12/29/2025
By Irma Silva

The Kennedy College of Sciences, Department of Biological Sciences, invites you to attend a Ph.D. Proposal Defense in Applied Biology by Brandon Reder entitled "Morphological and physiological analyses of avian ankle antagonist muscle function.”

Candidate: Brandon Reder
Degree: Doctoral
Date: Thursday, Jan. 8
Time: 1 – 3:30 p.m.
Location: Olsen Hall 234 or Zoom Meeting ID: 727 220 4017

Title: Morphological and physiological analyses of avian ankle antagonist muscle function

Committee Members:

  • Nicolai Konow (Advisor), Associate Professor, Biological Sciences, University of Massachusetts Lowell
  • Jeffery Moore (Committee Chair), Professor, Biological Sciences, University of Massachusetts Lowell
  • Jonas Rubenson, Professor, Kinesiology, Penn State
  • Andrew Biewener, Professor Emeritus, Department of Organismic and Evolutionary Biology, Harvard


Brief Abstract:

Skeletal muscle is the machinery powering movement across terrain, which is critical for tasks like perturbation negotiation. Most skeletal joints are spanned by muscle pairs that actuate with opposing torques, a phenomenon known as antagonist action. One such well-recognized antagonist pair includes the gastrocnemii (gravity-resisting extensors) and tibialis anterior (a swing-initiating flexor), which actuate the ankle across tetrapods. Tetrapods have either four or two legs. In quadrupeds, the hind limbs primarily act as motors that propel forward movement, whereas the forelimbs act as shock absorbers and brakes. Obligate bipeds lack forelimb functionality in locomotion and are relatively uncommon among extant tetrapods, humans and ground birds being the most ubiquitous examples. Supporting the body on two legs, with each leg assuming roles otherwise subserved by forelimbs is inherently less stable, raising the question how humans and ground birds remain such highly capable locomotors? Ground birds provide a convenient model to understand the structural and architectural adaptations to antagonistic ankle actuators for ground-based locomotion without forelimbs. Antagonist co-activation is well documented in electromyography studies of human locomotion. However, fascicle strain and muscle force (which requires surgical instrumentation) cannot be measured concurrently with electromyography (EMG) in humans. 

This ensemble of measurements is critical for understanding the timing and magnitude of muscle work and can be acquired from Guinea fowl (Numida meleagris). Similarly, studies of preparatory muscle activity during falls have examined EMG from an antagonist pair or measured EMG, strain, and force from the gastrocnemii. Combined activation, strain, and force measurements from an antagonist pair stands to provide a detailed understanding of the adaptive function of antagonism. The type and arrangement of myofibers vary across muscles and is shaped by the myosin heavy chain isoform content, and by fiber architectural arrangement (physiological cross-sectional area). Muscles of the distal limb often have long tendons that are useful for the elastic storage and rapid release (elastic recoil) of energy. This thesis seeks to integrate effects of myofiber type, arrangement, and elastic recoil to understand the implications of muscle structure on their biomechanical function. Effects of body and muscle size presents challenges that may be met through modifications to muscle fiber types and architecture. The greater stride frequency of small animals necessitates faster contracting muscles. Faster myosin isoforms or muscle architecture with relatively longer muscle fibers, with more parallel arrangement may be key to achieving high stride frequencies. Understanding scaling effects on antagonist structure and function will be enabled by focusing on ankle and foot antagonists across ground birds spanning 0.1 - 100 kg in body size. Overall, I seek to investigate (Aim 1) myosin isoform composition, and (Aim 2) myofiber architecture, as they relate to (using Guinea fowl) mechanical function during (Aim 3) bipedal treadmill locomotion and (Aim 4) impact-preparation during falls.