Why Strength Training is a Dead End

Part 5: Stronger, faster, higher?

Ook beschikbaar in het Nederlands

Photo by Mark Jefferson Paraan on Unsplash

But what about the evidence?! In the previous parts I have tried to show why the concept of strength as a fundamental or biomotor ability is ripe for retirement in my opinion. But there’s a shitload of data showing otherwise! Isn’t there?

And even if I were right, how important would that really be for what we do in practice? There is plenty of evidence that our faithful strength exercises work like a charm, right? If that were the case, my whole story would indeed be nothing more than academical pestering. So how ‘evidence-based’ is strength training for sports performance exactly?

FYI: I have a mild aversion to the term ‘evidence-based’. Jeremy Loenneke put it as follows: “The term ‘evidence based’ in the fitness industry is equivalent to ‘based on a true story’ in Hollywood… i.e. it means nothing.” And unfortunately, this doesn’t only hold true for the fitness industry.

Setting the stage

Now there are hundreds — if not thousands — of studies that we could examine here, but that seems a bit outrageous for a weekdays article (and I ain’t getting paid enough for that shit!). Fortunately, a quite extensive review was published recently that we can use as our thread (1). In this review, the authors examined (among other things) the effect of strength training on sprinting and jumping performance. And with strength training they especially refer to doing heavy squats.

Does the ‘king of exercises’ — as is claimed in this review as well — truly lead to faster sprints and higher jumps? Off we go!

Correlations, correlations, correlations…

“If the rooster doesn’t cock-a-doodle-doo in the morning,
then it will rain…
… or the rooster has died.” — A Westfries saying

Let’s barge right in: most of the studies show that people who can squat more kilos generally can also run faster and jump higher. So getting stronger works. I rest my face. Or does it?

These findings certainly are in line with the idea that strength training works, but in statistics lesson 1 you’re taught that correlation does not imply causation. In normal language, when two things occur together, this does not necessarily mean that the one causes the other.

An example: “Sleeping with one’s shoes on is strongly correlated with waking up with a headache. Therefore, sleeping with one’s shoes on causes headache.” This of course is a very dubious line of reasoning, as it may very well be that both things (sleeping with one’s shoes on and headache) are caused by a third variable: too much drinking. Could something similar be the case in our strength training studies? I think it could be.

A willing victim

Let us as an example examine one of these studies. Wisløff en co (2) found (among other things) that professional football players who could squat heavier generally could also sprint faster and jump higher (see figure below). Based on this they — and with them a lot of professionals — concluded that maximal strength determines sprinting and jumping performance of football players. Thus, they recommended maximal strength training.

Stronger, therefore faster and higher? (adapted from (2))

You’re probably feeling where I’m going with this already, as at least two cardinal sins have been committed here:

1. The investigators simply measured the amount of kilos that the football players could move with a squat. The fact that they talk about the effect of ‘strength’ — as if it were a fundamental property or ability of the body — is nothing more than a questionable interpretation of their data (see part 2).
2. Based on this data, you’re not at all allowed to conclude a causal relationship between squatting performance on the one hand and sprinting and jumping performance on the other. From a scientific perspective this truly is cringeworthy and points out once again that even published, peer-reviewed research can be of dubious quality.

Iso-absurdism

Even if we play along for a bit and assume a causal relationship, then the direction of this relationship still remains to be determined. After all, it might very well be that your level of sprinting determines your level of squatting and jumping. Ditto for jumping (why is “ditto” spelled with two t’s in English?!). All these studies however a priori assume that performance on a strength exercise reflects something fundamental and therefore they put it on the horizontal axis as an independent variable (as in the figure above). Indeed, the relationship between sprinting and jumping usually isn’t examined.

Yet, a quick look at the literature immediately reveals a few studies in which this relationship was investigated (3,4). And guess what. The higher people can jump, the faster they can sprint! Should we then conclude that you have to practice sprinting in order to get better at squatting and jumping? Or conversely, that you should practice jumping in order to get better at squatting and sprinting? This sounds ridiculous, of course, but based on the aforementioned studies these conclusions are just as (un)warranted as the popular idea that squatting makes you better at everything and its mother.

In fact, based on the traditional idea behind strength training (i.e. ‘overload’), the interpretation that an athlete should prioritize practicing sprinting or jumping is actually more likely. After all, in sprinting it is said to be important to exert as much force as possible onto the ground while the feet strike it; by doing heavy strength training an athlete supposedly gets better at producing more force and thus ‘logically’ at sprinting (5). However, the peak forces that muscles produce during maximal sprinting and jumping are often much greater than what you can achieve in practice with a barbell on your back. Therefore sprinting and jumping practice would actually be better forms of strength training than regular, um… strength training.

Bert & Ernie explain why correlation does not equal causation. With a banana…

An alternative explanation

Do I believe this myself? Not really. The above passage was mainly meant to stimulate some thought, but in my view it was headed in the wrong way from the start. I actually think that the ‘third variable’ is more likely.

In part 2 I’ve reasoned that squatting, sprinting and jumping are all ‘just movements’ and that the quality of movements is determined by a specific control of muscles with certain structural properties. So from this point of view there are two candidates for the role of third variable: coordinative and structural factors.

Ergo, someone who is able to squat pretty good generally is able to sprint and jump pretty good as well, because these movement are partly controlled in the same way and/or are partly dependent on the same structural properties. Or to put it simply, some people are just better movers. This indeed is also ‘just a hypothesis’, but — in contrast to the popular narrative — one that actually fits with the available knowledge of motor control and biomechanics.

