Smart Wearables and Implants Bring Real-Time Muscle Monitoring Into Daily Life
A sweeping review maps how miniaturized bioelectronic devices now track muscle electricity, mechanics, and oxygen continuously outside the clinic.
Summary
This 2026 review from Delft University of Technology surveys the state of wearable and implantable devices designed to monitor muscle activity in real time. Covering three major signal classes — electrophysiological (ECG, EMG, MMG), biomechanical (FMG, EIM, AMG, SMG), and oxygenation (PPG, electrochemical, luminescence-based sensors) — the authors trace the field's evolution from bulky clinical instruments to miniaturized, wireless systems. The review details advances in soft and flexible materials, device architectures, and sensing modalities. Key applications span disease diagnostics, neuromuscular rehabilitation, prosthetic control, and personalized fitness. The authors identify remaining challenges including signal fidelity, biocompatibility, power supply, and data integration, and outline directions for next-generation continuous muscle health platforms.
Detailed Summary
Skeletal, cardiac, and smooth muscles generate a rich repertoire of biosignals reflecting neural innervation, mechanical contraction, and metabolic state. Tracking these signals continuously, outside the clinic and during ordinary life, has become a central goal of bioelectronics research. This comprehensive review — authored by engineers at Delft University of Technology and published in Advanced Science — critically surveys the materials, device architectures, and sensing principles that are reshaping muscle monitoring.
The biological foundation is covered in depth. Skeletal muscle is organized from fascicles to myofibers to sarcomeres, where actin–myosin sliding drives contraction triggered by action potentials propagating through motor units (recruited smallest-to-largest per Henneman's size principle). Cardiac muscle relies on the sinoatrial node and conduction system for synchronized pumping, while smooth muscle, lining hollow organs, contracts slowly and sustainably under autonomic control. All three types depend on adequate oxygen supply; anaerobic fallback produces lactate and acidosis, hallmarks of fatigue.
Electrophysiological monitoring dominates the review. ECG captures cardiac action potentials at amplitudes of 10 µV–4 mV and has migrated from 12-lead clinical systems to flexible skin-conforming patches and implantable loop recorders. EMG records skeletal muscle activity and is being transformed by dry, stretchable electrode arrays and needle-free implantable variants. Magnetomyography (MMG), detecting magnetic fields from muscle currents, offers motion-artifact immunity and is advancing with quantum and optically pumped magnetometers.
Biomechanical sensing encompasses force myography (FMG), electrical impedance myography (EIM), acoustic myography (AMG), and sono-myography (SMG). These modalities detect volumetric changes, impedance shifts, and acoustic signatures during contraction, and are being realized in soft, body-conforming formats suited for prosthetic control and rehabilitation feedback. Tissue oxygenation monitoring relies on photoplethysmography, electrochemical biosensors, and luminescence-based oxygen sensing — each offering distinct trade-offs between invasiveness, sensitivity, and integration complexity.
A central theme is the transition from rigid, wired clinical hardware to flexible, wireless, skin-integrated or subcutaneous systems enabled by advances in conducting polymers, hydrogels, stretchable substrates, and low-power electronics. Applications highlighted include early diagnosis of arrhythmias and neuromuscular disease, post-surgical rehabilitation, prosthetic limb control, human–machine interfaces for augmented reality, and continuous athlete performance monitoring. The authors also flag critical open challenges: maintaining signal quality during motion, ensuring long-term biocompatibility for implants, managing power budgets for continuous wireless operation, and developing AI-ready data pipelines to translate raw biosignals into clinically actionable metrics.
Key Findings
- Muscle biosignals span electrophysiology (ECG/EMG/MMG), biomechanics (FMG/EIM/AMG/SMG), and oxygenation — all now targetable by wearables.
- Flexible, stretchable electrode materials and soft substrates are enabling skin-conforming, motion-tolerant sensor arrays for continuous EMG and ECG.
- Magnetomyography using quantum magnetometers provides motion-artifact-resistant muscle signal capture without skin contact.
- Electrochemical and luminescence-based oxygen sensors in implantable formats can track real-time muscle metabolic state.
- Key unsolved challenges include chronic biocompatibility, wireless power delivery, and AI integration for clinical-grade signal interpretation.
Methodology
This is a narrative expert review drawing on primary literature published predominantly over the past decade. The authors systematically organize findings by signal modality (electrophysiological, biomechanical, oxygenation) and by device category (wearable vs. implantable), synthesizing materials science, device engineering, and clinical application perspectives. No meta-analysis or quantitative pooling of results was performed.
Study Limitations
As a narrative review, the paper does not systematically evaluate the clinical evidence base or quantify device performance across studies, limiting direct comparison of technologies. Many featured devices remain at the prototype or early-validation stage, with limited long-term human data on reliability, biocompatibility, and real-world accuracy. The review's focus on materials and device innovation means regulatory pathways, cost-effectiveness, and patient usability receive limited treatment.
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