Research & evidence
Evidence shaping Kinegrade.
Kinegrade is being developed around established research on muscle strength, mobility, physical performance, longitudinal change, integrated physical-function measurement and remote assessment.
The objective is not to invent a proprietary measure of “muscle health.” It is to explore how clinically meaningful measurements can be collected more consistently, repeated at the right time and understood longitudinally.
Important distinction: the publications below support the clinical relevance, measurement properties or feasibility of established physical-function assessments. They do not constitute clinical validation of Kinegrade itself. Kinegrade-specific workflows, algorithms and intended uses will require their own validation.
Scientific approach
The measurement is only useful if the method is trustworthy.
Physical function is multidimensional. Strength, mobility, balance, endurance and functional performance describe different parts of a person’s physical capacity.
Kinegrade’s product direction is therefore based on established assessment methods rather than prematurely reducing physical function to a proprietary universal score. At the same time, emerging research suggests that multiple objectively measured domains can be combined into a broader longitudinal view of physical functioning.
The research also makes something else clear: the protocol matters. Body position, equipment, instructions, timing, number of attempts and testing environment can materially affect measurements. Longitudinal follow-up is only meaningful when measurements are sufficiently comparable over time.
Measure things that matter.
Strength, gait and physical-performance measures are associated with disability, frailty, independence and other clinically relevant outcomes across ageing populations.
Protocol is part of the measurement.
Research on handgrip strength in particular demonstrates how differences in posture, equipment and procedure can reduce comparability between measurements.
A trajectory can matter more than a snapshot.
Repeated measurement can reveal improvement, deterioration, recovery or stability that cannot be understood from a single isolated result.
Remote assessment is possible — but test specific.
Smartphone and virtual assessment studies are increasingly demonstrating feasibility and reliability, while also showing that not every test or setting can automatically be treated as interchangeable.
What the evidence suggests
Five implications for the Kinegrade product direction.
Standardize before interpreting.
A longitudinal system should record how a measurement was performed, not only the final number. Protocol variation can otherwise be mistaken for biological or functional change.
Measure change, not simply normality.
Reference values and thresholds are useful, but longitudinal care also requires understanding whether an individual has meaningfully improved or deteriorated relative to their own baseline.
Make reassessment part of the workflow.
Longitudinal evidence depends on repeated measurements. A measurement platform therefore has value only if reassessment actually occurs and comparable results can be retrieved over time.
Validate remote measurement one test at a time.
Recent evidence makes smartphone and home assessment a credible direction, but agreement differs between tests. Remote use should therefore be validated for the specific assessment, protocol, population and intended clinical use.
Build toward a physical-function profile — not an arbitrary score.
Recent work on the Measured Physical Functioning Index (MePFIX) provides scientific precedent for combining several objectively measured domains into a longitudinal view of physical functioning. For Kinegrade, the implication is to preserve validated individual measures while exploring higher-level domain summaries only when there is sufficient evidence to support them.
Emerging research direction
From isolated measurements to an integrated view of physical functioning.
The Measured Physical Functioning Index (MePFIX) was developed from FINFIT data involving 5,238 Finnish working-age adults. It combines ten objectively measured factors spanning body composition, cardiorespiratory fitness, muscular fitness, physical activity, stationary behaviour and time in bed.
The work is relevant to Kinegrade because it demonstrates a broader scientific direction: physical functioning can be approached as a multidimensional, measured construct and followed longitudinally, rather than represented only by disconnected test results.
Important: MePFIX is currently published as a preprint and was developed primarily as a population-level index for Finnish adults aged 20–69. It should not be presented as a validated Kinegrade score, rehabilitation outcome measure or smartphone-derived index.
Research library
Selected evidence informing the direction.
This is not intended to be a systematic review of the field. It is a curated library of publications particularly relevant to the questions Kinegrade is currently exploring.
Sarcopenia: revised European consensus on definition and diagnosis
EWGSOP2 places low muscle strength at the forefront of sarcopenia assessment, with muscle quantity or quality used for confirmation and physical performance used to identify severity. Grip strength, chair stand, gait speed, SPPB and TUG are among the measures discussed.
Cruz-Jentoft et al. · Age and Ageing · 2019 ↗Consensus guidelines for sarcopenia prevention, diagnosis and management in Australia and New Zealand
Evidence-informed consensus guidance for assessment and management of sarcopenia. The guidance reinforces standardized measurement of muscle strength and physical performance and the value of consistent measures when following an individual over time.
Zanker et al. · Journal of Cachexia, Sarcopenia and Muscle · 2023 ↗A Short Physical Performance Battery Assessing Lower Extremity Function
Foundational work on the Short Physical Performance Battery combined standing balance, walking and repeated chair rises in more than 5,000 older adults. Performance was associated with self-reported disability and subsequent adverse outcomes.
