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It was with great interest that we read the recent BMJ editorial by professors Lohmander and Roos1 that challenged the orthopaedic and sports world to have greater evidence to support interventions. We would place ourselves firmly on their bandwagon as we examine the evidence supporting physical performance tests (PPTs) in athletes.
A PPT is aptly named as each requires an athlete to perform a physical task that is believed to be a component of sports activity. PPTs are simple, portable, low-tech assessments and as such, are quite attractive. Representative of PPTs is the single leg hop test2 and its variations (triple, crossover, and timed 6 m hop), which are ubiquitous in sports rehabilitation environments. PPTs are routinely used to predict/determine if:
An athlete will be injured at some future time based on substandard performance of the test (injury prediction);
The athlete will perform at a higher level than his or her peers for the foreseeable future based on superior performance on the test (performance prediction); or
The athlete has sufficiently progressed through rehabilitation and is ready to return to sport based on the assumption that a change in the test score is meaningful (outcome/clearance).
Clinically, there appears to be dogma that these tests are useful, particularly as a piece of the return-to-play puzzle. Let's examine if these assumptions have support.
Can PPTs predict future injury?
Two recent systematic reviews3 ,4 showed that in the lower extremity, the majority of the published evidence examining PPTs and injury is of poor quality. With respect to the most frequently studied PPTs, there is strong evidence that the vertical leap and single leg hop are not predictive of injury and that the modified star excursion balance test might predict injury in high-school basketball players.
Can PPTs predict success in professional sport?
Further, authors have questioned the predictive validity of an often-used performance battery to determine the success of National Football League (NFL) players.5 One explanation may be that PPTs are preplanned, standardised activities and preplanned activities may lack the ability to discriminate higher and lower levels of skilled individuals.6
Are PPTs valuable as outcome measures in determining return to sport?
Outcomes measures are used to gauge the extent of one's functional decline or progression. Arguably, the most important outcome to the patient and practitioner is return to sport. A great deal hinges on this decision: Too slow a return to sport negatively affects the athlete and the team; too soon a return to sport and the athlete risks reinjury. PPTs have been recommended as part of a comprehensive return-to-play algorithm7 and evidence of their sound measurement properties, and therefore, their suitability as outcome measures would help solve this dilemma. Unfortunately, isolated performance tests lack the reliability, validity and known meaningful change to serve as a discriminative outcome measures during sports rehabilitation after injury or surgery. PPTs have been mostly used to differentiate those with and without pathology. For example, the single-leg hop test2 has been studied since 1982 and it can differentiate between male athletes with and without ACL pathology and between athletes with ankle instability versus not. However, the single leg hop test2 is unable to predict injury and it loses its ability to track meaningful gains in athlete function as time from surgery increases.2 ,3 Not a stellar resume for a 33-year-old test.
Why are we surprised?
With the lack of evidence to support a key component of the return-to-sport decision, it should come as no surprise that decisions made by practitioners vary greatly.8 Returning to competitive play is the most complex form of function and achieving a successful return is multidimensional (involving both physical and non-physical milestones). Nonetheless, lessons from other clinical populations suggest that PPTs may provide utility. Researchers specialising in geriatrics and, to a lesser extent, orthopaedics (joint replacement) have demonstrated that PPTs provide valuable information that is often not captured in other forms of measures (self-report and clinician report).
Self-report measures tend to capture the athlete's mindset as it relates to function whereas PPTs are less influenced by things such as emotion or mood.
When will the sports world take up this charge in earnest? Do PPTs truly have the utility to predict a complex multidimensional concept such as injury? When will PPTs receive the appropriate validation that their self-report cousins have received? When will return-to-play become more than a rough guess? When will an editorial such as ours no longer be needed?
The answers to these questions should begin to be formulated at the First World Sports Physical Therapy Congress in Bern, Switzerland. We look forward to seeing you there.
Contributors EJH originated the idea and wrote the first draft and final draft. CC revised the initial draft and created the second draft.
Competing interests None declared.
Provenance and peer review Not commissioned; externally peer reviewed.