Bias. It's everywhere. But one of the most annoying biases I've seen in a lot of the popular fitness publications, including websites, blogs, as well as paper magazines is what I call the "sport causality bias", or "elite athlete selection bias".
You've seen it. You've read it. If you want to get jacked, you should sprint, because elite sprinters are buff, compared to the long distance runners who are scrawny. If you want to protect your knees, you should wear knee sleeves because none of the big-time powerlifters who use knee sleeves have developed knee problems. You don't need to train with weights; just look at how jacked and ripped gymnasts are, and they just use their body weight.
However, by the same logic, if you want to be tall, then you should play basketball, because all of those basketball player are SO tall! And forget about being tall if you're going to do gymnastics--gymnastics must cause shortness because all the really good ones are short. And lawn bowling...well that must cause premature aging.
So why is it that the paragraph just above this one sounds so ludicrous, while the paragraph above it, which includes real-life examples of explanations/justification for training methods that are not only used in real-life, but also accepted by perfectly normal-thinking individuals?
The thing about becoming an elite athlete is that, when you really sit down and think about all the factors that need to come together, training, and even what I like to term as "blatant" genetics (the aspects of the genetic profile that contributes DIRECTLY to performance, like VO2max, or lung volumes, muscle fibre distribution, etc) play only a fraction of a role in determining who becomes, and who doesn't become part of the group of elite athletes upon which we make these broad generalizations (and false causal associations).
With the exception of a minority of sports (rowing, bobsled, luge come to mind), to become an elite or professional athlete requires fairly early entry into a sport. Which means there's a finite amount of time to reach that elite level. In fact, the countdown begins shortly after you're born.
Genetics aside, for now, you need to be born into an environment (and there will always be exceptions) where you have proper early nutrition, and developmental tools. This is why so much fuss is made about playing Mozart to infants and having weird black and white mobiles over the bed. A future potential elite athlete could easily be thwarted with an early vitamin D deficiency. And some of these factors aren't even under anyone's control (like rheumatic fever, or an unfortunate encounter with another disease, or tragic trauma). But, the odds are slim that you'll end up as one of these unfortunate children--most infants grow up to be healthy children these days. So let's say our future athlete makes it through infancy unscathed.
Childhood is where the most random factors needs to fall into place. Let's say that you have the perfect genetic profile to be the best tennis player EVER. Think about the random factors that need align for this to happen. Firstly, you (or your parents) need to have the idea to expose you to tennis, as opposed to something else. Secondly, you need to have the opportunity to gain that exposure (say, tennis lessons). Thirdly, you need to catch the right kind of environment where you're going to LIKE tennis (e.g. a talented child with a horrible experience is going to walk away). Fourthly, you need to be in an environment where you have the means to continue training (e.g economic access). Fifthly, you need to be in an environment where you are facilitated to participate (e.g. supportive parent(s), supportive coach, functional school environment). Sixthly, you need to be in an environment where the training your receive will nurture your abilities to the point where you are competitive (e.g. good genetics, bad training = reduced chance of success). Seventhly, you need to avoid early injury. Eighthly, you need to avoid youth burnout and stay interested in your sport. The list goes on. I haven't even touched on nutrition, coordinative development, team dynamics and the myriad of factors that cause drop-out by youth athletes in their sport, DESPITE the fact that they may be genetically EXCELLENT.
With the exception of Australia, and China (and perhaps a few other countries), talent-identification programs do not exist on a wide-scale level to identify children who might be promising sprinters/runners/gymastics/lifters/football players/etc. So, when we say that a certain body habitus is associated with a certain type of training, we're looking at not only a genetically elite (you can only excel at the elite level if you have a favourable genetic profile towards that sport and body habitus), but we're looking at the habitus that is selected for by the sport in the available population of people who HAPPENED to stumble into their sport. So when we think about a sport like gymnastics and start making assumptions about how body-weight exercises or "cross-fit"-style training and body-type results, what we're doing is making conclusions based on the tip of a complicated iceburg (the one below is by no means complete--apologies for the small font. I couldn't fix it.) and not taking into consideration, all of the other people who have been exposed to gymnastics who haven't achieved the classic gymnast-type body:
All of the people in the iceberg have the genetic potential to be elite gymnasts. And with the exception of the very bottom of the iceberg, have all been exposed to gymnastics training. But only the ones at the tip are the ones that the public really gets to see; and subsequently, the ones that have conclusions drawn about what kind of body is possible with a gymnastics style of training. In other words, the idea that gymnastics training produces this:
is based entirely on only the tiniest fraction of the actual population that has been exposed to that type of training. And we all know what happened to the big ship that didn't know 90% of an iceberg is actually under the water (think about how we could all have been spared Leonardo DiCaprio and that wailing Celine Dion song!)
