unrecognizable boxers in boxing gloves giving fist bump in studio

The Power Behind It: The Physics of the Fist

It was a crazy night. Lorraine was in the backseat with Biff, and George heard her cries as she struggled to fend Biff off. He approached the car and  yanked open the door. 

It was Biff back there trying to force himself on the girl George cared so much about. George froze. There glowering at him was his years-long nemesis, the one whose bullying he cowered under for so long. But seeing Lorraine’s stricken eyes, George summoned up all the courage a beaten-down, bullied man could manage. 

He looked straight at Biff and said, “No, Biff. You leave her alone!” Biff rose strong and menacing. As Biff laughed in his face and Lorraine begged him to help, righteous indignation flooded George. All the power he could muster flowed through his body and balled up in his fist. And just like that – His arm shot out, and his fist struck Biff’s jaw so hard the big bully spun and hit the ground, knocked out by one punch.

And just like that, his future family’s storyline transformed from a sad, struggling bunch to successful, productive people. A transformed narrative spilling into the next generation and beyond.

“Back to the Future” hit theaters in the fall of 1985 and endures to this day as a well-loved film. The secret of its success lies primarily in the familiar story of a nobody rising up to conquer the enemy. And the pivotal moment was right there in the high school parking lot, when the underdog delivered a well-placed punch and saved the day.

Sounds Good, But I Have Questions…

Right now, you may be thinking, yeah, I love that movie (I get it. It came out when I was a high school senior, and let me tell you, the story of the victim overcoming the bully resonated with me and still does), but nah, nobody could deliver a punch like that. Or at least not an underdog like me. Maybe a boxer, sure, or somebody like, oh, I don’t know – Chuck Norris? But me? I could never deliver a punch like that. Impossible.

But is it? Is it really impossible? Or is this seeming movie magic stuntman-delivered power possible in the real world? Or, more, precisely, could someone like me pack that kind of power into a fist? We kind of doubt it, but we’d like to think we could.

man hit by boxing glove
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And maybe you’d like to seriously entertain the idea of learning to exploit angles and momentum and velocity to stop an attack right then and there, at just the right moment, saving your own life and protecting your loved ones with your own hand as a weapon. Maybe you’d like to have that skill in your arsenal, empowering your confidence, and letting a would-be perpetrator know at a glance you’re not worth messing with. 

Sound good?

All right, let’s see how this is all possible because it is. It all starts with an understanding of fundamental physics principles and how the human body can be positioned to deliver. Pull up a chair, and let’s see how we can fight like a physicist.

She Told Me About This Book, and Wow…

Steph, our lead Instructor, is always looking for ways to understand and teach self-defense. She’s passionate about it, as are Richelle and I. So when she told me about this book she just got, Fight Like a Physicist: The Incredible Science Behind Martial Arts, by Jason Thalken, Ph.D.,  I was intrigued. How can physics principles make me a better defender? So I bought the book. And, like most books I buy, it sat on the shelf for months.

Until the other day. When I thought of writing this blog about how a well-delivered punch could save the day, I remembered. Oh yeah, it’s right in there, right in that book holding so much exciting information – and well, here we are.

So let’s explore together what this fascinating book teaches us about the physics of the fist.

What does it really take to end a fight?

Let’s start with momentum. If someone throws a 30-pound bag at your chest without warning, you’ll likely end up on the floor. Why? The power behind that throw is its momentum which, basically, is an object’s ability to knock you back when it hits you. Two factors come into play with momentum: the object’s weight (mass) and speed (velocity).  Velocity gives the object its direction. So let’s put this into practical terms: 

Alex is a 200-pound athlete, and he’s jogging down the street at 5 miles per hour. (200 x 5 = 1000). Andrea is a 100-pound gal jogging down the same street at 10 miles per hour, and they’re heading straight for you (100 x 10 = 1000). When they run into you, they both hit with the same momentum and equally knock you to the ground. 

Now let’s talk about the same principle, this time with a punch. Maria is delivering a punch to a guy who tried to drag her off into the woods. She slams a high-momentum “push” strike into his chin. His head rotates at the base of his skull, and wham! He’s knocked out, and she’s running to safety.

woman punching the hand of man wearing training gloves
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The key is high momentum. So how do we add momentum to our punches? The secret is using the entire body, not just your relatively small fist (how much does a fist weigh anyway? Less than 1 percent of your total body weight). An untrained person can throw a punch somewhere around 10-15 miles per hour. Speeding up their punches to hit a speed bag brings it up to around 20-25 mph. Neither is going to knock someone out and end things. You’ll probably just tick the offender off, making your situation worse. 

Ten percent of a professional fighter’s body weight gets behind their punches, up to 20 times more momentum than throwing a fist by itself. How do they do it? It starts with body positioning. Strong but loose stance, fists up to guard, ready for action. 

Pulling energy through their foot, they shoot it through their torso and out through their fist, right into the opponent. The motion is fast and fluid through the continuous rigid path joining fist to shoulder, connecting with their body’s center of mass (just below their belly button). When their fist hits the opponent, they expel air which provides the rigid path needed to get the mass behind the punch. Their center of mass sits firmly in the ground through their legs and hips, staying solidly in place while they push punches into their opponent.

