Background <p>This cross-sectional study examined whether exposure to long-term resistance and endurance training can counteract muscular weakness on a functional, neurological and structural level in adolescents with cerebral palsy (CP) compared to typically-developed peers (TD) depending on training status.</p> Methods <p>Five trained (4 males; mean age: 19.8) and four untrained adolescents with CP (3 males; 20.2) were compared to nine age- and sex-matched TD trained (7 males; 19.8) and nine untrained peers (7 males; 20.3). Isometric and isokinetic measurements assessed strength in knee flexion and extension, voluntary activation (VA) was assessed using the twitch interpolation technique and ultrasound imaging of the quadriceps was performed to assess anatomical cross-sectional area (ACSA) and architecture.</p> Results <p>Linear regression models revealed that CP trained had lower absolute isometric strength (dominant: -18% [-48; 11]; non-dominant: -35% [-58; -11]) than TD untrained while CP untrained showed between 29% and 33% lower strength than TD untrained. VA in CP trained (dominant: -13% [-23; -3]; non-dominant: -10% [-30; 11]) and CP untrained (dominant: -14% [-23; -4]; non-dominant: -8% [-29; 13]) showed similar deficits compared to TD untrained. CP trained showed higher ACSA than TD untrained in the dominant leg of the vastus lateralis muscle (+ 16% [-7; 38]), while the non-dominant side showed lower values (-18% [-45; 9]).</p> Conclusion <p>Exposure to long-term resistance and endurance training is associated with a reduced gap in muscle strength and muscle volume in the dominant leg of adolescents with CP while neural drive does not seem to be affected through training exposure. It is discussed that training load might have been too low in the non-dominant leg of CP trained to induce relevant neuromuscular adaptations.</p> Trial registration <p>ClinicalTrials.gov Identifier NCT05859360, date of registration May 16, 2023.</p>