Power Testing Without a Force Plate: What the Drop Jump Can Tell You in Clinic
Ask a physiotherapist to test knee extension strength and most will reach for a handheld dynamometer without thinking twice. Ask the same clinician to test lower limb power and the conversation usually stalls at "we don't have a force plate." Power gets left out of the assessment entirely, or it gets reduced to a subjective impression of how a patient looks when they jump. Neither is good enough for a domain that sits directly on the pathway back to running, cutting, and field sport.
The drop jump is one of the most useful tools you already have access to, and it doesn't need a force plate to be useful. What it needs is a consistent protocol, a way to capture ground contact time and jump height, and a normative framework to judge the result against. All three are achievable with equipment most clinics already own.
The power gap in most physiotherapy assessments
Range of movement gets measured with a goniometer or inclinometer. Strength, when it's tested at all, usually gets a manual muscle test score rather than a number. Power tends to fall off the bottom of the list altogether, not because it matters less clinically, but because clinicians associate it with lab equipment they don't have and don't have budget for.
That's a gap with consequences. Reactive strength, the ability to absorb load and reproduce force quickly through the stretch-shortening cycle, is exactly what's being asked of a knee, ankle, or Achilles tendon the moment a patient returns to running, jumping, or changing direction. Testing strength in isolation and assuming power will follow is an assumption, not a measurement.
What a drop jump actually tells you
The protocol itself is simple. The patient steps off a box of a fixed height, typically 20 to 40cm, lands, and immediately rebounds into a maximal vertical jump with minimal ground contact time. Two numbers come out of it: how long the foot was in contact with the floor, and how high the rebound jump was. Divide jump height by contact time and you get a reactive strength index, a proxy for how efficiently someone converts landing force into upward propulsion.
None of that requires a force plate. A slow-motion video on a smartphone, timed through an app such as MyJump2, gives contact time and flight time to a workable degree of accuracy from ordinary clinic footage. A tape measure against a wall marks jump height for a standing vertical jump variant if you want something even simpler. Force plates and jump mats can generate the same numbers with more precision, but for the vast majority of MSK caseloads the smartphone version is accurate enough to track change over time and flag patients who are meaningfully below where they should be.
What matters clinically is not chasing lab-grade precision, it's applying the same protocol every time, on the same equipment, so this month's number and last month's number are actually comparable.
Where it changes management: ankle instability and Achilles rehab
Landing mechanics and reactive strength are not academic curiosities in ankle and Achilles caseloads, they're central to how these patients fail and how they're rehabilitated. A randomised controlled trial of hop-stabilisation training in athletes with chronic ankle instability found that structured landing-focused training changed landing biomechanics and improved outcome measures compared with standard care (Ardakani et al., 2019). If landing quality and reactive capacity respond to targeted training, they need to be assessed in the first place, not inferred from a strength test alone.
A 2025 network meta-analysis comparing physiotherapy approaches for chronic ankle instability found balance and strength-based interventions delivered the strongest effects among the options studied (Yang et al., 2025), and earlier RCT work has shown that strength-training protocols meaningfully reduce the deficits seen in this population (Hall et al., 2015). Power sits downstream of both balance and strength, so a patient who tests well on strength but hasn't been retested on a landing task is only half assessed.
The same logic applies after acute ankle sprain. Accelerated, functionally-loaded rehabilitation has been shown to outperform standard protect-and-rest management on recovery of function (Bleakley et al., 2010), and a scoping review of rehabilitation evidence after lateral ankle sprain in athletes points to progressive functional loading, not time on the calendar, as the driver of readiness to return (Tee et al., 2022). Drop jump testing gives you an objective marker of that functional loading tolerance rather than a guess based on how many weeks have passed.
Achilles tendon rehabilitation tells a similar story. A systematic review of early functional rehabilitation after acute Achilles tendon rupture identified progressive loading and functional milestones, rather than fixed timeframes, as the components associated with better outcomes (Zellers et al., 2019). A tendon that has to tolerate rapid stretch-shortening load on return to sport needs to be tested under conditions that resemble that demand, and a controlled drop jump is the closest most clinics can get to that without a running track.
Building a low-tech drop jump protocol into a 30-minute slot
You don't need a dedicated power-testing session to make this routine. A basic protocol takes under five minutes once the patient is warmed up:
- Use a fixed box height for every session with that patient, and record what it was.
- Film from the side at a consistent distance, using slow-motion or a contact-time app.
- Run three trials and keep the best, discarding any where the patient visibly steps rather than falls off the box.
- Record contact time and rebound jump height separately, not just the combined index, so you can see which one is driving a poor score.
