Mark Sisson was kind enough to provide the following foreword for Get Strong, by Al Kavaldlo and Danny Kavadlo:

The Kavadlo Brothers first caught my attention in 2010 when I saw a video of them treating downtown New York City like one giant pull-up bar. They were making some very hard moves look easy and making the whole thing look like a lot of fun. As someone who’s personally made it my mission to empower people to take responsibility of their own health and enjoyment of life, I was impressed with how the brothers used their modern environment in such a primal way and were clearly having a good time doing it. I shared the video on my blog, Mark’s Daily Apple, a few days later in my weekly “Link Love” post.

Not long after that, I became aware that Al and Danny Kavadlo were also exceptional personal trainers, when I came across a two-part article that Al had written on the subject of being a fitness professional. I shared both parts of that article on my blog as well.

Over the next several years, the Kavadlo Brothers would appear on Mark’s Daily Apple numerous times, not only through links that I would share to their ever-growing body of quality content, but also as guest contributors. When Al released his first Dragon Door book and DVD, Raising The Bar, I was proud to give him my endorsement, and Al became my go-to guy for bodyweight training.

When the brothers released their book Street Workout a few years later, I came to better know and appreciate Danny’s strength and wisdom, and gave that book my endorsement as well. I’ve been on board with the Kavadlo Brothers ever since.

In my Primal Blueprint Fitness ebook, I promote a bodyweight training program, as I’ve personally built my physique using primarily bodyweight exercises. Still, some people are skeptical about the efficacy of a training program that doesn’t use any external weights for resistance. Is it truly enough, or just “good enough?” Can you really get big and strong without slinging heavy weights around?

It depends on what you mean by “enough,” of course, but the answer is generally “yes.” Bodyweight training is a legitimate option for anyone interested in building an impressive physique, increasing their strength, improving their athletic performance, mobility, and flexibility, and establishing excellent mind-body-space awareness. Plus, the ability to bust out some ridiculous moves on the pull-up bars at the local park has to count for something.

If you want to get as strong as possible, however, just doing more reps won’t cut it. You need intelligent progression. Progression isn’t just adding reps. Eventually, you have to make the exercises harder to keep getting stronger by adding weight or decreasing the amount of leverage you have.

And that’s part of the reason why some people opt for barbells over bodyweight training: It’s easier and far less humbling to add weights to a bar than to remove leverage from a bodyweight movement. In many cases, to progress in bodyweight means learning an entirely new movement from scratch. It’s harder to quantify than weight training and easier to get stuck. But that doesn’t mean it’s not effective. In fact, the degree of difficulty required to perform some of the more intermediate and advanced bodyweight exercises implies their effectiveness.

This is precisely why Get Strong is such a phenomenal program. In this book, the Kavadlo Brothers will guide you from the very beginning and help you build a proper foundation. From there, they’ll gradually progress you through four phases of strength, giving you the proper progressions and programing details to take you beyond what you ever thought possible. The brothers have also outdone themselves with their incredible visuals this time, adding some primal scenery to their usual urban jungle aesthetic. This book is packed with well thought-out, clearly delivered programming and beautiful imagery.

If you doubt the effectiveness of a pure bodyweight strength training program, then I challenge you to follow this program for 16 weeks and get back to me.