After analysing the 2013 MdS runner data I was somewhat alarmed at the high rate of injuries reported by runners. In August 2013, I noted that:
“From the research data it is clear that 77% (76.92%) of all finishers used cross-training in one form or the other as part of their preparation for the event. This high figure was somehow expected as cross-training has become in recent literature the preferred training methodology to follow. What wasn’t expected was the result received once the relationship between cross-training and pre-race injuries were assessed. Among cross-trainers 33% (32.69%) had pre-race injuries; however, this figure was substantially lower at 6% (5.77%) among those who had not used cross-training as part of their preparation” (http://theroadtomds.blogspot.com/2013/08/cross-training.html).
At the time I cautioned that we should “be careful how we interpret this data as there are some unanswered questions that remain before a definitive conclusion can be reached. On the one hand, runners with an existing injury may be using cross-training to maintain cardio fitness while resting the injury or on the other hand cross-training may be the cause of the injuries. At this stage we simply don’t know”.
Sixteen months later I still don’t have a definitive answer but a certain image is emerging from a large body of research conducted by a host of credible sport scientists.
Why is Cross-Training used?
For the past 16-months I have monitored discussions on cross-training carefully and have come to group the motivation for cross-training into the following primary groups.
Running Injury Prevention (the strength argument): In essence the logic used is that excessive repetitive motion (as in running) is causing some imbalance of muscular development which, if un-addressed, will translate into some form of injury. The idea of cross-training is that the cross-training activity should address the shortcoming of the primary sport.
Running Injury Prevention (the rest argument): The second injury prevention argument leads from an over-use perspective. The aim of using cross-training in this scenario is that the runners’ muscles need to be ‘rested’ while improving, or at the very least maintain, a constant fitness level. By engaging in other cross-training activities it is claimed that the primary ‘running muscles’ are rested which prevents running injuries.
What does the Research Say?
I set out to find what the research has to say pertaining to the four primary motivations as listed above. One thing that puzzle me from the outset, and which lead me to investigate the value of cross-training, was that the 2013 MdS data showed that of the top 100 runners only 50% made use of cross-training with no runners reporting pre-race injuries in this group. Among the last 10% of the field no runner used cross-training and again no pre-race injuries were reported. Of the remaining 80% of runners 70% made use of cross-training with a pre-race injury level of 23%. This significant relationship between cross-training and pre-race injury made me question what has become standard advice from most trainers, the use of cross-training.
An extensive body of research is becoming available and I encourage my readers to take the time to read some of the findings before deciding whether or not to make use of cross-training. What I have done here is to list the findings and key rational behind the findings in a highly condensed way.
David Honea, in his research noted that the use of cross-training by runners allowed them to maintain “VO2max and lactate threshold” but that it did “not preserve running performance”. The researchers Mutton, et al, and Flynn noted that cross training had no noticeable effect on performance improvement. Dr. Tanaka from the University of Tennessee noted that cross-training will allow you to maintain cardiovascular capacity but not performance. He noted that the reason for this is that when you cross-train you are “violating the principle of the specificity of training” Dr. Willem van Mechelen, noted, after reviewing running injury data, that the only way to prevent running injuries is not to run. He stated that the harder you run and the longer the running distance, the more likely you are to get injured. Ultimately he concluded that “unless cross-training means you simply do less of your primary sport, then, don’t expect it to protect you from injuries”.
From the research summarised a number of points become clear:
Cross-training will, however, maintain VO2max and lactic threshold levels, even when an athlete is not running,
Considering these findings it is clear that cross-training is not the way to go to prevent injury through rest, as it in-itself will impair running performance, and specific running muscle fitness, which could very well result in further injury. It is equally clear that cross-training will not improve a runner’s running performance. The ability of cross-training to maintain VO2max and lactic threshold levels, however, presents a strong case for using cross-training during injury recovery. The final motivation, that of strength development as a means of preventing running injuries, hangs in the balance as a large body of evidence exist to support the notion that if you would like to run you must develop your running muscles, this speaks to Tanaka’s principle of specificity. Over development of non-running muscles can add no benefit while over taxing of running muscles through cross-training has the potential to contribute to injuries.
I am acutely aware that cross-training has become one of the ‘untouchable’ elements of the ultra-running community and that it has become standard practice of personal trainers to develop cross-training programs for their clients. I am, therefore, certain that my conclusions will be met by some level of resistance, however, the research data continues to produce the same conclusion over and over again, and that is that the only real benefit cross-training has for a runner, is when it is used during injury recovery.
Once again, thank you for reading my blog.
Honea, D. 2012. The Impact of Replacing Run Training with Cross-Training on Performance of Trained Runners. Master of Science Thesis. Appalachian State University. Online at: http://libres.uncg.edu/ir/asu/f/Honea,%20David_2012_Thesis.pdf
Mutton D., Loy S., Rogers D., Holland G., Vincent W., Heng M.; Effect of run vs. combined cycle/run training on VO2max and running performance, Med Sci Sports Exerc, 1993, 25(12), 1393-1397
Flynn M., Carroll K., Hall H., Bushman B., Brolinson P., Weideman C.; Cross training: indices of training stress and performance, Med Sci Sports Exerc, 1998, 30(2), 294-300
Mechelen, W. 1992. Running Injuries: A Review of the Epidemiological Literature. Journal of Sport Medicine. Volume 14, Issue 5. Page 320 to 335.
Tanaka, H. 1994. Effects of Cross-Training. Journal of Sport Medicine. Volume 18, Issue 5. Pages 330 to 339.