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'Cycle Syncing' Doesn't Boost Strength Training Results

Medically reviewed by Carmen Pope, BPharm. Last updated on March 5, 2025.

By Dennis Thompson HealthDay Reporter

WEDNESDAY, March 5, 2025 -- Social media influencers tout the benefits of “cycle syncing” to boost strength training results among women.

The idea is that women who lift weights during their period build more muscle, because their bodies are flooded with the female hormone estrogen.

But there’s absolutely nothing to this trendy notion, a new small-scale study argues.

Researchers found no difference in the body’s response to heavy resistance exercise when performed during different times within the menstrual cycle.

“Our findings conflict with the popular notion that there is some kind of hormonal advantage to performing different exercises in each phase,” said lead researcher Lauren Colenso-Semple, who conducted the study as a doctoral candidate at McMaster University in Canada.

“We saw no differences, regardless of cycle timing,” she said in a news release.

Cycle syncing has been made popular by internet influencers who tout fitness apps that track cycles, researchers said in background notes.

These influencers say that women can lead healthier lives by altering their lifestyle -- their workouts, diets and other behaviors -- to align with their menstrual cycle.

For this new study, researchers recruited 12 healthy young women and monitored their menstrual cycles to confirm that their cycles were normal.

Contrary to popular belief, very few women -- about 12% -- have a consistent 28-day cycle and ovulate regularly on day 14 along the lines of the “textbook” menstrual cycle, researchers noted.

The women ingested a tracer molecule designed to help researchers track muscle protein levels, and then performed heavy resistance training during two distinct phases of their menstrual cycles One was during their period, the “follicular” phase, and the other was during the “luteal” phase that follows ovulation.

The follicular phase is characterized by peak estrogen levels, while the luteal phase is when progesterone levels are at their highest.

Weight lifting did promote the growth of new muscle, but researchers observed no effect from either cycle phase on the women’s production of muscle protein.

“Our work shows that women who want to lift weights and recondition their muscles should feel free to do so in any phase of their cycle,” senior investigator Stuart Phillips, research chair in skeletal muscle health at McMaster, said in a news release.

“There is no physiological difference in response to the exercise,” he concluded. “It is important to tailor your training to how you feel.”

The new study appears in The Journal of Physiology.

Disclaimer: Statistical data in medical articles provide general trends and do not pertain to individuals. Individual factors can vary greatly. Always seek personalized medical advice for individual healthcare decisions.

© 2025 HealthDay. All rights reserved.

Posted March 2025

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