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“Hi Bret, I read an article in Men’s Fitness that talked about how the trap bar deadlift is the best exercise for athletes and is perfectly correlated with 40 yd, vertical jump, and 10K run time. This seems too good to be true. Is there any merit to it? Thanks, Damion” 

Thanks for the link Damion, I tracked down the article and linked it below:


I would like for my followers to click on the article and read it, and to note how convincing it sounds. The average reader would buy into all of it without second guessing anything. One of the purposes of my blog is to teach my readers how to think critically and encourage them to adopt an evidence-based approach to their strength & conditioning. Therefore, I’m going to pick this article apart. Now, I’m sure that the strength coach mentioned in the article is highly skilled at building strength and power, designing programs, and coaching the lifts. But he could be even more effective if he was better-versed in sports science literature. I encourage my readers to click on all of the links I provide in this article and read the abstracts, interviews, and blogposts – it will make for an incredible learning experience. And if you don’t understand correlations, click HERE to learn more about them, as this will allow you to better follow the blogpost. And if you need some help understanding some of the biomechanical terms used in this article, such as relative, force, power, impulse, resultant, and moment arm, please click HERE.

The gist of the article is that it showcases California strength coach Ryan Flaherty‘s “force number.” According to Flaherty, an athlete’s force number is his or her maximum trap bar deadlift strength divided by his or her bodyweight. Athletes’ force numbers allegedly allow Flaherty to predict with 99% accuracy their 40-yard dash, vertical leap, and 10K run time.”

Here are some quotes from the article:

“It should be noted that the highest Force Number doesn’t come from the athlete with the highest peak ground force, but the athlete with the highest peak ground force relative to his body weight. It’s an important distinction, and one he notes when showing me the next slide, which compares each athlete’s Force Number with his 100-meter sprint time. The correlation is, to be sure, perfect. The sprinter with the highest force number has the fastest time, the next-highest force number aligns with the next-fastest time, and so on, all the way down the line. He has since tested his force theory on more than 6,500 athletes and consistently found, with 99% accuracy, that the larger the Force Number, the stronger the athlete is, the faster he can run, and the higher he can jump.

But once Flaherty had discovered his metric, he found that it was difficult to calculate on a larger scale, given the methods he was using at the time. A force-plate treadmill is large, unwieldy, and wildly expensive. You can’t exactly check it on a plane or buy it in bulk. So he went looking for a universally available lift as a substitute for determining peak ground force. “I took the data I had from the force-plate treadmill and started correlating it with various exercises,” he says. “It wasn’t correlating to the squat, it wasn’t correlating to the front squat, it wasn’t correlating to the power clean or the leg press either.”

The answer, ultimately, was the hex-bar deadlift.

When he ran the numbers, Flaherty found that the Force Number calculated from a one-rep max for the hex-bar deadlift yielded the exact same correlation as the ratio derived from force-plate treadmill numbers. He also discovered that the bigger your hex-bar deadlift, the bigger your Force Number. In other words: Congrats! You’re a better athlete. (For the record, Jamaican sprinter and reigning world’s fastest man, Usain Bolt, holds the highest Force Number ever recorded: 3.9.)”

2016-07-18 18.04.26-2

Points of Contention

Here are my points of contention:

