Women’s Physiology and Training

Overview

Dr. Stacy Sims, an exercise physiologist and nutrition scientist, emphasizes the critical physiological differences between men and women, especially in exercise, nutrition, and health. She advocates for women-specific research and approaches throughout all life stages—puberty, reproductive years, perimenopause, and menopause—to help women optimize health, fitness, and longevity by working with their unique physiology.

Sex Differences in Physiology

Most exercise and nutrition research is based on male data, often excluding women due to perceived hormonal complexity, recruitment challenges, and historical biases in science and medicine.
Female physiology changes significantly across life stages, affecting metabolism, training response, and injury risk. Key stages include puberty, reproductive years, perimenopause, and menopause, each with distinct hormone profiles.
Women have higher essential body fat (about 12% vs. 4–8% in men), smaller hearts and lungs, lower hemoglobin, and more endurance-oriented muscle fibers. Men have more fast-twitch fibers, greater anaerobic capacity, and higher oxygen-carrying capacity due to testosterone.
Puberty brings anatomical changes for girls (wider hips, altered Q angle, quad dominance), which increase injury risk and contribute to a high dropout rate from sports by age 14. Girls’ center of gravity shifts lower, affecting movement mechanics and comfort in activities like running, jumping, and swimming.
The Q angle (hip-to-knee angle) becomes more pronounced in women after puberty, leading to changes in running and jumping mechanics and increasing the risk of ACL injuries.
Women’s bodies are more sensitive to stress, nutrient intake, and hormonal fluctuations, which impact metabolism, recovery, and adaptation to training.

Training, Nutrition, and Weight Management

Women respond differently than men to fasting, calorie restriction, and training due to greater hypothalamic sensitivity and hormonal fluctuations. The hypothalamus in women is more sensitive to nutrient availability, making them more prone to negative effects from low-calorie or low-carb diets.
Fasted training and prolonged calorie restriction can lead to muscle loss, metabolic issues, and hormonal dysfunction in women, while men are less affected and may even benefit from these strategies.
Resistance training and increased protein intake are especially important for women, particularly from the mid-30s onward and during perimenopause/menopause, to maintain muscle mass, bone health, and metabolic function.
Post-exercise nutrition is more time-sensitive for women: 35g protein within 45 minutes is recommended to stimulate muscle protein synthesis, while men have a longer window and need less protein post-exercise (about 20g).
Women’s bodies are more sensitive to nutrient timing and meal regularity, especially in the morning to blunt cortisol peaks and support hormonal balance.
During the menstrual cycle, energy needs, insulin sensitivity, and training capacity fluctuate. After ovulation, progesterone increases insulin resistance and protein needs, so women should increase carbohydrate and protein intake during this phase.
Women should avoid extreme fasting (such as 20:4 “warrior” fasts) and ketogenic diets, as these can negatively impact blood sugar control, thyroid function, and overall health. Instead, overnight fasting (dinner to breakfast) is more appropriate.
Evolutionarily, women’s bodies are designed to conserve energy and protect reproductive function during times of low calorie intake, while men’s bodies adapt by becoming leaner and more efficient.

Injury Prevention and Exercise Strategies

Women are 3–4 times more likely than men to suffer ACL injuries, mainly due to anatomical (Q angle, wider hips) and neuromuscular differences (quad dominance, less posterior chain activation).
Injury prevention for women should focus on strengthening the posterior chain (glutes, hamstrings, calves) and incorporating lateral and explosive movement training (e.g., single-leg jumps, lateral movements).
Professional sports often include targeted warm-ups for injury prevention (e.g., FIFA protocols), but grassroots and recreational levels lack this, increasing injury risk for women and girls.
Hormonal fluctuations, such as increased estrogen around ovulation, can increase ligament laxity and injury risk. Progesterone also affects tendon properties.
Education on body mechanics and training adaptations is lacking for girls, contributing to high dropout rates from sports and increased injury risk during adolescence.

Menstrual Cycle, Menopause, and Hormonal Considerations

The menstrual cycle causes cyclic changes in insulin sensitivity, energy needs, and training capacity. Progesterone increases insulin resistance and protein needs after ovulation, while estrogen affects glucose utilization and recovery.
Tracking both physical and mental readiness, as well as changes in cycle length or bleed patterns, is essential for optimizing training and identifying stress or low energy availability. Changes in bleed pattern or cycle length can signal stress, under-recovery, or low energy availability.
Perimenopause (typically ages 35–52) brings major hormonal fluctuations, body composition changes (increased visceral fat), sleep disturbances, and new dietary/exercise needs. Symptoms include poor adaptation to training, increased body fat, mood changes, and disrupted sleep.
During menopause, high-intensity interval training and power-based resistance work are recommended to maintain muscle, bone health, and metabolic function. Less volume and more quality (short, sharp sessions) are preferred over long-duration, moderate-intensity exercise.
Menopause hormone therapy (MHT, formerly HRT) can be a tool for managing severe symptoms, but lifestyle interventions (exercise, nutrition, sleep) are foundational. MHT is not about “staying young” but about managing symptoms and quality of life.
Bone health is especially important for women, as bone density peaks around age 20 and declines with hormonal changes. Resistance training, vitamin D, and adequate protein are key for maintaining bone health.

