Women are not Small Men - a physio perspective
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Women Are Not Small Men: Why Understanding that Matters in Health and Performance
WRITTEN FOR CLINICIANS – From Caitlin Sargent’s training with Stacey Sims.
For far too long, the health and performance needs of women have been underrepresented in research and practice. From sports science to injury prevention and rehab, women have historically been treated as “small men,” with generalized protocols applied across the board. But here’s the thing: female physiology isn’t just a scaled-down version of male physiology. It’s different—sometimes subtly, sometimes profoundly—and acknowledging these differences is essential for us as health professionals.
A Brief History: The Research Gap
Women were not included in sport, let alone sports science research, until relatively recently. The reasons? Researchers historically argued that:
- Differences between men and women were small and could be generalized.
- The menstrual cycle made women “too complex” to study.
- Including women might “skew results” or lead to null findings.
- There weren’t “enough” peri- or post-menopausal women to include.
This lack of inclusion means we’re only just catching up on understanding the nuanced ways female physiology affects performance, recovery, injury, and health outcomes.
The Menstrual Cycle
A woman’s cycle affects her from head to toe. Estrogen and progesterone fluctuate and impact muscle growth, thermoregulation, fuel metabolism, cognition, and injury risk.
Estrogen:
- Anabolic (supports lean muscle growth)
- Enhances fat metabolism and bone formation (via IGF-1 stimulation)
- Increases clotting risk and serotonin sensitivity (brain fog, fatigue)
Progesterone:
- Catabolic (may inhibit muscle gains)
- Thermogenic (raises core temp by 0.5°C)
- Reduces sodium reuptake (fluid imbalance), raises respiratory rate
- Impairs insulin sensitivity and glycogen storage
Fun fact: Leucine competes with tryptophan to enter the brain. Too much leucine can reduce serotonin → CNS fatigue. But too little and tryptophan spikes → anxiety, brain fog. It’s a delicate dance.
Training Implications by Cycle Phase
High hormone phase (luteal phase) = increased fatigue, temperature, CNS load, and recovery time. 💡 Top Tip: Consider a deload week the week before menstruation.
Everyone is affected by their menstrual cycle differently and while some may not find any need to modify training in relation to their hormones, others may find it very beneficial. Women may need:
- More carbs pre- and intra-workout to perform at higher intensity
- More leucine-rich protein to counteract progesterone’s catabolism
- Specific strategies for hydration and thermoregulation
Hormonal Contraceptives & Performance
Synthetic hormones don’t mimic natural cycles. Key effects include:
- ↓ VO2 peak, cardiac output, and carb uptake
- ↑ Oxidative stress and inflammation (not offset by nutrition)
- ↑ Catabolic activity with progesterone-only pills (initial 6 months)
Important: Monitor how each athlete responds—some tolerate contraception well, others don’t. Adjust training loads and nutrition accordingly.
Menopause: The Next Performance Frontier
Post-menopause, women face:
- Decreased bone mineral density (up to 1/3 lost in 5 years)
- Blunted anabolic response to exercise
- Muscle catabolism and increased fat deposition
- Altered insulin sensitivity and gut microbiome changes
Power training becomes non-negotiable. Combine resistance work with higher protein and leucine to maintain lean mass and support MPS (muscle protein synthesis).
Adolescents & Puberty: A Crucial Window
During puberty, many girls plateau or even regress in motor performance. Factors include:
- Neuromuscular changes from growth spurts
- Shifting Q-angles, increasing injury risk (especially ACL)
- Increased estrogen = increased fat mass, changes in coordination
Message to practitioners: Normalize these changes. Reinforce that performance dips are temporary. Focus on technique, motor control, and confidence.
Low Energy Availability (LEA) & RED-S
LEA occurs when energy intake doesn’t match expenditure. It’s more common than we think:
- Up to 46% of recreational female athletes affected
- Subclinical LEA = poor sleep, training stagnation, low mood, increased body fat
- RED-S (Relative Energy Deficiency in Sport) affects everything: thyroid, bone, reproductive, immune and cardiovascular health
LEA is often unintentional. Appetite can be suppressed post-training, or athletes don’t realise how much fuel they need. A teen athlete may need 3,000–4,000 calories/day. That’s hard to hit without planning.
Our role? Educate on:
- Nutrient timing
- Fueling around training
- Supporting mental health and gut function
- Identifying red flags early
The Bottom Line: Shift the Lens
As health professionals, we must move beyond the male default. Understanding the complexity of female physiology isn’t about complicating treatment plans—it’s about optimising outcomes.
Whether you’re managing injury rehab, training periodisation, nutrition, or mental wellbeing, remember: ✨ Women are not small men. And when we tailor care with this in mind, we empower our clients to perform, thrive, and heal better.