  1. Any experienced strength coach knows that relative max trap bar deadlift strength doesn’t fully predict speed and power. Arizona Cardinals strength coach Buddy Morris once told me that strength is just one piece of the athleticism puzzle, and that the best athletes are often middle of the road with regards to maximum strength. Many of the strongest athletes at the professional level sit on the sidelines watching the starters do their thing.
  2. There are biomechanical reasons that help explain why the most explosive athletes might not be the strongest athletes – one of these is muscle leverages. Although top athletes may possess a greater percentage of fast-twitch muscle fibers, they also may possess small muscle moment arms in certain muscles. Large muscle moment arms have great leverage and are highly conducive to producing maximum force, but short muscle moment arms are highly conducive to rapid joint actions since they cause the joint to move through more range of motion at any given amount of shortening. This was clearly illustrated in Nagano & Komura 2003, and it’s been shown to be the case in sprinters’ Achilles tendon moment arms by Lee & Piazza 2009, Baxter et al. 2011.
  3. Vertical impulse (force x time) is highly correlated with vertical jump (biomechanically, the relationship should be perfect, but there are issues with the way it’s calculated, see McBride et al. 2010 and Kirby et al. 2011). This would infer that relative max trap bar deadlift strength would be highly correlated with vertical jump, but it won’t be perfect due to the differences in kinematics and force-velocity curves between the two movements. At the high school and even collegiate level, often the most explosive guys on the team are also the strongest in the gym, but this isn’t typically the case at the professional/elite level. Years ago, I trained a dunk specialist named Kenny Dobbs – he had a 48″ vertical jump but did 50-lb goblet squats to full depth for 10 reps. His power output was off the charts, but his maximum force was way underdeveloped. Christophe LeMaitre apparently possessed very low squat strength but was fast as the wind.
  4. Vertical force (nor resultant or total force) is not correlated with acceleration, and sports are mostly about acceleration and not maximum speed. This has been shown to be the case in Hunter et al. 2005, Morin et al. 2011, Morin et al. 2012, Kawamori et al. 2013Morin et al. 2015, Brughelli et al. 2011, Buchheit et al. 2014, Cross et al. 2015de Lacy et al. 2015, and Rabita et al. 2015. Athletes should produce just enough vertical force to raise their COM’s so that they can recycle their limbs and reapply horizontal force during acceleration. Only once maximum speed is reached is vertical force correlated with performance (Weyand et al 2000), but propulsive (net horizontal – braking) force is likely more highly correlated (Morin et al. 2012).
  5. The fastest athletes are not producing the highest amounts of vertical force. This was nicely depicted in Morin et al. 2011, where the researchers depicted a sprinter/long jumper versus a basketball player/bmx racer. They showed that body mass and total force production were virtually identical, but the sprint-trained athlete oriented his force production more horizontally, and therefore was much faster. It is the technique of force production, not total force production, that separates the fastest sprinters from the rest.
  6. I interviewed Matt Brughelli in 2010 and JB Morin in 2012 on my blog where we discussed much of these matters. I elaborated on JB Morin’s first landmark study HERE and his second big study HERE, and I once again interviewed JB Morin in 2015. This important information has been out there for a while and is not hard to find if one is searching around online.
  7. Just because an athlete produces great force in one direction does not infer that he or she will be able to produce great force in other directions. Contreras et al. 2016 showed that the front squat better increased power in the vertical direction whereas the hip thrust better increased power in the horizontal direction. This “force vector” specificity was recently shown to be the case with plyometric training as well by Antonio et al. 2016. Maximum relative hex bar deadlift strength likely correlates better with jumping than sprinting, especially in elite athletes.
