• Allison Fahrenbach

The Impact of Chronic Cardio on Female Hormonal Health

I have written before, on FB and on IG about the positive benefits of low intensity steady state cardio, but just as with anything, it's all about balance.

Cardio is incredibly healthy and can impact the body in positive ways, when integrated as part of a balanced program. But taken to excess, it can have the opposite impact, and can even be largely responsible for why you DON'T see the results in your physique that you're after.

This blog addresses the impact of chronic cardio on women in particular, because I feel women, more so then men, fall into this "cardio trap", thinking that hours and hours logged on the treadmill or elliptical are necessary.

The truth is, it's not only NOT necessary, its often counterproductive, mostly because of the hormonal shifts chronic cardio forces your body to make.

1. It decreases T3. The thyroid is extremely important when it comes to metabolism. Through the production of several hormones, your thyroid directly contributes to numerous biological functions, one of which, is weight control. Of particular interest when it comes to weight management, is the primary hormone T3, or what is clinically called triodothyronine. Keeping T3 levels with a healthy range is vital for both controlling and losing weight. Unfortunately, prolonged, intense bouts of cardio performed over the course of weeks and months, disrupt healthy production of T3, decreasing it and placing your thyroid at risk of enduring long term damage.

2. It decreases testosterone. For many women, when I mention testosterone decreases, they don't seem to think it's a big deal. But testosterone is not just a "male" hormones. It's also found in women, and it's vitally important for both burning fat and building muscle. Studies show that adding a lot of cardio to your routine not only decreases testosterone, but that it can also decrease thyroid stimulating hormone (TSH) which controls your thyroid function, and brings my back to the first point I mentioned, the decrease in T3.

3. It decreases growth hormone. Studies have found a significant decrease in Human Growth Hormone (HGH) as the result of excessive cardio. As its name suggests, HGH stimulates the growth of new tissue, including muscle.

4. It increases cortisol. Long cardio sessions, performed frequently, increase levels of the stress hormone cortisol. While low concentrations of cortisol let your body know that it’s time to burn up some extra fat, chronically high levels do EXACTLY the opposite. In fact chronically elevated levels of cortisol have been directly linked to weight gain, particularly around the midsection. This is because when cortisol becomes elevated and remains elevated, the body begins to make adaptations to aid in your survival. One of these adaptations involves storing more fat for emergency fuel AND burning up hard earned muscle.

So what does this all mean? Taken together, these varying hormonal changes mean that long, frequent cardio reduces the amount of muscle mass on your body and can even increase the amount of fat. This is a double edged sword in the sense that not only will it create a physique that won't look the way you'd like, it also winds up slowing the metabolism and rendering your body LESS effective at utilizing calories.

This is NOT to say that cardio is bad- I feel like I should keep emphasizing that point. It IS saying, however, that chronic cardio, particularly in the absence of sufficient strength training, can be. Cardio, when implemented properly, can be incredibly effective. But in and of itself, it will not create the physical change you're after and can do more harm than good.

Women need to engage in strength training. Strength training stimulates the growth and development of muscle fibers, which burn fat even when you’re at rest. Having a lot of dense, lean muscle tissue is integral in elevating your metabolism and helping you obtain the lean, defined physique that so many women claim to be after.

One study published in the journal Medicine & Science in Sports & Medicine separated women into two groups – one that did just aerobics and another that did both aerobics and strength training. At the end of 12 weeks, while BOTH groups lost "weight", the strength group had significantly reduced body fat, resting heart rate and blood pressure. That’s huge. Strength training not only improved their body composition, but their overall health.

Cardio simply doesn’t work the way you may think it does. Long, intense cardio workouts are going to put you into a hormonal state that encourages increased fat and decreased muscle, while possibly even doing long-term damage to your metabolism. Strength training with heavy weights, on the other hand, pretty much does exactly the opposite: making positive changes to your hormones, boosting your metabolism, and improving your overall health.

General guidelines:

  1. Keep low intensity cardio to three, maybe four sessions a week. Avoid doing hours of cardio every day, several days a week.

  2. If needed or desired, add in one to two sessions of HIIT

  3. Build the bulk of your exercise program around strength training, making it a goal to work in 3-5 solid 40-60 minutes sessions a week.


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