The Single-Leg Leg Extension Repetition Maximum Test assesses machine-based knee-extension strength on one leg at a time. It is useful for tracking quadriceps strength, comparing sides and monitoring progress across lower-limb strength programmes.
A client may show visible side-to-side difference during squats, step-downs or sit-to-stand tasks. Another client may be rebuilding knee-extension strength after a period of reduced training. The Single-Leg Leg Extension Repetition Maximum Test gives professionals a controlled way to assess unilateral knee-extension strength.
The result should be interpreted as machine-based knee-extension performance, not as a complete measure of knee function or lower-limb capacity.
Test name: Single-Leg Leg Extension Repetition Maximum Test
Purpose: Assess single-leg knee-extension strength
What it assesses: Machine-based quadriceps/knee-extension performance
Equipment: Leg extension machine, load stack or plates, Measurz for recording
Key finding: Maximum load completed for the target repetition standard
Best used with: Squat testing, leg press, sit-to-stand, jump testing and knee ROM tests
Key limitation: It does not measure full lower-limb function on its own
The Single-Leg Leg Extension Repetition Maximum Test measures the maximum load a client can extend through a defined knee-extension range for a target number of repetitions on one leg.
The test may be performed as a 1RM, 3RM, 5RM or another repetition maximum. The chosen repetition target must be recorded.
This test is used to assess unilateral knee-extension strength, compare sides, guide training loads and monitor progress.
It may be useful for lower-limb strength testing, knee strength monitoring, gym programming and performance profiling.
The test measures single-leg leg extension performance.
It may reflect:
Quadriceps knee-extension strength
Load tolerance
Side-to-side difference
Strength progress
Pain response
Control through the tested ROM
It does not measure whole-leg strength, squat ability, jump ability, knee health or sport readiness.
This test may be useful for gym clients, field sport athletes, older adults, lower-limb strength clients and people needing measurable knee-extension strength tracking.
It may not be appropriate when the machine setup causes symptoms, the client cannot control the movement or maximal testing is not suitable.
Leg extension machine
Load stack or plates
Adjustable seat/backrest
Adjustable shin pad
Measurz for recording
Optional metronome
Optional video
Adjust the seat, backrest and shin pad. Align the knee as closely as practical with the machine axis. Record all machine settings.
Decide the starting knee angle and finishing range. The same ROM must be used for both sides and retesting.
Choose whether testing is 1RM, 3RM, 5RM or another repetition maximum.
Use light warm-up sets and gradually increase load. Avoid testing maximal attempts without familiarisation.
Ask the client to extend the knee through the agreed ROM with control. Avoid swinging, hip lift or shortened range.
Allow adequate rest between attempts. Increase load only when the previous attempt meets the required standard.
The score is the heaviest load completed for the target repetition range with acceptable technique.
Record side, load, reps and target RM. If estimating 1RM from submaximal reps, label the result as estimated.
Interpret using absolute load, side-to-side comparison, bodyweight context, symptoms, ROM and previous baseline.
A lower score may suggest reduced machine-based knee-extension strength under the tested setup, but it does not identify the cause or represent full knee function.
Machine-based leg extension values vary widely by equipment, lever arm, ROM, age, sex, training history and body size. Avoid universal norms unless they match the machine and population.
Use the client’s baseline, side-to-side comparison and progress across sessions as the primary benchmarks.
Repetition maximum testing can be reliable when procedures are consistent. A 2020 systematic review supports good-to-excellent reliability for 1RM testing across exercises when familiarisation and standardised protocols are used.
For leg extension testing, setup consistency is especially important because seat position, pad placement and ROM affect the score.
Common errors include poor knee-axis alignment, changing pad position, using momentum, lifting the hips, shortening ROM, comparing results across different machines and ignoring pain.
The main limitation is that the test measures open-chain knee-extension performance only.
Use this test to monitor knee-extension strength, compare sides, guide training loads and support lower-limb strength tracking.
It is most useful when combined with leg press, squat, sit-to-stand, jump, hop and knee ROM tests.
Record side, machine type, seat setting, pad setting, knee angle/ROM, load, reps, RM target, RPE, pain score, symptom location, compensation notes, comparison side and retest date.
Useful notes include shortened ROM, hip lift, pain-limited effort, fast eccentric, poor control or side-to-side difference.
Single-Leg Leg Press Test
Back Squat 1RM Test
Single-Leg Sit-to-Stand
5-Time Sit-to-Stand Test
Vertical Jump Test
Knee Extension ROM Test
It measures machine-based knee-extension strength on one leg.
It provides useful knee-extension strength information, but it does not measure all lower-limb function.
Yes. Different machines can produce different results.
Side differences should be interpreted with pain, ROM, strength history and functional tests.
Yes. Pain score and symptom location are important for interpretation.
The test measures single-leg leg extension performance.
Machine setup and ROM must be standardised.
Do not treat the result as full lower-limb function.
Record side, load, reps and symptoms in Measurz.
Use with squat, leg press and functional tests.
Grgic, J., Lazinica, B., Schoenfeld, B. J., & Pedisic, Z. (2020). Test-retest reliability of the one-repetition maximum strength assessment: A systematic review. Sports Medicine - Open, 6, 31.
Suchomel, T. J., Nimphius, S., Bellon, C. R., & Stone, M. H. (2018). The importance of muscular strength: Training considerations. Sports Medicine, 48(4), 765–785.
Weakley, J., Mann, B., Banyard, H., McLaren, S., Scott, T., & Garcia-Ramos, A. (2021). Velocity-based training: From theory to application. Strength and Conditioning Journal, 43(2), 31–49.
