Scientists Reveal the Simplest Rule for Building Strength

New resistance-training guidelines show that any amount of strength training can significantly improve muscle, strength, and physical function.

The first major revision to resistance training guidelines in 17 years carries a straightforward takeaway. Doing any resistance training at all can boost strength, increase muscle size, improve power, and enhance physical function.

The updated guidance comes from the American College of Sports Medicine (ACSM), which released the recommendations as a Position Stand. The report draws on 137 systematic reviews that include data from more than 30,000 participants. This extensive analysis makes it the most comprehensive set of resistance-training guidelines produced to date.

“The best resistance training program is the one you’ll actually stick with,” says Stuart Phillips, distinguished professor in the Department of Kinesiology and an author on the Position Stand. “Training all major muscle groups at least twice a week matters far more than chasing the idea of a ‘perfect’ or complex training plan. Whether it’s barbells, bands, or bodyweight, consistency and effort drive results.”

A Long-Awaited Update in Strength Training Science

The new Position Stand arrives after years of rapidly growing research. ACSM last released official guidance on resistance training for healthy adults in 2009, before a surge of studies examining muscle health, aging, and the role of strength in long-term well-being.

“The new document reflects that surge in evidence and expands its recommendations to include more people and more types of training than ever before,” Phillips says.

A major theme throughout the updated guidelines is that the most meaningful improvement often comes from a simple change. Going from no resistance training to even a small amount can produce measurable benefits. While factors such as training load, workout volume, and frequency can be adjusted over time, experts say the priority for most adults should be creating a routine they can maintain consistently.

Strength Training Does Not Require a Gym

Another important shift in the updated guidance is the recognition that effective resistance training does not depend on access to a gym. Exercises using elastic bands, bodyweight movements, or simple home routines can still lead to clear improvements in muscle strength, muscle size, and everyday physical performance.

According to Phillips, rigid rules about the “ideal” workout plan are no longer supported by the evidence. Instead, the focus has shifted toward individual preferences, enjoyment, and the ability to stick with a routine over the long term. This approach is particularly important for adults who want to remain strong, healthy, and physically capable as they age.

Find a Routine You Enjoy and Stick With It

Highly trained athletes will still need more specialized programs tailored to their sports. However, for most adults the core advice is straightforward. Choose a resistance training routine that you enjoy and make it a regular habit.

The full ACSM Position Stand is now available in Medicine & Science in Sports & Exercise.

Reference: “Resistance Training Prescription for Muscle Function, Hypertrophy, and Physical Performance in Healthy Adults: An Overview of Reviews” 16 March 2026, Medicine & Science in Sports & Exercise.

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