Topics in Research on Motion Systems in Jena

Our research into motion systems of land vertebrates covers a wide range of specific aims and questions. All have in common our fundamental interest in understanding evolutionary transformations and the functional and structural conditions underlying the broad diversity of locomotor and non-locomotory behaviour in mammals, birds, reptiles, and amphibians.
As any biological system has a history, we search to reconstruct the framework of licenses and limitations against the background of phylogeny which has determined the possible evolutionary transformations in motion systems. Evolutionary adaptation can never produce optimal solutions to a single function. Natural systems are generally multifunctional. History and multifunctionality are two principle differences between biological and technical systems which we have to have in mind when thinking about and working into the transfer of biological principles into technical solutions.

Locomotion in small mammals

In this long-term project we investigated so far a broad diversity of species belonging to various mammalian taxa: kowaris and opossums (Dasyuroides byrnei, Monodelphis domestica), rodents (Galea musteloides, Rattus norvegicus), lagomorphs (Ochotona rufescens), tree shrews (Tupaia glis), primates (Eulemur fulvus, Microcebus murinus, Saguinus oedipus, Saimiri sciureus), dogs (Canis lupus f. familiaris), ferrets (Mustela putorius f. furo), elephant shrews (Macroscelides proboscideus) and hyraxes (Procavia capensis). They all share a number of common principles in limb geometry and limb movement. Three propulsive elements move in a zig zag configuration with maximum angular excursion in the most proximal pivot. In both forelimbs and hindlimbs, the proximal and the distal propulsive elements move nearly in parallel to each other during the course of a stride cycle, a principle similar to the classical pantograph. Like in this drawing instrument, which is used to a duplicate and enlarge a graph, the movement of the proximal limb element is via the mobile middle element translated into the distal element. So, the arches covered by the feet are scaled relative to the arches covered by the shoulder and the knee joint. The scaling factor is determined by the relative lengths of the limb elements to each other, the intralimb proportions. Linkage of the first and the third element in the limbs is mediated by a biarticular muscle, the long head of the triceps brachii muscle in the forelimb and the gastrocnemius of the triceps surae muscle in the hindlimb.

Principles of limb geometry in symmetrical gaits of small mammals: the fore- and hindlimbs are composed of three propulsive elements and one contact element, they share the same effective length, the same total angular excursion and step length. The proximal (red) and the distal (green) propulsive element of a limb move nearly in parallel to each other (pantograph).

Collaborative projects:

DFG Innovation Group „Motion Systems“ (1996-2001):

Competence Centre for Interdisciplinary Prevention at the University of Jena

Key publications:

Walking Machines, Climbing Robots, Sensory Perzeption and Neural Control

The robustness of motion in small mammals and their extraordinary dynamic stability against external disturbances has inspired engineers worldwide to develop “intelligent” limbs for walking machines which rely on facilitated mechanics instead of massive control, a key prerequisite for autonomous walking in machines.
In several collaborative projects, we contributed with our studies to new concepts of limb construction, for example in explaining the relevance of three limb segments and their length proportions. For the transfer of biological principles into the engineering of a small, low-mass and agile climbing robot, we studied how rats, primates, and chameleons deal with the challenges of inclined, small-diameter substrates.
Current activities in this topic focus on the possible sensory input to the central motor control by mechanoreceptors, e.g. the carpal sinus hairs or the proprioceptors within the limb which measure tension of muscles or joint capsules. In rats as best representatives for the locomotor skills of small mammals we apply serious disturbances to the cyclic locomotion (trapdoor, perforated treadmill, removal of tactile hairs) in order to find out how the limbs react on and compensate for these challenges. Timing of kinematics events in all limbs together with muscle activation inform about the information transfer in the spinal control centers.

Challenging substrates: A rat is walking across a trapdoor device (top) and the instant at which the trapdoor opens is determined by a preselected threshold of force exerted by the limb (not necessarily the peak force). In contrast, on a perforated treadmill (bottom), the rat can anticipate the disturbance (hole) to a certain degree by sensing the substrate properties prior to foot contact. Electrodes implanted in the triceps and biceps muscles inform about the activity of the muscles controlling the elbow joint. The biarticular long head of the triceps muscle also “measures” the effective limb length.

Collaborative projects:

DFG Priority Program „Autonomous Walking“ (1997-2003):

BMBF Joint Project „InspiRat: A Biologically Inspired small climbing robot for the inspection of linear structures in semi-structured technical environment“ (2006-2011)

FESTO AG Bionic Learning Network „AirArm – pneumatic 4 - axis kinematics with inherent flexibility“

DARPA „Biologically-based network controller for dynamic legged locomotion“ (2010-2012)

DFG Joint Project „Technical, non-visual characterization of substrate contacts using carpal vibrissae as a biological model“

Key publications:

Dogs in Motion

Dog breeds constitute a unique model to study the functional consequences of intraspecific variation in size and shape of the musculoskeletal system, because this sort of variation is the product of artificial selection instead of a priori unknown evolutionary factors.
Supported by the Society of Cynological Research, numerous pedigree breeding clubs and their umbrella organization (“Verband für das deutsche Hundewesen” VDH), we investigated the locomotion of 32 dog breeds with respect to the influence of body size and body proportions on gait parameters and limb kinematics. More than 300 hundred dogs participated in the study and they covered a size range from about 2 kg up to more than 70 kg. In anticipation of scaling effects we are surprised to observe that variation in size has only minor effects on variation in limb proportions and limb kinematics. The geometry of the limbs is highly uniform across the breeds, only pedomorphic breeds show some deviations from the common pattern. Obviously, intraspecific variability of intra- and interlimb proportions is strongly limited in dogs.
Using high-resolution X-ray fluoroscopy we investigated the details of lumbar spine movements in beagles in symmetrical gaits. The growing relevance of our insights into the motion of healthy dogs in veterinary practice leads to the emergence of promising collaborations with veterinarians from several universities. Since 2014, HEEL, the world market leader for homeopathic healthcare, supports a comprehensive investigation into the dynamics of limb joints, with 250 dogs participating in the study.

