Spinal muscular atrophy (SMA) is an autosomal recessive neuromuscular disease caused by the degeneration of motor neurons in the anterior horn of the spinal cord, due to the absence of the SMN1 gene and the resulting lack of SMN protein. Some patients with particularly severe forms (types 0 or 1) die before the age of 2 in the absence of treatment, while others retain autonomous walking throughout their lives, with no reduction in life expectancy. Three treatments aimed at restoring SMN (TRS) protein expression have recently been approved by the US Food and Drug Administration and the European Medicines Agency (i.e. Nusinersen / Onasemnogene Abeparvovec / Risdiplam). Patients treated with TRS after the onset of symptoms (symptomatic patients) may show significant motor improvement, but retain difficulties such as muscle weakness and fatigue leading to limitations in activities of daily living. The aim of this study is to adapt a fatigability test, widely validated in its original version in different populations (QIF test), but adapted in this protocol to the motor level and low abilities of certain SMA patients. Our objectives are to determine whether these assessments are feasible in SMA patients, reproducible, and relevant for monitoring this population, either routinely or for future clinical trials.