Elsevier

The Knee

Volume 26, Issue 5, October 2019, Pages 978-987
The Knee

Test–retest reliability and discriminative ability of forward, medial and rotational single-leg hop tests

https://doi.org/10.1016/j.knee.2019.06.010Get rights and content

Abstract

Background

Single-leg hop tests are commonly performed in the forward direction to evaluate functional performance. However, athletes move in multiple directions during pivoting sports. The first aim of this study was to examine test–retest reliability of single-leg hop tests in the forward, medial and rotational direction in non-injured athletes. Second, the discriminative ability to detect leg asymmetries with these hop tests in anterior cruciate ligament (ACL) reconstructed athletes was determined.

Methods

Sixteen recreational non-injured participants (eight females, eight males; 22.4 ± 1.9 years) were tested twice (one-week interval) and performed the single hop for distance (SH), triple hop for distance (TH), medial side triple hop for distance (MSTH) and 90° medial rotation hop for distance (MRH). Intraclass correlation coefficients (ICCs), standard errors of measurement (SEM) and smallest detectable differences (SDD) were calculated. Discriminative ability was determined in 32 ACL-reconstructed participants (four females, 28 males; 24.4 ± 4.6 years; six months postoperative) who performed the same hop tests once.

Results

The ICCs ranged between 0.93 and 0.98. The SEM and SDD were respectively 2.6–4.1% and 7.2–11.3% of the mean hop distance of the group. The proportion (%) of ACL-reconstructed participants passing the ≥ 90% limb symmetry cut-off was 62.5 (SH), 59.4 (TH), 40.6 (MSTH) and 46.9 (MRH).

Conclusion

Excellent test–retest reliability of forward, medial and rotational hop tests was found. This allows clinicians to make informed interpretations of changes in hop test distances when retesting athletes. Medial and rotational hop tests are more likely to show limb asymmetries in ACL-reconstructed participants compared to forward hop tests.

Introduction

Physical performance measures such as single-leg hop tests are frequently used to assess the functional status of an athlete, detect limb asymmetries and monitor progression throughout an intervention [1], [2], [3], [4]. These tests are easy to administer and only require minimal equipment, time and expertise [1].

A series of four single-leg hop tests including single hop for distance (SH), triple hop for distance (TH), crossover hop for distance and 6 m timed hop was originally described by Noyes et al. [5]. A limitation of the original hop test battery is that these tests predominantly consist of straight movements in the forward direction [6]. However, athletes move in multiple directions during pivoting sports [7]. Exclusively focusing on forward hop tests might limit the potential to elicit relevant deficits, typically expressed in terms of limb asymmetry, in function of performance enhancement, prevention or rehabilitation [8], [9], [10]. However, studies evaluating both relative and absolute reliability measures of multidirectional hop tests in comparison with forward-directed hop tests are lacking. Several test–retest reliability studies focusing on forward hop tests have been published in non-injured [2], [11], [12], [13], [14], [15], [16] and injured athletes [3], [15], [17], but the methodological quality is generally low [1], [18], [19]. Before multidirectional hop tests can be used confidently as an outcome measure across an intervention, it is critical that the measurement properties are known [1], [18], [19]. This will allow clinicians to make informed clinical decisions whether an observed change in the performance of hop tests is a meaningful change.

A decreased performance on the traditional set of hop tests has been related to self-reported function [20], [21] and re-injury risk after anterior cruciate ligament (ACL) reconstruction [22], [23], [24]. Nevertheless, increased limb asymmetry has been reported during the side hop compared to the SH in the forward direction, leading to a lower percentage of ACL-reconstructed patients reaching satisfactory limb symmetry [17], [25], [26]. Therefore, the inclusion of multidirectional hop tests within the return to sport decision-making process after ACL reconstruction has been recommended to detect limb asymmetries [6], but more rigorous data are needed to support this suggestion.

The first aim of this study was to examine the test–retest reliability of single-leg hop tests in the forward, medial and rotational direction. Secondly, we aimed to investigate the discriminative ability to detect limb asymmetries of medial and rotational hop tests, in comparison with forward hop tests in a population of participants after ACL reconstruction.

Section snippets

Test–retest reliability in non-injured participants

Sixteen recreational participants (eight females, eight males; age: mean ± SD = 22.4 ± 1.9 years; weight: mean ± SD = 68.1 ± 10.3 kg; height: mean ± SD = 176.3 ± 9.3 cm; body mass index: mean ± SD = 21.8 ± 2.1 kg/m2) participated in the study. All participants participated in multidirectional sports (11 football (soccer), four volleyball, one multisport including kickboxing) [7]. Inclusion criteria for the study were (1) age 18–45 years, (2) no musculoskeletal injuries of the lumbar spine or

Test–retest reliability in non-injured participants

Excellent test–retest reliability was found for all hop tests, with ICC values ranging from 0.93 to 0.98. The SEM for SH, TH, MSTH and MRH were respectively 5.7–7.1 cm, 14.1–16.3 cm, 12.0–15.4 cm and 5.9–7.0 cm (2.6–4.1% of the mean distance of each hop test). The SDD for SH, TH, MSTH and MRH were respectively 15.7–19.6 cm, 39.1–45.1 cm, 33.3–42.7 cm and 16.4–19.5 cm (7.2–11.3% of the mean distance of each hop test). The absolute differences, ICC, SEM, SDD and SDD/hop distance values of all hop

Discussion

The main finding of this study was that medial and rotational hop tests have excellent test–retest reliability, similar to forward hop tests. Additionally, leg asymmetries in hop distances are more likely revealed with medial and rotational hop tests, compared to forward hop tests.

In order to interpret differences during and/or following an intervention appropriately, an indication of the test–retest reliability is necessary. This is the first study to determine relative and absolute

Conclusion

Excellent test–retest reliability of forward, medial and rotational hop tests was reported in this study. These results allow clinicians to make informed interpretations of changes in hop test distances when retesting athletes. Medial and rotational hop tests are more likely to elicit limb asymmetries compared to forward hop tests in non-injured and ACL-reconstructed participants.

Acknowledgements

None.

Declaration of Competing Interest

None.

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