Other studies with DAVID devices

DAVID devices are trusted in clinical and scientific research worldwide.

They provide precise, reliable data on strength, endurance, and neuromuscular function, helping researchers explore chronic back pain, rehabilitation outcomes, and age-related changes. These studies confirm DAVID as both a treatment solution and a scientific tool.

The Back Muscle Surface Electromyography-Based Fatigue Index: A Digital Biomarker of Human Neuromuscular Aging

Researchers explored whether a back-muscle surface EMG (sEMG) metric—the instantaneous median frequency (IMDF) fatigue slope during controlled back-extension exercise—can distinguish younger from older adults with chronic low back pain, and whether that metric is reliable over time.

Objective

Identify if an sEMG-derived fatigue index (IMDF slope) from lumbar extensors can:

  • Differentiate younger vs. older adults with chronic low back pain, and
  • Demonstrate acceptable test–retest reliability for potential clinical/fitness use.

Method

  • Participants: 243 adults (final analyzable sEMG n≈222) with non-specific chronic low back pain, ages 18–90.

  • Protocol: Three sessions (baseline, 1–2 days later, ~6 weeks later). Maximal isometrics followed by:

    • a static fatigue test (80% MVC), then

    • a cyclic back-extension task at 50% MVC (25 slow repetitions, upright to ~40° flexion, metronome-paced).

  • Measurements: Bilateral sEMG at L5 (multifidus), L2 (longissimus), L1 (iliocostalis). IMDF computed over time; the IMDF slope across the 25 cycles was the primary fatigue index.

  • Analysis: Mixed-effects models for age/sex/test-day effects; reliability assessed with Generalizability Theory (ICC-like dependability and SEM).

Outcomes

  • Age discrimination: Younger participants showed steeper (more negative) IMDF slopes—i.e., greater frequency decline—than older participants during the cyclic task, indicating the index differentiates age-related neuromuscular status.
  • Sex pattern: Differences were more pronounced in males.
  • Reliability: Moderate-to-good relative reliability of the IMDF slope across sessions; absolute error varied by electrode site, so single-person readings can be noisy.
  • Robustness: Pain intensity, disability, and physical activity levels had limited impact on the IMDF-slope differences.

Ebenbichler G., Habenicht R., Blohm P., Bonato P., Kollmitzer J., Mair P., Kienbacher T. The Back Muscle Surface Electromyography-Based Fatigue Index: A Digital Biomarker of Human Neuromuscular Aging? Bioengineering. Basel; MDPI; 2023; 10(3): Article 300.

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Age and gender related neuromuscular changes in trunk flexion-extension

Muscle fatigue in the back extensors can reveal important information about neuromuscular aging and functional decline. In chronic low back pain (cLBP), these patterns may differ between younger and older adults and between men and women. This study explored how back muscle fatigue develops under load and whether the measurements are reliable for clinical and research use.

Objective

Determine age (<40 vs >60) and sex effects on lumbar extensor activation and trunk/hip kinematics in a standardised flexion-extension task.

Method
25 older and 24 younger healthy adults; sEMG at L5/T4; static standing/half/max flexion positions; accelerometers for kinematics; permutation ANOVA.

Outcomes

Older men had a lower half-flexion relaxation ratio and smaller activity changes; older groups showed reduced gross trunk ROM.

Implications

Age/sex substantially alter normative patterns; do not generalise young-adult references to older adults when assessing function/outcomes.

Ebenbichler G., Habenicht R., Kollmitzer J., Seitz P., Mair P., Kienbacher T. Age- and sex-specific effects in paravertebral surface electromyographic back extensor muscle fatigue in chronic low back pain. Frontiers in Aging Neuroscience. Lausanne; Frontiers Media; 2020; 12: Article 35. doi:10.3389/fnagi.2020.00035.

Link to study

Feasibility & reliability of functional muscle tests in lung transplant recipients

Objective
Assess the feasibility/reliability of back extension strength, handgrip, and Biering-Sørensen endurance in early post-transplant rehab.

Method
50 recipients tested at discharge, days later, and ~2 months later; ICCs, SEM; correlations between tests.

Outcomes
Back-extension strength testing feasible; Biering-Sørensen feasible for ~⅔ at baseline; ICC strength 0.97–0.98, endurance ~0.69; grip correlated strongly with back strength (≥0.75).

Implications
Well-controlled isometric back-strength testing is safe/reliable; handgrip can proxy back strength when endurance tests are not tolerated.

Kienbacher, T., Paul, B., Habenicht, R., Wolf, M., Riegler, S., Kollmitzer, J., & Ebenbichler, G. R. (2018). Feasibility and reliability of functional muscle tests in lung transplant recipients. American Journal of Physical Medicine & Rehabilitation, 97(6), 420–427

Link to Study

 

Age & gender neuromuscular pattern in cLBP patients

Objective
Compare age (</40, 40–59, ≥60) and sex effects on lumbar extensor activation/kinematics during a standardized trunk task in cLBP.

Method
Cross-sectional; 216 cLBP patients; sEMG (L5/T4) in standing/half/max flexion; 3D accelerometry; permutation ANOVA, ridge regression.

