Tuesday, November 3, 2009
1. Injury rates may be high because racing and the training required to race (intervals, tempo runs) stresses the musculoskeletal system well above any safety factor that evolved in response to persistence hunting. High injury rates among racers, then, may not be relevant to the hypothesis.
2. I did a quick google scholar search of injury rates among race horses and found "fractures and tendon injuries in National Hunt horses in training in the UK: a pilot study" published in the Equine Veterinary Journal. The authors found that 25% of the National Hunt race horses sustained either a fracture or a tendon/ligament injury during a single race season. Should we conclude from these high rates of injury that horses didn't evolve to run?
3. What we need are injury rates among runners persistence hunters. Or at least populations that run long slow distance and only LSD. I'm not aware of any of the injury studies that decompose the data in this manner. And anecdotal stories about the tarahumara isn't data. But even the relevance of these injury data collected from people raised on concrete and cars is questionable.
4. I'd also be interested in chronic injury rates among endurance mammals such as wolves or wildebeest.
5. As with any evolved response, trade-offs occur. What is the fitness cost of plantar fascitis or IT band syndrome?
Tuesday, October 13, 2009
The link between red meat and colon cancer is decades old and reviews of the evidence suggests a cautiously solid association. The association quickly led to the hypothesis that high dietary intake increases risk of colon cancer but recent reviews of both prospective and intervention studies do not support the hypothesis that high dietary fat increases risk of colorectal cancer. Interestingly, at least one intervention study found no decreased risk of colorectal cancer over a 10 year period after replacing meat with vegetables in the diet.
The news article highlights the poor training of science journalists. The biomedical literature highlights the difficulty in assessing causation in complex functional systems.
A good review is:
Diet, nutrition and the prevention of cancer
Timothy J Key, Arthur Schatzkin, Walter C Willett, Naomi E Allen,
Elizabeth A Spencer and Ruth C Travis
Public Health Nutrition: 7(1A), 187–200
Tuesday, July 28, 2009
Friday, July 3, 2009
Thursday, July 2, 2009
A Doctor of Osteopathy (DO), a chiropractor, a physical therapist, a massage therapist, an accupuncturist, a macrobiotic, an herbalist, a medieval court physician, a therapeutic touch practitioner, a scientologist, a Navaho medicine man, a homeopath, a podiatrist, a Christian scientist, a Catholic exorcist, a surgeon, and a physiologist walk into a bar. They overhear a man telling the bartender that his son's lungs are full of phlegm making it difficult to breath and the lungs are chronically infected. The child was also not growing well and had developed distal intestinal obstruction syndrome. Finally, the child is missing his vas deferens and his sweat is very salty.
So they went to the boy to search for dysfunctional cranial rhythms, and subluxed vertebrae, and hip muscle imbalances, and myofacial trigger points, and disrupted qi, and bodies out of balance with nature and the cosmos, and yin and yang, and the four humours, and an out of tune aura, and body thetans, and disrupted nilch’I hwii’siziinii, and tubercular miasms, and excessive overpronation, and fear, ignorance, and sin, and evil spirits but none could convince all the others that their prediction was true. Except the physiologist who correctly predicted the boy would have a mutated CFTR gene. She won $16 that day.
Wednesday, July 1, 2009
Although there are zero papers showing that correctly matched running shoes reduce injury rate, there is a single paper, published in 2006 and available to Rinaldi when he did his 10 months of research for the article, showing that runners fit by the Sports Science Institute of South Africa Sports Medicine running shoe clinic had an equal frequency of injuries in the year following shoe purchase to matched runners that had not been to the clinic. Since some of the control group (those that had not been to the clinic) were getting professional advice on shoe fit, we might expect the difference in injury rate to be small. Indeed, if all of the control runners were getting professional advice, we expect the injury difference to be zero (assuming the advice was the same).
So maybe both groups were just getting good advice and the frequency of injury in both groups was low? The authors do not report the percentage of runners who were injured in the year following running shoe purchase, only the raw number of total injuries. The shoe-clinic group had 93 injuries and 94 runners. The control group had 115 injuries and 83 runners (note that the control group ran more and the frequency of injury/running day were very close). Clearly some runners had multiple injuries. Regardless, these must reflect high injury rates (typical statistics are something like 50-80% or runners are injure per year). So there is no evidence from this one study that correctly matching foot kinematics to running shoe will reduce injury rates at all much less 85%.
