Association between isometric knee extensor strength at 20º and 90º measured using a hand-held dynamometer in recreationally active adults

Lewis, Ellie, Flett, Olivia, Poller, Daniel, Puncher, Abbey, Moor, Elissa and Samuel, Dinesh (2024) Association between isometric knee extensor strength at 20º and 90º measured using a hand-held dynamometer in recreationally active adults. CPS Annual Conference 2024, , Manchester, United Kingdom. 11 - 12 Oct 2024.

Abstract

Purpose: assessment of muscle strength is an integral part of everyday practice and is used in both the clinical and sporting environment. Quadriceps strength forms the foundation for optimal performance and functionality in several activities ranging from daily tasks to high-intensity sports. Existing measures of knee muscle strength using equipment lack accessibility and application to a range of environments. Several factors impact measurements, including the joint angle, tester strength, and the participants ability to produce a maximal voluntary contraction. The present study aimed to examine the association between knee extensor (KE) strength measured using a Hand-held dynamometer (HHD) at 20º and 90º in recreationally active young adults.


Methods: A convenience sample of 50 participants aged 18-35 years were recruited to this cross-sectional study. Exclusion criteria consisted of any previous/ ongoing lower extremity or traumatic spine injury within the previous six months, a neurological condition and chronic lower back pain. Participants completed a 90º and 20º isometric knee extensor strength test measured using a Lafayette HHD. During the 90º test participants sat on a custom-built chair with their hips and knees positioned in 90º flexion, measured with a goniometer. They were instructed to keep their arms across their chest without trunk flexion. At 20º a supine position was used to minimise the difficulty of maintaining the 20º angle of the knee in sitting. The participant flexed their dominant knee to 20º, and this position was maintained through the placement of a rolled towel below the knee. Participants were instructed to maintain knee-to-towel contact throughout testing. Consistent standardised verbal instructions were used for both 90º and 20º tests. The maximum of three trials was used to calculate the peak torque which was normalised for leg length. A correlational analysis was conducted using Spearman’s to examine the relationship between the two variables. Intraclass correlation coefficient (ICC) was utilised to evaluate variability between trials. The significance value was p<0.05 and the r values were categorised using the Portney Watkins classification.

Results: The mean age of the sample was 24.04 (± 0.9) years and included 15 males and 35 females. Overall mean peak torque at 90º and 20º was 172.9 (±60.4) Nm, and 82.6 (±25.7) Nm respectively. An excellent correlation (r=0.81; p<0.001) was noted between 90º and 20º isometric knee extensor strength measurements. Intraclass correlational coefficient was 0.81 and 0.90 (p<0.001, 95% CI) at 90º and 20º respectively.

Conclusions: A high level of correlation between the two strength tests suggests that the 20º isometric knee extensor strength test might be a suitable alternative to the standard 90º KE test. Strengths include repeatability, easy application to a range of environments, and accessibility of the 20º test which makes it more suitable for wider population groups.

Impact: The high correlations and excellent repeatability between the 20º and 90º KE strength measurements noted in this study provides supporting evidence for an alternative test that could be widely implemented without the need for specialist equipment allowing clinicians to measure knee extensor strength in a range of settings.

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Contributors

Author: Dinesh Samuel

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