A 23-year-old lacrosse player begins a resistance training program for the first time. He chooses exercises that includes most major muscle groups. After about 3 1/2 weeks he is noticing some strength gains in his lower-body exercises. Which of the following best describes this athlete's increased lower body strength?
a. Muscle hyperplasia
b. Increased antagonist inhibition
c. Muscle hypertrophy
d. Muscle hypertrophy and muscle hyperplasia
e. Improved motor control