Taylor KL et. al. Negative effect of static stretching restored when combined with a sport specific warm-up component. J Sci Med Sport. (2009) 12(6):657-61.
There is substantial evidence that static stretching may inhibit performance in strength and power activities. However, most of this research has involved stretching routines dissimilar to those practiced by athletes. The purpose of this study was to evaluate whether the decline in performance normally associated with static stretching pervades when the static stretching is conducted prior to a sport specific warm-up. Thirteen netball players completed two experimental warm-up conditions. Day 1 warm-up involved a submaximal run followed by 15 min of static stretching and a netball specific skill warm-up. Day 2 followed the same design; however, the static stretching was replaced with a 15 min dynamic warm-up routine to allow for a direct comparison between the static stretching and dynamic warm-up effects. Participants performed a countermovement vertical jump and 20m sprint after the first warm-up intervention (static or dynamic) and also after the netball specific skill warm-up. The static stretching condition resulted in significantly worse performance than the dynamic warm-up in vertical jump height (-4.2%, 0.40 ES) and 20m sprint time (1.4%, 0.34 ES) (p<0.05). However, no significant differences in either performance variable were evident when the skill-based warm-up was preceded by static stretching or a dynamic warm-up routine. This suggests that the practice of a subsequent high-intensity skill based warm-up restored the differences between the two warm-up interventions. Hence, if static stretching is to be included in the warm-up period, it is recommended that a period of high-intensity sport-specific skills based activity is included prior to the on-court/field performance.
My Comments: As I discussed recently in The Importance of Context, people these days seem to love them some absolutes and there tends to be no shortage of them to go around, especially when it comes to training. Always do this, never do that, you get the idea. The situational context is irrelevant, there are simply black and white absolutes that apply across the board.
And a recent never is that you should never ever static stretch before high-intensity training of any sort with endless coaches and gurus repeating that idea. And certainly this seems to be based on quite a body of research. A number of studies have shown that extensive static stretching done immediately prior to various types of exercise performance such as vertical jumping, sprinting and weightlifting impair strength and/or power output.
Now, as I mentioned in Warming Up for the Weight Room Part 1, even if static stretching does decrease strength and power outputs, there may still be times to do it before training. Usually this is in the case of a severe muscular tightness that impairs either technique or safety. In that context, proper technique and not hurting the person is far outweighed by any decrease in performance.
However, I made another point in that article which was this: many of the studies don’t really reflect how athletes typically go about their training. That is, anyone who has trained as an athlete or actually coached athletes in the real world knows that it’s fairly rare (especially among strength/power type athletes, endurance guys are often years behind the curve) to go straight from static stretching immediately into high-performance work. At the very least some type of drills are generally done between the two, usually more than that (e.g. multiple progressive intensity sports specific warm-ups) is done.
There is also an issue of the extent of stretching: many of the negative performance studies have used levels of static stretching that far exceed what most athletes would ever do in practice (again, something anyone who’s actually worked with athletes would know). That is, it would be rare to hold a stretch for 2-4 minutes in the real world, static stretching of perhaps 30 seconds per muscle group would be far more realistic. Yet it is generally that type of extremely prolonged static stretching that has been tested and found to impair performance (some studies have shown shorter stretching periods to have a similar negative impact).
Which brings us to today’s study which set to test the above in a more real-world type of situation.
The study examined 13 netball players from the Australian Institute of Sport. Both groups first performed a sub-maximal run as a general warm-up. Then one group performed static stretching (9 stretches held for 30 second each) and the other performed a dynamic warm-up consisting of 16 rather common dynamic movements. Both the static and dynamic warm-ups lasted 15 minutes. After a short-rest, both groups were tested on 20m sprint and vertical jump. Then both groups performed a netball specific skill warm-up consisting of various short sprints, shuffling, accelerations, direction changes and jumping. Then the performance tests were performed a second time to see if anything had changed.