  8. To say that a maximal strength exercise can predict 40 yd (a horizontal acceleration test), vertical leap (a vertical power test), and 10K (an endurance test) performance is impossible, as these events are suited to individuals who possess unique genes, anatomies, fiber type percentages, muscle moment arms, muscle volumes, pennation angles, fascicle lengths, and more. I would expect maximal relative hex bar deadlift strength to have an especially poor correlation with 10K performance. Kenenisa Bekele and Leonard Patrick Komon hold the current 10K world records; do you think they have strong trap bar deadlifts?
  9. The relative vertical force correlations with speed registered on a force treadmill would not perfectly match the maximal relative hex bar deadlift forces on a force plate. It’s not that simple. For example, Kawamori et al. 2014 showed that gaining strength on sled towing improved acceleration not by increasing horizontal force, but by decreasing vertical force, thereby improving the effectiveness of force production.
  10. If Usain Bolt’s force number was indeed 3.9, this would infer that he could hex bar deadlift 807 lbs (since he weighs 207 lbs). Usain Bolt doesn’t do heavy hex bar deadlifts. I wrote about his training HERE in 2013. If I had to guess, he can probably hex bar deadlift 365 lbs for 5 reps or so, which yields an estimated 1RM of 411 lbs, which is approximately a force number of 2.0. Moreover (this is really damning for Flaherty’s claim), using mathematical formulas, Taylor & Beneke 2012 demonstrated that out of Usain Bolt, Tyson Gay, and Asafa Powell, Bolt displayed the least vertical stiffness and the least relative peak vertical forces (I divided their max vertical forces by their bodyweight to confirm this – Bolt produced 17 N/lbs, Gay produced 20 N/lbs, and Powell produced 19 N/lbs), and Janjić et al. 2016 demonstrated using mathematical formulas that out of Carl Lewis, Maurice Green, and Usain Bolt, Bolt produced the lowest amounts of vertical force and relative vertical force (Lewis 2.77, Green 2.96, Bolt 2.59).
  11. Usain Bolt likely produces the highest amounts of net horizontal impulse out of the top sprinters. This is critical for speed (Morin et al. 2015).
  12. I find it highly unlikely that Flaherty has tested his theory with 6,500 athletes and found that the force number predicted speed and jumping performance with 99% accuracy. I do believe that maximal lower body strength is critical for speed, but not perfectly correlated as Flaherty suggests. Maćkała et al. 2015 showed a .65-.73 correlation with max squat strength and speed in sprinters, depending on the length of the sprint and whether time or speed was measured (the relationship in half squat strength and acceleration and vertical jump is very high in international soccer players, as shown by Wisløff et al. 2004). A meta-analysis showed that increased squat strength does improve acceleration (Seitz et al. 2014). I would hypothesize that max hex bar deadlift strength (and especially relative max hex bar deadlift strength) would be even more highly correlated with sprinting performance, simply because it utilizes the hammies better than regular squats (but not as well as deadlifts according to Camara et al. 2016). Hamstrings are major producers of horizontal force (Morin et al. 2015, JB elaborated HERE on his blog). But again, the relationship would be far from perfectly linear.
  13. The hex bar deadlift is a great exercise. I chose it as my top lift (if I could only do one lift) in THIS blogpost from 2013. But max strength and relative max strength in any lift are not the end-all-be-all with regards to developing good athletes. In fact, an overemphasis on strength development without proper balance of other qualities can yield a lesser athletic and less powerful athlete.


