Full ROM includes both effective and less effective parts of a movement. Hypertrophy is driven by mechanical tension, especially in the lengthened position under load, but some ROM portions (like full lockout) may not contribute much to muscle fiber recruitment. For example, in a biceps curl, the tension drops at the top (shortened position) due to biomechanics, this part of full ROM adds little hypertrophic value.

Studies show training in the lengthened position (deep stretch) can promote hypertrophy, but it is especially true for certain muscles like hamstrings, triceps, and glutes.

But overemphasizing stretch in exercises not well-suited for it can:

• Reduce stability.
• Increase injury risk.
• Shift stress to passive structures (like tendons or joints).

In some lifts, using full ROM means lowering the total load, reducing tension in the most hypertrophic range. An example is a partial leg press (deep range only) with heavier weight can produce more quad growth than full lockouts with less load. Keep in mind muscle architecture & biomechanics plays a role. They do not all respond the same to stimulus. 

Overload over ROM for hypertrophy. What that means is the main driver of hypertrophy is progressive mechanical tension over time. While lengthened tension can enhance growth, it's not a one-size-fits-all rule. Some exercises are better done in a shortened range (e.g., lateral raises) to maintain tension and avoid momentum.

This study found that full ROM training produced significantly greater adaptations in muscle strength and lower-limb hypertrophy compared to partial ROM. However, no significant superiority of either ROM was found for changes in muscle thickness, pennation angle, and fascicle length. https://pubmed.ncbi.nlm.nih.gov/34170576/

This systematic review concluded that performing resistance training through a full ROM confers beneficial effects on hypertrophy of the lower body musculature compared to partial ROM. However, research on the effects of ROM for the upper limbs is limited and conflicting, precluding strong practical inferences. https://pmc.ncbi.nlm.nih.gov/articles/PMC6977096/?utm_

This meta-analysis revealed a trivial standardized mean difference in favor of full ROM compared to partial ROM for muscle hypertrophy. Sub-group analyses suggested a potential hypertrophy benefit to partial ROM training at long muscle lengths compared to using a full ROM. https://journal.iusca.org/index.php/Journal/article/view/182?utm_

This study compared changes in strength and regional muscle hypertrophy between different ROMs in the knee extension exercise. Results showed that training in the initial phase of the movement (long muscle lengths) promoted greater relative hypertrophy in certain muscle regions than training in other ROM configurations.https://pubmed.ncbi.nlm.nih.gov/33977835/

The sensation of a deep stretch during an exercise does not necessarily indicate that the muscle is under effective mechanical tension, which is a primary driver of hypertrophy. For example, the article "Why stretch-mediated hypertrophy is overhyped" discusses that while lengthened training may lead to greater muscle growth, the term "stretch-mediated hypertrophy" is often misused. It emphasizes that simply feeling a stretch is not synonymous with the mechanical tension required for muscle growth. https://www.strongerbyscience.com/stretch-mediated-hypertrophy-overhyped/?utm_

Some research indicates that prolonged and intense stretching protocols can result in small increases in muscle size. A systematic review and meta-analysis found that chronic static stretching could lead to small magnitude increases in muscle hypertrophy, especially when higher stretch durations and frequencies were employed. However, the practical applicability of such protocols is limited due to the extensive time commitment required. https://sportsmedicine-open.springeropen.com/articles/10.1186/s40798-024-00706-8?utm_