You might ask, "Why is this guy making such a big deal about this?"
Again, this goes back to the blog-theme of "good idea, poor reasoning." What I'm NOT saying is that body-weight training, gymnastics, or "cross-fit" style training is a poor training method. But what I am saying is that if we're going to propose that these styles of training (or any style of training for that matter, whether it's plyos, or the new-fangled 300 fad) are useful, we should be looking for other, less biased reasons as to why they are useful. If someone gave you a drug and said that it would cure your cancer, based on all the cancer survivors who took the drug, I'm pretty sure you'd be curious about all the people who got the same drug who didn't survive (and potentially were killed due to a drug complication!) So why are we so ready to accept the idea that a certain body-type is caused by a certain type of training, when all we're looking at (in this line of reasoning) is the people who are good and have excelled at it (i.e. the tip of the iceberg)?
Did you read Bouchard's book "Genetics of Fitness and Physical Performance" or "Physical activity and health".
Second Article:
Most Girls Have Normal Growth After Gymnastics
By Denise Mann
WebMD Feature
Feb. 22, 2000 (New York) -- Many researchers have suggested that gymnasts may stunt their growth because of their intense exercise regimens. However, a new study published in the February issue of the Journal of Pediatrics suggests that short people may flock to gymnastics. Short stature is considered an advantage in this sport because a shorter person's center of gravity is closer to the ground than that of taller athletes.
A research team led by Ego Seeman, MD, an endocrinologist at the Austin and Repatriation Medical Center in Melbourne, Australia, reports that while active gymnasts did have reduced standing height, sitting height, and leg length compared with nongymnasts, once they retired from gymnastics, they caught up with control subjects in terms of height.
According to the study, adult gymnasts who had been retired for eight years had no deficit in sitting height or leg length and no menstrual dysfunction.
Gymnasts may exercise for as many as four hours per day, and such vigorous exercise may disrupt normal hormone cycles, which can delay puberty and affect height. Numerous studies have shown that the young female athlete is at risk for the "female athlete triad" -- meaning that the development of disordered eating may lead to menstrual dysfunction (amenorrhea) and subsequent premature osteoporosis or bone loss.
But "[a]t least in this study, we find no adverse consequences on final height or menstrual cyclicity and see little justification for shackling the passion and Herculean spirit of the elite athlete," the authors write. "Several authors regard gymnastics as a form of child abuse, even though few, if any, studies confirm any long-term serious [adverse effects] in retired athletes."
In the study, researchers measured sitting height and leg length of 83 active gymnasts and 42 retired gymnasts. They compared the measurements with those of 154 nongymnast control subjects. Twenty-one of 83 gymnasts and 110 control subjects were assessed every 6 months for 2 years.
During the two-year follow-up period, standing height, sitting height, and leg length worsened among the 21 gymnasts. The growth in sitting height, especially, slowed before the age of 13 1/2 but picked up later. But in the one year following retirement, sitting height improved in all 13 of the gymnasts followed that long. Leg length among gymnasts increased at the same rate as it did in control group during the two years of follow-up, the researchers report.
"Short stature in active gymnasts is partly due to selection of individuals with reduced leg length. Reduced sitting height is likely to be acquired but is reversible with cessation of gymnastics," the authors conclude. "A history of gymnastic training does not appear to result in reduced stature or menstrual dysfunction in adulthood."
"[G]ymnastics delays puberty, but puberty may eventually emerge, promoting upper body growth, which may impair gymnastic performance, forcing retirement," Seeman and colleagues speculate.
Gymnastics is not hazardous to your health, says Nancy Marshall, former Olympian and the Portland, Ore.-based director of the USA Gymnastics Athlete Wellness Program. USA Gymnastics is based in Indianapolis.
"In fact, [the sport] can be health enhancing because it is a weight-bearing sport that helps strengthen bones and build muscles," she tells WebMD. "Gymnastics is not something that would stunt growth or have long-term negative effects."
"You have small people attracted to the sport for the same reason that tall people are attracted to basketball -- it's a place where they can excel," she points out. "It's easier to twist and do somersaults because they are closer to the ground and require less rotation."
Like the new report, Marshall says, "most studies conclude that small kids are attracted to gymnastics, and if there is one delay in development, they will usually catch up within five years."
Is it the training that makes them smaller?
Thus, female gymnasts are not underweight for their heights, but they are unusually small in stature, compared with both other athletes and the general population. Does the diminutive size of gymnasts increase their risk of injury? Does their reduced size mean that their skeletal systems are also less well-developed, compared with female athletes in other sports? As it turns out, the “skeletal ages” of gymnasts are often average or “on time for chronological age” during childhood, but by late adolescence most gymnasts’ skeletons may be classified as late-maturing. Gymnasts also tend to reach menarche later than young women in the general population, and later than young females in other sports. For example, young female swimmers have skeletal ages which are average or advanced in childhood and adolescence, compared with sedentary females(3). To summarise, female gymnasts tend to be short, they begin to menstruate later than usual, and their skeletons are rather non-robust. What is responsible for all of this?
Some sports-medicine experts believe that specific – but not well-identified – characteristics of gymnastics training do indeed hinder growth. For example, researchers from Deakin University in Australia and Western Washington University in the United States who analysed 35 clinical reports (cross-sectional, historical, and prospective cohort studies) found that élite-level gymnasts may indeed be at increased risk of adverse effects on growth(4). This group found that adolescent-female-gymnasts’ skeletal systems matured at decreased rates during periods of regular gymnastics training, but then began to catch up during periods of reduced training or else retirement, suggesting that something about gymnastics training was affecting growth and maturation. The Deakin-Washington researchers found that the greater the number of years of gymnastic training, the greater the reduction in growth; they also found that gymnasts tended to have more problems with their spinal growth, compared with elongation of the bones in the arms and legs (5).
Injuries to the distal radius
In addition, a special concern for gymnasts has been the possibility that the great stresses placed on the forearms during gymnastics training may lead to reduced growth in the radius, one of the two key bones in the forearm. The rationale behind this concern is that stress-related injuries to the distal radius are rather common in female gymnasts; potentially, these injuries could lead to premature closures of the radial growth plates and thus abnormal growth of the bone. In one review, distal-radius stress was found in 10-85% of all female gymnasts, and abnormal ulnar-radial length differences (which can occur when the distal radial growth plate closes too early) were detected in up to 20% of the gymnastic wrists which were radiographed. Four studies actually revealed significant correlations between training intensity and ulnar-radial length differences (URLD), suggesting a possible “dose-response” relationship, and three studies found greater URLD in gymnasts, compared with non-gymnasts (6).
These Australians don’t agree
Nonetheless, many experts believe that gymnastics is taking a bad rap, and they have evidence to support their contention. In a recent investigation carried out with male gymnasts, who also are shorter than the population at large, researchers from the Department of Human Biology and Movement Science at RMIT University in Melbourne, Australia, measured height, sitting height, leg length, lengths and breadths of the humerus, radius, femur, and tibia, diet, serum insulin-like growth factor (IGF-1), testosterone, and cortisol in pre-pubertal and early pubertal gymnasts and similar-aged, normally active non-gymnasts; measurements were taken every three to four months over an 18-month period(7). At baseline, the gymnasts were shorter than members of the control group, primarily because of reduced leg lengths, not sitting heights (sitting heights are basically trunk statures). In addition, the lengths and breadths of the humerus, radius, femur, and tibia were smaller in the gymnasts, compared with controls. However, no difference was found between the groups in levels of IGF-1, a compound which promotes growth, nor in concentrations of cortisol, which can retard growth and interfere with bone accretion. The truly key finding was that after 18 months of follow-up, no differences were found between the groups for changes in height, sitting height, leg length, humerus-radius-femur-tibia size, IGF-1 levels, or cortisol. In other words, the short stature of the male gymnasts was due to “selection bias” rather than gymnastics training. Gymnastics work did not slow growth in the gymnasts; rather, the individuals were already short when they began their gymnastics training, possibly because of inherited factors. Indeed, research has found that gymnasts have parents who are shorter than average(8).
Ex-gymnasts get bigger!
To keep things interesting, a similar study carried out with female gymnasts added a few new twists to the story (9). In research carried out at the Department of Endocrinology at the University of Melbourne, sitting height and leg length were measured in 83 active female gymnasts, 42 retired gymnasts, and 154 healthy control individuals. The study determined that active female gymnasts had delayed bone age (by about 1.3 years), reduced overall height, diminished sitting height, and lower leg length. However, when the analysis was narrowed to just gymnasts training for less than two years, the deficit was found only in leg length, and indication that females with shorter legs went into the sport and that gymnastics might then begin to whittle away at spinal growth. In fact, only the deficit in sitting height (a reflection of the length of the spine) worsened during the two years of follow-up (after the initial two-year period). An interesting trend, however, was that in 13 gymnasts who were monitored during the immediate 12 months after their retirement, sitting-height growth accelerated, resulting in a considerable reduction in the deficit in sitting height. In fact, adult gymnasts who had been out of the sport for eight years exhibited no deficits in sitting height, leg length, or menstrual function, an indication that the growth-retarding effects of gymnastics were not permanent. The Australian researchers involved in this study wisely concluded that the short stature of active gymnasts is partly due to selection bias (individuals with shorter legs go into the sport) and partly due to some aspect of participation in the sport (after all, sitting height was downgraded by the gymnastics training). However, there did not appear to be any long-term skeletal problems.
