Uploaded July 2026 | Updated September 2026, 2 weeks ago
It's not that you're not working hard enough. It's that no one told you about fast-twitch muscle fibers — and what happens to them when you go years without demanding anything explosive from your body.
Andy Galpin, PhD breaks down the cellular science of muscle aging: the soleus, the gastroc, the size principle, and why the Achilles tendon epidemic after COVID was a direct consequence of people simply... stopping. He also explains exactly what it takes to preserve the fast-twitch fibers you still have — and why it doesn't require as much as you think.
If you want to catch yourself from a fall at 75, carry your luggage at 80, and live independently at 90 — this is the conversation that explains why.
Watch the full conversation: youtu.be/gnnXgKIYv6g
**P.S. When you're ready, here are two ways Dr. Stephanie can help you:
Subscribe: The Mini Pause — My weekly newsletter packed with the most actionable, evidence-based tools for women 40+ to thrive in midlife. drstephanieestima.com/newsletter
Build Muscle: LIFT — My progressive strength training program designed for women in midlife. Form-focused, joint-friendly, and built for real results. drstephanie.ca/lift
It's not that you're not working hard enough. It's that no one told you about fast-twitch muscle fibers — and what happens to them when you go years without demanding anything explosive from your body.
Andy Galpin, PhD breaks down the cellular science of muscle aging: the soleus, the gastroc, the size principle, and why the Achilles tendon epidemic after COVID was a direct consequence of people simply... stopping. He also explains exactly what it takes to preserve the fast-twitch fibers you still have — and why it doesn't require as much as you think.
If you want to catch yourself from a fall at 75, carry your luggage at 80, and live independently at 90 — this is the conversation that explains why.
Watch the full conversation: youtu.be/gnnXgKIYv6g
**P.S. When you're ready, here are two ways Dr. Stephanie can help you:
Subscribe: The Mini Pause — My weekly newsletter packed with the most actionable, evidence-based tools for women 40+ to thrive in midlife. drstephanieestima.com/newsletter
Build Muscle: LIFT — My progressive strength training program designed for women in midlife. Form-focused, joint-friendly, and built for real results. drstephanie.ca/lift
