Why Women Over 35 Should Lift Heavy: Insights from Dr. Stacy Sims

At CrossFit Golden Gate, we work with many women in their 30s, 40s, and beyond who want to feel strong, confident, and in control of their bodies. But one of the biggest myths we still hear is that women should stick to light weights or high-rep workouts as they get older.

Exercise physiologist Dr. Stacy Sims, a leading expert on female physiology and performance, says the exact opposite. For women over 35, lifting heavy and doing resistance training is essential, not optional. Here’s why:

1. It Fights Muscle and Bone Loss

As estrogen naturally declines in your late 30s and 40s, your body loses some of its ability to maintain lean muscle and bone density.
Heavy strength training provides the mechanical stress needed to keep both strong and responsive. It helps preserve muscle tissue, protect your joints, and prevent the bone density loss that leads to osteoporosis later in life.

At CrossFit Golden Gate, our strength programs are designed to build confidence under the barbell—teaching proper technique, smart progression, and safe intensity that deliver results.

It Builds Power and Stability

Dr. Sims emphasizes power, not just strength. Quick, explosive lifts and resistance training help preserve fast-twitch muscle fibers, which are key for balance, agility, and preventing injury.

As we age, these fibers naturally diminish, which can make you feel slower or less coordinated. Heavy lifting and plyometric-style training keep your body quick, responsive, and capable—both in the gym and in everyday life.

3. The Hormonal Response Is a Game-Changer

As estrogen and progesterone levels decrease, the body’s natural anabolic (muscle-building) environment weakens. But heavy resistance training can restore and stimulate key hormonal pathways that protect your muscle, bone, and metabolism.

Here’s how it works:

Heavy Lifting Stimulates Growth Hormone and IGF-1

Estrogen used to help trigger recovery and growth. When it drops, lifting heavy steps in to boost growth hormone and IGF-1, two powerful hormones that:

  • Increase muscle protein synthesis

  • Support tissue repair and collagen production

  • Keep bones dense and strong

Improves Insulin Sensitivity and Metabolic Function

Lower estrogen often means higher insulin resistance, which can lead to stubborn fat gain around the midsection.
Strength training reverses that trend by increasing muscle mass, which improves blood sugar control and keeps your metabolism active and efficient.

The more muscle you have, the better your body handles carbohydrates and the easier it becomes to maintain a healthy body composition.

Boosts Testosterone and DHEA Naturally

Women produce smaller amounts of testosterone and DHEA, but these hormones still play a big role in muscle tone, energy, and confidence.
Heavy lifting supports healthy production of both, improving strength, mood, and libido naturally.

Regulates Cortisol and Stress

Estrogen used to buffer the body’s stress response. Without it, cortisol (the stress hormone) can stay elevated longer, leading to fatigue, cravings, and disrupted sleep.
Lifting heavy helps recalibrate your body’s stress response, lowering cortisol levels over time and improving emotional resilience.

4. It Keeps Your Body Responsive

As Dr. Sims explains, women become less sensitive to training stimuli as estrogen drops—which means your body needs a stronger signal to adapt.

That’s exactly what heavy strength training does: it sends the message that your body still needs to maintain strong, metabolically active muscle and bone.

“You have to lift heavy enough to tell your body, ‘I still need this muscle and bone.’” — Dr. Stacy Sims

It Improves Confidence and Quality of Life

Beyond the biology, heavy lifting changes how women feel. It builds confidence, reduces anxiety, and creates a sense of empowerment that carries far beyond the gym.
Our members at CrossFit Golden Gate often say strength training helped them reconnect with their bodies, trust their strength, and feel calmer and more capable in daily life.

The Bottom Line

“You don’t need more cardio—you need more strength.” — Dr. Stacy Sims

If you’re a woman over 35, lifting heavy is one of the most powerful things you can do for your long-term health, hormones, and confidence.

At CrossFit Golden Gate, we’ve been teaching women how to lift safely and effectively since 2012. Our experienced coaches specialize in strength training for every stage of life—from pre- and postnatal, to perimenopause, and beyond.