FYI: Besides these correlation studies there are a number of studies in which it was found that higher level athletes were ‘stronger’ than those of lower level. For instance, Sheppard en co (6) found that the group of volleyball players that could jump the highest was able to squat more kilos than the group that barely got off the ground.

The problem with these studies is in essence the same as with correlation studies though. An important difference between professional and amateur basketball players is, for example, the number of digits on their bank accounts. But if I hand my neighbor a sack of hundred-dollar bills, he probably still isn’t able to dribble past six opponents before slam dunking the ball. I would make a friend for life though. Anyway, it is again unfounded to conclude causality.

Training studies!

These are nowhere near as numerous as the correlation studies, but fortunately they do exist. In a training study (if you do it well) you have several groups of comparable level train by different means. This allows for fair comparison of their (lack of) progress. Accordingly, each group has to perform a test before training commences (in order to determine their baseline) and again afterwards. Moreover, one of these groups has to be a control group as it is not uncommon for people to ‘mysteriously’ improve on a test without any further practice.

If you’ve met all these requirements and at the end of the study find that a particular group has improved more than the control group, then you’re allowed to conclude that the particular training method has worked. In short, you actually may conclude causality now. Time for celebrations!

And put on your party hat, because a meta-analysis of training studies has shown that squatting may lead to faster sprints (5)! Admittedly, some studies didn’t employ a control group, but all in all the evidence is convincing: after a period of serious squat training, gains in sprinting performance of on average 3.11% were noted. This magnitude is certainly relevant in practice. Performing strength exercises (such as squats) may thus definitely help to improve a goal movement (such as sprinting).

Before you get all excited and start reaching for your dancing shoes however, it pains me to say that I have to spoil the fun a little. There are 2 reasons for this:

1. Even though good old strength exercises may induce positive adaptations, there are quite some clues that this especially holds true for relative novices (7). Experienced coaches use the adage ‘strong enough’ for a reason (usually when an athlete can squat 2 times body weight). If an athlete is very trained, heavy strength training could even hinder explosive performance, but that’s another story altogether.
2. Even though strength training may help improving goal movements, this actually is not what it’s about in practice. After all, the most important question in practice — given the limited availability of time and energy — is how one reaches one’s goals efficiently. If the goal is to improve sprinting or jumping, then there is substantial evidence that traditional strength training is a relatively inefficient solution. For sprinting — brace yourself — sprint exercises are often a better choice (8), while derivatives from Olympic weightlifting or plyometrics may often be superior for jumping (9).

This limited transfer of training shouldn’t be all that surprising however. After all, in part 2 we’ve already seen that even for very simple strength exercises there may be a serious degree of specificity to take into account. Performing particular strength exercises is, as such, first and foremost a sport in itself. Nevermind the balloons.

Conclusion

Performing strength exercises such as squats may definitely contribute to faster sprints and higher jumps. The evidence for this isn’t as strong as is often claimed however and — more importantly — there are better options in many cases.

Put into greater perspective, we may conclude that the dogma of traditional strength training is based on very dubious assumptions. Assumptions that are needlessly limiting. It’s time to cast off the blinders and to focus on improving transfer of training.

Practical pointers

• If you wish to employ traditional strength training for improving sport performance, then mainly do so for relative novices.
• For the improvement of sprinting performance, more specific sprinting exercises are often better options.
• For the improvement of jumping performance, explosive exercises such as Olympic weightlifting derivatives and plyometrics are often better options.

References

1. Suchomel, T. J., Nimphius, S. & Stone, M. H. The Importance of Muscular Strength in Athletic Performance. Sports Med.46, 1419–1449 (2016).
2. Wisløff, U., Castagna, C., Helgerud, J., Jones, R. & Hoff, J. Strong correlation of maximal squat strength with sprint performance and vertical jump height in elite soccer players. Br. J. Sports Med.38, 285–288 (2004).
3. McCurdy, K. W. et al. The Relationship Between Kinematic Determinants of Jump and Sprint Performance in Division I Women Soccer Players. J. Strength Cond. Res.24, 3200–3208 (2010).
4. Alemdaroğlu, U. The Relationship Between Muscle Strength, Anaerobic Performance, Agility, Sprint Ability and Vertical Jump Performance in Professional Basketball Players. J. Hum. Kinet.31, 149–158 (2012).
5. Seitz, L. B., Reyes, A., Tran, T. T., de Villarreal, E. S. & Haff, G. G. Increases in Lower-Body Strength Transfer Positively to Sprint Performance: A Systematic Review with Meta-Analysis. Sports Med.44, 1693–1702 (2014).
6. Sheppard, J. M. et al. Relative Importance of Strength, Power, and Anthropometric Measures to Jump Performance of Elite Volleyball Players. J. Strength Cond. Res.22, 758–765 (2008).
7. Van Hooren, B. & Bosch, F. Influence of Muscle Slack on High-Intensity Sport Performance: A Review. Strength Cond. J.38, 75–87 (2016).
8. Rumpf, M. C., Lockie, R. G., Cronin, J. B. & Jalilvand, F. Effect of Different Sprint Training Methods on Sprint Performance Over Various Distances: A Brief Review. J. Strength Cond. Res.27, 1767–1785 (2015).
9. Hackett, D., Davies, T., Soomro, N. & Halaki, M. Olympic weightlifting training improves vertical jump height in sportspeople: a systematic review with meta-analysis. Br. J. Sports Med.50, 865–872 (2015).

NB: Part 6 is on the back burner for now, so we immediately proceed to part 7!

≪ Part 4 | Part 7 ≫