M. STUMPF. JOHN D. POLK. JOHN F. OATES, WILLIAM L. JUNGERS, CHRISTOPHER P. HEESY, COLIN P. GROVES, AND JOHN G. FLEAGLE Introduction Gorillas, perhaps because of their size, always seem to be the ...
Functional interpretations of limb bone structure frequently assume that diaphyses adjust their s... more Functional interpretations of limb bone structure frequently assume that diaphyses adjust their shape by adding bone primarily across the plane in which they are habitually loaded in order to minimize loading-induced strains. Here, to test this hypothesis, we characterize the in vivo strain environment of the sheep tibial midshaft during treadmill exercise and examine whether this activity promotes bone formation disproportionately in the direction of loading in diaphyseal regions that experience the highest strains. It is shown that during treadmill exercise, sheep tibiae were bent in an anteroposterior direction, generating maximal tensile and compressive strains on the anterior and posterior shaft surfaces, respectively. Exercise led to significantly increased periosteal bone formation; however, rather than being biased toward areas of maximal strains across the anteroposterior axis, exercise-related osteogenesis occurred primarily around the medial half of the shaft circumferenc...
Relative limb proportions can be used to discriminate among primates that use different locomotor... more Relative limb proportions can be used to discriminate among primates that use different locomotor behaviors, with humans having relatively longer lower extremities and suspensory and knuckle walking apes having relatively long forelimbs. Understanding the developmental and evolutionary origins of this differentiation is key to explaining human and hominoid locomotor evolution. This research tests the hypothesis that greater limb differentiation is associated with higher evolutionary autonomy for limb segment lengths. Humeral, ulnar, femoral and tibial lengths were measured for large samples of Homo, Pan, Gorilla, Pongo,Hylobates, Macaca, Cercopithecus, Ateles, and Alouatta. Species-specific phenotypic correlations, measures of evolvability and autonomy were obtained for each bone following mean-standardization for sex and population differences. In general the elements of animals showing greater limb differentiation tended to have greater autonomy, but this was not always the case f...
Broad allometric studies of the musculoskeletal system have frequently sought to explain how loco... more Broad allometric studies of the musculoskeletal system have frequently sought to explain how locomotor variables have been influenced by body mass. To examine animals that vary widely in body mass, these studies have included taxa that differ in their locomotor adaptations and phylogenetic relatedness. Because these sources of diversity could obscure the effects of body mass, this study was designed to test the effects of adaptive differences in limb proportions and phylogeny, as well as body mass, on locomotor kinematics and extensor muscle mechanical advantage. More specifically, two hypotheses were tested in a sample of closely related animals: (i) that, among animals with similar body mass, those with longer limb segments should adopt more extended limb postures to moderate the joint and midshaft bending moments that they experience, and (ii) that body mass will have similar influences on joint posture and joint moments in closely related and diverse mammalian samples. Three-dim...
Hydrogen sulfide is a colorless, noxious gas with the distinctive smell of rotten eggs. This comp... more Hydrogen sulfide is a colorless, noxious gas with the distinctive smell of rotten eggs. This compound is a powerful reducing agent that is encountered in a number of industrial processes. When hydrogen sulfide is present, it exposes workers to the potentially lethal effects of the rapid hypoxemia that results from exposure to this agent. The "warning sign" is the characteristic smell of rotten eggs; this smell should alert anyone in the area that a potentially serious risk exists. The immediate removal of the victim and administration of high-flow oxygen is essential. Neurologic sequelae may require anticonvulsants and care must be exercised to observe for cardiac, hepatic, and renal insufficiency. Depending on the concentration, hydrogen sulfide can rapidly overcome a potential victim.
Differences in rhythmicity (relative variance in cycle period) among mammal, fish, and lizard fee... more Differences in rhythmicity (relative variance in cycle period) among mammal, fish, and lizard feeding systems have been hypothesized to be associated with differences in their sensorimotor control systems. We tested this hypothesis by examining whether the locomotion of tachymetabolic tetrapods (birds and mammals) is more rhythmic than that of bradymetabolic tetrapods (lizards, alligators, turtles, salamanders). Species averages of intraindividual coefficients of variation in cycle period were compared while controlling for gait and substrate. Variance in locomotor cycle periods is significantly lower in tachymetabolic than in bradymetabolic animals for datasets that include treadmill locomotion, non-treadmill locomotion, or both. When phylogenetic relationships are taken into account the pooled analyses remain significant, whereas the non-treadmill and the treadmill analyses become nonsignificant. The co-occurrence of relatively high rhythmicity in both feeding and locomotor systems of tachymetabolic tetrapods suggests that the anatomical substrate of rhythmicity is in the motor control system, not in the musculoskeletal components.
Functional interpretation of limb bone cross-sectional geometry depends upon knowledge of the mag... more Functional interpretation of limb bone cross-sectional geometry depends upon knowledge of the magnitude and direction of habitual loading. Quantification of bone loading has only been possible using invasive, in vivo strain measurement and a non-invasive alternative ...
Patterns of diversity in gorilla cranial morphology REBECCA M. STUMPF. JOHN D. POLK. JOHN F. OATE... more Patterns of diversity in gorilla cranial morphology REBECCA M. STUMPF. JOHN D. POLK. JOHN F. OATES, WILLIAM L. JUNGERS, CHRISTOPHER P. HEESY, COLIN P. GROVES, AND JOHN G. FLEAGLE Introduction Gorillas, perhaps because of their size, always seem to be the ...
Functional interpretations of limb bone structure frequently assume that diaphyses adjust their s... more Functional interpretations of limb bone structure frequently assume that diaphyses adjust their shape by adding bone primarily across the plane in which they are habitually loaded in order to minimize loading-induced strains. Here, to test this hypothesis, we characterize the in vivo strain environment of the sheep tibial midshaft during treadmill exercise and examine whether this activity promotes bone formation disproportionately in the direction of loading in diaphyseal regions that experience the highest strains. It is shown that during treadmill exercise, sheep tibiae were bent in an anteroposterior direction, generating maximal tensile and compressive strains on the anterior and posterior shaft surfaces, respectively. Exercise led to significantly increased periosteal bone formation; however, rather than being biased toward areas of maximal strains across the anteroposterior axis, exercise-related osteogenesis occurred primarily around the medial half of the shaft circumferenc...
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Conference Presentations by John Polk
Papers by John Polk