How To Throw A Powerful Jab: Jack Dempsey Was Right

December 12, 2020

The jab may be one of the most important punches in boxing. In fact, jabs make up two-thirds of the total punches thrown in elite amateur boxing [5]! Safe to say, learning how to throw a powerful jab is likely to be one key to boxing success.

To perform a power jab/left jolt both Jack Dempsey and the research agree; the key events are a lead step forward that allows for the body’s momentum to carry forward into the target (whether an active drive or a falling step) and a braced lead arm that transmits that momentum into the target.

It seems the new research on throwing powerful jabs aligns with what Jack Dempsey has been saying all along. So let’s break this down.

Jack Dempsey Was Right About Throwing A Powerful Jab

Jack Dempsey, besides being one of the greatest heavyweight boxers of all-time, wrote one of the most important books on the sport ever. Published in 1950, his book Championship Boxing: Explosive Punching and Aggressive Defence [1], is as relevant today as it was seventy years ago.

While styles, equipment, and rule changes have altered boxing immensely since Dempsey’s heyday in the 1920s, the fundamental lessons found in his work are as true as ever.

As a sports scientist, I spent the latter half of the 2010s researching punching performance in boxers [2]. Without a doubt, Dempsey influenced my work, but as a young PhD student, I was convinced that I was going to revolutionize the sport by unlocking the secrets of how to punch…

Long story short, Dempsey was right.

My results so closely aligned with Dempsey’s writings that it was almost frustrating. Obviously looking back now I see the value in confirming the works of a master, but at the time, I developed a bit of a grudge towards the old man.

One word of warning before jumping into how research “proved” Dempsey right. I am a firm believer that there is no one way to throw a punch.

I do believe that there are key events that should occur during a punch to make it effective (for example – a weight shift from the rear to lead legs during a cross or pre-loading the lead leg on a left hook), but within that framework, there are athlete and context-specific influences which make it impossible to say “this is the way you HAVE to punch”.

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With that caveat, let’s look at Dempsey’s view on the power jab and what sports science has to say. 

Dempsey was not a big fan of what he called the jab. For him, using a quick lead hand strike to manage range, set up attacks, and develop a defensive framework was a waste of time.

He viewed feints as a more effective tool for many of these actions than the jab.

Although, in Dempsey’s case it is easier to rely on feints when the whole planet fears your knockout power and swarming offense. He also disliked the jab due to what he called the “defensive fallacy” which meant that every time you threw a jab to defend, you left yourself open for a counter.

In Dempsey’s mind, if you were going to put yourself in danger of a counter you might as well try to take your opponent’s head off in the process.

In his book, he downplayed the jab and instead recommend the use of the “left jolt”, which is known more commonly today as the power jab.

Thrown from long range, the left jolt/power jab is a useful punch as the closer distance of the lead hand to an opponent can allow for quick punishing punches that closes distance and sets up an aggressive follow-up.

Falling step 1
Falling step 2

Illustrations of the falling step in Championship Boxing. I respect the style, but in no way endorse the use of dress shoes for boxing.

To perform a left jolt/power jab, Dempsey recommends using a technique he calls the “falling step”. He describes this as moving from one’s stance into the punch by simply lifting the lead foot and letting your body fall forward (thus the name), before landing the punch and letting the lead foot recover.

This punch would have very little torso rotation and instead relies on using your bodyweight to produce force.

This concept of using bodyweight as the key source of punching force is of course well understood in the field and in research [3].

To transfer the bodyweight that the falling step sends into a target Dempsey writes that a boxer must use their “power line”, an imaginary line that runs from the knuckles, through the arm, and into the shoulder.

He repeatedly hammers home the concept of bracing the fist and arm for impact.

This key concept has gained a lot of press in recent years after the increased interest in effective mass during striking [4]. Effective mass in boxing is a puncher’s inertial contribution to punching force. That is, how much of their weight they can put behind a punch.

Dempsey inherently understood this concept like many other combat sports experts (Bruce Lee included), but his ability to simply explain how to perform and train this idea in his book elevates his contribution to the sport.  

