New research reveals the surprising gap between wearable technology and regulatory approval
The Promise of Real-World Walking Speed
Walking ability is a key determinant of quality of life, essential for daily activities and maintaining independence. Because walking relies on multiple physiological systems—neurological, cardiovascular, and pulmonary—gait assessment has become central to clinical evaluation.
Walking speed has been associated with disease severity, prognosis, and functional status across numerous conditions, including multiple sclerosis, heart failure, and stroke. Even in healthy elderly individuals, slower walking speed can predict higher mortality risk and dementia. This makes walking speed an extraordinarily valuable health indicator.
However, traditional walking tests conducted in clinical settings have a significant problem: the Hawthorne effect. People change their behavior when they know they’re being observed. Some walk faster to appear capable, while others deliberately slow down to qualify for clinical trials. These tests capture only a brief snapshot, potentially influenced by mood, fatigue, or stress.
Wearable sensors offer an alternative by capturing every movement in daily life over extended periods. Continuous monitoring over weeks or months provides an ecologically valid picture of real-world mobility that is robust to transient behavioral changes.
The Study: Examining What’s Actually Approved
Researchers from Belgium, Germany, and the United Kingdom conducted a systematic review to identify evidence on real-world gait speed measurements that have received or are seeking regulatory approval from agencies like the European Medicines Agency (EMA) and U.S. Food and Drug Administration (FDA).
They searched MEDLINE and EMBASE databases, screened 503 records, and included only studies published from 2019 onward that clearly demonstrated intent for regulatory qualification. They supplemented their systematic review by manually searching FDA and EMA websites for Letters of Intent and qualification opinions.
Key Criteria for Regulatory Approval
To be considered for regulatory approval, a digital outcome must demonstrate:
- Feasibility: Practical and acceptable for real-world use
- Reliability: Consistent measurements under identical conditions
- Accuracy: Close agreement with gold standard measurements
- Validity: Accurately measures what it intends to measure
- Sensitivity to change: Detects meaningful changes over time
- Minimal Clinically Important Difference (MCID) : The smallest change perceived as beneficial by patients
Key Findings: One Success, Many Failures
The Only Regulatory Success Story
Stride Velocity 95th Centile (SV95C) for Duchenne Muscular Dystrophy stands alone as the first and only regulatory-qualified digital primary efficacy endpoint.
In 2023, the EMA qualified SV95C as a primary endpoint in superiority studies for ambulatory patients with DMD aged 4 years and older. Measured with the ActiMyo wearable device (Sysnav, France), SV95C represents the 5% fastest strides in daily living.
The evidence supporting this qualification is substantial:
- Accuracy: Within 5% of reference 6-minute walk test measurements
- Reliability: Intraclass correlation coefficient of 0.97
- Validity: Significant correlation with 6MWT (0.54-0.68) and NSAA (0.64-0.78)
- Sensitivity to change: Significant decline as early as 3 months (p < 0.001)
- MCID: 0.1 m/s, corresponding to a 36-meter difference in 6MWT
What’s Been Approved vs. What’s Still Waiting
| Disease | Device/Outcome | Current Status | What This Means |
|---|---|---|---|
| Duchenne Muscular Dystrophy | SV95C (ActiMyo) | ✅ EMA APPROVED (2023) | Only one that made it through – can be used as main measure in clinical trials |
| Multiple Sclerosis | actibelt | 📋 FDA Letter of Intent Accepted | Company has told FDA they want approval – still needs more evidence |
| Sarcopenia | actibelt | 📋 FDA Letter of Intent Accepted | Same device, different disease – still needs separate validation |
| Parkinson’s Disease | AX3/Dynaport | 🔬 Research Stage Only | Studies show it works, but not ready for regulatory approval yet |
| Huntington Disease | Biostamp | ❌ FDA Rejected | FDA said the measure didn’t show clear impact on what matters to patients |
| Various Conditions | Multiple devices | 🔬 Research Stage Only | €50 million EU project still hasn’t delivered a validated tool |
How to read this table: The checkmarks and symbols show the current regulatory status. Only SV95C for Duchenne Muscular Dystrophy has actually been approved. The others are either still in early stages, waiting for more evidence, or have been rejected.
The Regulatory Pathway – Simple Explanation
| Step | How Many? | What Happens |
|---|---|---|
| FDA Letters of Intent | 4 total | Companies tell the FDA: “We want to get our device approved for this disease” |
| • Biostamp (Huntington) | ➜ REJECTED (2020) | |
| • actibelt (MS) | ➜ ACCEPTED (still working on it) | |
| • actibelt (sarcopenia) | ➜ ACCEPTED (still working on it) | |
| • Actimyo (DMD) | ➜ ACCEPTED (this one succeeded!) | |
| EMA Qualification Opinions | 1 total | This is the only one that made it all the way through – SV95C for DMD |
| EMA Scientific Advice | 1 total | EMA gave advice on actibelt for MS, hip fracture, and sarcopenia |
| FDA Fully Validated | 0 | NO device or outcome has been fully validated by the FDA yet |
How to read this table: This shows the journey a device must take to get approved. Four devices started the process, but only one (SV95C for DMD) made it through all the steps.
