As I say in this blog and in the Testosterone book, if we want to look like warriors with high testosterone, we must become one. We are made to move, but we live seated. That’s killing us and it’s killing our testosterone.
It’s much better to do something than nothing, and if you like to run or you love cycling, by all means, do it. You just need to know that those are not the best exercises to optimize testosterone and, in fact, they can lower your hormone levels.
Why is that? Because we need to move and we need to rest. So if you run too much, your body won’t have time to recover and, in order to keep with your rhythm, it will have to sacrifice some things, like your testosterone. As we can see in this study  male distance runners have reduced serum testosterone and Prolactin levels.
Remember what we said in the Testosterone Book: “our bodies are amazing, but they are not almighty“. If they need to sustain a great effort, they need to sacrifice resources.
Our bodies operate with a software that has not changed since we were cavemen. If we have a strenuous physical activity, it thinks that we are in the middle of some crisis. Our bodies don’t understand that, now, some people run all the time for pleasure, and not for hunting or escaping a predator.
The best type of exercise
As we saw, the optimal type of exercise for our testosterone is high intensity interval training, and weight lifting, combined with long periods of rest.
Running is not necessarily bad, but running is a strenuous activity that, when sustained a lot, can lower our testosterone. In fact, any endurance sport can do that. Running and cycling tend to morph in this kind of activity in some cases, and you have to avoid that. Check the title of this other study : Testosterone Is Significantly Reduced in Endurance Athletes.
In fact, there is something more harmful that endless cardio on a bike or running, and it’s high intensity exercise sustained during too much time.
Interval training is better than running
We recommend short High Intensity Interval training because it seems optimal to burn fat and you won’t likely overtrain. So, for testosterone optimization purposes, it’s a superior activity . You will burn fat (remember that abdominal fat and testosterone are negatively correlated) and you will improve your cardiac health and resistance.
Am I advocating that you stop running or cycling if you like it? By all means no. But don’t do it a lot. If you don’t like it very much, you will be better with interval training, weights and some running here and there. If you must choose between them, running is better than cycling, (see studies  and ) in order to burn fat. Even when traditional running and cardio is a sub-optimal way of losing fat.
Walking is better than jogging
In fact, I see some runners that jog at a slower speed than I walk, if you are doing that, stop and walk. Walking is, in fact, a better exercise than jogging .
I always advocate longs walks, their benefits are immense, remember that we are made to move, and walking has so many benefits that we would need a book to name them all, physiologically and psychologically.
And why I talk about cycling? Cycling can become a strenuous activity, if you are doing it that way, and you want more testosterone, you should think about stopping it. In fact, cycling and testicles are not a good match. Cycling exerts some nasty pressure on our testes, if you keep doing that too much time, too many times, you are doing yourself a disservice.
Again, this is not an anti-runner campaign. If you enjoy it, do it, it’s much better than doing nothing, but if you want to optimize your exercise and increase your testosterone, you should be putting traditional cardio where it belongs, and it’s not at the top
 Reduced Serum Testosterone and Prolactin Levels in Male Distance Runners. Garry D. Wheeler, MS; Stephen R. Wall, MA; Angelo N. Belcastro, PhD;David C. Cumming, MB, ChB
 Testosterone Is Significantly Reduced in Endurance Athletes without Impact on Bone Mineral Density
L. Maïmouna,b, S. Lumbrosoc, J. Manettad, F. Parisc, J.L. Lerouxe, C. Sultanc
 King, J., Panton, L., Broeder, C., Browder, K., Quindry, J., & Rhea, L. (2001). A comparison of high intensity vs. low intensity exercise on body composition in overweight women. Medicine and Science in Sports & Exercise, 33, A2421
 Comparison of fat oxidation over a range of intensities during treadmill and cycling exercise in children.
Zakrzewski JK, Tolfrey K. School of Sport, Exercise and Health Sciences, Loughborough University, Loughborough, LE11 3TU, UK.
 Higher fat oxidation in running than cycling at the same exercise intensities. Capostagno B, Bosch A. Dept. of Human Biology, University of Cape Town, South Africa.