Schwellnus, MP and G Stubbs (2006). Does running shoe prescription alter the risk of developing a running injury? International SportMed Journal, Vol.7, pp. 138-153.
Sunday, June 28, 2009
Friday, June 26, 2009
by Chris McDougall has the difficult task of living up to its reputation. After the first few chapters, I had my doubts that it could. But doubt gave way to intrigue, then to fun, and then thrill. The book reads like a novel. It's hard to put down, because the short chapters end with little mysteries that are only uncovered in the next chapter. Kinda like The DaVinci Code, only better. Two chapters could be excerpted as stand-alone essays, one on running shoes and injury, and one on the running man theory of human bipedalism. The running man chapter should be nominated for the Best American Science Writing series.
That said, I do have some criticisms. I'm skeptical of the romantic portrait of the tarahumara that McDougal paints, but that is a small issue. I'm also skeptical that the tarahumara do not get running injuries. McDougal states this several times but doesn't offer any evidence other than anecdote. Indeed, one of the tarahumara has a typical running injury during the Leadville race but this is dismissed as a function of running in running shoes for the first time. But he was also running in Colorado for the first time so maybe that was the cause? Or more likely, Tarahumara are humans like the rest of us and get injured. This is an important point because McDougal is building the case that there is way to run injury free, and this way includes both running techique and avoiding modern running shoes. McDougal quite correctly asks why running isn't like every other sport, that is, one requiring practice of a certain techniqe. Nevertheless, while the evidence that certain kinematics (such as "overpronation") cause injury is, essentially non-existent, there also isn't good evidence that running a certain way (such as chi or pose running) reduces injury. Ditto for shoes. McDougal makes the oft-heard claim among barefoot runners that running injuries have increased since the advent of the modern shoe. I've not found the citation documenting this but even if it is true, that doesn't necessarily implicate the modern running shoe. Since the 70s (when the first modern shoes started to appear), americans have also gained alot of weight and become more sedentary. We drive cars *everywhere*. And modern marathon advertisers have spent big money to get the couch-to-5K crowd running 26.2. So while I'm sympathetic to the idea that certain running kinematics and retro shoes are less likely to contribute to injury, I want to emphasize "contribute" because the one variable that we do know that causes an increased rate of running injury is running itself.
Wednesday, June 17, 2009
I'm picking on Outside but they're just parroting the dogma from nearly every running shoe company, shoe store fit specialist, podiatrist, sports medicine M.D., chiropractor, and textbook. The only contrarians seem to be the loud-mouthed minimalists on letsrun.com, the hippy barefoot runners, and everyone who has recently read Born to Run. But given the universal acceptance of the "personally fit running shoes are necessary to reduce injury" model, you'd think there would be more evidence for this than something like, say, the ability of psychics to predict the next bus bombing. Here is the abstract of a recent paper from the British Medical Journal.
British Journal of Sports Medicine 2009;43:159-162
Is your prescription of distance running shoes evidence-based?
C E Richards1,2, P J Magin1 and R Callister2
1 Discipline of General Practice, School of Medicine and Public Health, University of Newcastle, Australia
2 School of Biomedical Sciences, University of Newcastle, Australia
Dr C Richards, Discipline of General Practice, Bowman Building, School of Medicine and Public Health, University of Newcastle, University Drive, Callaghan 2308, Australia; firstname.lastname@example.org
Objectives: To determine whether the current practice of prescribing distance running shoes featuring elevated cushioned heels and pronation control systems tailored to the individual’s foot type is evidence-based.
Data sources: MEDLINE (1950–May 2007), CINAHL (1982–May 2007), EMBASE (1980–May 2007), PsychInfo (1806–May 2007), Cochrane Database of Systematic Reviews (2nd Quarter 2007), Cochrane Central Register of Controlled trials (2nd Quarter 2007), SPORTSDiscus (1985–May 2007) and AMED (1985–May 2007).