Supplements and Dietary Considerations

Women often benefit from creatine (3–5g/day, no loading needed), vitamin D3 (preferably D3 for better absorption), and, based on bloodwork, omega-3 and iron supplementation. Creatine supports muscle, brain, and gut health, and is especially helpful for women who may have lower stores.
Gut microbiome diversity is crucial for hormonal health, as certain gut bacteria help metabolize sex hormones. Ketogenic diets can reduce this diversity and are not recommended for women. Aim for at least 30 different plants per week to support gut health.
Women should aim for a diverse diet with regular protein intake at each meal, and meal timing that supports hormonal balance and recovery. Higher protein needs are especially important during perimenopause and menopause due to anabolic resistance.
Iron needs are higher for women, especially those who are active or menstruating. Low iron can cause fatigue, poor performance, and cognitive issues. Supplementation should be tailored (e.g., every other day, away from training) and based on bloodwork, as reference ranges are shifting with population health.
Vitamin D3 is important for muscle, bone, and immune health, especially in winter or with low sun exposure. Omega-3s are particularly helpful in perimenopause and postmenopause for inflammation and cellular health.
Women should avoid relying on supplements alone; focus on whole foods, meal diversity, and regular eating patterns.

Sleep and Chronobiology

Women experience more sleep disturbances due to hormonal fluctuations, especially before menstruation and during perimenopause. Progesterone increases core temperature and disrupts melatonin, affecting sleep quality.
Women are more affected by jet lag, with circadian rhythms and melatonin peaks occurring earlier than in men. Women’s circadian rhythms are slightly shorter, making eastward travel easier and westward travel harder.
Good sleep hygiene and regular meal timing support better hormonal and metabolic health. Eating late or skipping breakfast can disrupt circadian alignment, increase cravings, and impair appetite regulation.
Chronobiology (the study of biological rhythms) is important for both men and women. Women’s cortisol peaks earlier and is more sensitive to food intake in the morning, so eating soon after waking helps blunt the cortisol response and support hormonal balance.
Sleep is essential for physical and mental recovery, memory consolidation, and overall well-being. Women should prioritize sleep, especially during times of hormonal change.

Recommendations / Advice

Women should individualize nutrition and training based on life stage, menstrual cycle, and symptom tracking, adjusting intensity and recovery as needed. Use sessional rating of perceived exertion (physical and mental) to guide daily training.
Regular high-protein meals, frequent resistance training, and support for gut microbiome diversity are recommended for all women. Focus on whole foods, colorful fruits and vegetables, and a variety of plant sources.
Avoid extreme fasting or ketogenic diets; instead, prioritize overnight fasting, meal diversity, and appropriate meal timing. Eat within 30 minutes of waking, and avoid eating 2–3 hours before bed.
Track menstrual cycles and note changes in physical/mental readiness to adjust training and recovery. Monitor bleed patterns and cycle length for signs of stress or low energy availability.
During perimenopause and menopause, increase high-intensity and power-based resistance training, and consider additional protein and gut-supporting foods. Use lifestyle interventions as the foundation, and discuss hormone therapy with a healthcare provider if needed.
Injury prevention should be a priority, especially for girls and women in sports. Strengthen the posterior chain, include lateral and explosive movements, and educate about anatomical and hormonal differences.
Men should also be aware of these differences to better support women in their lives—partners, daughters, colleagues, and athletes.

Decisions

Women should adapt training and nutrition by life stage and menstrual cycle.
Resistance training is prioritized for women’s health at all ages.
Supplements (creatine, vitamin D3, iron, omega-3) are recommended as needed, based on individual needs and bloodwork.
Track menstrual cycles and physical/mental readiness to optimize training and recovery.
Prioritize gut health and dietary diversity for hormonal and metabolic health.

Action Items

Women: Track menstrual cycles, bleed patterns, and physical/mental readiness to adjust training and nutrition. Increase protein intake, especially post-exercise and during perimenopause/menopause.
Trainers/coaches: Integrate posterior chain and lateral movement exercises for female athletes, and educate about anatomical and hormonal differences. Implement targeted warm-ups and injury prevention strategies.
Individuals in perimenopause/menopause: Increase high-intensity and power-based resistance training; evaluate diet for adequate protein and gut-supporting foods; consider symptom-driven adjustments and, if needed, discuss hormone therapy with a healthcare provider.
Monitor iron, vitamin D, and omega-3 status through bloodwork, and supplement as needed.
Prioritize sleep hygiene and regular meal timing to support hormonal and metabolic health.

Questions / Follow-Ups

How can medical and fitness education better address women’s physiological differences and ensure women-specific protocols?
What additional research is needed on female-specific responses to training, nutrition, and supplements?
How can awareness and education about menstrual cycles, perimenopause, and menopause be improved for both women and men?
What strategies can be implemented at the grassroots and recreational levels to reduce injury risk and support girls’ participation in sports?
How can women be empowered to track and understand their own physiological changes, and how can this knowledge be better integrated into healthcare and fitness practices?