Cardiac troponin T (cTnT) is elevated in neuromuscular conditions without apparent cardiac disease, including Amyotrophic Lateral Sclerosis (ALS). The reason for this increase is unclear. Since cTnT is found in both cardiomyocytes and skeletal muscle cells, we aimed to investigate the latter as a possible cTnT source. We examined the correlation of cTnT in venous blood to lower motor neuron (LMN) involvement on Electromyography (EMG). A positive correlation between EMG findings and cTnT levels would indicate that cTnT is a biomarker for LMN involvement in ALS. This observational cohort study was conducted on a tertiary referral centre for neuromuscular diseases in Stockholm, Sweden. Consecutive patients with ALS were included. EMG was performed during diagnostic work-up, and high-sensitive cardiac troponin T (hs-cTnT), plasma creatine kinase (CK), and serum neurofilament light (NfL) were analysed within 6 months of the EMG. King's stage and score on the Revised Amyotrophic Lateral Sclerosis Functional Rating Scale (ALSFRS-R) closest to hs-cTnT sampling were noted. In total, 50 ALS patients diagnosed between 1 January 2014 and 31 December 2018 were included and followed until death, invasive ventilation, or the 14 August 2024. Hs-cTnT correlated positively with the number of muscular regions involved (