The CARRA registry is North America’s largest database for pediatric rheumatic conditions. Childhood myositis (CM) is a rare rheumatic condition affecting 2-4 per million North American children causing muscle weakness. Untreated CM makes it hard for children to do routine activities such as walking and playing. In severe cases, it damages muscles and organs, which can be life-threatening.

Children with CM have their muscle strength checked regularly to monitor and ensure their treatments are working. The Childhood Myositis Assessment Scale (CMAS) and Manual Muscle Test (MMT-8) are examples of strength tests, but they are time-consuming, require trained professionals, and are hard to perform in busy clinics or during telemedicine visits.

Impact and Significance: The CARRA registry has collected data on children with CM since 2019. However, 60% of these muscle strength tests were incomplete, making it hard to draw clear conclusions about patient outcomes.

Creating a valid, easy-to-administer tool would improve assessment rates and clinicians’ confidence in measuring muscle strength over telemedicine.

The timed squat test (TST) counts the number of squats a person can do in 30 seconds. It is a simple and quick test that has a high correlation with CMAS and MMT-8 measures of muscle strength. However, we do not know how many squats the average healthy child should be able to do.

We propose to collect data on the number of timed squats that healthy children can do to create an easy-to-use tool that can compare muscle strength.

Methods/Activities: We will enroll healthy, ethnically diverse children aged 4-18 years old from Toronto public schools to perform as many squats as possible in a 30-second timeframe. The data will be used to create TST curves showing the typical ranges for boys and girls of different ages.

Educational resources will be created to help clinicians and caregivers use this tool.

We will initially use the TST curves and resources at selected CARRA sites and then expand to all CARRA sites. The project will use the CARRA registry to see if using the tools and resources improves data completeness.

This project will create an inexpensive and inclusive tool that monitors muscle strength, advancing CARRA’s mission of conducting collaborative research to prevent and treat pediatric rheumatic diseases.