Final answer:
The advantage described is associated with static stretching, which involves holding a muscle in a stretched position to increase flexibility and range of motion without triggering the stretch reflex.
Step-by-step explanation:
The advantage associated with the flexibility training that involves both relaxing and concurrent elongations of the stretched muscle, without stimulation of a stretch reflex, is most closely associated with static stretching. Static stretching involves slowly stretching a muscle to its end point and holding that position for a period of time. It's a form of exercise that increases joint flexibility, improves range of motion, and can reduce the risk of injury. This type of stretching does not involve the muscle's stretch reflex, which can prevent the muscle from stretching too far, too fast, and is therefore associated with a more controlled elongation of the muscle.