Collaborative projects:

HEEL „Investigation of Joint Dynamics in Dogs“

AOVET “3-Dimensional In-vivo Biomechanics of the Canine Occipitoatlantoaxial, Thoracic and Lumbosacral Spine”

Key publications:

Diagnostic Potential of Motion Analyses

The impact of intraspecific variation in structure and function on motion principles and animal performance can also be investigated in animal models regularly used in preclinical medical research and genetics. Research approaches in these fields usually involve much larger sample sizes than most of the studies in evolutionary morphology. Preclinical projects experimentally induce particular aberration from the normal condition be it by a lesion in the central nervous system or a dysfunction of a certain joint. More challenging but equally promising is the search for phenotypic effects of genotypic changes. Here, we learn much about physiological and functional plasticity in the motion system which is able to compensate the initial genetic aberration during the maturity of the system in the individual’s ontogeny.
On the other hand, our long-term experience in motion analyses facilitates the identification of diagnostic parameters for the description of certain pharmacological effects or other treatment methods and assists in further characterization of phenotypes in transgenic animal models.

Collaborative projects:

Reaching and Grasping in Laboratory Rats after Lesions in the Sensorimotor Cortex

Diagnostic Potential of Motion Analyses in Painful Joint Diseases

Characterization of Phenotypes in Transgenic Mice

Key publications:

Idiomotion in Mammals

The behavioral repertoire of most mammals predominantly consists of more or less stationary, so-called idiomotory activities, which are directed in their motivation to the animal itself or to con-specifics. Idiomotion plays a dominant role in grooming, in food gathering, and in social interactions. Therefore, it appears plausible to expect a relevant evolutionary impact of these behaviors and their underlying movements on structure and function of the motion system. Still, this impact has not been considered so far. A few comparative studies of grooming in mammals have been done in the context of neurobiological questions. We started to fill this gap in our knowledge with analyses of the three-dimensional movements of limbs and trunk in dogs, rodents and lagomorphs.

Terrestrial Locomotion in Birds

Comparison of limb kinematics during terrestrial locomotion in seven species of birds belonging to various taxonomic groups (Corvus monedula, Coturnix coturnix, Eudromia elegans, Gallus gallus, Haematopus ostralegus, Recurvirostra avosetta, Vanellus vanellus) revealed common principles in limb geometry and body mechanics. Birds like quadruped mammals – but unlike humans – show no clear distinction between the two mechanical principles of moving the center of body mass. Inverse pendulum mechanics and spring-mass mechanics are mixed with a greater portion of the latter in all velocities and gaits. Similar to humans is that the two limb joints serve differently in adjusting the mechanics of the limb, with the intertarsal joint playing a crucial role for the whole-limb stiffness.
Another part of the project explores the influence of body mass on the variation of gait parameters and limb kinematics. For this purpose, we compared the intraspecific variation in chicken breeds covering a size range from 0,4 kg to 5 kg.
In addition, the collaboration with information scientists in this project offers new methodological approaches in the processing of huge samples of raw data (here: 7,749 stride cycles from a total of 1,267,320 X-ray frames). Reliable software programs for automatic landmark tracking on X-ray radiographs (a those existing for marker-based motion analysis) would enable us to process much more than selected “ideal” sequences of steady-state locomotion and invite attention also to the spectrum of variation and physiological plasticity.

Collaborative projects:

DFG Joint Project „Locomotion in Birds“ (since 2009)

Key publications:

Reconstruction of the Quadrupedal Locomotion in Early Tetrapods

We explored how a detailed comparison of locomotion in a taxonomically diverse sample of living quadruped amphibians and reptiles can support the reconstruction of quadrupedal locomotion in extant early tetrapods. Together with colleagues from the Museum of Nature in Gotha, we tested our approach at the fossil remains of stem amniotes (†Orobates pabsti) of the Thuringian Bromacker Formation. These fossils represent one of the very seldom “track-trackmaker”-associations, with footprints and nearly complete skeletons in the same deposits. With grant support from the Volkswagen Foundation, we studied footprints, gait parameters and limb kinematics and their relationship to speed and gait in salamanders, squamates, and alligators in order to find out which character combination does closely match the fossil recording and which combination does not.

Collaborative projects:

„Functional morphology of stem group amniotes“ (since 2012), financed by Volkswagen Foundation

Key publications:

Feeding Mechanisms of Vertebrates

This topic focuses on the evolution of head structures with special interest on the jaw apparatus and feeding mechanisms. In dog breeds, we study how the movements of the jaws together with exerted bite forces are functionally related to the shape of the teeth, the structure of the periodontium, the jaw muscles and the overall shape of the skull.
Another project explores how feeding mechanisms evolved in early land vertebrates. Newts in different stages of their life cycle are investigated during feeding in water and on land with particular attention on the their exceptional phenotypic plasticity.

Collaborative projects:

Key publications:

Research Projects of other Institutions

Researchers from other laboratories and institutions regularly use the facilities provided by our biplanar X-ray video fluoroscopy for their own research projects to study, for example, the sound production in the syrinx of songbirds, the movements of the owl’s neck, the head movements of spitting cobras when they spray out their venom or the activity of the jaws of a beavers when it gnaws at a wooden branch.
Furthermore, the X-ray video fluoroscopy is of particular importance for medicines or veterinarians who test new chirurgical practices, treatments and therapy methods in animal models.

Guest Researchers:

Joint Publications: