Strength Testing with the Leg Extension

assessment Feb 15, 2018

Why Use Leg Extension Strength Testing?

Assessing the muscular strength of the lower limbs generally involves compound movements which is an excellent method to determine global lower limb strength.

However, it is often important to more finely identify deficits in individual muscle groups for injury risk analysis and the development of appropriate treatment techniques.

Why Is Quadriceps Strength Important?

The quadriceps group of muscles is a major muscle group of the lower limb and one of the primary absorbers of stress when it comes to activities of daily living and sporting performance.

From the research we know that:

  • Less than 85% via the Limb Symmetry Index (LSI) in knee extension strength is considered poor and warrants further rehabilitation (Lepley, 2015)
  • Leg extension strength is a critical component of many daily activities such as rising from a chair and climbing stairs, movements that are required for maintaining independence and mobility throughout the lifespan (Paasuke, Ereline, Gapeyeva, Joost, Mottus, & Taba, 2004)
  • Preoperative quadriceps muscle strength deficits and meniscus injuries have significant negative consequences for the long-term functional outcome after ACL reconstruction. (Eitzen et al 2009)
  • The Quadriceps can be exposed to more than 5x bodyweight in force depending on running speed. (Dorn et al 2012)
  • A normal Hamstring:Quadriceps ratio is considered to be 50% to 80% as averaged through the full range of knee motion. (Rosene et al 2001)

How To Perform Leg Extension Test

The subject first completes an adequate warm-up to prepare for the testing.

The subject is seated on a leg extension machine with shin against a shin pad. On the assessor's cue the subject will extend their knee to full extension at a set range of motion against a set resistance. The subject is encouraged to perform as many full repetitions as possible until failure. This process is repeated on both legs with the number of successful repetitions noted for each side.

Results can be compared from side to side or against reference data to assess injury risk or track the progression of quadriceps strength over time.

Are you using Single-Leg Extension Testing with your patients and clients?

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