Final answer:
The false statement is that fast fatigable motor units have a small force production, when in reality they are capable of generating a large amount of force but fatigue quickly.
Step-by-step explanation:
The statement that is FALSE regarding motor units found within the human body is: B. Fast fatigable motor units have a small force production. In reality, fast fatigable motor units are capable of producing a large amount of force but they fatigue rapidly. Slow motor units are indeed dense with capillaries, rich in mitochondria, and contain the oxygen-binding protein myoglobin. They contract slowly and can sustain activity for long periods due to their efficient use of oxygen, but they do not produce a large force. Conversely, fast fatigable motor units contract quickly and are able to generate a large amount of force due to the presence of enzymes that rapidly hydrolyze ATP, which is essential for muscle contraction. These units, however, are more prone to fatigue because they rely on anaerobic metabolism that generates less ATP compared to aerobic metabolism in slow motor units.