The exercise world is full of cults and tribes.

Some believe the only way to get strong is by lifting heavy weights.

But more and more research is showing you can make the same gains by lifting lighter weights.

The caveat is that lifting must be done to fatigue.

A recent study shed some light on why lifting even with lighter loads leads to the same gains as heavy loads.

Why Light Loads to Failure Work

More Muscle Fibers Join In: As your muscles get tired, your body calls upon more and more muscle fibers to help out. This increased recruitment means more of your muscle gets a workout.
Mechanical Tension: When these new muscle fibers are activated, they experience more "tension" or strain, which is a big trigger for muscle growth.
Metabolic By-Products: The "burn" you feel when your muscles are fatigued is due to the buildup of things like lactate. This metabolic stress isn't just uncomfortable; it might directly tell your muscles to grow!
Other Factors: The study also touches on how fatigue could lead to tiny muscle damage, release of growth-promoting hormones, and changes in proteins that control muscle size.

The Other Benefit

As you can see from the image above, more muscle fibers were damaged in the heavy lifting group. And more fibers were fatigued in the lighter lifting group.

Remember, these groups had the same gains.

As a physical therapist this graphic is important.

It shows how valuable lighter loads can be for the injured population, or a population that wants to minimize their risk of injury.

Summary

It’s always hard to determine what the best exercise is.

This is because it’s a very individualized thing. Everyone is different.

And because research will always be discovering more and more about what works best.

But we do know what the worst exercise is…and that’s not exercising at all.

This study provides more evidence for why lighting lighter loads to fatigue may be an optimal strategy for many individuals.

Study

Grgic, J., & Schoenfeld, B. J. (2024). Fatigue-induced skeletal muscle hypertrophy: A narrative review. American Journal of Physiology-Cell Physiology, 326(5), C1235-C1242.

Link to the article: https://journals.physiology.org/doi/full/10.1152/ajpcell.00266.2024