- Repeat at the same time of session (post-warm-up, pre-fatigue) at every review point.
If a patient can't safely tolerate a drop jump yet, a countermovement jump measured with a tape measure against a wall, or a single-leg hop for distance, gives you a lower-demand power marker to track while loading capacity builds.
Interpreting the numbers without an arbitrary cut-off
The temptation with any jump-based test is to reach for a symmetry comparison, left versus right, and set a pass mark at some round number. Resist it. A fixed symmetry threshold ignores that the uninjured side can itself be detrained, and it tells you nothing about whether either limb is actually performing where it should for that patient's age, sex, and training background.
A more defensible approach is to compare the result against what would be expected for that patient's profile and track the percentage change over successive sessions. A patient scoring well below their expected range on reactive strength, even with a strength test that looks adequate, is telling you something the strength number alone missed. That's the value of testing power as its own domain rather than assuming it tracks strength one-to-one.
Longitudinal tracking matters as much as the single-session number. A drop jump score means little in isolation, it becomes clinically useful once you can show a trend line moving toward the expected range, or flag that it's plateaued while strength keeps improving, which points to a different rehab emphasis.
Making power testing routine, not exceptional
Benchmark PS was built around exactly this problem: physiotherapists know power testing matters but don't have consistent, low-cost ways to run it session to session. Benchmark's power domain works with the tools already sitting in most clinics, smartphone jump apps, medicine balls, and tape measures, and expresses results as a percentage of the patient's expected score based on age, sex, and weight, with the trend tracked alongside your strength and range of movement data over time.
If you're testing strength and range routinely but leaving power to guesswork, that's a gap worth closing. Book a walkthrough of how Benchmark handles power testing alongside the rest of your assessment battery, no extra hardware required.
References
- Ardakani MK, Wikstrom EA, Minoonejad H et al. Hop-Stabilization Training and Landing Biomechanics in Athletes With Chronic Ankle Instability: A Randomized Controlled Trial. Journal of athletic training. 2019;54(12):1296-1303. PubMed
- Yang YS, Lai PC, Liu ZW et al. What Will Deliver the Best Bang-For-Your-Treatment-Buck? Treatment Effects of Physical Therapy Approaches to Managing Chronic Ankle Instability: A Network Meta-Analysis of Randomized Controlled Trials. The Journal of orthopaedic and sports physical therapy. 2025;55(1):26-44. PubMed
- Hall EA, Docherty CL, Simon J et al. Strength-training protocols to improve deficits in participants with chronic ankle instability: a randomized controlled trial. Journal of athletic training. 2015;50(1):36-44. PubMed
- Bleakley CM, O'Connor SR, Tully MA et al. Effect of accelerated rehabilitation on function after ankle sprain: randomised controlled trial. BMJ (Clinical research ed.). 2010;340:c1964. PubMed
- Tee E, Melbourne J, Sattler L et al. Evidence for Rehabilitation Interventions After Acute Lateral Ankle Sprains in Athletes: A Scoping Review. Journal of sport rehabilitation. 2022;31(4):457-464. PubMed
- Zellers JA, Christensen M, Kjær IL et al. Defining Components of Early Functional Rehabilitation for Acute Achilles Tendon Rupture: A Systematic Review. Orthopaedic journal of sports medicine. 2019;7(11):2325967119884071. PubMed
Frequently Asked Questions
Can you test power reliably without a force plate?
Yes. Smartphone apps such as MyJump2 can calculate contact time and jump height from video with accuracy sufficient for tracking clinical change, and a tape measure works for simpler vertical jump variants. Precision instrumentation isn't necessary for most MSK caseloads, consistency of protocol is what matters.
What does the drop jump measure that a strength test doesn't?
A drop jump captures reactive strength, the ability to absorb landing force and redirect it into upward propulsion quickly. This stretch-shortening cycle capacity doesn't automatically follow from isolated strength gains, so it needs its own test to catch deficits that strength testing alone would miss.
Is drop jump testing appropriate for ankle sprain and Achilles rehab patients?
It's highly relevant once a patient has progressed enough to tolerate the loading, since both conditions require the tendon or joint to cope with rapid stretch-shortening demand on return to sport. Evidence supports progressive functional loading over fixed timeframes as the better predictor of readiness, and a controlled drop jump gives you an objective functional loading marker rather than a calendar-based guess.
Should I compare left and right drop jump scores?
A fixed symmetry threshold isn't a reliable standard, since the uninjured limb can itself be undertrained. Comparing each limb's result to a normative expectation for that patient's age, sex, and weight, and tracking the trend over time, gives a more defensible picture than a left-right ratio alone.