And the results? Well, in keeping with previous work, the static stretching routine did in fact hurt performance on the 20 m sprint and vertical jumping compared to the dynamic warm-up. However, after performing the specific skills warm-ups described above, results were no different on the second set of performance tests. That is, any loss of performance due to static stretching was eliminated simply by performing a variety of sport specific skills prior to the maximal effort testing.
Basically, by testing the athletes in a situation that more accurately reflects how athletes actually train, they found that much of the concern over static stretching is unfounded. As they state in the discussion:
The results suggest that if an inhibitory effect was present after static stretching, that the SKILL component of the warm-up routine was able to dissipate the negative effect. This supports the suggestion by Young and Behm that practice attempts of the required tests may offset potential negative effects of static stretching.
The also note that their results are in contrast to another study examining both a dynamic performance warm-up and a static-stretching warm-up but in that study, the static stretching was done after the performance warm-up and immediately prior to the testing. Basically, order of warm-up matters which I also discussed in Warming Up for the Weight Room Part 1. And so long as it’s followed by some sort of dynamic, skill specific, progressive warm-up (e.g. progressively heavier warm-up sets in the weight room, increasingly faster pickups in sprinting, etc), static stretching appears to not be quite the absolute no-no that many have made it out to be.
Quoting from the researchers conclusions:
The most important findings from this study were that a dynamic warm-up routine is superior to static stretching when preparing for powerful performance; however, these differences can be eliminated if followed by a moderate to high intensity sport specific skill warm-up.
Summing Up: Basically, static stretching is only a problem if it’s done too extensively (e.g. stretches held for very extended periods) and is not followed by appropriate sport-specific warm-ups between the end of static stretching and maximal performance (testing or training). Which isn’t how real athletes generally train anyhow. Which is something any performance coach who has actually worked with athletes should know anyhow.
Mercader J. Mozambican grass seed consumption during the middle stone age. Science. (2009) 326(5960):1680-3.
The role of starchy plants in early hominin diets and when the culinary processing of starches began have been difficult to track archaeologically. Seed collecting is conventionally perceived to have been an irrelevant activity among the Pleistocene foragers of southern Africa, on the grounds of both technological difficulty in the processing of grains and the belief that roots, fruits, and nuts, not cereals, were the basis for subsistence for the past 100,000 years and further back in time. A large assemblage of starch granules has been retrieved from the surfaces of Middle Stone Age stone tools from Mozambique, showing that early Homo sapiens relied on grass seeds starting at least 105,000 years ago, including those of sorghum grasses.
My Comments: In recent years, there has been quite an explosion in interest in the supposed diet of our paleolithic ancestors, essentially in an attempt to explain part of why humans are having so much trouble with the modern diet. So far as I can tell the first paper was written in the Mid-80’s or so but even more recently it’s become quite the fad/cult/area of interest for a lot of people.
Now, while an entire article could be written about this, it’s important to note that nobody knows for sure what we ate during our evolution. Even researchers in the field (Cordain and Eaton are two of the major ones) have arrived at rather drastically different conclusions about what our diets contained based on their assumptions because it’s all basically a lot of guesswork. We end up with estimations based on a bunch of assumptions and not much more.
Much of it comes from an analysis of a book called the Ethnographic Atlas, a work done years ago by non-scientists who wrote down (sort-of) what extant non-modernized people were eating. From that, various researchers, making various assumptions about the relative proportions of animal and vegetable foods in the diet have thrown out some ideas about what our evolutionary diet contained. Those researchers have often reached utterly differing ideas based on which built-in assumptions they started with. Other suggestions about our ancestral diet have been made by examining the current intake of extant hunter-gatherer tribes with the implicit assumption that their food intake is representative of our intake during our evolution.
I’d note that it’s unlikely that there was any singular evolutionary diet in the first place. Humans have shown the ability to adjust to all but the most extreme environments and show an amazing ability to adapt to drastically differing diets as well. Human ancestors evolving in say Alaska would have had far different foods available than someone living in the arid plains in Africa. Even examining the extant hunter-gatherer tribes demonstrates this in spades: the diet of an Alaskan Inuit is radically different from say an African Bushman simply due to the difference in environment and what is available to them. So there is no single ancestral diet in terms of the quantities, proportions or types of food that would have been eaten in the first place.
