Final answer:
The gluteus maximus is the strongest muscle in the human body because it has the most motor units.
Step-by-step explanation:
The primary reason why the gluteus maximus is the strongest muscle in the human body is that it has the most motor units. Motor units are nerve cells and muscle fibers that work together to produce muscle contractions. The gluteus maximus has a wide range of motor units, which gives the nervous system a wide range of control over the muscle and allows for a stronger contraction.