Review methods: English language articles were identified via keyword and medical subject headings (MeSH) searches of the above electronic databases. With these searches and the subsequent review process, controlled trials or systematic reviews were sought in which the study population included adult recreational or competitive distance runners, the exposure was distance running, the intervention evaluated was a running shoe with an elevated cushioned heel and pronation control systems individualised to the wearer’s foot type, and the outcome measures included either running injury rates, distance running performance, osteoarthritis risk, physical activity levels, or overall health and wellbeing. The quality of these studies and their findings were then evaluated.
Results: No original research that met the study criteria was identified either directly or via the findings of the six systematic reviews identified.Conclusion: The prescription of this shoe type to distance runners is not evidence-based.
Tuesday, June 16, 2009
• Do these stretches (link to stretches) because the muscle needs to be loose and flexible to recovery and remain healthy. Definitely don't do strength exercises becaus tight, inflexible muscles are what's causing the pain in the first place
• Do these strength exercises (link to strength exercises). You need a strong core to allow the weakened muscle to recover and reduce future injury. Definitely do not stretch it because you will tear scar tissue in the weakened muscle.
More generally, there is a huge industry of health care professionals and gadget makers throwing advice at us on how to reduce the probability of injury. Stretch! Orthotics! Core Strength! Pose (or Chi) running! Barefoot! Nike Free! Medial Posting! 300-500 Miles! Compression Shorts! The list is endless.
Let me compare the sports medical advice with something like the advice to take vaccines. The flu vaccine has an efficacy of 50-75%. The polio vaccine has reduced the rate of polio cases from >100,000 year to ~1000/year. The smallpox vaccine has reduced smallpox from >50,000,000/year to ZERO.
So my question to M.D.s, chiropractors, yoga gurus, podiatrists, sport shoe companies, physical therapists, and CW-X, is, if your advice reduces running injuries, how come we're not seeing fewer injured runners?**
Finally, Kolata's article goes well with my post yesterday. Too few of us really challenge our own beliefs with hard data.
*a 30C dilution is a solution that has been diluted 1/100, thirty times. The probability that a single molecule of the solute remains in the water is fantastically small. Now that is a weak solution!
*There is good evidence that running less reduces the rate of injuries.
Does drinking a moderate amount of alcohol increase health? A nice summary with a healthy dose of skepticism thrown at the moderate alcohol -> healthier body studies.
Monday, June 15, 2009
So what had I done to augment the soreness? Well, I pool ran for the first time in over a year on Wednesday, and pool ran again on thursday. To get a good workout pool running, you need to have very fast turnover. I ran Tuesday evening, 5 miles and easy, on grass. I hadn't run in 8 days prior to this. I went to the sports medicine doctor on Thursday morning, and in her series of diagnostic tests, she asked/facilitated various explosive jumps and deep stretches. And finally, I was reading about how letsrun.com posters had dealt with piriformis issues and I tried a few of the stretches that several posters swore by. There are many other antecedents that could effect pain (sleep patterns? stress? diet? sitting on the couch all day thursday? maybe just the way I slept or got out of bed that morning?) but this is a pretty good start. But how do I "know" which of these activities to avoid in the future to keep from aggravating my piriformis?
Humans will combine experience with biases (preconceived ideas or beliefs) to infer cause. If a belief is strong enough, it probably would not even occur to the person that there are multiple potential independent and interacting causes. The one prior event that matches the belief is recalled to memory but the other events are left in the dustbin of the brain. This is an example of the well-known and pervasive "confirmation bias". Confirmation biases reinforce prior belief and make alternative causes even less likely to be believed.
But I'm well trained to seek multiple potential causes - that's what I do for a living (although the discounting of some potential causes such as sleep, stress, and diet, and the complete refusal to even entertain planetary alignment & evil demons reflects my own set of beliefs). So I list out potential causal candidates, like I did above. But these causal candidates are a tiny fraction of the literally thousands of activities that I've engaged in over the last few days. The ones I listed reflect my own biases. Note that I put sleep, and stress, and diet in parentheses because I don't believe these as serious candidates for this case. Also note that I would never even entertain the possibility of an imbalance in my humors, spinal misalignment, or qi, much less something like planetary alignment or evil spirits.
