Dalen-Lorentsen T, Bjørneboe J, Clarsen B, Vagle M, Fagerland MW, Andersen TE. Does load management using the acute:chronic workload ratio prevent health problems? A cluster randomised trial of 482 elite youth footballers of both sexes. Br J Sports Med. 2020 Oct 9:bjsports-2020-103003. doi: 10.1136/bjsports-2020-103003. 

By Diego Méndez, PT


During the last decade, there has been a very large growth in publications relating training load and sports injuries. However, this association validity has recently been questioned.1,2

It is “logical” that abrupt variations in training load can lead to the development of sports injuries, but logic does not represent a source of scientific evidence. Anyone might think: «but there are so many publications that find significant associations between training load and injuries».3-6 However, as Impellizzeri et al. recently published Association does not equal Causation (citing the well-known example of shark attacks, ice cream sales, and summer).1 The fact that 2 variables coexist does not mean that 1 causes the other, but rather that they may have a common cause and that there is no direct relationship between the two.

So, What is lacking in the field of science to really know if there is a causal relationship between spikes in training load and injuries? A Randomized Clinical Trial (RCT) where a population is randomized into a group with spikes in load and another without, and the results are prospectively evaluated in terms of an epidemiological measure the author considers relevant.

This has not been done yet, but in recent days, Dalen-Lorentsen et al. published a clinical trial carried out on 482 youth soccer players of both sexes, with which they came close to meeting that goal.7

Twenty-five youth soccer teams were randomized into an intervention group (IG) and a control group (GC) (actually there were more teams but after several post-randomization withdrawals, 25 remained). In the IG, the coaches had to plan the training loads for the following week, trying to keep the acute:chronic workload ratio (ACWR) within the 0.8-1.5 values ​​proposed by Hulin et al.8 In the CG, the coaches were not given any limitations when planning. The primary outcome measure was the appearance of health problems through the Oslo Sports Trauma Research Center questionnaire on Health Problems (OSTRC-H). The follow-up was carried out for 10 months. They sought to compare the prevalence of health problems between the IG and the CG. No statistically significant differences have been found between both groups, concluding that the use of ACWR as a preventive approach is not effective.


After a critical reading of the study, and assuming my little methodological training, I present the following comments:

  • The response rate in collecting data related to training load has been very good (74%).
  • A broad definition of health problems has been used, which is recommended for this type of study.9 However, by not discriminating sports injuries from illness, the association could be underestimated, as illness could not be related to training loads. Performing a differentiated analysis between health problems in general and overuse injuries specifically, could be more illuminating. In any case, the authors have admitted this fact as a limitation of the study..
  • Another positive point of the study is to carry out an individual training load planning for each player, taking into account the data of the previous weeks of each one. This exposes the importance of individualization of planning in high performance sport.
  • The authors proposed ACWR as the only preventive approach in relation to load management. It has been stated previously that this metric should not be used in isolation, but in conjunction with other moderating variables such as chronic load (to mention a simple variable to monitor and that is related to training load).10 The ACWR reflects only the progression of training loads, and not a player’s readiness to compete. Therefore, a poorly trained player, and therefore with a higher risk of injury when exposed to a competition, could present «ideal» ACWR values.11
  • Training load data has not been included in the article. It is therefore impossible to show whether the ACWR limits proposed by the authors have actually been met in the IG.
  • The CG did not register any training load data. I consider this an important flaw in the study, since it makes it impossible to compare the loads performed by both groups.
  • Adherence to the intervention by the coaches was poor. 45.4% of the coaches reported having carried out the intervention exactly as proposed, 27.3% had carried it out partially and the remaining 27.3% did not answer whether they had carried it out. As is often the case with most preventive interventions, they only work if they are done.


To conclude with the commentary on the published study, I would like to congratulate the authors for making a great contribution with the first RCT on training load and health problems in the scientific literature. I believe that there is a long way to go and several details to improve, but the first step has been taken. Congratulations!!



  1. Impellizzeri FM, Menaspà P, Coutts AJ, Kalkhoven J, Menaspà MJ. Training Load and Its Role in Injury Prevention, Part I: Back to the Future. J Athl Train. 2020 Sep 1;55(9):885-892. doi: 10.4085/1062-6050-500-19.
  2. Impellizzeri FM, McCall A, Ward P, Bornn L, Coutts AJ. Training Load and Its Role in Injury Prevention, Part 2: Conceptual and Methodologic Pitfalls. J Athl Train. 2020 Sep 1;55(9):893-901. doi: 10.4085/1062-6050-501-19.
  3. Andrade R, Wik EH, Rebelo-Marques A, Blanch P, Whiteley R, Espregueira-Mendes J, Gabbett TJ. Is the Acute: Chronic Workload Ratio (ACWR) Associated with Risk of Time-Loss Injury in Professional Team Sports? A Systematic Review of Methodology, Variables and Injury Risk in Practical Situations. Sports Med. 2020 Sep;50(9):1613-1635. doi: 10.1007/s40279-020-01308-6.
  4. Griffin A, Kenny IC, Comyns TM, Lyons M. The Association Between the Acute:Chronic Workload Ratio and Injury and its Application in Team Sports: A Systematic Review. Sports Med. 2020;50(3):561-580.
  5. Moreno-Pérez V, Prieto J, Del Coso J, et al. Association of acute and chronic workloads with injury risk in high-performance junior tennis players [published online ahead of print, 2020 Sep 2]. Eur J Sport Sci. 2020;1-13
  6. Myers NL, Aguilar KV, Mexicano G, Farnsworth JL 2nd, Knudson D, Kibler WB. The Acute: Chronic Workload Ratio Is Associated with Injury in Junior Tennis Players. Med Sci Sports Exerc. 2020;52(5):1196-1200.
  7. Dalen-Lorentsen T, Bjørneboe J, Clarsen B, Vagle M, Fagerland MW, Andersen TE. Does load management using the acute:chronic workload ratio prevent health problems? A cluster randomised trial of 482 elite youth footballers of both sexes. Br J Sports Med. 2020 Oct 9:bjsports-2020-103003. doi: 10.1136/bjsports-2020-103003.
  8. Hulin BT, Gabbett TJ, Blanch P, Chapman P, Bailey D, Orchard JW. Spikes in acute workload are associated with increased injury risk in elite cricket fast bowlers. Br J Sports Med. 2014 Apr;48(8):708-12. doi: 10.1136/bjsports-2013-092524.
  9. Nielsen RO, Shrier I, Casals M, Nettel-Aguirre A, Møller M, Bolling C et al.. Statement on methods in sport injury research from the 1st METHODS MATTER Meeting, Copenhagen, 2019. Br J Sports Med. 2020 Aug;54(15):941. doi: 10.1136/bjsports-2019-101323.
  10. Gabbett TJ. Debunking the myths about training load, injury and performance: empirical evidence, hot topics and recommendations for practitioners. Br J Sports Med. 2020 Jan;54(1):58-66. doi: 10.1136/bjsports-2018-099784.
  11. Bowen L, Gross AS, Gimpel M, Li FX. Accumulated workloads and the acute:chronic workload ratio relate to injury risk in elite youth football players. Br J Sports Med. 2017;51(5):452-459