Effects of Different Stiffness Settings During Robotic Isokinetic Training in Children With SMA

N/ANot Yet RecruitingNCT07822711

Peking University Third Hospital13 enrolled

Overview

This randomized, within-participant, contralateral-limb-controlled clinical trial will compare individually optimized compliant and rigid stiffness settings of a portable isokinetic knee training robot in children with spinal muscular atrophy. At least 13 children aged 6 to 12 years will be enrolled. For each participant, one leg will be randomly assigned to the compliant setting and the contralateral leg to the rigid setting using sequentially numbered, opaque, sealed envelopes. Both legs will receive the same training volume, number of repetitions, and angular velocity for up to 8 weeks. The primary outcome is the between-setting difference in the change from baseline in peak isokinetic knee-extension torque. Secondary outcomes include knee-extension range of motion, quadriceps cross-sectional area on magnetic resonance imaging, femoral nerve conduction measures, and sit-to-stand performance. Knee pain, suprapatellar skin temperature, fatigue, and other adverse events will be monitored throughout the study.

Spinal muscular atrophy is characterized by progressive muscle weakness and impaired motor function. Quadriceps weakness limits knee extension, transfers, standing, and other activities of daily living. A portable isokinetic knee training robot has previously been shown to provide safe, quantifiable resistance training in children with spinal muscular atrophy. The present study will investigate whether the stiffness of the human-robot interaction affects rehabilitation outcomes. Participants will be randomized to one of two laterality schemes: (A) compliant setting for the left leg and rigid setting for the right leg, or (B) rigid setting for the left leg and compliant setting for the right leg. An independent statistician will generate the random sequence, which will be concealed in sequentially numbered, opaque, sealed envelopes. The study is open label. Before training, participants will undergo bilateral quadriceps magnetic resonance imaging, femoral nerve conduction testing, biomechanical assessment, and determination of the individually optimized compliant stiffness. Under the compliant setting, stiffness will be selected within the predefined safe range as the level that produces the highest mean peak knee-extension torque across five repetitions while the movement remains painless, without obvious fatigue, and with a stable trajectory. Training will continue for up to 8 weeks, with no more than five sessions per week. During each session, the robot will be worn on one leg at a time while the contralateral leg is stabilized. Participants will perform seated knee extension and flexion at a target angular velocity of 45 degrees per second, adjusted when clinically necessary. The initial knee angle will be 90 degrees, and movement will occur within each participant's maximum voluntary pain-free range of motion. A standard set will consist of 10 continuous extension-flexion repetitions, with at least six sets per leg and approximately 1 minute of rest between sets. The number of repetitions, sets, and rest duration may be adjusted according to participant tolerance, but the training dose will be matched between the two legs. Total session duration will be approximately 35 minutes. The robot software will record training data, including knee-extension peak torque and joint angle. After the intervention, bilateral quadriceps magnetic resonance imaging, femoral nerve conduction testing, and biomechanical assessments will be repeated. Participants will be evaluated in person before and after the intervention and contacted weekly by telephone during training to assess knee pain, discomfort, fatigue, and subjective changes in strength.

Interventions

Portable Isokinetic Knee Training Robot With an Individually Optimized Compliant SettingDEVICE

The compliant setting will be individualized within the device's predefined safe stiffness range. At each candidate stiffness, the participant will perform five knee-extension repetitions. The stiffness producing the highest mean peak knee-extension torque while the movement remains painless, without obvious fatigue, and with a stable trajectory will be selected. The assigned limb will then train at this setting for up to 8 weeks, no more than five sessions per week. Each session will use a target angular velocity of 45 degrees per second, an individualized maximum voluntary pain-free range of motion, at least six sets of 10 extension-flexion repetitions per leg, and approximately 1 minute of rest between sets. Training volume will be matched to the contralateral limb.

Portable Isokinetic Knee Training Robot With a Rigid SettingDEVICE

The assigned limb will train with the device's predefined rigid stiffness setting for up to 8 weeks, no more than five sessions per week. Each session will use a target angular velocity of 45 degrees per second, an individualized maximum voluntary pain-free range of motion, at least six sets of 10 extension-flexion repetitions per leg, and approximately 1 minute of rest between sets. Training volume will be matched to the contralateral limb.

Eligibility

Sex: ALLMin age: 6 YearsMax age: 12 Years

Medical Language ↔ Plain English

Inclusion Criteria: 1. Age 6 to 12 years. 2. Diagnosis of spinal muscular atrophy. 3. Able to maintain an independent seated position. 4. If receiving disease-modifying treatment, including nusinersen or risdiplam, the participant must have received a stable dose for at least 6 months before enrollment and must not change the treatment regimen during the study. Exclusion Criteria: 1. Any other major disease or medical condition that, in the investigator's judgment, would interfere with safe participation or interpretation of the study results. 2. The legal guardian declines to provide written informed consent, or the participant is unable to complete the study procedures. 3. Unable to undergo magnetic resonance imaging or electromyography and nerve conduction testing. 4. Blood pressure above the 95th percentile for age, sex, and height, as assessed by a clinician. 5. Lacks the cognitive capacity to understand or comply with the requirements of study participation.

Outcomes

Primary Outcomes

Between-setting difference in the change from baseline in peak knee-extension torque

Peak isokinetic knee-extension torque will be measured separately for each limb using the portable isokinetic knee training robot and reported in newton-meters. For each participant, the change from baseline will be calculated for the compliant-setting limb and the rigid-setting limb. The primary outcome is the within-participant difference between these two changes: (post-intervention minus baseline change for the compliant setting) minus (post-intervention minus baseline change for the rigid setting).