So I turn to my experience (or maybe the experience of others). Of course it is these experiences that shape our biases, which in turn, shape our experiences (that is the strength of the memory of past events will be a function of our biases). But let's pretend my experience is objective. I've not had a sore piriformis before but I have had this injury wax and wane over the past month. What are the common activities that occurred prior to soreness feeling worse? Again, I simply cannot ask this objectively because the ability to recall activities in memory reflects my beliefs. So I turn to my logbook. But I write very little in my logbook with no notes at all on my diet, sleep, feeling of stress, etc., etc., etc. Regardless, certainly there are far too many common antecedents, most unrecognized, to infer causation with an confidence. My belief structure rejects most of these antecedents and narrows the list down to the few that fit my worldview (overuse and stretching) And now my inference engine looks for consistency; which of these consistantly preceded augmented soreness? That is our brain is searching for a pattern. Psychologists have a field day with freshman classes showing how humans frequently find patterns (associations between events) when non actually exist. There is too little data (coincidence between activity and increased soreness) and too much noise (all the spuriously correlated activities that have nothing to do with soreness and all of the un-recalled variables that might have contributed to the soreness). It's a futile exercise if the signal-to-noise ratio is low (I'll write about a case with a high signal-to-noise ratio later).
The point of all of this is, our ability to infer causation using our own experience when the effects are temporally far removed from the cause is utterly confounded by our belief structure and our proclivity to find pattern when none exists. If we want to know what works (avoiding injury, recovering from injury, performing at peak ability) in sport, then we have to exploit the methods of inference that overcome the many cognitive biases and illusions. These methods are the manipulative experimental methods of science.
Unfortunatly, we cannot do most of the manipulative experiments on humans that we'd really like to do. For example, I'd really like to know if running barefoot reduces injury. To do this, I'd need a population of humans that are cloned from a single genotype and raised in a common laboratory environment. They've each had the exact same diet, light, sleep, exercise, and education, all in their little cages. I'd then randomly assign 50 pairs to 50 different gyms with an indoor 200m track. Within each pair, one would always run with a modern running shoe and one barefoot. Same diet, same sleep schedule, same training schedule. And yes, they would never leave the gym. Then after two years, I'd stop the experiment and tabulate the rate of injury. Of course, maybe my shoe choice was particularly bad or maybe there is a genotype x shoe interaction (the shoe on the lab genotype caused more injury but wouldn't have on some other genotype). Or maybe there is no effect of shoes on a gym track but there is on a road or on a trail So I'd have to repeat the experiemnts using different genotypes, different shoes, and different surfaces. Not gonna happen.
Anything other than a controlled, manipulative experiment will have confounding factors. Without much ability to manipulate, what the science of sport (and most modern medicine) is left with is the attempt to control these confounding factors using statistics and, hopefully, large sample sizes. This is "evidence-based medicine" and it's the only game in town for inferring what works and what doesn't. There are huge problems with every evidence-based medicine study, but the best studies are better than our many experiments of one.
Note that Science Based Medicine has a really nice blog post this morning on, essentially, how the sort of confirmation bias that I've discussed above, can lead to pseudoscience quackery among professionals in health related fields. It's a long post and he only gets to the confirmation bias part near the end, but it's a worthy read.
Thursday, June 11, 2009
Middle class folk from industrial countries don't worry too much about the major macronutritient diseases that kill millions (mostly children) throughout the world. Instead, we continuously argue about the proper proportions of macronutrients - our carbohydrates, fats, and proteins - the form these should come in, and how best to prepare them. So we have low-fat diets, Atkins diets, various flavors of vegetarianism (those that consider fish vegetables and those that consider fish animals), various flavors of carnivorous diets (red meat v. no red meat), vegan diets, the paleo diet, raw food diet, etc., etc,. etc.
Too much to blog about in one post but I will make one comment on any diet that purports to be "natural" or more in tune with our "nature" or "evolutionary past". The health claims of these diets assume that humans have not evolved since the pleistocene, that is, back when we were gathering nuts and scavenging lion kills on the African savannah. But there is a huge new research program in human evolutionary genetics that documents pervasive genetic adaption over the last few thousand years. The poster child of this phenomenon is the recent evolution of the regulation of the lactase gene, which has allowed both northern europeans and some africans to adapt (via natural selection) to the behavior of drinking milk from farm animals, as adults. Marlene Zuk has a nice essay from the NYT science section from earlier in the year. Note that the recent, accelerated genetic evolution theory is not uncontroversial (although certain instances like the lactase regulation is, indeed, uncontroversial). If you are interested, John Hawkes frequently blogs about this stuff and since he works in this field, his views merit close attention. In his most recent blog, John mentions Richard Wrangham's most recent book that is receiving a lot of interest: "Catching Fire: How Cooking made us Human". A seed interview with Wrangham about his book is short and sweet.
