Critical IllnessTWITCH FORCENCT07891273
Beyond Voluntary Effort: Reliability and Validity of Magnetic Femoral Nerve Stimulation for Assessing Quadriceps Strength in Critically Ill Patient
A study testing Magnetic Femoral Nerve Stimulation in people with Critical Illness and ICU-acquired Weakness, run by Daniel Langer.
Trial summary
Intensive care unit-acquired weakness (ICU-AW) is a common complication of critical illness and can negatively affect recovery and long-term physical functioning. Early and reliable assessment of muscle strength is essential for detecting muscle weakness and monitoring changes during an intensive care unit (ICU) stay. Read more about this study
- Who is it for?
- Ages 18 years and older
- Conditions the study is for
- Critical Illness, ICU-acquired Weakness
- What is being tested?
- Magnetic Femoral Nerve Stimulation
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 33 participants
- Where
- No sites listed yet
- Study dates
- Dec 2026to May 2027
- Phase
- Interventional
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 18 years and older
- All sexes
- No healthy volunteers
- Adult, Older adult
Who may be able to join
- Voluntary written informed consent of the participant has been obtained prior to the initiation of any study-related measurements
- Adults (≥18 years)
- Expected to remain in the ICU for more than an additional 2 days starting from study enrolment
- Fully cooperative, as assessed daily during routine clinical care by ICU physiotherapists using five standardized commands ("open/close your eyes", "look at me", "open your mouth and stick out your tongue", "nod your head", and "raise your eyebrows when I have counted to 5")
- Quadriceps muscle strength of at least 3/5 on the Medical Research Council (MRC) scale for knee extension.
Who cannot join
- Medical instability A: Cardiorespiratory instability
- Mean arterial pressure < 60 mmHg or > 110 mmHg
- Fraction of inspired oxygen (FiO₂) ≥ 60%
- PaO₂/FiO₂ ratio < 200
- Respiratory rate > 30 breaths·min-¹ B: Neurological instability
- Intracranial pressure > 20 mmHg
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- Cerebral perfusion pressure < 70 mmHg C: Surgery within the past 24h D: Body temperature > 40
- Contraindications to magnetic stimulation A: Implanted metal or electronic devices, including
- Lower limb prostheses
- Internal and external fixation devices of the lower limb
- Vascular stents
- Cardiac pacemakers or defibrillators
- Implanted nerve stimulators B: Lower limb structural, skin, or soft tissue conditions
- Acute or chronic injuries
- Wounds preventing supine positioning
- Lower limb amputation C: Neuromuscular conditions
- Pre-existing central or peripheral neuromuscular disorders
- Neuromuscular blocking agents in the preceding 48h D: Morbid obesity (body mass index >35 kg/m2) E: Pregnancy
- Palliative care
Trial locations and contacts
No sites are listed yet. Contact the study team or a site near you to ask about taking part.
About this study
Intensive care unit-acquired weakness (ICU-AW) is a common complication of critical illness and can negatively affect recovery and long-term physical functioning. Early and reliable assessment of muscle strength is essential for detecting muscle weakness and monitoring changes during an intensive care unit (ICU) stay. However, conventional strength assessments, such as manual muscle testing, require voluntary muscle contractions, making them unsuitable for patients who are not yet cooperative and limiting the possibility of assessing muscle strength during the early stages of critical illness. Magnetic femoral nerve stimulation offers an alternative, non-volitional approach to assessing quadriceps muscle strength. Nevertheless, the reliability and validity of this technique in critically ill patients remain insufficiently established.
This prospective methodological study aims to investigate the reliability and convergent validity of quadriceps twitch force measurements obtained using magnetic femoral nerve stimulation in critically ill patients.
Read more
A total of 33 cooperative adult patients admitted to medical or surgical ICUs will be included. Participants will undergo repeated quadriceps twitch force assessments over two consecutive days, performed by two assessors. Measurements will be conducted using a custom-developed frame designed to facilitate standardized quadriceps strength assessment at the bedside. Both single and paired magnetic stimulation techniques will be evaluated.
The primary outcome is the intra-rater reliability of paired twitch force measurements. Secondary outcomes include the inter-rater reliability of paired twitch force measurements, the intra-rater and inter-rater reliability of single twitch force measurements, and the convergent validity of twitch force measurements assessed through their association with maximal voluntary contraction force and potentiated twitch force. Reliability and agreement will be evaluated using intraclass correlation coefficients and complementary measurement error analyses.
Establishing these measurement properties could support objective, non-volitional muscle strength assessment in critically ill patients, including those unable to participate in conventional strength testing. This could facilitate early baseline strength assessment, longitudinal monitoring of muscle recovery, and the evaluation of interventions aimed at preventing or treating ICU-AW..
