Leveraging 3D Printing and LEGO Robotics for Muscle Physiology Studies in Mice

Introduction: As movement experts, studying contractile function of muscle is relevant to Physical Therapy (PT) and rehabilitation. Isokinetic dynamometry systems for translational studies in mice can cost ~20K USD. Furthermore, most dynamometry systems require advanced mechanical and software engineering skills to customize testing and training protocols. We tested the feasibility of using a K-12 science, technology, engineering, and math (STEM) education robotics kit to perform muscle testing and plyometric exercise (stretch-shortening contractions) on the tibialis anterior (TA) muscle in a mouse model. Methods: We studied a convenience sample of three mice (1 yr-old, male, BLAJ, Strain#012767, The Jackson Laboratory), which lacked the protein dysferlin, and modeled human limb-girdle muscular dystrophy type-2B (LGMD2B). We combined custom 3D-printed parts with a Spike Prime LEGO robotics kit to create a robotic ankle dynamometer for mice. The dynamometer had a footplate connected to a torque transducer and LEGO stepper motor, such that, the ankle could be moved into plantarflexion and dorsiflexion at a fixed velocity and forces generated by the dorsiflexors and plantarflexors could be measured. After optical and mechanical calibration of our dynamometer, we performed a single bout of plyometric exercise on the ankle dorsiflexors of BLAJ mice (4 sets of 10 repetitions, 3 min rest between sets, 90-160° of plantarflexion, 300°/s angular velocity). During exercise, mice were anesthetized with inhaled isoflurane and muscle contractions were elicited through neuromuscular electrical stimulation. Three days post-exercise, we collected the exercised (left) and unexercised (right) TA muscles, froze them in liquid nitrogen, made 10µm-thick sections, and stained the sections with hematoxylin and eosin to evaluate muscle damage. Results: We found that 15.05±3.3 % of muscle fibers in TA muscles exposed to plyometric contractions were damaged. In contrast, only 1.21±0.74 % of muscle fibers in unexercised TA muscles were damaged (P = 0.014799, paired t-test, N = 3). Discussion: Our pilot study suggests that 3D printed parts can be combined with LEGO robotics to prototype devices that are suitable for muscle physiology studies in small animal models, such as mice. BLAJ mice, which lack the protein dysferlin not only serve as a model for human LGMD2B, but also are a model for pronounced post-exercise muscle damage – therefore, our plyometric exercise protocol in BLAJ mice can be used to test the effectiveness of rehabilitative and pharmacological therapies in reducing post-exercise muscle damage. Our findings are limited in their scope due to the small sample size. Also, we found that LEGO stepper motors can lose accuracy at angular velocities above 300°/s (60% of max velocity). Conclusions: Our study suggests that 3D printing and LEGO robotics can be leveraged to prototype devices for translational kinesiological studies, such as for dynamometry. The simplicity and low cost of building a functional dynamometer could increase global inclusion, diversity, and equity in muscle biology research. NIH R03HD091648, AR3T Pitch Award through NIH P2CHD086843, NIH R01AR079884-01 (P.L. Jones PI), & Wayne State Warrior Funder. BLAJ mice gifted by the Jain Foundation, Inc. This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.