Original articleTest-retest reliability and convergent validity of the Ruffier Index in children under 12 years oldFiabilité test-retest et validité convergente de l’index de Ruffier chez les enfants de moins de 12 ans
Introduction
Physical fitness is a health indicator; therefore, its assessment at an early age is considered a particularly important prevention strategy, as it represents the point of departure from which to implement measures aimed at its improvement [1]. Even though it is laboratory tests that allow for an optimal assessment of physical fitness, field tests emerge as an interesting alternative, especially in school environments and physical education contexts, since they are more economical and much easier to administer.
Among the diverse field-based tests available to assess fitness, the Ruffier test [2] takes a prominent place. The Ruffier test measures the cardiovascular adaptation to exercise by means of a straightforward protocol that allows for the calculation of a post-effort recovery index, known as Ruffier Index (RI), which derives from the heart rate (HR) record obtained at different points.
The Ruffier test has been considered as a useful measuring tool for assessing physical capacity in healthy children [3], and is still being used for this purpose [4], [5], [6]. In spite of this, the existing scientific evidence regarding its reliability and validity in this population is scarce. This is a matter of concern, since these two criteria are critical in ensuring the integrity and credibility of data derived through field-based tests [7].
In accordance with Weir [8], the type of reliability most widely addressed in the field of sports science is test-retest, since it indicates the degree of consistency of a physical performance measure over time in a stable population. Validity is the extent to which a test accurately assesses the domain that is intended to be measured. Validity can be determined by demonstrating that two tests that measure the same construct correlate well (convergent validity).
Although some authors argue that the RI has been, and still is, being used as way of collecting information regarding aerobic fitness [9], the effort demanded by its protocol is short and submaximal. Therefore, it is considered and anaerobic test [10]. However, since the RI tests the efficacy of the circulatory system to respond to submaximal exercise, it provides information regarding post-exercise restitution capacity, a physiological variable that has been identified as belonging to the group of energy capacities with an aerobic basis [11]. In this regard, in healthy adults, the performance of squats over a 45second period has been confirmed as a submaximal test that allows for the indirect estimation of maximal oxygen uptake (VO2max) [12]. Therefore, it is plausible to think that the convergent validity of RI can be identified by means of analysing the degree of correlation between this index and the VO2max. Under these circumstances, the objective of this study was to analyze the test-retest reliability and convergent validity of RI when performed by children, with the intention of informing on its potential applicability to this population.
Section snippets
Participants
All the children who were invited to take part in the experiment were enrolled in the last cycle of primary education in four state schools of the north of Spain. Those children who presented any health-related problem that could prevent them from performing the tasks the program involved were excluded. Before the experiment started, written consents were requested from the parents and school headmasters. This study was reviewed and eventually approved by the local ethics committee.
Anthropometry
The
Results
Out of the 364 participants who were initially tested, 12 could not finish all the tasks; therefore, the final sample consisted of 352 children (mean age: 10.41 ± 1.02 years; 47.2% girls). The anthropometric characteristics of the sample, as well as the mean values obtained for RI and Course-Navette, both in general and stratified by gender, are shown on Table 1. The RI obtained when HR was registered subjectively differed from the RI obtained when HR was registered objectively, both in the test (RIp
Discussion
The results of this research indicate that the RI showed a “poor” test-retest reliability when performed by children under 12$years of age. We did not find any study that provided information regarding the test-retest reliability of the RI in this population, a fact that limits the discussion of our findings. In a sample of twelve moderately active university students, Nsenga et al. [20] observed that the test and retest scores of Ruffier were fairly closely correlated with each other (r = 0.78).
Conclusion
The findings of this study indicate that the RI shows a “poor” test-retest reliability and a convergent validity ranging from “acceptable” to “poor”, when administered to children under 12 years of age. This information should be taken into account when using this test to assess fitness level in this population.
Disclosure of interest
The authors declare that they have no competing interest.
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