We've got moments arms covered—what about muscle force? Unlike in humans, most fly muscle parameters are unknown. So we built an optimization pipeline in OpenSim to identify Hill-type parameters to produce measured fly kinematics. This revealed coordinated, testable muscle synergies across behaviors

We began by tracing muscle fibers, origins/insertions, and paths from high-resolution X-ray scans across specimens. This allowed us to recover moment arms around each joint center and cross-sectional area as a prior on muscle strength.

In plain terms: torque = force x moment arm.

🪰 How do dozens of tiny fly muscles cooperate to move a leg?

We’re excited to share the first 3D, data-driven musculoskeletal model of Drosophila legs based on Hill-type muscles, running in OpenSim and MuJoCo simulation environments.

Preprint: arxiv.org/abs/2509.06426

3-2/ EVEN without antennae, the coordination between head rotations and foreleg movements remains! 😱😱😱

3-1/ Or, head-immobilized flies will still move their antennae and forelegs in a fascinatingly coordinated fashion. 🤯

3/ Surprisingly, each body part operates independently of the others' sensory feedback. Even with amputated forelegs, flies still move their antennae and head! This suggests an open-loop (not feedback-based) coordination mechanism. 🤖

2/ By simulating these motions in a biomechanical model, we discovered the reason: synchronization ensures forceful and unobstructed interactions between the forelegs and antennae. This efficiency guarantees a thorough cleaning job. 💪✨

1/ In our study, we explored how flies synchronize their head, antennae, and forelegs during goal-directed antennal grooming. We found that when targeting an antenna, flies perform three distinct motor actions. But why these specific movements?

🧵 Ever seen a fly perform a full self-care ritual? 🪰 They meticulously rub their head and clean their antennae, ensuring every speck of dirt is gone. But how do they coordinate all those tiny body parts so seamlessly?👇