At some point in your life, you might have heard the phrase: “What is not defined, cannot be measured. What is not measured, cannot be improved. What is not improved, is always degraded”. This sentence highlights the importance of measuring variables. In this sense, measurement is as important as the test chosen to do so. Not all tests assess the same parameters, which makes it difficult to choose the right one.

The functional assessments of players has traditionally been done through laboratory tests, which require specialised personnel and equipment that increase its cost. Also, these are individual tests, so the time needed increases when a group is to be assessed. These limitations, as well as the fact that most tests are not specific for football, have led to the development of field tests in the last few years that allow assessing the physical condition associated with football, reflect the real demands of this sport, and at the same time it involves less time and money.

Yo-Yo Intermittent Recovery Test

Currently, a test that is mostly used by coaches and trainers is the Yo-Yo Intermittent Recovery Test or Yo-Yo IR.¹ The Yo-Yo IR has been validated in footballers² and has proven to be more sensitive to changes in performance than the maximum oxygen consumption (VO_2max).³ There are three versions of this test: level 1, level 2 and submaximal. The Yo-Yo IR-1 assesses an individual’s ability to repeat high-intensity intermittent efforts, which inversely relates to the injury risk in footballers.⁴ It consists in racing back and forth until exhaustion within a 20-metre stretch and at a speed that increases progressively following a “beep” emitted at regular intervals, marking the pace of the race. In between each back-and-forth period, there are 10-second pauses for active recovery. The test starts at 10 km/h, and it is designed for younger athletes or amateurs who have less cardiorespiratory capacity. The Yo-Yo IR-2 starts at 11.5 km/h and, unlike the previous one, it is designed for elite athletes. On the other hand, the submaximal test could be useful to carry out the physical evaluation during an injury rehabilitation or competitive periods.⁵

The Yo-Yo IR is a field test widely used to assess the VO_2max as an alternative method to that done in the lab. In fact, a review published in the prestigious Sports Medicine magazine, recommended its use to measure the VO_2max in footballers when there is not a laboratory available.⁶ A group of researchers from the Department of Nutrition, Exercise and Sports, University of Copenhagen, Denmark proposed some formulas to estimate the VO_2max based on the results obtained from the Yo-Yo IR:³

Yo-Yo IR-1: VO_2max (ml/min/kg) = distance covered in the test (metres) x 0,0084 + 36,4

Yo-Yo IR-2: VO_2max (ml/min/kg) = distance covered in the test (metres) x 0,0136 + 45,3

Yo-Yo Intermittent Recovery Test and other field tests

The relationship between the Yo-Yo IR and other field tests has been studied with young footballers and elite athletes. A research carried out by the California State University (California, USA) with female university football players showed a great correlation between the distances covered in the Yo-Yo IR-1 and Yo-Yo IR-2.⁷ However, the results were not similar between the Yo-Yo IR-1 or Yo-Yo IR-2 with other field tests such as the 30-m Sprint Intervals, the Sixty-Yard Shuttle or the Pro-Agility Shuttle.⁷ On the other hand, in sub-elite and elite Norwegian and Dutch footballers, there was a correlation between both Yo-Yo IR, as well as a correlation between the Yo-Yo IR-2 and the Repeated Sprint Ability (better known as RSA).⁸ It is worth mentioning that there was a moderate correlation between the Yo-Yo IR-2 and the VO_2max measured from a laboratory in sub-elite athletes, although this was not the case for elite athletes. There was a correlation between the Yo-Yo IR-1 and the VO_2max assessed at a laboratory in both groups of footballers.⁸

Conclusions

Having a way of estimating the VO_2max in a simple and not expensive way provides a wide range of possibilities for coaches and trainers of most football teams (those that are not professional and most surely do not have a laboratory to measure these variables). Also, due to its specificity, and simplicity to be carried out, the Yo-Yo IR is a very useful test to examine the ability to make repetitive high-intensity intermittent efforts. And the fact that it can be done to a group of athletes at the same time facilitates its implementation for big groups as it is usually the case in football teams.

Javier S. Morales

References:

1. Krustrup P, Mohr M, Amstrup T, Rysgaard T, Johansen J, Steensberg A, Pedersen PK, Bangsbo J. The yo-yo intermittent recovery test: physiological response, reliability, and validity. Med Sci Sports Exerc. 2003;35(4):697-705.
2. Krustrup P, Mohr M, Nybo L, Jensen JM, Nielsen JJ, Bangsbo J. The Yo-Yo IR2 test: physiological response, reliability, and application to elite soccer. Med Sci Sports Exerc. 2006;38(9):1666-73.
3. Bangsbo J, Iaia FM, Krustrup P. The Yo-Yo intermittent recovery test: a useful tool for evaluation of physical performance in intermittent sports. Sports Med. 2008;38(1):37-51.
4. Malone S, Owen A, Newton M, Mendes B, Collins KD, Gabbett TJ. The acute:chonic workload ratio in relation to injury risk in professional soccer. J Sci Med Sport. 2017;20(6):561-565.
5. Fanchini M, Castagna C, Coutts AJ, Schena F, McCall A, Impellizzeri FM. Are the Yo-Yo intermittent recovery test levels 1 and 2 both useful? Reliability, responsiveness, and interchangeability in young soccer players. J Sport Sci. 2014;32(20):1950-1957.
6. Stølen T, Chamari K, Castagna C, Wisløff U. Physiology of soccer: an update. Sports Med. 2005;35(6):501-36.
7. Lockie RG, Jalilvand F, Moreno MR, Orjalo AJ, Risso FG, Nimphius S. Yo-Yo Intermittent Recovery Test Level 2 and Its Relationship With Other Typical Soccer Field Tests in Female Collegiate Soccer Players. J Strength Cond Res. 2017;31(10):2667-2677.
8. Ingebrigtsen J, Bendiksen M, Randers MB, Castagna C, Krustrup P, Holtermann A. Yo-Yo IR2 testing of elite and sub-elite soccer players: performance, heart rate response and correlations to other interval tests. J Sport Sci. 2012;30(13):1337-45.