Dr. Stacy Sims: Why women need different training rules

Sports science recruitment has historically prioritized 18–22-year-old men; women were excluded because menstrual cycles were deemed ‘too complex’. As a result, guidelines on caffeine, fasting, training loads, and recovery are largely male-derived and generalized to women. Women who follow male-style fasted training, extreme intermittent fasting, or male-centric volume and intensity patterns frequently see slower progress, weight gain, hormonal disruption, and fatigue instead of improvement.

The female hypothalamus has more kisspeptin-sensitive regions that monitor nutrient availability. In women, low energy intake or carb restriction quickly triggers conservation mode: down-regulated thyroid, disrupted menstrual cycles, increased fat storage, and muscle loss. A woman doing early-morning fasted training plus delayed eating is likely burning lean mass and stressing her endocrine system, whereas a man on the same routine can often lean out and maintain muscle. Sims recommends women have at least ~15 g protein (strength) or 15 g protein + ~30 g carbs (cardio/strength) before training and avoid long fasting windows.

In the low-hormone follicular phase (roughly days 1–13 if ovulating), women are more resilient to stress, handle carbs well, and tend to perform best physically and cognitively—this is a prime window for PRs, high‑intensity work, and heavy lifting. After ovulation, rising progesterone raises core temperature, reduces heat tolerance, increases protein needs (~12% higher), and promotes insulin resistance to divert glucose and amino acids to the uterine lining. From about day 23 to bleeding, many women feel flat and recover worse; this is an ideal period for deloads, technique work, and more fueling, not maximal efforts. Tracking symptoms and the bleed pattern, then matching training intensity to how you actually feel, is central.

Women are born with more endurance-oriented fibers and less upper‑body strength, have a wider Q‑angle, smaller hearts and lungs, and more quad dominance. This raises ACL injury risk (3–4× higher than men), especially in jumping/cutting sports, and accelerates functional decline with age. Sims stresses hamstring, glute, and calf strengthening plus lateral and single‑leg plyometrics to rebalance forces through the knee. Across the lifespan, resistance training plus higher protein intake improves body recomposition, protects bones, maintains metabolic health, and is the cornerstone for fat loss—much more effective for women than piling on more cardio.

From roughly 35 to early 50s, fluctuating estrogen and progesterone alter blood lipids, increase visceral (abdominal) fat via changes in liver fat handling, disrupt sleep, and blunt exercise adaptations. Many women are misdiagnosed with anxiety or depression and given SSRIs instead of being told they’re in perimenopause. Sims advises shifting toward high‑intensity intervals and power-based resistance training (less volume, more quality), higher protein, fiber-rich diverse plants for gut health, and, when needed, menopause hormone therapy as a low-dose tool to reduce severe symptoms—not as an anti-aging ‘replacement’ to stay young.