I've put this book on my list, but what I'm really curious is what (if any) selection has occurred in response to cooking?
Sunday, June 7, 2009
A good summary of the competing models (part I, part II, part III, part V) is on the Science of Sport blog. Read these and the comments. If you only read one read, part V and the comments.
Schwellnus also recommends passive stretching of the model to at least temporarily relieve the cramp since this causes a spinal reflex that relaxes the tensed (cramped) muscle. A recent chapter in the Olympic Textbook of Medicine in Sport, which includes Schwellnus as an author, recommends regular stretching of the muscles that generally cramp and proper carbohydrate and fluid intake prior to exercise (in order to delay muscle fatigue, not because this directly decreases probability of cramping).
Schwellnus, M P
Cause of Exercise Associated Muscle Cramps (EAMC) -- altered neuromuscular control, dehydration or electrolyte depletion?
Br J Sports Med 2009 43: 401-408
Wednesday, June 3, 2009
"But running is not just exercise. It's a great stress reliever and an inexpensive source of neurotransmitters like dopamine that wash the body with good feelings."
That is, running makes us high. The general idea is that running long and fast signals the secretion of endogenous opioids, which are our own version of morphine (of which heroine is a derivative) and these endogenous opioids (or endorphins), bind to receptors on cells in brain circuits that make us feel euphoric.
Gina Kolata, a reporter for the New York Times, criticized the endorphin hypothesis of runner's high in her book Ultimate Fitness. I don't have the book but she also had an article in the Milwaukee Journal Sentinal that suggested that runner's high does not come from an "endorphin rush". Most recently, however, she's changed her mind based on a new study that shows (according the the authors and Kolata) (1) endogenous opioid activity increases after a 2hr run compared to before the run and (2) perceived euphoria is greater after the 2hr run than before, and, importantly, (3) the level of opioid activity is positively correlated with perceived euphoria. Here is a lay summary of the paper.
As I understand the original paper, the authors did not actually measure levels of the endogenous opiods but measured the levels of the binding of an radioactive opioid antagonist, which they could detect with PET. Since the antagonist and the endogenous opioids compete for the same binding sites, then if measured levels of the antagonist decrease, the conclusion from the authors is that endogenous opioid activity is increased (they quickly dismissed alternatives, such as downregulation of opioid receptors, but I didn't really spend enough time to evaluate these).
One note - the authors note that runners were both (1) told that they were being treated with opioids ligands and (2) confirmed that they had previously experienced runner's high. Runner's tend to be a well educated group and I'm guessing that more than one figured out what the study was about. It's a nice study but I'm not completely confident that a placebo effect can be ruled out and it still isn't measuring endogenous opioid activity directly.
Also note that there is a group that argues that runner's high is due to endogenous cannibinoids and not opioids. Amby Burfoot has a comment on this.
Tuesday, June 2, 2009
1) I teach Human Anatomy & Physiology to many kinds of pre-health students including nursing, athletic training, sports medicine, exercise physiology, the various therapies (occupational, physical), psychology, and a few pre-meds. We spend a year talking about how the different organ systems function in health (mostly) and disease (a little, since pathophysiology is an upper level class), generally at the molecular and cellular level. The students learn about enzyme function, and protein channels, and protein transporters, and cell signaling, and all that good stuff. I usually spend a full lecture on "how we know what we know and why we believe what we believe" which is a lecture on evidence-based medicine (in the broad sense) and especially how science (in the broad sense) is the only game in town that allows us to overcome the many cognitive biases that get in the way of gaining reliable knowledge. A few students like the lecture but many don't because I really challenge many of their beliefs.
2) I run and ski and there's lots of bad information out there on endurance physiology and on how to avoid injury in these sports and how to treat injuries.
So this blog gives me space to draw attention to these areas. Since I don't have time to write a bunch of essays, mostly they will be links but sometimes I might write something longer.