How to Assess 1RM

How to Assess 1 Repetition Maximum Knee Extension Strength (0 - 90 degrees) using a Knee Extension Machine

• Requires a knee extension machine.

• All 1-RM testing should begin with the uninvolved limb and alternated between limbs.

• The tester will instruct the patient to extend the knee against the resistance of the machine in a slow and controlled fashion.

• Trials are deemed successful when the patient has achieved the targeted angle of knee extension and maintained it for 2 seconds.

• Resistance is increased after a successful trial on each limb by 2.00 to 14.00 kg, at the tester’s discretion, depending on the difficulty of the previous repetition.

• Failure is defined as 3 unsuccessful attempts to lift the weight to the targeted angle, with a rest interval of up to 60 seconds given between attempts.

• The final 1-RM values for the involved and uninvolved legs are to be recorded.

• Testing must be done at 90-0 knee extension. As time progresses clearly the resistance of the test needs to increase.

Reference: Sinacore et al. Diagnostic Accuracy of Handheld Dynamometry and 1-Repetition- Maximum Tests for Identifying Meaningful Quadriceps Strength Asymmetries JOSPT 2017 47 (2) 97-107.

How to Assess 1 Repetition Maximum Knee Extension Strength using a Handheld Dynamometer

• A digital HHD can be used to test the uninvolved limb, followed by the involved limb.

• Patients will be seated on a standard treatment table, with the dynamometer fixed to the table leg using an inelastic strap.

• The strap should be secured to allow no more than 85° of knee flexion during the quadriceps muscle contraction (see figure above)

• To aid trunk and pelvis stabilisation, participants should grasp the edge of the treatment table. Patients will complete 3 practice trials (50%, 75%, and 100% perceived effort), followed by 3 maximal effort contractions lasting 5 seconds, with 60-second rest intervals.

• The force sensor will be placed just proximal to the ankle joint, with an inelastic strap countering all resistance to knee extension.

The tester should stabilise the position of the HHD in relation to the shank but do not provide any counterforce.

• The peak force is to be recorded for each trial in kgs

References

Sinacore et al. Diagnostic Accuracy of Handheld Dynamometry and 1-Repetition- Maximum Tests for Identifying Meaningful Quadriceps Strength Asymmetries JOSPT 2017 47 (2) 97-107