Biology subjects

Biewener, A. A.

Publications and source records attributed to Biewener, A. A..

4 recordsLinked to original sources

bioRxiv2026

The muscle coordination required for efficient locomotion scales with body size

AO_SCPLOWBSTRACTC_SCPLOWMuscle efficiency decreases with increasing size, largely due to a relative decrease in its mechanical output. Muscle mechanical output depends on its activation, strain, and strain rate and thus varies between different muscles within a limb during locomotion. Distinct muscle coordination patterns are required for efficient cycling, and so we would expect that the coordination patterns for efficient cycling or indeed locomotion would change across animal sizes. We tested whether muscle coordination would change with muscle size using data derived from human cycling: this paradigm allowed for controlled changes in both crank torque and cadence, allowing the multifactorial problem of muscle power output to be decomposed. We used kinematic and pedal data from 12 cyclists undergoing steady pedalling at cadences from 80 to 140 r.p.m. and generated musculoskeletal simulations of their movements. We introduced novel multisegment muscle models in the simulation that incorporated the internal muscle mass and thus accounted for the scaling effects of muscle tissue inertia. We solved the simulations for the muscle activity that was required to minimise the metabolic cost during cycling for each condition. The masses of the muscle models were scaled across five orders of magnitude. The predicted muscle activations were classified by Principal Component analysis to identify whether the coordination of muscle activity was modulated across models with different sized muscles. Analysis of variance revealed significant changes in coordination at the large-scale factors. This study shows how the coordination of muscle activity during locomotion will likely change across a range of body sizes due to the non-linear effects of the inertial mass within the muscle tissues.

bioengineering↗

bioRxiv2026

A view of bird's eyes -- Pigeons lock their eyes in place during flight

Vision in most animals follows a fixate-and-saccade pattern. Birds fixate their viewing direction, then rapidly shift this gaze through head and eye movements. We used a head-mounted eye-tracking system in flying pigeons to relate eye to head movement and map eye position within the head. After take-off, the birds increased pupil size and adopted a fixed and consistent eye position in their head. In different visual environments, eye position returned to within 1{degrees} during flight. When flying, the birds positioned their eyes close to the primary horizontal axes of their vestibular systems. Because visual neurons share a common reference frame with the vestibular system, a consistent flight gaze position may actively align vision with mechanosensation and facilitate perception of self-motion. One-Sentence SummaryA head-mounted eye-tracking system shows that pigeons adopt a consistent eye-in-head position during free flight

animal behavior and cognition↗

bioRxiv2024

Landing on a dime: the biomechanics and kinematics of lovebirds (Agapornis roseicollis) landing on a swinging perch

Birds frequently must land safely and accurately on moving branches or power lines, and seemingly accomplish such maneuvers with acrobatic precision. To examine how birds target and land successfully on moving supports, we investigated how peach-faced lovebirds (Agapornis roseicollis) approach and land on a swinging perch. Lovebirds were trained to take off from a hand-held perch and fly [~]6 m to land on a servo-controlled swinging perch, driven at three sinusoidal frequencies, in a purpose-built flight corridor. Lovebird flight and landing kinematics were recorded using a motion capture system. A force-torque sensor mounted to the landing perch recorded the birds horizontal and vertical landing force and pitch torque. In support of our hypothesis for stable landings, lovebirds timed their landings in a majority of trials (51.3%), when the perch was approaching either extreme of its motion with its velocity nearing zero (27.5% in the same direction as the birds approach - SDs, and 23.8% in the opposite direction to the birds approach - ODs). As a result, lovebirds exhibited a robust bimodal strategy for timing their landing to the phase of the swinging perch. Less commonly, lovebirds landed when the perch was moving at high velocity either toward the birds approach (12.3%) or in the same direction as the birds approach (11.5%); with the remainder (21.9%) of trials distributed over a broad range of swing phases. Landing forces were greatest in the horizontal plane, with vertical forces more varied and of smaller magnitude across all landing conditions. This reflected the shallow flight trajectory (center of mass approach angle: -13.2 + 3.0o SEM relative to horizontal) that the lovebirds adopted to decelerate and land. Increased landing force correlated with greater landing speed of the bird relative to the perch (R2 = 0.4296, p < 0.0001). The lovebirds initiated landing with a consistent body pitch angle (81.9 + 0.46o SEM relative to horizontal) across all landing conditions, using the horizontal perch reaction force to assist in braking when landing. Correspondingly, the landing angle of the feet relative to the perch support was 56.9 + 2.8o. Subsequent head-down body pitch rotation of the bird after landing was not well correlated and generally opposite to the initial direction and magnitude of landing pitch torque, which was generally negative due to foot rotation and ankle flexion at landing. Flexion of the birds hind limb joints (ankle: - 29.2 + 9.2o, knee: -13.6 + 7.4o, and hip: -4.0 + 3.4o at landing, combined with their horizontal approach trajectory, reduced the magnitude of landing torque by aligning the birds center of mass trajectory more closely to the landing perch (3.61 + 0.21 cm) than if they landed from above the perch. Landing pitch torque and body pitch rotation also increased uniformly in response to increased perch swing frequency. In contrast to landing forces, landing pitch torque was more varied across landing conditions, as well as in relation to the phase of landing. In general, higher landing force was encountered when the perch was moving towards the approaching bird. Our results indicate that lovebirds regulate their approach trajectory and velocity to time the phase of landing to a moving perch, providing insight for designing biologically-inspired unmanned aerial vehicles capable of landing on moving targets.

animal behavior and cognition↗

bioRxiv2019

Tuning of feedforward control enables stable muscle force length dynamics after loss of autogenic proprioceptive feedback

Animals must integrate feedforward, feedback and intrinsic mechanical control mechanisms to maintain stable locomotion. Recent studies of guinea fowl (Numida meleagris) revealed that the distal leg muscles rapidly modulate force and work output to minimize perturbations in uneven terrain. Here we probe the role of reflexes in the rapid perturbation response of muscle by studying the effects of proprioceptive loss. We induced bilateral loss of autogenic proprioception in the lateral gastrocnemius muscle (LG) using self-reinnervation. We compared ankle kinematics and in vivo muscle dynamics in birds with reinnervated LG and intact LG. Reinnervated and intact muscles exhibit similar force-length dynamics, with rapid changes in work to stabilize running obstacle terrain. Reinnervated LG exhibits 23ms earlier steady-state activation, consistent with feedforward tuning of activation phase to compensate for lost proprioception. Modulation of force duration is impaired in rLG, confirming the role of reflex feedback in regulating force duration in intact muscle.

physiology↗