Lower Extremity Performance Measures in Athletes, Part 1

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´╗┐Lower Extremity Performance Measures in Athletes, Part 1

Abstract and Introduction

Abstract


Objective To review the measurement properties of physical performance tests (PPTs) of the knee as each pertain to athletes, and to determine the relationship between PPTs and injury in athletes age 12 years to adult.

Methods A search strategy was constructed by combining the terms 'lower extremity' and synonyms for 'performance test', and names of performance tests with variants of the term 'athlete'. In this, part 1, we report on findings in the knee. The Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) guidelines were followed and the Consensus-based Standards for the selection of health Measurement Instruments (COSMIN) checklist was used to critique the methodological quality of each paper. A second measure was used to analyse the quality of the measurement properties of each test.

Results In the final analysis, we found 29 articles pertinent to the knee detailing 19 PPTs, of which six were compiled in a best evidence synthesis. The six tests were: one leg hop for distance (single and triple hop), 6 m timed hop, crossover hop for distance, triple jump and single leg vertical jump. The one leg hop for distance is the most often studied PPT. There is conflicting evidence regarding the validity of the hop and moderate evidence that the hop test is responsive to changes during rehabilitation. No test has established reliability or measurement error as assessed by the minimal important change or smallest detectable change. No test predicts knee injury in athletes.

Conclusions Despite numerous published articles addressing PPTs at the knee, there is predominantly limited and conflicting evidence regarding the reliability, agreement, construct validity, criterion validity and responsiveness of commonly used PPTs. There is a great opportunity for further study of these tests and the measurement properties of each in athletes.

Introduction


Tests of physical performance are employed at multiple levels and throughout the sporting world. These tests, in combination, are being used more frequently as part of pre-season screening, although test findings appear to be more specific than sensitive. The advantage of physical performance tests (PPTs) is that the tests are easy to administer, are not time consuming and do not require a great deal of expertise. Further, PPTs do not require expensive equipment, and can be completed in multiple settings and locations.

For PPTs to be useful as outcome measures, we need to know what constitutes a meaningful change in score. Further, these tests should possess some key measurement properties such as reliability, validity and responsiveness. A meaningful change in score is often captured by the minimal clinically important difference or the minimal important change (MIC), which is the smallest change in a score detectable by the patient. The MIC should be greater than the minimal detectable change in order for the PPT to identify a relevant change in the patient's status. Reliability is the degree to which a measurement is free from error. The interested reader is also directed to Davidson's discussion of these topics.

Validity discerns whether a test measures what it is intended to measure. There are different types of validity. Criterion validity is a measure of how well the PPT under investigation correlates with a gold or criterion standard. Included in criterion validity is predictive validity, which would be, for example, how well a PPT predicts an outcome such as injury. Construct validity, the degree to which a PPT correlates with a latent construct such as strength or function, can be of either a convergent or divergent/discriminant nature. In convergent validity, one would expect a PPT that measures function to correlate well with, say, another test of function such as an established self-report measure. Discriminant validity is the opposite: one would expect low correlation between two measures that assess different constructs. Whether PPTs provide useful information is of some debate and whether each test possesses the necessary measurement properties to be considered a valuable outcome measure is also a matter of contention.

To examine the evidence behind individual PPTs, we conducted a systematic review of measures typically used to assess lower extremity performance in athletes. Our goals in conducting this systematic review were to coalesce the literature on PPTs, subject the literature and measurement properties to a quality analysis, and provide a best evidence synthesis. We hypothesised that PPTs would have moderate evidence regarding their measurement properties but have little or no ability to predict injury in athletes.

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