If you read the linked article on Men’s Fitness and believed it, you got guru’d. Developing the best athletes requires careful consideration and proper blends of strength and power exercises (where muscle group, ROM, muscle action, force vector, bar velocity, type of loading, and level of stability must be considered), plyometrics, sprints, sled towing, agility work, medball work, and technique work must be prescribed. Moreover, training can be individualized according to force-velocity profiling for added benefit (Morin et al. 2016).


  2. Longer moment arm results in smaller joint moment development, power and work outputs in fast motions
  3. Built for speed: musculoskeletal structure and sprinting ability
  4. Ankle joint mechanics and foot proportions differ between human sprinters and non-sprinters
  5. Relationship between relative net vertical impulse and jump height in jump squats performed to various squat depths and with various loads
  6. Relative net vertical impulse determines jumping performance
  7. Relationships between ground reaction force impulse and kinematics of sprint-running acceleration
  8. Technical ability of force application as a determinant factor of sprint performance
  9. Mechanical determinants of 100-m sprint running performance
  10. Relationships between ground reaction impulse and sprint acceleration performance in team sport athletes
  11. Acceleration capability in elite sprinters and ground impulse: Push more, brake less?
  12. Effects of running velocity on running kinetics and kinematics
  13. Mechanical determinants of acceleration and maximal sprinting speed in highly trained young soccer players
  14. Mechanical Properties of Sprinting in Elite Rugby Union and Rugby League
  15. Strength, speed and power characteristics of elite rugby league players
  16. Sprint mechanics in world-class athletes: a new insight into the limits of human locomotion
  17. Faster top running speeds are achieved with greater ground forces not more rapid leg movements
  18. Sprint Research, Biomechanics, and Practical Implications – An Interview With Matt Brughelli
  19. 21 Questions for JB Morin on the Topic of Speed
  20. Sprinting Performance is Not Solely About Force Put Into the Ground
  21. Why is Christophe LeMaitre so Damn Fast?
  22. Effects of a six-week hip thrust versus front squat resistance training program on performance in adolescent males: A randomized-controlled trial
  23. Vertical- vs. horizontal-oriented drop-jump training: chronic effects on explosive performances of elite handball players
  24. Effects of weighted sled towing with heavy versus light load on sprint acceleration ability
  25. How Does Usain Bolt Train?
  26. Spring mass characteristics of the fastest men on Earth
  27. Model for assessment of the velocity and force at the start of sprint race
  28. Acceleration capability in elite sprinters and ground impulse: Push more, brake less?
  29. Selected determinants of acceleration in the 100m sprint
  30. Strong correlation of maximal squat strength with sprint performance and vertical jump height in elite soccer players
  31. Increases in lower-body strength transfer positively to sprint performance: a systematic review with meta-analysis
  32. An Examination of Muscle Activation and Power Characteristics While Performing the Deadlift Exercise With Straight and Hexagonal Barbells
  33. Sprint Acceleration Mechanics: The Major Role of Hamstrings in Horizontal Force Production
  34. Sprint Acceleration Mechanics: The Major Role of Hamstrings in Horizontal Force Production (blog)
  35. If You Could Only Do One Lift…
  36. Interpreting Power-Force-Velocity Profiles for Individualized and Specific Training


  • Claidio says:

    Hi Bret,
    For some reason the trap bar deadlifts kinks my upper back almost every time. Regular barbell deadlifts do not. I have a small frame and the trap bar forces your angles a certain way. Ends up causing more harm than good for me. But the deadlift rules (at least for me).

  • Kurt Hester says:

    Great article. Our football program had a lot of talent last year and we went 9-5 with a few high draft picks. We had great starters put no back ups. Our guys played 80 plays a game on both sides of the ball. So I decided to take as much stress off their bodies as possible & kept CNS response to a minimal as well as spinal loading. 1st day of training was hex bar deadlifts @78-83% for doubles with no grinding of reps & KB swings 4×5. 2nd day was snatch pull @78-83% for triples & floor hip thrust 4×3 @85%. I found that the athletes stayed healthy & on the field but interestingly our pre & post squat maxes only deviated 3% plus or minus. What recommendations would you have for inseason football training to keep athletes fast with a high power output.

  • Patrick O'Flaherty says:

    I emailed Ryan twice back in September 2015 as I read the same / similar article on STACK asking him to provide me a 40 yard dash time based on my age, weight and hex bar deadlift max so that I could either confirm or refute his claim and he would not respond. What a fraud!

  • Jason says:

    Please stop writing infer when you mean imply, it implies that you’re a moron.


    • Thanks for the tip. But if you read over this article and focused on the grammar instead of the science, logic, and 36 scientific references, then I don’t think there’s any helping you bro.

  • Oliver says:

    Funny I heard this mentioned on a podcast last week and instantly thought, not a chance is that true, so it was nice to stumble upon this. You could convince me it correlates well with vertical jump and maybe sprint speed, but a 10k run, really? I’m shocked people believed that bit. Nice analysis to break it down.

  • Austin Ferns says:

    Nice article and obviously you are correct in what you say as I thought the same thing. However as is the norm in these types of article a great deal of information is left out and they are simplified for the masses. An increase in any athletes TBD by a significant amount will improve all performance parameters given a small increase in body mass.
    I would also imagine given his amazing speed Bekele’s leg strength is superior to other elite 10k runners.

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