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

Jul 4, 2025

Dr. Stacy Sims, an international exercise physiologist and nutrition scientist, shares her expertise on how women's fitness differs from men's. She explains the impact of puberty on biomechanics and why popular training methods like Zone 2 may not be suitable for women. The conversation highlights the crucial role of strength training during perimenopause, revealing how moderate intensity can raise cortisol levels. Sims discusses strategies for avoiding muscle loss and injuries while emphasizing the need for tailored approaches to optimize women's health.

Ask episode

AI Snips

Chapters

Books

Transcript

Episode notes

INSIGHT

Sex Differences in Muscle Fibers

Women are born with more endurance-type muscle fibers, favoring aerobic capacity.
Men have more fast-twitch fibers suited for power and speed, influencing training needs.

INSIGHT

Biomechanics and ACL Injury Risk

Women's quad dominance and biomechanics increase risk of ACL injuries during direction changes.
Strengthening glutes and hamstrings reduces injury risk and improves posture and movement.

ADVICE

Injury Prevention Training Tips

Focus on strengthening posterior chain muscles like glutes and hamstrings to prevent ACL injuries.
Drop traps and engage back muscles during shoulder movements to avoid frozen shoulder.

Get the Snipd Podcast app to discover more snips from this episode

Get the app

Why do women and men get vastly different results from the same workout and diet plan? In this Fitness Friday episode on the Habits and Hustle podcast, I sit down with Dr. Stacy Sims, exercise physiologist, who reveals the differences that affect every aspect of how women should approach fitness and nutrition.

We dive into how puberty creates a biomechanical shift that changes everything and reveal why popular fitness trends like Zone 2 training and Orange Theory classes may actually be working against women's biology. We also share the specific strategies women need to combat muscle loss, maintain bone density, and optimize body composition.

Dr. Stacy Sims is an international exercise physiologist and nutrition scientist who specializes in sex differences in training, nutrition, and environmental conditions. She's the author of "Roar" and "Next Level" and has spent decades researching how women's unique physiology requires different approaches to health and fitness.

What we discuss:

Why women are born with different muscle fiber types than men
Why Zone 2 training isn't optimal for most women throughout their lives
The importance of power-based and strength training for women's longevity
How perimenopause changes training needs
Why moderate intensity workouts can increase cortisol and visceral fat
Why women need heavy lifting (0-6 reps) during perimenopause
Why women are more prone to ACL injuries and frozen shoulder

Thank you to our sponsor:

Momentous: Shop this link and use code Jen for 20% off

Therasage: Head over to therasage.com and use code Be Bold for 15% off

TruNiagen: Head over to truniagen.com and use code HUSTLE20 to get $20 off any purchase over $100.

Magic Mind: Head over to www.magicmind.com/jen and use code Jen at checkout.

Bio.me: Link to daily prebiotic fiber here, code Jennifer20 for 20% off.

David: Buy 4, get the 5th free at davidprotein.com/habitsandhustle.

Find more from Dr. Stacy Sims:

Website: https://www.drstacysims.com/

Instagram: https://www.instagram.com/drstacysims

Find more from Jen:

Website: https://www.jennifercohen.com/

Instagram: @therealjencohen

Books: https://www.jennifercohen.com/books

Speaking: https://www.jennifercohen.com/speaking-engagements