- Conditions
- Critical Illness, ICU-acquired Weakness
- Being tested
- Magnetic Femoral Nerve Stimulation
- Keywords
- critical illness, ICU-acquired weakness, femoral nerve magnetic stimulation, quadriceps muscle strength, non-volitional muscle strength assessment
- Medical subject headings
- Critical Illness
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
Magnetic Femoral Nerve StimulationDiagnostic test
Participants will be positioned prone in their hospital bed, with the knee flexed at approximately 90° using a dedicated measurement setup. A magnetic stimulation coil will be placed over the femoral nerve to elicit involuntary quadriceps muscle contractions. The resulting twitch force will be measured using a strain gauge dynamometer attached at the ankle. Stimulation intensity will be progressively increased to establish supramaximal stimulation, after which both single and paired magnetic stimuli will be applied to assess quadriceps twitch force.
| Study group | Role | What they receive |
|---|---|---|
| Magnetic Femoral Nerve Stimulation | Experimental | All participants will undergo quadriceps muscle strength assessments over two consecutive days, following the same standardized measurement sequence. On the first day, the first assessor will perform single and paired twitch force measurements using magnetic femoral nerve stimulation, alongside maximal voluntary contraction and potentiated twitch force assessments. On the second day, single and paired twitch force measurements will be repeated by the first assessor in the morning and by a second assessor in the afternoon to evaluate intra-rater and inter-rater reliability. Receives: Diagnostic Test: Magnetic Femoral Nerve Stimulation |
What is being measured
The primary outcome is the main question the study is designed to answer.
Intra-rater reliability of paired quadriceps twitch force measurements
Intra-rater reliability of paired quadriceps twitch force measurements will be assessed using the intraclass correlation coefficient (ICC) with 95% confidence intervals, comparing measurements performed by the same assessor on two consecutive days. Measurement error and agreement will additionally be evaluated using the standard error of measurement (SEM), minimal detectable change (MDC95), and Bland-Altman analysis.
Measured: Day 1 and Day 2 (two consecutive days)
Secondary outcomes (7)
Inter-rater reliability of paired quadriceps twitch force measurements
Inter-rater reliability of paired quadriceps twitch force measurements will be assessed using the intraclass correlation coefficient (ICC) with 95% confidence intervals, comparing measurements performed by two different assessors on the second day. Measurement error and agreement will additionally be evaluated using SEM, MDC95, and Bland-Altman analysis.
Measured: Day 2 (morning and afternoon)
Intra-rater reliability of single quadriceps twitch force measurements
Intra-rater reliability of single quadriceps twitch force measurements will be assessed using the intraclass correlation coefficient (ICC) with 95% confidence intervals, comparing measurements performed by the same assessor on two consecutive days. Measurement error and agreement will additionally be evaluated using SEM, MDC95, and Bland-Altman analysis.
Measured: Day 1 and Day 2 (two consecutive days)
Inter-rater reliability of single quadriceps twitch force measurements
Inter-rater reliability of single quadriceps twitch force measurements will be assessed using the intraclass correlation coefficient (ICC) with 95% confidence intervals, comparing measurements performed by two different assessors on the second day. Measurement error and agreement will additionally be evaluated using SEM, MDC95, and Bland-Altman analysis.
Measured: Day 2 (morning and afternoon)
Convergent validity of single twitch force with maximal voluntary contraction
Convergent validity will be assessed by examining the association between single quadriceps twitch force measurements obtained using magnetic femoral nerve stimulation and maximal voluntary contraction (MVC) force, using Pearson's correlation coefficient (r).
Measured: Day 1
Convergent validity of paired twitch force with maximal voluntary contraction
Convergent validity will be assessed by examining the association between paired quadriceps twitch force measurements obtained using magnetic femoral nerve stimulation and maximal voluntary contraction (MVC) force, using Pearson's correlation coefficient (r).
Measured: Day 1
Convergent validity of single twitch force with potentiated twitch force
Convergent validity will be assessed by examining the association between single quadriceps twitch force measurements obtained using magnetic femoral nerve stimulation and potentiated twitch force, using Pearson's correlation coefficient (r).
Measured: Day 1
Convergent validity of paired twitch force with potentiated twitch force
Convergent validity will be assessed by examining the association between paired quadriceps twitch force measurements obtained using magnetic femoral nerve stimulation and potentiated twitch force, using Pearson's correlation coefficient (r).
Measured: Day 1
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted23 Oct 2026
- Study startDec 2026 (estimated)
- Primary completionMay 2027 (estimated)
- Study completionMay 2027 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for Critical IllnessStudies of the same condition, open and under way.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase N/A
- Primary purpose
- Other
- Allocation
- Not applicable
- Intervention model
- Single group
- Masking
- None (open label)
- Enrolment
- 33 participants (estimated)
Sponsor and investigators
- Lead sponsor
- Daniel Langer
- Sponsor type
- University, hospital or other
- Collaborators
- Universitaire Ziekenhuizen KU Leuven
- Responsible party
- Sponsor-investigator, Daniel Langer, KU Leuven
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT07891273
- Sponsor's protocol ID
- S71944
- Acronym
- TWITCH FORCE
- Status last verified
- Oct 2026
- First submitted
- 16 Oct 2026
- Last updated
- 23 Oct 2026
- Results posted
- No
- Data monitoring committee
- No
- FDA-regulated drug
- No
- FDA-regulated device
- No
- Individual data sharing
- No