Category: Contributor’s corner

Rugby and CTE

By Ken Quarrie 

I have been seeing claims that some people are “sowing doubt” with respect to CTE (Chronic Traumatic Encephalopathy) and are thus acting like tobacco companies did with respect to heart diseases and lung cancer. I want to make a few comments about this. Before I get to the CTE issue, it is worthwhile that I put some background about me on the record, so that people are able to judge whether I am likely to have biases that might sway me to one position or another.

I was brought up in New Zealand, in a family where rugby was *very* important. Dad played rep rugby for Wanganui and Waikato, and was an All Blacks triallist. As a kid I was a fan and obsessively read books about rugby and the All Blacks. I played the sport from childhood until my late 20’s. I had some really enjoyable times along the way. I also sustained (at least) five concussions. I was immersed in the Otago Uni/Dunedin rugby heavy drinking culture.

I found that as I got older there were fewer aspects of the “rugby” culture with which I identified – @XTOTL captures some of that here: I also had a good friend injured at the age of 15 in a scrum. He has been in a wheelchair since 1984.

As well as rugby, as a kid I loved science. I have managed to combine those two loves into a career. I wouldn’t call myself a rugby “fan” anymore. I am a rugby scientist, and it helps to have a little distance from your object of study. Nevertheless, I still work for NZ Rugby (conflict of interest klaxons!). Having worked on independent research studies examining risks for injury in the 1990’s, I took a role with NZ Rugby in 2000 as their first “Injury Prevention Manager”. I realised that, as a scientist, my employment represented a conflict of interest, but I believed I could have a greater impact on improving player safety and welfare from within rugby than from the outside.

I have been adamant with NZ Rugby and World Rugby that I must be allowed to conduct research without interference about what I can study, how I can analyse it, and what I can say about it. A look at my research outputs will reveal an eclectic mix of rugby studies. So when people “poison the well” by implying that any research funded by or conducted by sports organisations must necessarily be “suspect” I feel personally attacked. Doing good science is what I care about.

Doing good science is what I care about.

From a personal level, the welfare of players has, and does, take precedence for me over considerations of “tradition” or “maintaining the essence of the game”. But managing risks does not imply “eliminating all risks”. Reasonable people can look at an issue and disagree about it.

So – the “tobacco company line”. Tobacco companies systematically downplayed the risks of their products, and attempted to “sow doubt” in the public mind. How is the CTE/concussion debate different? A key difference is that, despite there having been strong claims made about what causes CTE, how it develops, and what clinical outcomes it leads to, the reality is that the science of CTE is very young. There really *is* a lot of doubt about a number of the issues!

The issues include whether CTE is, as has been claimed by some, a primary, progressive neurodegenerative disease. Questions remain about the cause(s) of the pathology. Questions remain about the “pathognomonic lesion” – i.e. what distinguishes CTE from other pathologies. Questions remain about the prevalence of the pathology. MAJOR questions remain about the relationship between having CTE pathology in the brain and any given clinical outcome. Do I think brain injuries are bad for health? Yes, undoubtably. I also think that the public perception of the strength of the evidence, and the prevalence of CTE as a public health issue doesn’t match the scientific understanding of it *at this point*.

So to accuse “rugby” as having acted like tobacco companies to sow doubt about CTE is simply a smear, and a lazy and demonstrably false one at that.

If former rugby players are struggling – for whatever reason – my heart is with them. I pledge to do my best to understand more about the long term health outcomes of playing rugby, so that people can better understand the risks and make informed choices about play. People involved in rugby, like Colin Fuller, @Sharief_H, @drkeithstokes, @drsimonkemp, @mattjcrossie, @Scienceofsport and yours truly and many others have identified and documented risks in rugby via research studies and injury surveillance. Many changes to rugby have been made as a result of that work. RugbySmart, BokSmart and other injury prevention programmes have been widely recognised within the sports science/sports medicine communities as having had positive effects on the risks of injuries. Likewise, the @NZRugbyFound has done great work on tertiary prevention. So to accuse “rugby” as having acted like tobacco companies to sow doubt about CTE is simply a smear, and a lazy and demonstrably false one at that.