Guralnik et al. · Journal of Gerontology · 1994 ↗Gait Speed and Survival in Older Adults
Pooled longitudinal data demonstrated a strong relationship between usual gait speed and survival in older adults, helping establish gait speed as a clinically informative measure of overall health and function.
Studenski et al. · JAMA · 2011 ↗Meaningful Change and Responsiveness in Common Physical Performance Measures in Older Adults
This study estimated meaningful changes for gait speed, SPPB and six-minute walk distance. It is especially relevant to longitudinal monitoring because it distinguishes measurement change from change likely to matter clinically.
Perera et al. · Journal of the American Geriatrics Society · 2006 ↗Prognostic value of grip strength: findings from the PURE study
In a large multinational prospective cohort, lower grip strength was associated with mortality and cardiovascular outcomes after adjustment for other factors. The study illustrates the broader health information contained in a simple objective strength measure.
Leong et al. · The Lancet · 2015 ↗Strength, but not muscle mass, is associated with mortality in the Health ABC cohort
In older adults, quadriceps and grip strength were strongly associated with mortality while muscle size itself was not strongly associated. The findings helped shift attention from muscle quantity alone toward functional muscle performance.
Newman et al. · Journal of Gerontology A · 2006 ↗Grip Strength across the Life Course: Normative Data from Twelve British Studies
Nearly 50,000 participants contributed to age- and sex-specific grip-strength reference curves spanning much of the life course. The work illustrates the importance of appropriate reference populations when interpreting an individual result.
Dodds et al. · PLOS ONE · 2014 ↗Differences in handgrip strength protocols to identify sarcopenia and frailty
Review of handgrip-strength protocols found substantial variation in posture, arm position, dynamometer settings, repetitions and other procedural details. The authors emphasize the need for standardized protocols to make measurements comparable.
Sousa-Santos & Amaral · BMC Geriatrics · 2017 ↗Grip strength measurement: Towards a standardized approach in sarcopenia research and practice
This systematic review examined how grip strength was being measured in sarcopenia research and whether proposed standardized protocols were actually being followed. It directly supports the need to capture measurement protocol alongside the result.
Schaap et al. · European Geriatric Medicine · 2016 ↗Measurement and Interpretation of Handgrip Strength for Research on Sarcopenia and Osteoporosis
Review of dynamometer types, testing positions, reference values and interpretation of handgrip strength. It highlights why accurate measurement and consistent testing conditions are essential when comparing results.
Lee & Gong · Journal of Bone Metabolism · 2020 ↗Assessment of Function and Disability in Longitudinal Studies
Gill reviews progress in the longitudinal measurement of physical function and disability in older adults, including the role of performance-based testing and emerging measurement technologies.
Gill · Journal of the American Geriatrics Society · 2010 ↗Changes in muscle strength and physical function in older patients during and after hospitalisation
Repeated measurements during and after acute hospitalisation demonstrated that different aspects of physical function can follow different trajectories. Knee-extension strength declined during hospitalisation while other measures changed differently.
Hartley et al. · Age and Ageing · 2021 ↗A Coordinated Multi-study Analysis of the Longitudinal Association Between Handgrip Strength and Cognitive Function
Coordinated analyses across multiple ageing cohorts found positive associations between change in grip strength and change in cognitive functioning. The study does not establish causation, but illustrates the potential value of longitudinal physical measures within a broader understanding of ageing.
Zammit et al. · Journals of Gerontology Series B · 2021 ↗Enjoyment of life and declining physical function at older ages
An eight-year longitudinal analysis of older adults examined future functional impairment using gait speed and disability measures. The study is useful here less as a measurement-validation paper and more as an example of physical function as a longitudinal health outcome.
Steptoe et al. · CMAJ · 2014 ↗Depression Among Nonfrail Old Men Is Associated With Reduced Physical Function and Functional Capacity After 9 Years
A nine-year follow-up study used TUG, sit-to-stand, functional reach and step testing to examine later physical and functional capacity. It demonstrates how objective physical-function measures can capture long-term differences in ageing trajectories.
Almeida et al. · JAMDA · 2017 ↗Validation of Smartphone Accelerometry for the Evaluation of Sit-To-Stand Performance
Smartphone-derived sit-to-stand timing in adults aged 65–89 closely agreed with force-plate and motion-system measurements and was associated with lower-extremity power, supporting the technical potential of phone-based functional testing.
Song et al. · Journal of Aging and Physical Activity · 2022 ↗Validity and Reliability of a Smartphone Application for Home Measurement of Four-Meter Gait Speed
A smartphone-based home four-metre gait-speed assessment showed strong agreement with video measurement and high test–retest reliability, including sessions completed independently by older adults.