Gymnastics training may even do some good
Indeed, some research has suggested that gymnastics training carried out at a young age (especially before puberty) may actually confer residual benefits on bone density in adulthood and thus may decrease the risk of osteoporosis and bone fracture in later life. In research completed at the Department of Medicine at the University of Melbourne, scientists measured bone-mineral density with dual-energy X-ray absorptiometry in 45 active, pre-pubertal female gymnasts whose average age was 10.4 years, in 36 retired female gymnasts aged 25 years, and in 50 controls (10). As it turned out, bone-mineral densities were actually higher in the active, pre-pubertal gymnasts at weight-bearing sites, compared with controls, and these differences increased in magnitude over a 12-month period during which the gymnasts trained actively. In fact, over 12 months the increase in bone-mineral density was up to 85% greater in the gymnasts, compared with non-gymnasts. Among retired gymnasts, bone-mineral density was significantly higher than in control subjects at all sites examined, except for the skull (perhaps because gymnasts are taught never to land squarely on their pates); up to 20 years of retirement did nothing to lessen this gymnastic advantage. All bets are off, however, if there is a deficiency of nutrient and/or calorie intakes during gymnastic training. When that is the case, overall growth will be stunted, maturation (including sexual maturation) will be delayed, and the skeletal system may indeed end up being sub-par. Gymnasts must make sure their diets are completely adequate in calories, protein, carbohydrate, vitamins, minerals, and anti-oxidants.
Conclusions
So what’s the bottom line? Gymnasts are shorter than “normal” individuals and other athletes, but much of the height difference is caused by genes, not the gym. The only real mechanism which has been proposed to account for a gymnastics-related slowing of growth rate has been bony growth-plate damage in response to the stresses and high impacts of gymnastics training. There is some evidence to support this mechanism, but it is confined to the radius of the arm and thus does not apply to the leg-length and sitting-height differences which have been observed in gymnasts. There is simply no convincing evidence to suggest that gymnastics training forces gymnasts’ growth plates to close down prematurely. There is, however, evidence to show that some gymnasts grow at slow rates during training and engage in “catch-up” growth once gymnastics training ceases, suggesting that gymnastics can temporarily stunt growth. We believe that in many cases the cause of such slowdowns may be related to poor diet, however, rather than the rigours of gymnastics training per se.
Jim Bledsoe
References
- “Intensive Training in Elite Young Female Athletes”, British Journal of Sports Medicine, Vol. 36, pp. 13-15, 2002
- Human Growth in Context (1999). Pp. 281-289. London: Smith-Gordon.
- “Physical Growth and Biological Maturation of Young Athletes”, Exercise and Sports Science Review, Vol. 22, pp. 389-434, 1994
- “Intense Training in Elite Female Athletes: Evidence of Reduced Growth and Delayed Maturation?”, British Journal of Sports Medicine, Vol. 36, p. 310, 2002
- “Short Stature and Delayed Puberty in Gymnasts: Influence of Selection Bias on Leg Length and the Duration of Training on Trunk Length”, Journal of Pediatrics, Volume 136, pp. 149-155, 2000
- “Does Repetitive Physical Loading Inhibit Radial Growth in Female Gymnasts?”, Clinical Journal of Sports Medicine, Vol. 7(4), pp. 302-308, 1997
- “Short Stature in Competitive Prepubertal and Early Pubertal Male Gymnasts: The Result of Selection Bias or Intense Training?”, Journal of Pediatrics, Vol. 137(4), pp. 510-516, 2000
- “Growth and Development of Male Gymnasts, Swimmers, Soccer and Tennis Players: A Longitudinal Study”, Annals of Human Biology, Vol. 22, pp. 381-394, 1995
- “Short Stature and Delayed Puberty in Gymnasts: Influence of Selection Bias on Leg Length and the Duration of Training on Trunk Length”, Journal of Pediatrics, Vol. 136(2), pp. 149-155, 2000
- “Exercise before Puberty May Confer Residual Benefits in Bone Density in Adulthood: Studies in Active Prepubertal and Retired Female Gymnasts”, Journal of Bone and Mineral Research, Volume 13(3), pp. 500-507, 1998
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