Ever since I started writing for this site a couple years ago, I’ve been dancing around mentioning a highly-apparent but difficult-to-describe phenomenon. Simply put, NFL players have been changing dramatically in recent years. What was once a subtle distinction between players has grown to become a hard schism. And in the process, long-time NFL trends/ wisdoms have been overturned.
Anterior vs Posterior
All humans (athletes or not) can be divided into one of two camps- those favoring anterior efficiency, and those favoring posterior efficiency. Anterior muscle groups (generally called flexors) are those located on the front of the body- the biceps, chest muscles, abs, shins, etc. Posterior muscle groups (generally called extensors) lie on the back of the body- the back muscles, triceps, buttocks, calves, etc. For reasons that are not currently understood (although this study may point to an embryonic genesis), humans generally tend to favor either posterior or anterior development. Biomechanical efficiency (meaning muscular response-time and blood/ lymph flow) tilts either towards the front-side or the back-side of the body.
Cat-like vs Dog-like
To understand the general characteristics of anterior muscle groups vs posterior muscle groups, it can be instructive to study the two main classes of mammalian carnivores- the cat-like felids vs the dog-like canids. Although there are exceptions within each group, the felids (cats) evolved to favor anterior efficiency, while the canids (dogs) evolved to favor posterior efficiency*. Felids are usually quick and agile, with fast reflexes and excellent short-burst acceleration. They are often ambush predators, lying in wait and bursting towards their prey in brief but intense hunts. Canids are generally less quick, but are able to run at top speed for far longer distances. Canid hunts often range over miles, where they rely much less on short-area burst, instead favoring long-term stamina.
*in four-legged animals, the terminology generally goes ‘ventral’ for anterior, and ‘dorsal’ for posterior
For a human example, consider a slap (generated via the anterior biceps/ chest muscles), vs a punch (generated by the posterior triceps and back muscles). A slap is quick to fire and relatively weak, while a punch is stronger and takes longer to land. Anterior muscles are fast-acting quick-twitch muscles. Posterior muscles are generally stronger, more enduring, and slower-firing.
NFL trends
While NFL players, like other humans, can be divided by anterior-dominance vs posterior-dominance, historically the best players showed high levels of efficiency in all areas relevant to their position- anterior-type QBs would show high levels of posterior thoracic efficiency, posterior-type RBs would show high levels of anterior lumbar efficiency, etc.
However, over the past several years, this historical trend has been overturned. For reasons that are complex and better explained elsewhere, divisions between anterior-dominance and posterior-dominance have widened significantly in recent years. Anterior-dominant players are generally showing much-decreased levels of posterior efficiency, while posterior-dominant players are showing much-decreased levels of anterior efficiency. These trends are accelerating and have become particularly pronounced in recent seasons.
Although there are a number of implications to this continuing change, the single biggest trend that has emerged in recent years is that anterior-dominant players are increasingly struggling to stay healthy over the course of full NFL seasons. Even non-contact positions (like QB) show the evolution of this change.
QBs drafted since 2010 (with meaningful/ recent starts), divided by biomechanical efficiency
Anterior Dominant QBs
| Sam Bradford | 80/128 games started |
| Cam Newton | 116/119 games started |
| Andy Dalton | 113/116 games started |
| Colin Kaepernick | 72/79 games started |
| Tyrod Taylor | 44/47 games started |
| Andrew Luck | 76/102 games started |
| Robert Griffin III | 42/80 games started |
| Teddy Bridgewater | 30/61 games started |
| Derek Carr | 62/64 games started |
| Jameis Winston | 45/48 games started |
| Trevor Siemian | 25/32 games started |
| Carson Wentz | 29/35 games started |
| Mitchell Trubisky | 12/12 games started |
| Deshaun Watson | 7/15 games started |
| DeShone Kizer | 15/15 games started |
Posterior Dominant QBs
| Russell Wilson | 108/108 games started |
| Kirk Cousins | 57/57 games started |
| Blake Bortles | 61/61 games started |
| Marcus Mariota | 42/48 games started |
| Jared Goff | 23/23 games started |
| Dak Prescott | 33/33 games started |
With the exception of QBs drafted in 2017, not a single anterior-dominant QB drafted since 2010 has avoided missing time due to injury. And the trend has only accelerated- anterior-dominant QBs have missed more and more time over the past few years.
Whereas with the exception of Marcus Mariota (who shows noticeable lower-body issues), every single posterior-dominant QB drafted since 2010 has started every possible game. Overall, anterior-dominant QBs have started 81% (768 out of 953) of their expected games (with much of the missed time coming in recent seasons), whereas posterior-dominant QBs have started 98% (324 out of 330) of their expected games.
A biomechanical analysis of the situation reveals that this trend is far more than a statistical anomaly. Posterior muscles are simply stronger and more enduring (evolved to continuously oppose the force of gravity), and QBs who favor using these muscles in their throwing motions are therefore far more likely to stay healthy. So with anterior-dominant players generally showing less and less involvement from their posterior muscle groups, it follows naturally that these players will suffer additional injuries. The forces they generate derive from muscles evolved to function in short bursts- and as fatigue and overuse set in, injury likelihood rises dramatically. As such, posterior-dominant players are likely to increasingly dominate the NFL scene- and this trend has already begun.