Exercise
12 Mar 2023
High-Intensity Training: benefits and potential injury risk — Part III
In a 2019 study that our search associated with the relationship between the rising popularity of HIIT and a consequent rise in the prevalence and incidence of injury, the authors concluded that people who practise some form of HIIT are exposed to a greater risk of injury, mainly to the shoulders and knees.
The researchers analysed the American national injury register (National Electronic Injury Surveillance System – NEISS) from 2007 to 2016 and found more than three million records they considered to be associated with HIIT. Most of the injuries recorded involved the knees, shoulders and ankles, with men aged between 20 and 39 the most affected. Comparing the period from 2007 to 2011 with 2012 to 2016, they observed a significant increase in injuries, which they correlated with the growing popularity of HIIT — a rise in popularity they measured through Google search trends. In our view, the conclusions the authors reached do not rest on a good level of evidence. In presenting the NEISS records as sufficient proof for associating injuries with HIIT, they risked a crude generalisation: those records do not include a description of the type and characteristics of the training the person was doing, only a brief description of what happened and the equipment involved.
The popularity of high-intensity training has remained high in recent years, and the large body of scientific work on the subject has followed that trend. However, while the effects of this kind of training and its practical application in different contexts are well studied — and, as we have seen, those contexts are not limited to recreational and sporting activity but also extend to the clinical setting — the possible harms, in particular the prevalence and incidence of injury and how to avoid it, are in our view under-represented. Most studies addressing injury directly are tied to one particular type of high-intensity training, CrossFit, while other types appear more often only indirectly where injury is concerned.
The level of evidence in the studies that looked at injury directly cannot be considered the highest: in most cases these were retrospective studies based on self-completed questionnaires. We do not mean that this choice is inappropriate or poorly grounded in the literature, but rather that the community of professionals who stand to benefit from applying high-intensity training would be better served by studies with a higher level of evidence. Randomised controlled trials exploring this theme would certainly give practitioners more confidence, as well as helping to dispel myths and inappropriate intervention protocols.
What emerged clearly from our analysis is that in this kind of training — which can bring many benefits — the best way to avoid injury is to ensure adequate, supervised preparation, making sure the technical fundamentals are understood and correctly implemented and that protocols are respected. The considerable technical demand of the exercises normally used in this type of training, combined with a lack of supervision and irregular practice, appear to be the main risk factors for injury.
References:
Rynecki, N. D., Siracuse, B. L., Ippolito, J. A., & Beebe, K. S. (2019). Injuries sustained during high intensity interval training: are modern fitness trends contributing to increased injury rates? J Sports Med Phys Fitness, 59(7), 1206-1212. https://doi.org/10.23736/S0022-4707.19.09407-6