The deltoid muscle can effectively contract through its entire ROM because of the upward rotation of the scapula, which serves to maintain tension in the deltoid muscle. If the deltoid loses tension, it becomes

Actively insufficient

Explanation:

The deltoid is a muscle attached by tendons to the bones localized on the top of the shoulder (clavicle, scapula and humerus). The amount of force generated by a multi-joint muscle decreases as the muscle moves the joints simultaneously. A multi-joint muscle becomes actively insufficient when it shortens over both joints simultaneously and it no longer has the ability to develop an effective tension. Moreover, a muscle is passively insufficient when it can't be stretched to its fullest length across multiple joints simultaneously.