Lee et al. · Bioengineering · 2024 ↗Virtual Assessment Protocols for Timed-Up-and-Go, Chair Rise and 1-Minute Sit-to-Stand
Virtual TUG and chair-stand protocols in community-dwelling older adults demonstrated high test–retest and inter-rater reliability. Importantly, the tests did not perform well as predictors of falls or healthcare utilisation, illustrating the difference between reliable measurement and validated clinical prediction.
Saunders et al. · Archives of Physical Medicine and Rehabilitation · 2025 ↗Remote assessment of physical function in older people: feasibility, safety and agreement with in-person administration
Remote 5-times sit-to-stand and TUG showed good agreement with in-person testing. Agreement was weaker for four-metre walking and SPPB, demonstrating why remote and clinic measurements should not automatically be treated as interchangeable.
van Schooten et al. · Age and Ageing · 2025 ↗The Measured Physical Functioning Index Describing Population Level Physical Ability
Using FINFIT data from 5,238 Finnish adults, the authors developed MePFIX by combining ten objectively measured factors across body composition, cardiorespiratory fitness, muscular fitness, physical activity, stationary behaviour and time in bed. The work provides relevant scientific precedent for treating physical functioning as a multidimensional measured construct that can be followed over time.
For Kinegrade, its relevance is conceptual rather than product-validating: MePFIX was developed primarily for population-level analysis in working-age adults and should not be treated as a ready-made clinical or smartphone-derived Kinegrade score.
Vasankari et al. · Preprints.org · 2025 · DOI 10.20944/preprints202511.0855.v1 ↗Digital Technologies and Biomarkers for Locomotor Capacity Assessment in Older Adults
A 2026 systematic review evaluated digital approaches to locomotor capacity, including strength, balance, power and related functional domains. The field shows considerable potential, but robust evidence for measurement properties and translation into clinical use remains incomplete.
Zhou et al. · Journal of Medical Internet Research · 2026 ↗Remote & digital assessment
The evidence supports the direction — not a shortcut around validation.
This is particularly relevant to Kinegrade’s ambition to let selected physical-function assessments happen outside the clinic.
Smartphone accelerometers, camera-assisted workflows and virtual assessment protocols increasingly demonstrate that useful objective functional measurements can be collected remotely.
But the evidence also argues against treating “remote physical assessment” as one generic technology. Reliability and agreement depend on the test, protocol, environment, device, population and what the resulting measurement will be used for.
Implication for Kinegrade
Remote reassessment should be protocol-aware.
A credible Kinegrade workflow should know which assessment is being performed, how it is being performed, whether the conditions are acceptable and whether that result can legitimately be compared with the patient’s previous measurement.
Increase measurement frequency.
Suitable home assessments could reduce the need for a professional to administer every follow-up test personally.
Preserve measurement validity.
Convenience has little value if changes in environment or protocol make longitudinal results misleading.
Connect remote and clinical measurement.
The product could create continuity between assessments occurring at home, in a clinic and through connected measurement devices.
Validate each intended workflow.
Technical agreement, test–retest reliability, clinical usefulness, safety and usability are separate questions that need to be evaluated.
Evidence in context
What this research supports — and what it does not.
It is important not to turn associations in the scientific literature into product claims that the evidence does not support.
Physical-function measurement can be clinically informative.
- Muscle strength is an important component of physical function and sarcopenia assessment.
- Gait speed, chair-stand testing, SPPB and other standardized performance tests provide complementary functional information.
- Repeated measurements can characterize functional trajectories.
- Measurement protocol and reference population affect interpretation.
- Selected functional tests can be performed remotely or measured using smartphones with promising reliability.
- Emerging population-level research provides precedent for combining multiple objectively measured domains into an integrated view of physical functioning and following that construct over time.
Published evidence does not validate Kinegrade.
- Kinegrade cannot infer overall health from a single physical-function measure.
- Associations between strength and health outcomes do not prove that changing strength alone changes those outcomes.
- Remote and clinic measurements cannot automatically be assumed to be interchangeable.
- Kinegrade-specific interpretation, alerts or decision support require validation for their intended use.
- The clinical and commercial value of improving reassessment workflows is still being tested with healthcare organisations.
- MePFIX should not be represented as a validated Kinegrade score or assumed to apply directly to rehabilitation, disease-specific pathways, adults over 69 or smartphone-derived measurements.
Work with us
Help translate evidence into a useful clinical workflow.
Kinegrade is currently speaking with healthcare professionals, researchers and organisations working with physical-function measurement.
We are particularly interested in assessment protocols, reassessment practices, meaningful change, remote measurement, reference data, integrated physical-function models, healthy ageing, rehabilitation, sarcopenia and outcome measurement.