And this skill isn’t limited to professional fighters. It’s all true for anybody who’s willing to put in the time to train. You can do this too. Yes, you. You can learn to put your weight behind your punches, adding high-momentum strikes to your arsenal. We can show you how.

What Can This Mean For Defending Ourselves?

Imagine having a tool in your self-defense toolkit you don’t need to be huge or super-strong, or even particularly tall to employ effectively. Imagine having – right there at the ends of your arms – the point of contact to stop an attacker. Imagine positioning your body in such a way as to deliver maximum impact with minimum effort. 

Do you want to do more than just imagine? When you join us, you start the journey of developing those hands of yours into effective weapons, one class at a time, one lesson at a time, with friends to cheer you on.

It all starts with an understanding of fundamental physics principles and how the human body can be positioned to deliver.

How We Teach The Physics of the Fist

Here’s how we do it: We think of our bodies as a whip. The power comes from the ground, through our strong base of support in our legs (the handle), spiraling through our torso and whipping out through our arm, into the point of contact: the fist (the tip of the whip). And our muscles push our body weight to punch through, not to, the target.

woman in blue sports bra and black leggings doing exercise
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We start with a solid, strong posture, which looks like the front foot pointed at the opponent, the back foot out, and at a 45-degree angle. Ball those hands into tight fists, thumbs across the fingers. Bend those arms, and keep the fists up close to your face but not too close. Bend those knees, but keep that back straight. 

Jab? Twist that front foot and bring energy through your leg, into your torso. Exhale as you shoot your front fist out, lean into it, twist that torso, crunch to the opposite side, and push that punch through the pad.

Reverse? Twist that back foot as you bring your back fist through, twist through the torso, whip that hip, slam that punch through the pad.

And these are just the basics. We add an uppercut, hammer fist, hook, and so much more to our selection. Because there are so many kinds of punches, and so much nuance to each one, we are ever-evolving as we receive our instructor’s correction, improving our punching skills to keep us fit and ready. 

It’s a whole lot more than just throwing our arms around, wouldn’t you say? And a whole lot more effective. The good news is, a powerful punch is available to anybody willing to learn, whether a 200-pound muscle-bound guy or a 5-foot 100-pound woman. It’s available to you.

Do I Really Need This?

Short answer? Yes.

Long answer? Yeeeeessssss. 

Here’s why: the world we live in isn’t safe. And we can’t just hide in our houses or walk around anywhere we want and pretend everything’s okay. We know better. If you need convincing, take a look at the news. I know it can be overwhelming at times, and you may feel helpless to do anything about it. Truth is, we are helpless to change the fact we’re living in a dangerous world where people don’t think twice about taking a life.

But the thing we can change – the thing we need to change for our own sake and for the sake of everyone we love – is how we prepare ourselves to face this world. It’s incumbent on each of us to face the truth and strengthen ourselves in the face of it. 

We can choose to learn how to become strong from the inside out. We can evolve continuously so we can face dangers from without and within fearlessly.

active black boxer punching heavy bag while exercising in gymnasium
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While we can’t change anyone else, we must change ourselves. The good news is, we don’t have to do it alone. In fact, it would be foolish to try, and we know it. Ever tried something challenging? Yep, we know how it goes, don’t we? It works for a while. We’re riding the excitement and adrenaline, and it’s thrilling. 

Then we hit a plateau. At this point, we either give up or keep moving forward. Without a team spurring us on, what chance do we have to keep going? For most of us trying alone, the plateau slides down into eventually giving up. Have you seen that pattern in your life?

At Tigress’ Roar, we welcome you into a group that’s been there, done that, and continues to learn and grow. We’re doing something most wouldn’t even attempt because it seems too hard. But we’re on a journey together, offering encouragement when someone gets confused or frustrated or wants to give up. Realizing we can’t do this alone, we link arms and move forward together. Because it’s just that important, and we know it.

What will it take for you to decide to empower yourself? I’ve heard and said most of the reasons not to. Not enough time. Not enough money. I don’t think I need this. And, my go-to for years, if I’m honest: I’m too afraid. 

But are all these objections really valid? Before saying Yes or No, it’s wise to take a brutally honest look at your schedule and priorities. It’s what I did. And yeah, I do have time. I do have the money for this (I can discipline myself to spend more wisely and set aside the funds). Do I want to be trapped in my fear? No. I’m not a victim anymore, and I’m not going to live in that mindset. I’m not going to assume anyone else is going to protect me when push comes to shove. It’s not their job. It’s mine.

After taking that honest appraisal of your work schedule, your activities, and your relationship responsibilities, I hope you’ll come to the conclusion I did: I need this, and I don’t want to do this alone. I want to join a team of powerful, growing women. Women like me.

Women like you. Will you join us? I hope the answer is Yes. 

Learn how to form and deliver your best punch in a safe, welcoming environment. Become a Tigress.

Join Us.


Thalken, J., 2015, Fight like a physicist: the incredible science behind martial arts, YMAA Publications Center, Inc.

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