A maximal voluntary isometric contraction (MVIC) is the backbone assessment: the patient produces a maximal effort against a fixed resistance while you capture the force live. Peak force or torque tells you strength capacity, and the shape of the rise tells you how fast they can produce it. Both readings depend on one thing being clean, the baseline the effort starts from. Most of the setup decisions in an MVIC are really decisions about protecting that baseline.
The knee angle you test at is one of those decisions, and the right answer depends on your device. This trips people up because the strength literature and the rate-of-development literature point at different angles for different reasons.
The two things you are measuring
Peak torque is a post-onset measurement. It is the highest value the curve reaches, so it does not care much where the contraction started or what the baseline was doing beforehand. A small, steady offset shifts the whole curve but barely moves the peak.
Rate of force development (RTD) is the opposite. It is the slope of the very first part of the rise, measured in the first 75 to 200 milliseconds after onset. It cares enormously about where onset is and whether the limb was moving before force registered. Anything that muddies the baseline or lets the limb load before the sensor sees it will distort RTD while leaving peak roughly intact (Maffiuletti et al. 2016).
That difference is why one angle does not serve both metrics on every device.
Why limb weight is the deciding factor
Seated with the thigh supported, 90 degrees of knee flexion puts the shank hanging close to vertical. In that position the weight of the lower leg acts almost straight down through the knee axis, so it creates very little turning moment at the knee and almost no pre-load at the ankle interface. The baseline sits quiet, and onset is crisp.
At 60 degrees of knee flexion the shank is raised toward horizontal. Now the weight of the lower leg pulls it down and away from the joint axis, creating a real gravitational moment the patient has to work against. Before the dynamometer registers any extensor push, the patient is already lifting and stabilizing the limb against gravity. On a device that cannot subtract that limb-weight offset, the early part of the trace reflects the limb moving against gravity, not force developing against the sensor. Onset lands in the wrong place and RTD becomes untrustworthy.
An instrumented dynamometer that measures the passive limb-weight torque at the test angle and subtracts it removes this problem, because the reported signal is the active extensor torque with the gravity component taken out. Hand-held dynamometers and simple tension-gauge setups do not do this. They report whatever tension is in the line, gravity offset included.
The recommendation
On a hand-held or tension-gauge dynamometer that cannot correct for limb weight, test RTD at 90 degrees of knee flexion. The shank hangs near the joint axis, the gravity offset is negligible, and the baseline stays clean enough to trust the onset and the early slope.
Keep peak-torque testing at 60 degrees if that is your strength protocol. Sixty degrees is where the quadriceps produces peak isometric torque and where the return-to-sport thresholds in the literature are referenced, and peak survives the gravity offset because it is a post-onset measurement. You can capture a clean peak at 60 degrees even on a simple device.
Test RTD at 60 degrees only if your device corrects for limb weight. With gravity compensation, the baseline at 60 degrees is as clean as at 90, and you get both a peak at the reference angle and a trustworthy rise from the same trial.
In short: peak torque is angle-driven and device-tolerant, RTD is device-driven. If one setup has to do both on a device without gravity correction, split the difference by taking peak at 60 degrees and RTD at 90 degrees, and record which angle produced which number.
Getting a clean baseline at either angle
- Take up the slack, do not zero out the limb. Cue the patient to relax and let the interface take up any slack, but do not tare the device to nothing. A little passive tension is normal and lets the system see a countermovement dip if one happens. See Taring the dynamometer and what a good baseline looks like.
- Standardize the cue. "Push as hard and as fast as possible" for a fast, explosive effort, held for about five seconds. Keep the wording and the encouragement volume the same across trials and patients.
- Watch for a countermovement. A small dip before the rise, or a limb that resettles before the push, will corrupt RTD at any angle. This is the same failure the gravity offset causes at 60 degrees, arriving by a different route.
What to do next
- For the full knee extension setup, including seat, straps, tether perpendicularity, and moment-arm measurement, read Setting up a reliable isometric knee extension assessment.
- Before the first recorded trial, work through Preparing the patient for their first MVIC.
- If you are unsure whether a recorded rise is real or an artifact of the limb loading early, Correcting the auto-detected onset shows how to inspect and reset onset by hand.
References
- Maffiuletti NA, Aagaard P, Blazevich AJ, Folland J, Tillin N, Duchateau J. Rate of force development: physiological and methodological considerations. Eur J Appl Physiol. 2016;116(6):1091-1116. doi:10.1007/s00421-016-3346-6
- Tillin NA, Pain MTG, Folland JP. Identification of contraction onset during voluntary and evoked isometric contractions. J Electromyogr Kinesiol. 2013;23(4):991-994. doi:10.1016/j.jelekin.2013.04.001
- Norris R, Morrison S, Price A, et al. Inline dynamometry provides reliable measurements of quadriceps strength in healthy and ACL-reconstructed individuals. The Knee. 2024;46:136-147. doi:10.1016/j.knee.2023.12.006