Jack Dempsey Power Line

Dempsey’s interpretation of the power line. Note, this is also an excellent isometric exercise for improving punching performance. The folks at Boxing Science have been doing great work with isometrics for boxing and have tons of resources on their site.

The Science Of How To Throw A Powerful Jab

A major component of my research was using force plates to monitor ground reaction forces during maximal punches.

In layman’s terms, this research examined how boxers used their lower body to produce punching forces and which component of the lower body was key to maximizing impact force.

The studies used a cohort of elite boxers that stood on the force plates and were asked to punch a bag as hard as they could using whatever technique they would normally use. When asked to jab as hard as possible the results matched closely to those defined by Dempsey’s falling step.

The boxers used a step towards the target, with timing and movement matching that described in the falling step.

Their lead leg touched down moments before their punch landed or as it landed, and they performed very little rotation throughout the movement.

Based on the data, it became clear that those with the strongest jabs had less weight on their rear legs as they prepared to jab.

Something Dempsey points out as he argues clearly against shifting weight back before throwing the lead hand.

Upon impact, those that did not stop their forward momentum also performed better. Dempsey was right again. “Falling” was a key to the power jab.

The more active the boxers were upon landing in stopping their attacking motion, the less force they produced.

The other component of the research into punching force was the muscle activation patterns through a technology called electromyography. Like the lower body research, the examination of muscle activation found which muscles were most active during the punch and identified what pattern resulted in greater impact forces.

The results found one key point that differed from Dempsey’s description. There was muscle activity in the rear leg as it propelled the fighters towards the target.

Although, the keys for maximizing the power jab were all related to stiffening the attacking arm.

Not rotating the torso or driving forward with the legs.

The lats were used to stabilize the shoulder joint and triceps to stabilize the elbow.

There were no measurements at the forearm, but I would put dollars to dimes that there would be similar results. The power line delivered and my hopes of showing up The Manassa Mauler and his ilk were dashed. Jack Dempsey was right.

Power Jab GSP
Here GSP is clearly driving off his back leg to perform a power jab.

The left jolt/power jab obviously has its limitations as it sends a fighter moving forward with great speed and can potentially leave you open for a counter if an opponent is able to cut an angle or slip effectively, but when used properly such a tool can be a valuable attack for any fighter.

To any aspiring sport scientist, learn from my experience, reinventing the wheel isn’t always a bad thing. Confirming the ideas of expert coaches and athletes add to our knowledge of the sport as much as developing revolutionary concepts. The search for truth, even if it is a small truth relating to punch people in the face, is worth pursuing.   

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1. Dempsey, J. (1950). Championship Fighting: Explosive Punching and Aggressive Defense. Long Beach,CA: Centerline Press.

2. Lenetsky, S. (2018). Biomechanical Assessment and Determinants of Punching in Boxers. (PhD), Auckland University of Technology, New Zealand.  

3. Lindsay, R. S., & Lenetsky, S. (2020). The contribution of expert coaches’ experiential knowledge in understanding punching performance in boxers. Journal of Emerging Sport Studies, 3.

4. Lenetsky, S., Nates, R. J., Brughelli, M., & Harris, N. K. (2015). Is effective mass in combat sports punching above its weight? Human Movement Science, 40, 89 – 97.

5. Kruszewski, M., Kruszewski, A., Kuźmicki, S., Sklepiński, Ł., Kępa, G., & Landowski, K. (2016). Boxing techniques based on the analysis of boxing tournament finals during Olympic Games in London in 2012. Journal of Combat Sports and Martial Arts7(1), 61-66.

About the author 

Seth Lenetsky

Seth is a US-born sport scientist currently based out of Victoria, British Columbia. Educated in New Zealand, Seth's research focus is on expanding the understanding and optimizing the performance of combat sports athletes. As a practitioner, Seth has worked extensively with elite boxing, Taekwondo, fencing, and mixed martial art competitors. He currently works in the industry as the High-Performance Director of Boxing British Columbia. He can be found on Twitter at @Science4FandV.


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