Isometrics vs. Full ROM Training: New Research Challenges How We Think About Muscle Growth

I’ve long been a proponent of full  range of motion (ROM) training. Moving a weight through the entire path of a lift helps maximize mechanical tension and recruit more muscle fibers—two key drivers of growth.

But emerging research suggests we may need to rethink how much movement is actually required.

A 2025 study compared traditional full-ROM reps to isometric training—holding a muscle under tension without movement—and found that isometrics may build just as much muscle. Possibly even more.

That doesn’t mean you should ditch your full-ROM training. But it does give us another useful tool.

What the Research Showed

In the study, weight-trained subjects trained each leg differently. One leg performed full-ROM leg extensions to failure, while the other performed isometric holds at the very beginning of the movement.

Both approaches were matched for time under tension (TUT) at roughly 30 seconds per set, with subjects training twice per week for six weeks.

At the end of the study, the quadriceps trained with isometrics grew by 2%, while the full-ROM leg grew by 1%. 

Technically, that’s double the growth. In practical terms, it’s a difference of just 1%. And statistically, the results weren’t significant. Six weeks is a short time frame for trained individuals to show meaningful hypertrophy changes, so a longer study may have revealed clearer separation.

Still, the

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