Ken Quarrie is the Chief Scientist for NZ Rugby. All views expressed are his own, and do not necessarily represent the position of his employer. The above article was compiled, with permission, from a thread of tweets by @KenQuarrie. For more on the topic, you can follow Ken at @KenQuarrie. You can also view Ken’s publications here – Ken’s Google Scholar Profile. 

The string that gets pulled too often: the hamstring

by Tim Klein

Have you ever watched an athlete pull up, holding the back of their thigh, with an agonising look on their face? Some of you may have even thought to yourself: “there goes his/her hamstring.”

Well you are not alone. Scientists have also taken notice of the menace that are acute hamstring injuries and are devising methods to prevent the very scenario described above. In soccer players, hamstring muscle injuries are responsible for 12-16% of all injuries1 – with an injury occurring every 1000 hours of exposure (during the match or training)2. Hamstring injuries are particularly nasty because they have a habit of coming back (a group of Danish athletes showed they have 25% chance re-injuring it the following season)3. The question then remains, how to reduce the risk of these injuries? Well, a logical answer might be to strengthen the muscle, but which exercises work best?

Peterson and colleagues4 set out to test if eccentric strengthening of the hamstring, using an exercise called the ‘Nordic hamstring exercise’, can protect the hamstrings from new and/or recurring hamstring injuries.

They looked at 50 Danish soccer teams that were in two groups: Control and Intervention. The difference being that the intervention group were given a 10-week program of the Nordic hamstring exercise. The injury occurrences were then tracked over the next 12 months.

They found that the Nordic hamstring exercise program reduced the injury rate of new injuries (i.e. not reported in the 12 months prior to the study) by 60% and the injury rate of recurring injuries by a whopping 85%! These results suggest that this simple, time- and user-friendly exercise could be used to subdue the menace of hamstring injuries.

The study looked at soccer players, but one could argue that these findings can be carried over to any sport involving running. These types of injuries often occur while running and not necessarily during a sports-specific movement. It could then be suggested that the eccentric strengthening of the hamstring could help keep these nasty injuries at bay in any sport that involves running or sprinting.

This all sounds amazing, but it is important to consider some factors that this study did not do. Firstly, this study was open (i.e. all the teams – including the control – knew the aims of the study). This could have led to bias in reporting or training. Secondly, the authors did not record compliance to the program after the first 10-week period. This means that there was no way of knowing what sessions the teams did. For example, they could have used other eccentric strengthening exercises. This means that the Nordic hamstring exercise may not be the wonder-exercise it is made out to be.

However, a recent review by van Dyk and colleagues5 showed that including the Nordic hamstring exercise in injury prevention programs can reduce hamstring injuries by up to 51%.

To conclude, the Nordic hamstring exercise seems effective in preventing hamstring injuries. It is simple, cost-effective and would be easy to add to a team workout regimen. Like with any new exercise, it should be eased into the program to reduce stiffness the following morning. It seems a viable option to make that darn string harder to pull.


  1. Arnason, A., Sigurdsson, S.B., Gudmundsson, A., Holme, I., Engebretsen, L. and Bahr, R., 2004. Risk factors for injuries in football. The American journal of sports medicine32(1_suppl), pp.5-16.
  2. Ekstrand, J., Hägglund, M., Kristenson, K., Magnusson, H. and Waldén, M., 2013. Fewer ligament injuries but no preventive effect on muscle injuries and severe injuries: an 11-year follow-up of the UEFA Champions League injury study. Br J Sports Med47(12), pp.732-737.
  3. Petersen, J., Thorborg, K., Nielsen, M.B. and Hølmich, P., 2010. Acute hamstring injuries in Danish elite football: a 12‐month prospective registration study among 374 players. Scandinavian journal of medicine & science in sports20(4), pp.588-592.
  4. Petersen, J., Thorborg, K., Nielsen, M.B., Budtz-Jørgensen, E. and Hölmich, P., 2011. Preventive effect of eccentric training on acute hamstring injuries in men’s soccer: a cluster-randomized controlled trial. The American journal of sports medicine39(11), pp.2296-2303.
  5. van Dyk, N., Behan, F.P. and Whiteley, R., 2019. Including the Nordic hamstring exercise in injury prevention programmes halves the rate of hamstring injuries: a systematic review and meta-analysis of 8459 athletes. British journal of sports medicine53(21), pp.1362-1370.

Merging Talent and Athletic Development: the Composite Youth Development (CYD) Model