Outcomes
≥60 group showed highest standing activity, smallest activity changes, lower HFR ratio; females had larger ROM; lumbothoracic flexion and standing activity influenced HFR.

Implications
Task captures impaired neuromuscular regulation; supports individualized, age/sex-tailored exercise programming.

Kienbacher, T., Paul, B., Habenicht, R., Wolf, M., Starek, C., Riegler, S., & Ebenbichler, G. R. (2016). Age and gender related neuromuscular pattern during trunk flexion-extension in chronic low back pain patients: analyses of the spectral electromyographic parameters. Journal of NeuroEngineering and Rehabilitation, 13(1), 94.*

 

Link to Study

Neural Control Differences Between Concentric and Eccentric Phases in Cyclic Trunk Extensions

Muscle fatigue and neural control differ depending on whether a muscle shortens (concentric) or lengthens (eccentric). In back extension exercise, understanding these differences can improve rehabilitation and training approaches.

Objective

To compare how back muscles are activated during the concentric and eccentric phases of a cyclic trunk extension exercise, and to explore the influence of age and sex.

Method

Eighty-seven healthy adults aged 18–90 performed 25 repetitions of trunk flexion and extension at 50% of maximum strength. Movements were paced to a controlled speed from upright to forward flexion and back. Surface EMG recorded activity from key back extensor muscles, measuring both amplitude (RMS) and frequency (median frequency, IMDF) over time.

Outcomes

  • Concentric contractions showed higher muscle activation at the start and increased further over repetitions, indicating progressive fatigue.
  • Eccentric contractions had lower activation and remained stable, showing less amplitude-related fatigue.
  • Frequency analysis revealed similar fatigue-related changes in both phases, though slightly more pronounced in concentric contractions.
  • Age and sex did not significantly influence these patterns.

Implications

Concentric back extensions produce greater neuromuscular activation and visible fatigue, while eccentric work achieves similar fatigue with lower muscle activation. These insights suggest eccentric training may provide an efficient and less strenuous option for rehabilitation and exercise programs.

Ebenbichler G., Unterlerchner L., Habenicht R., Bonato P., Kollmitzer J., Mair P., Riegler S., Kienbacher T. Estimating Neural Control from Concentric vs. Eccentric Portions of a Cyclic Back Extension Exercise. Frontiers in Physiology. Lausanne; Frontiers Media; 2017; 8: Article 299.

Using Spectral EMG Fatigue to Detect and Monitor Back Muscle Aging

Introduction
As people age, muscles lose mass and quality, especially in the back. This can lead to sarcopenia and functional decline. Surface EMG (sEMG) fatigue measures—specifically changes in the median frequency spectrum—offer a possible non-invasive way to detect and track these changes if done with standardized protocols.

Objective

  • To compare back muscle fatigue (via spectral EMG) between younger (<50 years) and older (50-90 years) healthy adults.
  • To test the day-to-day and long-term reliability of these EMG fatigue measures.
  • To assess whether older adults’ EMG fatigue measures are stable enough for clinical use.

Method

  • Participants: 86 healthy volunteers; 44 younger (~33 years), 42 older (~67 years), balanced for gender.
  • Protocol:
    1. Maximum isometric back extension to assess maximal force.
    2. After rest, a sustained isometric back extension at 80% of maximum for 30 seconds in a seated, lean-forward posture of 30°.
    3. Tests repeated after 1-2 days and approximately 6 weeks.

  • Measurements: sEMG recorded bilaterally from three lumbar back extensors (at L1, L2, and L5). Key metrics: initial median frequency (IMF-EMG), the rate of decline of median frequency over the sustain (slope), torque produced, and left-vs-right imbalance scores.

Outcomes

  • Older adults showed higher initial median frequencies in some recording sites, particularly at L5.
  • The rate of frequency decline (i.e. fatigue) was less pronounced in older participants vs younger, especially at L5 and when considering the electrode with the largest negative slope or combining all electrodes.
  • Tests showed good to excellent relative reliability (ability to distinguish between individuals) for both age groups; but the absolute reliability (how precise the measure is) was much less robust—slopes had considerable variability.
  • Gender did not significantly affect the fatigue slopes or initial frequency differences.

Implications

  • Spectral EMG fatigue measures appear sensitive to age-related changes in back muscles and could serve as biomarkers for risk of sarcopenia.
  • Because the initial frequency (IMF) has better absolute reliability, it might be more useful than the fatigue slope for tracking individual changes.
  • For clinical and research settings, strict standardization of posture, electrode placement, and load is critical to ensure reliable results.
  • These measures may be useful in screening older adults and evaluating outcomes of interventions aimed at improving muscle endurance and quality.

Kienbacher T., Paul B., Habenicht R., Starek C., Wolf M., Mair P., Ebenbichler G. The potential use of spectral electromyographic fatigue as a screening and outcome monitoring tool of sarcopenic back muscle alterations. Journal of NeuroEngineering and Rehabilitation. London; BioMed Central; 2014; 11: Article 106. doi:10.1186/1743-0003-11-106

Overview Supporting Studies

Spine
Hip and Knee
Shoulder