SHOCKING: Why Cardio is SABOTAGING Your Baby-Making Plans

September 23, 2025

Code to Conception

Daily micro-protocols for the 90-day miracle window

| September 23, 2025 |

🔬 Pre-Bump Biology  

Too much cardio can quietly switch off fertility signals. When high-volume aerobic training collides with low fueling, women lose ovulation and men take a testosterone hit—right down to sperm DNA fragmentation. The fix? Fuel the work, cap the hours, and protect your eggs and sperm during this 90-day pre-conception sprint.  

🧬 Protocol Drop  

Today’s 1-Step Protocol: 

Keep vigorous cardio ≤75–90 minutes per week and never let energy availability (EA) fall below 45 kcal/kg fat-free mass per day. Translation: add ~300–400 extra calories on cardio days—especially carbs pre, during, and post training—to prevent ovulation loss or testosterone crashes. 

👉 Read the full study summary

📚 Glossary Pop  

Energy Availability (EA): The calories left for your body after subtracting what you burn in exercise. When EA drops too low (<30 kcal/kg fat-free mass/day), the brain senses “starvation mode,” dialing down hormones like GnRH, LH, and testosterone that are essential for ovulation, sperm health, and conception.  

Send this to your running buddy—make sure both of you fuel smarter, not less, in your fertility window.
P.S. Tomorrow Teaser
Think your go-to sweat session is making you “fitter for fertility”? Think again. High-intensity group cardio—when stacked on calorie deficits—can silence the very hormones that trigger ovulation. Tomorrow, we expose the class women flock to that’s secretly hijacking their cycles.

Want to learn more?

Koltun, K. J., et al. (2020). Energy availability and LH pulse frequency in exercising women. Journal of Clinical Endocrinology & Metabolism, 105(1), 185–193. https://doi.org/10.1210/clinem/dgz030 

De Souza, M. J., et al. (2021). REFUEL RCT: Increased energy intake and menstrual recovery in exercising women. Human Reproduction, 36(8), 2285–2297. https://doi.org/10.1093/humrep/deab149 

Zhang, H., et al. (2024). Physical activity, sedentary behavior and infertility: Non-linear dose–response. Reproductive Biology and Endocrinology, 22. https://doi.org/10.1186/s12958-024-01186-x 

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