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Background: This study aimed to explore muscle strength production and its underlying neuromuscular characteristics in sedentary and trained individuals with intellectual disability (ID) compared with healthy sedentary individuals., Methods: Three adult groups (age: 25.07 ± 0.70) consisting of sedentary individuals with ID (IDSG), trained individuals with ID (IDTG) and a control group (CONT) participated in the present study. Peak torque (PT) during maximal voluntary isometric contraction, voluntary activation level (VAL), surface electromyography (sEMG) recordings, electrophysiological (M max ) and potentiated twitch torque (PTT responses) of the knee extensor muscles and thigh muscle volume were assessed., Results: Compared with CONT and IDTG, respectively, IDSG presented significantly lower PT (-48% and -42%), VAL (-24% and -9%), sEMG (-49% and -29%), M max (-41% and -39%) and PTT (-32% and -28%) values. These deficits were reduced between IDTG compared with CONT (i.e. PT: -10%; VAL: -16%; and sEMG: -28%) or did not differ anymore (PTT and M max ). Normalising PT to thigh muscle volume and/or computing theoretical PT value overwhelm strength production differences between IDTG and CONT. Training background influences the outcomes with IDTG exhibiting greater PT, VAL, sEMG, M max and PTT than IDSG., Conclusions: Strength production deficit in IDSG was related to both muscular and neural characteristics compared with healthy controls whereas this deficit mainly arises from neural characteristics for IDTG., (© 2019 MENCAP and International Association of the Scientific Study of Intellectual and Developmental Disabilities and John Wiley & Sons Ltd.)