Dr. Stacy Sims04 July 2025

Episode 464: Dr. Stacy Sims: Why Women Are Not Small Men and Need to Train Completely Differently

1Frameworks

7Insights

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Frameworks in this episode

Peak Performance5 steps

Perimenopause Polarized Training Triad

Replace lost hormonal stimulus with heavy strength, HIIT, and sprints

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Insights & moments

The myth-busts, hot takes, explainers, and tools worth keeping.

Myth Buster· 1

Myth Buster07:30

Frozen Shoulder Is Not Just an Unexplained Sign of Aging

Sims links frozen shoulder risk to the combination of a wider female shoulder girdle, movement cues derived from male anatomy, and hormone-related changes in connective tissue. She recommends using a wider position where appropriate, dropping the traps, recruiting the back, and extending through the hips rather than hitching the shoulders during lifts.

Male-derived grip-width cues can load female shoulders poorly
Push-ups and pull-ups may require a wider setup for women
Hormonal changes alter tendon and bursa characteristics
Back-muscle recruitment can reduce strain on the shoulder

“our shoulders as women, we need to be wider.”
Dr. Stacy Sims · 08:00

“If we're thinking about dropping our traps and we're using our back muscles to pick something up and then extending through the hips to lift…”
Dr. Stacy Sims · 09:30

#frozen shoulder#shoulder mechanics#perimenopause#movement

Hot Take· 1

Hot Take03:00

Why Zone 2 and Keto Trends May Solve the Wrong Problem for Women

Sims challenges the direct transfer of male-derived zone 2 and ketogenic protocols to women. Her argument is that XX physiology already has strong endurance and fat-oxidation capacity, so women often need more deliberate development of speed, power, and fast-twitch function instead.

Popular aerobic and fat-burning protocols often originate in male data
XX physiology already tends toward endurance and fat use
Power and fast-twitch capacity may be the more important training gap
Protocols should match the physiology and life stage of the user

“all that's based on male data because being born that XX, you already have all of that capacity.”
Dr. Stacy Sims · 03:00

“What we need to work on throughout our entire life is working on that power base and the fast twitch.”
Dr. Stacy Sims · 03:00

#zone 2#ketogenic diet#women's training#male data

Explainer· 3

Explainer01:00

Why XX and XY Bodies Start With Different Muscle-Fiber Strengths

Sims says people born XX tend to have more oxidative, endurance-oriented fibers and greater capacity to use fat and oxygen over long durations. People born XY tend to start with more fast-twitch, glycolytic fibers suited to speed, reaction, and high-intensity output, making aerobic development a more prominent training need for them.

XX physiology tends toward slow-twitch oxidative fibers
Those fibers support fat oxidation and sustained aerobic work
XY physiology tends toward fast-twitch power fibers
Training needs should account for the capacity already present

“If you are born XX then you have more endurance type fibers. So um your slow twitch your oxidative very aerobic type fibers.”
Dr. Stacy Sims · 01:00

“When we look at XY, they're born with more of the fast twitch glycolytic powerbased fibers. So good at speed, good at um quick reaction…”
Dr. Stacy Sims · 01:30

#sex differences#muscle fibers#physiology

Explainer02:00

Puberty Changes How Girls Run, Jump, Swing, and Land

Hormonal exposure during puberty changes the female center of gravity, hips, and shoulder girdle. Sims argues that girls often receive no movement retraining after those changes, which can make their bodies feel unfamiliar and contribute to dropping out of sport.

The center of gravity moves from the chest toward the hips
The hips and shoulder girdle widen
Movement skills learned before puberty may need to be retaught
Biomechanical change can contribute to girls leaving sport

“So our center of gravity goes from being up in the chest area down to the hip area.”
Dr. Stacy Sims · 02:00

“We aren't taught how to run again, how to jump, how to swing, how to land, or any of those things.”
Dr. Stacy Sims · 02:30

#puberty#biomechanics#girls in sport

Explainer14:00

The Three Ways Estrogen Supports Muscle Strength

Sims describes estrogen as acting at three levels of strength development: satellite cells involved in building muscle fibers, nerve signaling that rapidly recruits fibers, and the contractile proteins that generate force. Declining estrogen can therefore show up as reduced strength, power, and lean-mass support rather than as a single isolated symptom.

Estrogen supports satellite-cell activity
It contributes to rapid nerve conduction and fiber recruitment
It supports the contractile proteins that create strong contractions
Decline affects both lean-mass development and force production

“It's on the satellite cell to develop more muscle fibers. It's on the nerve endings to be able to say, "Yep, let's create a really…”
Dr. Stacy Sims · 14:30

“So when you lose estrogen, you're losing the impetus for those three main points of strength and and lean mass development.”
Dr. Stacy Sims · 15:00

#estrogen#muscle#strength#perimenopause

Takeaway· 2

Takeaway05:00

Shift From Quad-Dominant Training to Protect the ACL

Female posture and center of gravity can create greater quad dominance, while insufficient hamstring strength leaves less opposition to cutting forces. Sims recommends emphasizing the posterior chain through glute, hamstring, extension, and hip-flexor work to improve posture, direction changes, and injury resilience.

Quad dominance can raise change-of-direction injury risk
Hamstring strength helps counter forces involved in ACL tears
Deadlifts, Romanian deadlifts, bridges, and hip thrusts develop the posterior chain
Strong hip flexors help clear the leg instead of stumbling

“we don't have the hamstring strength to counter some of those cutting motions that causes an ACL tear.”
Dr. Stacy Sims · 05:00

“all the glute work where you're thinking about deadlifts, you're think about um Romanian deadlifts, you're thinking about um hip um or glute bridges, hip…”
Dr. Stacy Sims · 10:00

#ACL#posterior chain#injury prevention#strength

Takeaway12:30

The Loudest Menopause Expert May Be Speaking Outside Their Lane

Sims says menopause information becomes confusing when specialists present themselves as authorities beyond their actual field. She distinguishes her exercise-physiology and nutrition expertise from individualized hormone-therapy expertise and recommends referral to specialists who understand that treatment's nuances.

A large audience does not prove cross-disciplinary expertise
Specialists should state the boundary of their competence
High-level knowledge is different from individualized clinical authority
Use referrals when a question falls outside the speaker's lane

“unfortunately those with some of the loudest microphones tend to not stay in their lane.”
Dr. Stacy Sims · 12:30

“I'm not going to be a definitive person on that because that is not my area.”
Dr. Stacy Sims · 12:30

#menopause#expertise#misinformation