Poor Core Stability Evident in SSc Patients, Affecting Life Quality

Patients with scleroderma have poor core stability, as measured by trunk muscle strength and endurance, affecting both their physical capacity and daily performance, a Turkish study found.

Previous studies largely neglect trunk muscles in scleroderma patients, focusing instead on upper and lower limb muscle weakness, its researchers stated. Assessing and maintaining trunk muscle strength is important to life quality in people with scleroderma (also called systemic sclerosis or SSc).

“Core stability exercises can be added to training programs in SSc patients to maintain and/or improve physical functions, functional performance and to be more independent in daily life activities,” the researchers wrote.

The study, “Association between core stability and physical function, functional performance in patients with systemic sclerosis,” appeared in the International Journal of Rheumatic Diseases.

Scleroderma can weaken muscles and limit joint movement, affecting their daily life and physical abilities.

The disease’s widespread muscular and skeletal involvement also affects a person’s core stability, the ability to control and move the trunk muscles of the upper body including the chest, back, abdomen, and shoulders. 

Scientists at Dokuz Eylül University in Izmir investigated — for what they believe to be a first time — the relationship between core stability and physical function and functional performance by assessing trunk muscle strength and endurance in scleroderma patients.

A total of 40 patients treated at a rheumatology center between 2018 and 2020 were included in their study. Most were women (34 patients, 85%), and patients had a mean age of 50.1 and mean body mass index (a measure of body fat) of 25.73 kg per square meter. Two patients (5%) were smokers, and nine (22.5%) were ex-smokers.

Their average disease duration was 7.29 years, and most — 24 or 60% — had limited cutaneous SSc, while the remaining 16 (40%) were diagnosed with diffuse cutaneous SSc. Ten of these patients, 25%, also had pulmonary arterial hypertension.

Scleroderma patients had poorer trunk endurance compared with reference data for healthy and inactive women, as measured by the mean trunk extensor test time — 49.87 seconds for patients, and 82.5 seconds for the reference group — and a lesser mean trunk flexor endurance test time (32.17 seconds patients, 105.9 seconds reference group).

The trunk endurance test involves lying flat with only hips and legs supported by a table and fixed; the upper body is held in a horizontal position by trunk muscles for as long as possible. The trunk flexor test is similar, but the trunk is held at a 60-degree angle with knees and hips flexed and feet fixed.

Trunk muscle strength was also poorer in patients relative to the referenced group, as measured by modified sit-up repetitions (17.42), trunk extensor muscle strength (7.48 kg), and think flexor muscle strength (6.20 kg) . The sit-up test was started in the hook-lying position, with the arms crossed over the chest, knees flexed, and feet fixed. To complete a full sit-up, the patients’ scapulae had to touch the mat when prone, and elbows touch the knees when sitting.

Physical function, measured by Health Assessment Questionnaire Disability Index (HAQ‐DI) score, was 1.02 (scores range from 0, indicating no disability, to 3, indicating severe disability). A near majority, 47.5% of patients, had scores of 1 or more, meaning moderate to severe functional limitations.

Functional performance was measured using the 6-minute walking test (6MWT), where the distance walked in six minutes is assessed, and the five repetition sit-to-stand test (STS), which involves rising from a chair and sitting back down five times. Scleroderma patients again showed poorer performance compared with reference data, with a mean walking distance of 380.2 meters in the 6MWT and a mean STS time of 10.48 seconds.

Higher HAQ-DI score and STS time were moderately-to-strongly correlated with lesser trunk muscle strength and endurance, while better performance on the 6MWT had a strong correlation with greater trunk muscle strength and endurance. 

“This study results show that core stability is negatively affected in patients with SSc. As the core stability decreases the physical function and functional performance deteriorate,” the researchers wrote.

“We suggest that assessment of general muscle strength and endurance in SSc should contain trunk muscles and not be restricted to upper and lower extremity muscles,” they concluded.