Enabled: Lecture Exam Ill (50 quest, 4 points ea..! i Saved One of the reasons you might struggle to lift a heavy object with your arm fully extended is because Multiple Choice 51 motor neurons cannot release as much ACh in that posture. full extension results in decreased overlap between thick and thin filaments in the muscle in extension, the proximity of Z discs to thick filaments restricts the sliding movement within sarcomeres. in that posture, some myosin heads overlap actin in the wrong orientation and tug actin in the wrong direction