Final answer:
The third widely accepted test of muscular endurance is the lateral endurance test.
Step-by-step explanation:
The third widely accepted test of muscular endurance used by physical therapists and orthopedic specialists to test core endurance over strength is the lateral endurance test. This test involves flexing the neck towards the shoulder to test the strength of the muscles on both sides. Any difference in strength between the two sides may suggest damage on the weaker side. The lateral flexion of the neck also tests both flexor and extensor muscles at the same time.