Exploring the interplay between quantitative muscle strength, functional performance, and patient-reported outcomes...

Amyotrophic lateral sclerosis (ALS) shows marked clinical heterogeneity, while standard clinical assessments may fail to capture its multidimensional burden. Integrating quantitative muscle strength, functional tests and patient-reported outcomes (PROs) may improve disease characterization. Ten ambulant adults with ALS were enrolled in a cross-sectional pilot study. Functional performance was assessed with the Revised ALS Functional Rating Scale (ALSFRS-R), Six-Minute Walk Test (6MWT), Ten-Meter Walk Test, Timed Up and Go, Berg Balance Scale and a fatigability index, lower-limb strength with dynamometry, and PROs with ALS Assessment Questionnaire-40 (ALSAQ-40), Hospital Anxiety and Depression Scale, Fatigue Severity Scale and Modified Fatigue Impact Scale (MFIS). Despite relatively preserved ALSFRS-R scores (40.6 ± 2.8), participants showed reduced 6MWT (61.3 ± 21.7% predicted), marked fatigability (- 47.3 ± 112.3%) and a lower-limb strength index of 58.2 ± 13.8% predicted. The ALSAQ-40 score averaged 183.1 ± 59.5. Fatigue was prominent, while anxiety and depression remained mild. Muscle strength correlated positively with ALSFRS-R gross motor score and inversely with anxiety. ALSAQ-40 and MFIS components showed significant associations with both functional and walking performance. Even at ambulant stages, measurable muscle weakness and fatigability co-occur with functional and PROs changes in ALS, supporting the use of multidomain, sensitive clinical assessment. The trial was registered at ClinicalTrials.gov (NCT06199284) on 29/12/2023.