Unilateral Lower Limb SuspensionULLS23NCT05801185
Single Nuclei Sequencing in Human Skeletal Muscle After Unloading
A study testing Unilateral lower limb suspension in people with Unilateral Lower Limb Suspension, run by Karolinska Institutet at 1 site in Sweden.
Trial summary
Injuries often require people to undergo some degree of limb immobilization. This comes at a high cost in terms of muscle mass and function losses. At the molecular level, it is completely unknown how the different cells in the muscle respond to this complete lack of mechanical stimuli. Read more about this study
- Who is it for?
- Ages 18 to 40 yearsHealthy volunteers can take part
- Conditions the study is for
- Unilateral Lower Limb Suspension
- What is being tested?
- Unilateral lower limb suspension
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 20 participants
- Where
- 1 siteSweden
- Study dates
- 5 Mar 2023to Dec 2026
- 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 to 40 years
- All sexes
- Healthy volunteers accepted
- Adult
Who may be able to join
- Healthy young adult men and women
Who cannot join
- An age younger than 18 or older than 40 years
- Contraindications to magnetic resonance imaging (MRI)
- Contraindications to maximal intensity resistance exercise
- Contraindications to unloading (i.e., ULLS)
- Very high physical activity levels (determined using a standard Godin Leisure-Time Exercise Questionnaire (GLTEQ))
- Hypertension (>140/90 mm Hg)
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- History of malignancy
- History of coagulation dysfunction
- History of musculoskeletal or neurological disorders
- History of cardiovascular disease
- History of cerebrovascular disease
- History of respiratory disease
- History of gastrointestinal disease
- History of renal disease
- History of past or present condition requiring long-term drug prescriptions.
Trial locations and contacts
1 site in 1 country. Contact the study team or a site near you to ask about taking part.
About this study
Injuries often require people to undergo some degree of limb immobilization. This comes at a high cost in terms of muscle mass and function losses. At the molecular level, it is completely unknown how the different cells in the muscle respond to this complete lack of mechanical stimuli.
The investigators will explore cell type specific changes in skeletal muscle after a short period of unloading, and specifically examine the behavior of myogenic stem cells with particular attention to potential unloading-induced maturation into fast- or slow-twitch muscle fibers.
Read more
Twenty healthy young participants will perform a 5-day Unilateral Lower Limb Suspension (ULLS) intervention, where one leg is continuously subjected to unloading, i.e., lack of mechanical stimuli. Before and after the ULLS period, participants will perform muscle function testing and MRI scans to assess muscle size in the lower limbs. Immediately after the ULLS, two muscle biopsies will be obtained, one from each leg. The tissue will be employed for single-nuclei RNA sequencing analysis and immunohistochemistry experiments.
This project will be the first to analyze cell type specific changes induced by complete, short-term lack of mechanical stimuli in skeletal muscle. This will add a new dimension to the understanding of the processes directing this type of muscle atrophy (i.e., muscle loss in otherwise healthy individuals) and thus help to develop effective countermeasures to offset muscle changes.
- Conditions
- Unilateral Lower Limb Suspension
- Being tested
- Unilateral lower limb suspension
- Keywords
- ULLS, single nuclei RNA sequencing, Skeletal muscle
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
Unilateral lower limb suspensionOther
Participants will perform a 5-day unloading intervention using the ULLS model. Short-length crutches, aided by handgrip and forearm support distal to the elbow will be used to assist in any upright or ambulatory activity. One foot (randomized in a counterbalance manner) will be equipped with a shoe having a 10-cm thick sole, which permits the unloaded limb to move passively about the hip joint while adopting a near straight position.
| Study group | Role | What they receive |
|---|---|---|
| Unilateral lower limb suspension | Experimental | Participants will perform a 5-day unloading intervention using the ULLS model. Short-length crutches, aided by handgrip and forearm support distal to the elbow will be used to assist in any upright or ambulatory activity. One foot (randomized in a counterbalance manner) will be equipped with a shoe having a 10-cm thick sole, which permits the unloaded limb to move passively about the hip joint while adopting a near straight position. Receives: Other: Unilateral lower limb suspension |
What is being measured
The primary outcome is the main question the study is designed to answer.
Single nuclei RNA sequencing
Single nuclei RNA sequencing from skeletal muscle (m. vastus lateralis) from both legs
Measured: Immediately after the 5-day unilateral unloading intervention
Secondary outcomes (3)
Muscle mass
Muscle volume of quadriceps muscle group (and individual muscles) assessed by MRI in both legs
Measured: Before and immediately after the 5-day unloading intervention
Concentric isokinetic torque of knee extensor muscles
Concentric isokinetic torque of knee extensor muscles at 30°/s, 90°/s, 180°/s and 300°/s, measured with an isokinetic dynamometer unilaterally in both legs
Measured: Before and immediately after the 5-day unloading intervention
Isometric torque of knee extensor muscles
Isometric torque of knee extensor muscles at 60° knee flexion, measured with an isokinetic dynamometer unilaterally in both legs
Measured: Before and immediately after the 5-day unloading intervention
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted6 Apr 2023
- Study start5 Mar 2023
- Primary completionJul 2026 (estimated)
- Study completionDec 2026 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for Unilateral Lower Limb SuspensionStudies of the same condition, open and under way.
- More trials run by Karolinska InstitutetThe sponsor's other registered studies.
- 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
- Basic science
- Allocation
- Not applicable
- Intervention model
- Single group
- Model description
- Participants will perform a 5-day unloading intervention using the ULLS model. Short-length crutches, aided by handgrip and forearm support distal to the elbow will be used to assist in any upright or ambulatory activity. One foot (randomized in a counterbalance manner) will be equipped with a shoe having a 10-cm thick sole, which permits the unloaded limb to move passively about the hip joint while adopting a near straight position.
- Masking
- None (open label)
- Enrolment
- 20 participants (estimated)
Sponsor and investigators
- Lead sponsor
- Karolinska Institutet
- Sponsor type
- University, hospital or other
- Responsible party
- Principal investigator, Rodrigo Fernandez Gonzalo, Karolinska Institutet
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT05801185
- Sponsor's protocol ID
- Dnr 2022-04662-01
- Acronym
- ULLS23
- Status last verified
- Aug 2025
- First submitted
- 13 Mar 2023
- Last updated
- 31 Jul 2026
- Results posted
- No
- FDA-regulated drug
- No
- FDA-regulated device
- No
- Individual data sharing
- No