The news release reports on a British study comparing bone development in 12- to 14-year-old boys who played football (or soccer, as it’s known in the United States) to those involved in competitive cycling or swimming and to active boys who did not regularly play sports.
The release touts the bone-building benefits of playing football but omits that the study on which it reports identified almost no significant difference in bone development measures between highly competitive soccer players and boys who were active but not involved in sports. It also left out any discussion of the risks or the financial costs associated with playing soccer competitively.
Bone development during childhood and adolescence has lifelong implications for health. Poor bone development during youth increases adults’ risk for osteoporosis and fractures, which can lead to other negative health outcomes. The news release also is important because soccer is the most popular sport in the world. In 2014, more than 3 million youth (boys and girls, ages 5-19) were members of the U.S. Youth Soccer organization, which claims to include 85 percent of all registered youth soccer players in the United States. However, the rate of youth soccer injuries also has increased, more than doubling between 1990 and 2014.
It’s important to note that the release (or the study on which it’s based) does not offer any guidance to the families of the vast majority of children who are more casual athletes, nor does it mention what role weight-bearing sports might play on girls’ bone development. At this point, the conclusions could be useful to researchers continuing to study exercise and bone health, but readers should approach these conclusions with caution.
The news release provides no discussion of costs. While a soccer ball isn’t terribly expensive, the boys involved in this study weren’t casually kicking the football around the back yard or the neighborhood soccer pitch; they were “aspiring professionals who played as much as nine hours a week,” according to the study’s lead author. That level of training almost guarantees that the boys were participating in traveling soccer teams, and while the costs might be lower in the United Kingdom, where the study was conducted, in the United States, playing on a traveling soccer team is far from cheap. A September 2015 USA Money article described a California family who spent $17,500 annually for their four boys to play competitive soccer, including club fees of $675 per month, $1,500 per year for a private coach, more than $1,000 for cleats and other gear, $100 participation fees per child per tournament, along with the costs of tournament travel. Those costs, of course, might well be higher than average, but the bottom line is that the news release provides no information about the likely cost of having a child playing competitive soccer/football.
The news release states that lower back bone mineral content (BMC) among football players was 7 percent higher than that for adolescents who were involved in cycling; BMC measurements in the upper leg were 5 percent higher. This is the only specific information offered in the release, although the study found statistically significant differences – none of them reflecting differences of more than 10 percent — in other comparisons between the swimmers, cyclists and football players. Most importantly, the news release doesn’t explain that the only statistically significant difference between football players and the boys in the active control group was higher scores on a measure of vitamin D levels.
Furthermore, the release offered no context of the benefit. Five percent higher BMC in healthy individuals who all have BMC levels within normal limits is not of certain clinical significance. What sort of benefit could a regular individual playing soccer expect if high level athletes saw a 5 percent increase?
The news release included no discussion of the potential harms of playing soccer, especially in a highly competitive environment. In a 2010 report on soccer injury risks, the American Academy of Pediatrics noted that soccer “has a higher injury rate than many contact/collision sports such as field hockey, rugby, basketball and (American) football.” Lower leg and foot injuries are most common, and the rate of concussions is similar to those suffered by American football and hockey players.
The news release excluded some important aspects of the study methods and findings. First, this was an observational study. The authors appear to have accounted for many of the factors that could influence bone growth, but there could be others – such as nutritional intake – that would have influenced the findings. The discussion section of the study states that football players’ increases in BMC were higher than those for active youth not involved in regular sports; however, those differences were not statistically significant. In addition, the study notes that soccer players spent more hours training and had trained for more years than had either cyclists or swimmers, a fact that would have been expected to contribute to greater bone mass among the soccer players. The data analysis accounted for bone mass at the beginning of the study but did not include hours spent training as a variable in the final comparison of the young athletes’ bone development. Finally, of course, the study did not include any female athletes, so it provided no information about whether playing soccer might benefit adolescent girls’ bone growth.
The news release notes that poor bone growth before age 30 can increase an individual’s risk of fractures and osteoporosis later in life, but it does not engage in disease mongering.
The news release notes that funding for the study came from a Marie Sklodowska-Curie fellowship, provided by the European Union. The researchers do not appear to have any conflicts of interest in connection with this study.
The study itself compared the bone growth benefits of playing soccer to those of participation in non-weight-bearing sports (cycling and swimming), providing one discussion of alternatives. In addition, the news release quotes the article’s lead author, Dr. Dimitrios Vlachopoulos, noting that other high-intensity weight-bearing sports such as tennis, basketball and badminton could have similar effects as playing soccer. This is particularly important given that the study findings actually showed no significant differences in bone growth between boys who played football competitively and boys who were active but not involved in any regular sports participation.
It would have been helpful if the release had mentioned some of the other comparative benefits/harms of soccer with swimming and cycling such as cardiovascular benefits, the overall fitness benefits, and the potentially better safety profiles of swimming and cycling versus soccer.
The release doesn’t mention availability. True, soccer is the world’s most popular sport and there are opportunities to play — but not all families are able to invest the time and expense required for intense participation in a sport.
The original article notes that this was the first study to comprehensively evaluate bone acquisition in adolescent male athletes. However, health experts have long understood that exercise is a key to healthy bone growth. The most important finding of the study, which is addressed in the news release, actually may have been that participation in non-weight-bearing sports such as cycling or swimming does not seem to produce better bone growth.
The headline and first sentence of the news release state that playing football improves bone development in boys, but the data suggest that for all but one measure (a test of vitamin D levels), there were no significant differences between boys who played football and active, non-sports-involved boys. Thus, although playing football likely does improve bone development, this study did not show that it improved bone development over active participation in other weight-bearing sports such as running, tennis, weight-lifting, etc. In addition, because the study only examined boys competing at high levels in their sports, it provides little information about the value of more casual participation in soccer.