The term athlete conjures thoughts of elite sportsmen or women but encompasses our
active population whether development to international athlete, weekend warrior, social
netball player or runner trying to keep fit and healthy. Injuries can not only result in a
significant period of time off sport and training but also come with the added complication of
a tertiary injury on return to sport or a recurrence of the injury that has just been
rehabilitated. For sports physiotherapists one of our roles is to minimise the risk of injury
recurrence and subsequent injury on an athletes return.
There are a variety of factors that must be addressed to achieve this including:
- A progressive rehabilitation programme that is sports and individual specific
- The use of additional aids such as strapping and bracing where appropriate
- The alteration of technique as required.
- Graduated exposure to training and competition
- Ensuring appropriate criteria are achieved throughout the rehabilitation journey.
- Appropriate timing of their return related to both their physical and mental readiness.
One of the greatest challenges, particularly after significant injuries such as ACL ruptures is
how as therapists we can objectively determine if an athlete is ready to return to sport. In
recent years the use of horizontal plyometric tests such as the triple hop, cross-over hop,
and hop for distance have been utilized as the “gold standard” of return to play testing post
ACL reconstruction. These were utilized in the absence of other options, but recent research
has thrown doubt at their ability to provide valuable information for the return to play
process, particularly for knee injuries.
Force plates have historically been expensive, complicated to easy and not easy to access
and therefore not an option for private practice health care in New Zealand but with
increasing competitiveness in this market and increasing research worldwide supporting the
benefits of the use of these in the “everyday” and elite population these will become
“commonplace” in the near future in physiotherapy practices worldwide.
When utilising ACL ruptures as our example we know the majority of these injuries are non-
contact in nature, involving single leg deceleration, change of direction, landing and pivoting.
Typically, a return to sport post ACL reconstruction (or conservative management of an ACL
rupture) involves a battery of tests including strength assessment and a combination of
horizontal hop tests to assess limb symmetry in addition to sport specific assessments.
Unfortunately, what we see anecdotally and in the research is despite passing this battery of
tests reduced performance on return and high reinjury rates are common. The question must
be asked “what are these tests really telling us and is it valuable information with regards to
their return to sport?”. It has been shown (Abrams et al, Nagai et al) that horizontal hop
performance returns to “normal” from a limb symmetry perspective prior to quadricep
strength symmetry returning. This may result in us overestimating their readiness to return to
Kotsafaki et al, 2021 assessed a group of male athletes using vertical hop testing who had
been cleared to return to sport with greater than 90% limb symmetry quadricep strength and
horizontal hop distance. They identified that despite passing horizontal hop return to play
measures only 83% and 77% passed limb symmetry expectations from a vertical hop height
perspective during single leg jump and single leg drop jump respectively. In the control
group 98% and 100% limb symmetry was achieved.
In reasoning the above findings, it has been surmised that vertical and horizontal hops
measure different aspects of lower limb function. Kotsafaki et al, 2021 identified that the
knee joint contributes approximately a third to vertical hop height but only an eighth to
horizontal hop distance.
Jump height is mostly related to the concentric phase of a vertical jump task and assesses
the ability to take off with powerful extension of the hip, knee and ankle (Linthorne N).
Kotsafaki et al, 2021 concluded that the greater knee work contribution during vertical hops
likely explains the performance deficits that are more apparent than they are during
horizontal hop testing.
When considering more than the concentric propulsive phase the eccentric braking phase
and reactive strength should play an important role in the return to sport assessment of
athletes post ACL reconstruction. This requires the use of force plate technology to
effectively measure and is unable to be assessed during standard horizontal hop tests.
Force plates allow us the ability to assess a multitude of metrics including (but not limited to)
many that are relevant in this population:
- Ground contact time
- Eccentric impulse
- Concentric impulse
- Reactive strength
- Jump height
- Landing force
- Eccentric utilization ratio
be completed both bilaterally and unilaterally. Bilateral assessments give us an indication
into the strategy utilized to complete the jump while unilateral assessments give us a greater
insight into the capacity available.
There are many essential elements to ensuring a thorough return to play assessment is
completed including unilateral movement competency, change of direction and jump landing
competency, strength of the lower limb, proprioception, plyometric ability and successful
graduated return to training demands in addition to mental readiness to return. Force plates
allow us to ensure that we are assessing throughout the mid to late-stage rehab to identify
remaining deficits. At the very least this allows us to ensure that deficits are reduced to an
appropriate level and an athlete is returned as safely to their chosen sport as possible and at
a “gold standard” level allows us to assess these components throughout the rehabilitation
programme ensuring that deficits are minimized and programmes are specifically targeted to
the individuals impairments reducing unnecessary rehabilitation and an increase in time to
return to sport safely.
Research utilising force plates has grown substantially over the past few years and continues
to evolve. This growth allows for ongoing benchmarking in specific populations allowing for
expectations to be set that are not only derived from limb symmetry. The use of force plates
is not limited to ACL injuries but has the ability to provide beneficial data throughout the
rehabilitation and return to sport process of athletes with both upper and lower limb injuries.
Kotsifaki A, Korakakis V, Graham-Smith P, Sideris V, Whiteley R. Vertical and Horizontal
Hop Performance: Contributions of the Hip, Knee, and Ankle. Sports Health.
Kotsifaki A, Van Rossom S, Whiteley R, Korakakis V, Bahr R, Sideris V, Jonkers I. Single
leg verical jump performance identifies knee function deficits at return to sport after ACL
reconstruction in male athletes. British Journal of Sports Medicine 2022;0:1-10.
Abrams GD, Harris JD, Gupta AK, et al. Functional performance testing after anterior
cruciate ligament reconstruction: a systematic review. Orthop J Sports Med
Nagai T, Schilaty ND, Laskowski ER, et al. Hop tests can result in higher limb symmetry
index values than isokinetic strength and leg press tests in patients following ACL
reconstruction. Knee Surg Sports Traumatol Arthrosc 2020;28:816–22
Linthorne NP. Analysis of standing vertical jumps using a force platform. Am J Phys