At best we can probably say with some degree of certainty that our ancestors didn’t have many of the foods available to us today. That is, Cap’n Crunch, Ben and Jerry’s Ice Cream and Bud Light weren’t part of our evolutionary diet because they didn’t exist (much to the loss of our ancestors). Beyond that, we can’t say with much certainty what they did eat; it’s mostly guessing because folks weren’t alive to say for sure. And while it may be safe to assume that extant hunter-gatherer tribes are representative, it’s still an assumption.
Now, while there are many different interpretations to the ‘paleo-diet’ craze, at least one thing that most seem to agree on was that refined grains were absolutely not part of the evolutionary diet. Bloggers, apparently unclear on the concept of irony, go on constantly about how ‘Paleo man didn’t have grains, so you shouldn’t eat them.’ Apparently that same logic doesn’t apply to the computers they use to blog with, the Internet that they blog on, their Blackberries that they use to Twitter about their blog updates, modern cars that they use to get to work or the houses they live in. Paleo man didn’t have those either but I don’t see these folks giving those up. Guess they only want to give up the easy stuff when it’s convenient. But I digress.
That is, it’s generally assumed that refined grains (being currently blamed for much of modern health problems) weren’t a major part of our diet until the agricultural revolution, about 10,000 years ago. It’s also assumed that that span of time is insufficient for man to have evolved to deal with them. I’ll only address this second assumption by pointing readers to a new book called The 10,000 Year Explosion: How Civilization Accelerated Human Evolution wherein the authors make a rather good argument that, contrary to common belief, not only did human evolution continue once humans became civilized, that it accelerated.
Rather, in looking at today’s second paper, I want to address that first assumption: that our evolutionary diet was devoid of any type of refined cereal grain. I imagine that, if you’ve read this far, you can guess what I’m going to say about it and what the second study concluded.
The researchers were examining cave artifacts in a cave site in Mozambique which have been dated to somewhere between 42000 and 105,000 years ago. They mention that excavation in 2007 retrieved 555 artifacts. Of those, 70 stone tools were analyzed and were chosen to represent the broadest range of potential plant uses. This includes scrapers, grinders, points, flakes and miscellaneous tools. These were analyzed and while 20% contained no starch residue, the other 80% were found to contain starch granules with the number on each tool ranging from 1 to 650. It’s worth noting that the quantity of granules found on the scrapers was massively larger than what is found naturally in the cave, that is, they were brought into the cave.
The majority of starch granules (89%) were identified as sorghum, a grass showing a large complex of cultivated, wild and weedy types. The researchers note that the starch granules found on the tools analyzed are structurally identical to modern sorghum plants. As the researchers state:
The Mozambican data show that Middle Stone Age groups routinely brought starchy plants to their cave sites and that starch granules go attached to and preserved on stone tools. I cannot prove that starch from all stone tools represents direct tool function…These early grinders are simply modified cobbles and core tools, with a suspected use that conforms to the technological action of “diffuse resting percussion” and “pounding”, which allows the grinding of plant materials.
Put differently, while more research will certainly be needed to verify or refute this claim, data that is a bit more direct than “Assumptions based on a book some guys wrote years and years ago” suggest that as far back as 100,000 years ago, humans had found a way to refine and consume at least some grains for their diet. Or as the researchers state more directly in the abstract above:
A large assembly of starch granules has been retrieved from the surfaces of Middle Stone Age tools from Mozambique, showing that early Homo Sapiens relied on grass seeds starting at least 105,000 years ago, including those of sorghum grasses.
And even if you don’t buy the argument of the book I referenced above, that 10,000 years is more than sufficient to allow adaptation to changes in diet, it would be hard to argue that 105,000 years isn’t time enough to adapt to some degree.