What Makes a Good Digital Outcome?
| Quality | What It Means | SV95C’s Performance |
|---|---|---|
| Accuracy | How close is the measurement to the truth? | Within 5% of hospital walking test – EXCELLENT |
| Reliability | Does it give consistent results? | Score of 0.97 out of 1.0 – EXCELLENT |
| Validity | Does it measure what it should? | Correlates well (0.54-0.78) with standard tests – GOOD |
| Sensitivity | Can it detect small changes? | Detects decline as early as 3 months – GOOD |
| MCID | What change actually matters to patients? | 0.1 m/s (10% decline) – CLEARLY DEFINED |
How to read this table: This shows the five qualities a digital outcome must have to get approved. SV95C performed well on all of them, which is why it succeeded where others failed.
Why Approval Is So Difficult
The Regulatory Hurdle
Qualification is time-consuming and resource-intensive. The authors identify several key challenges:
Condition-Specific Validation: Current regulatory frameworks require validation within a specific context of use. This means separate and extensive validation is needed for each medical condition, despite walking speed being relevant across many diseases.
Large-Scale Challenges: The MOBILISE-D project, a €50 million initiative funded by industry and the EU Innovative Medicines Initiative, faced major obstacles. Despite substantial investment and collaboration with technology companies, clinicians, and patient groups, the project has not yet delivered a validated functional digital mobility assessment tool.
Time-Limited Funding: Grant-funded projects operate within fixed timeframes that may not align with the lengthy regulatory qualification process. Qualification often requires years of data collection and analysis that exceed typical project timelines.
Evidence Gaps: Most studies remain small-scale academic investigations with small sample sizes, lacking robust datasets and a clearly articulated intention to pursue regulatory qualification.
The Success Story: What Made SV95C Different?
The qualification of SV95C for DMD succeeded because of several key factors:
- Focused effort: Long-term, dedicated research with multiple studies demonstrating strong metric properties
- Patient-level data: Large normative databases and real-world evidence
- Early regulatory engagement: Ongoing dialogue with EMA throughout development
- Clear clinical meaning: SV95C correlates with established clinical endpoints like 6MWT
- Patient relevance: Measures what matters to patients—real-world mobility
What This Means for Patients and Doctors
For Clinical Trials
Digital outcomes like SV95C can significantly reduce sample sizes needed for clinical trials. For example, a phase III ataluren study for DMD required 105 patients per arm to show a 30-meter difference in 6MWT. For SV95C, only 14 patients per arm with DMD aged 7 years or above provides sufficient statistical power (80%) to demonstrate significant stabilization.
This means:
- Smaller, faster trials: Fewer patients needed to demonstrate drug efficacy
- Reduced costs: Lower recruitment and monitoring expenses
- Faster drug development: Accelerated pathway to market
- Less patient burden: Fewer clinical visits and assessments
For Clinical Practice
Wearable technology could provide digital measures to assess disease progression and guide treatment strategy at the individual level. However, widespread adoption requires:
- Regulatory approval: Ensures outcomes are clinically meaningful and reliable
- Patient-centered design: Intuitive apps and interfaces that present clear information
- Clinician trust: Easy interpretation and alignment with clinical decision-making
The Road Ahead: Recommendations
Streamline Qualification Pathways
The authors propose simplifying the qualification process by:
Unified Regulatory Approach: The EMA provides a unified pathway for pain treatment approvals across diseases. A similar approach for walking speed could accelerate adoption across multiple indications.
Bridging Different Contexts: Demonstrating validity in one condition could support faster implementation in others with similar pathophysiology.
Harmonized Methodologies: Standardizing devices, algorithms, and study designs would facilitate comparisons and meta-analyses.
Design Studies for Regulatory Success
To support regulatory qualification, studies must:
- Align with regulatory expectations: Early and ongoing dialogue with agencies like EMA and FDA
- Beyond feasibility: Rigorously evaluate full psychometric properties in target populations
- Adequate sample sizes: Sufficient power to demonstrate reliability and validity
- Long-term collaboration: Partnerships between developers, clinicians, patients, and regulators
- Publish negative results: Learning from failures to improve future efforts
Future Research Priorities
The authors identify several critical areas for future investigation:
- Broader disease validation: Beyond DMD to conditions like Parkinson’s, MS, and sarcopenia
- Patient-centered outcomes: Ensuring measures are meaningful to patients, not just researchers
- Machine learning integration: Predictive models for early diagnosis and personalized treatment
- Long-term studies: Understanding how digital outcomes relate to meaningful clinical endpoints
- Regulatory pathway adaptations: Developing frameworks that accommodate the unique characteristics of digital measures
The Bottom Line
Walking speed measured by wearable devices shows considerable promise for accelerating drug development and improving patient care. However, most published studies are insufficient to obtain regulatory approval, which remains a critical step toward expanding digital outcomes’ reach in clinical practice.
The qualification of SV95C for DMD demonstrates what is possible with focused, long-term effort. Yet, this remains an exception rather than the rule. The gap between technological capability and regulatory acceptance is substantial, and bridging it requires:
- Extensive validation efforts across broader disease populations
- Regulatory pathway adaptations that recognize the unique characteristics of digital measures
- Improved standardization of devices, algorithms, and study methodologies
- Patient-centered design that empowers individuals and builds trust
- Global collaboration to harmonize approaches across regulatory jurisdictions
As the authors conclude: “With this approach, not only will they increase knowledge in the community, but they will also increase the number of tools that can directly find routine use.”
Reference: Poleur M, Tychon C, Gilbert S, Daumer M and Servais L (2026) Real-world walking speed as a digital biomarker and outcome measure for clinical trials—a systematic review, regulatory status and future directions. Front. Digit. Health 8:1726549. doi: 10.3389/fdgth.2026.1726549
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