If you’ve followed me for a while, you know I’m all about helping women work with their physiology, not against it. And while I’ve covered this extensively for women aged ~25+, an area of emerging interest for me—especially with a teenage daughter—has been learning and researching more about what happens to girls during puberty.
It’s what led to the launch of my latest course, Next Gen, earlier this year, and it’s opened my eyes—as both a mom and a scientist—to just how much we still have to learn about puberty and its impacts.
Puberty is one of the most misunderstood and underserved stages of a girl’s life—especially when it comes to training, performance, and overall health. If you’re a parent, coach, teacher, or mentor to active girls, I want to help you show up better informed and better equipped.
Here are 10 little-known (but hugely important) facts about training and supporting girls through puberty:
1. Girls often experience performance declines during puberty—and it’s totally normal and temporary!
Speed, power, and coordination often drop off mid-puberty due to rapid shifts in body proportions (like limb length and hip width) and changes in center of gravity. Neuromuscular control lags behind, which means their brain has to “re-learn” how to move their changing body. Many girls are misjudged as unmotivated, when in reality, they simply need targeted skill retraining—not less sport.
2. The risk of ACL injuries skyrockets.
Girls are up to 8x more likely than boys to tear an ACL during puberty. Increased joint laxity (due to estrogen), combined with altered biomechanics and quad dominance, significantly raise the risk. Neuromuscular training focused on landing mechanics and strength is essential.
3. Sleep gets harder—and hormones are to blame.
Puberty delays melatonin release, pushing teens’ natural sleep times later. Add early school start times and social stress, and many girls get chronically short-changed on sleep. Even if they spend 8 hours in bed, hormonal shifts can disrupt REM cycles, leading to poor recovery, reduced focus, and mood fluctuations.
4. Early sport specialization can backfire.
Contrary to popular belief, specializing early doesn’t improve long-term performance outcomes. It increases the risk of injury and burnout. Girls benefit from multisport participation, which promotes motor skill development, resilience, and longer, more enjoyable athletic careers.
5. Eating “enough” isn’t always enough.
Due to growth spurts and high energy demands, girls can fall into low energy availability—even while eating three meals a day. Poor timing (like missing pre/post workout nutrition), high training volume, and fatigue-related appetite suppression all play a role. Energy imbalance can disrupt menstrual function, impair bone health, and reduce strength and endurance. To learn more about LEA, check out my LEA on Microlearning.
6. Girls may have better fatigue resistance than boys.
Girls tend to have more oxidative (Type I) muscle fibers, making them more fatigue-resistant and often better suited for endurance-based training. When coaches recognize and leverage this, they can help girls train smarter and recover more effectively.
7. Bone injuries spike because bones grow faster than muscles.
During puberty, skeletal growth can outpace the ability of muscles and tendons to adapt. This mismatch can lead to growth plate injuries and stress fractures—especially in under-fueled or over-specialized athletes. These aren’t just “bad luck”—they’re preventable with proper training load management and adequate fueling.
8. The menstrual cycle can be a performance advantage.
Whatever your age, tracking your own menstrual cycle can be a powerful tool, so learning to do this from puberty can be immensely helpful. However, during puberty, the cycle can be very irregular, so girls need to know that it might take a while (2-3 years usually) after the first period (menarche) to settle into a “normal” rhythm with a cycle occurring every 4-5 weeks or 25-40 days. During the first two years, it is entirely normal for periods to be irregular, skipped, or vary in length as hormones adjust to a consistent rhythm. Helping girls understand this—and normalizing it—will help both their physical performance and confidence.
9. Be cautious with OC use.
Because of menstrual cycle irregularity during puberty, many girls are put on OCs (oral contraceptives) when they shouldn’t be. The “period” on hormonal birth control is a withdrawal bleed triggered by stopping synthetic hormones—it’s not a true menstrual cycle. This distinction matters when monitoring readiness, recovery, or identifying red flags like amenorrhea. Unless the OC is needed for health issues or for what it is intended—birth control—then it is better for teenage girls to hold fire on using OCs.
10. Not all “health foods” are healthy.
Ultra-processed plant-based meat substitutes, though marketed as healthy, can negatively impact the gut microbiome—which is especially concerning for growing, active girls. Gut health influences everything from hormone balance to energy levels and immune strength. I always advocate a whole-foods, nutrient-dense approach to fueling, whatever your age or life stage.
If any of this was new to you—you’re not alone. That’s exactly why I created the Next Gen course. And from now through September 14, it’s on sale with 30% off.
I hope you’ll join me in helping to empower the Next Generation!
IN OTHER NEWS…
My Motivation Behind Creating Next Gen
Learn a little more about why I created Next Gen in this short video (yes, filmed while on school pick-up duty!).
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Gurls Talk Podcast
If you’re keen to learn more on the topic of keeping girls in sport, puberty, and first periods, you might enjoy this Gurls Talk podcast.
What’s the Ideal Breakfast for a Busy Woman?
I know it’s back-to-school season in the northern hemisphere, and I know just how hectic this time of year can be, especially after the lazier (aka less chaotic) days of summer. If you’re struggling to start the day off right from a fuel perspective, check out this short video where I chat with Mel Robbins about the ideal breakfast. (Oh, and here’s the recipe for high-protein overnight oats—it’s a winner in our house!)
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Sprint Interval Training
If you missed it, my last newsletter was on HIIT (high-intensity interval training) and SIT (sprint interval training), and the physical and cognitive benefits of both. Remember that this type of training doesn’t need to be running—it can be cycling, rowing, swimming, kettlebells…the list goes on! What matters is the intensity and the timing. Listen to me and Loretta chat more about our favorite SIT modalities in this Instagram reel.
Stay strong, stay well!
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