Reliability and Validity of the Ground Reaction Force Asymmetric Index at Seat-Off as a Measure of Lower Limb Functional Muscle Strength: A Preliminary Study

Ae-Ryoung Kim,Dougho Park,Yang-Soo Lee

doi:10.3390/app11146527

Abstract

This study examined the reliability of the newly developed ground reaction force asymmetry index (GRF AI) at seat-off using a low-cost force plate and the validity of this new test by comparing it with other muscle strength-measuring methods and walking speed. This study was a cross-sectional design in general hospital setting. A convenience sample of 47 community-dwelling adults aged ≥40 years was performed. GRF AI is the measurement value obtained by shifting the weight to the right and left while performing sit-to-stand (STS). GRF AI assessed using GRF data at seat-off during an STS test with maximal weight shift to the right and left side and repeated 4 weeks later. Hip and knee extensor strength were measured using hand-held dynamometry; hand grip strength and walking speed were measured using a standardized method. Intrasessional intrarater reliability of the right and left side at Sessions 1 and 2 were high (intraclass correlation coefficients [ICC] = 0.947 and 0.974; 0.931 and 0.970, respectively). In addition, the intersessional intrarater reliability of a single test trial (ICC = 0.911 and 0.930) and the mean of three test trials (ICC = 0.965 and 0.979) was also high. There was a low correlation between right-side GRF AI and right hand grip strength (r = 0.268) and between left-side GRF AI and left hand grip strength (r = 0.316). No significant correlations were found between the GRF AI and other parameters. Although the reliability of the GRF AI was high, the validity was poor. To be clinically useful, this test should be further refined by modifying the test protocol.

Highlights

Muscle weakness is impaired in diverse medical conditions, including Parkinson’s disease [2], motor neuron disease [3], myopathy [4], neuropathy [4], stroke [5], major surgery [6,7], infection [8], and sarcopenia [9]
The manual muscle test (MMT) is a grading scale used to measure muscle strength that was first applied in patients with poliomyelitis in 1915 [11]
The results of this study indicate that the ground reaction force asymmetry index (GRF asymmetry index (AI)) has high intrasession and intersession intrarater reliability and poor validity for lower limb muscle strength

Summary

Introduction

Impairments in muscle strength can serve as a predictor of important outcomes, such as mortality, hospital length of stay, and hospital readmission [10] In light of these facts, practical tests for measuring muscle strength are needed. In addition to MMT, conventional methods of measuring muscle strength include a hand-held dynamometer (HHD) [12] and isokinetic dynamometry [13]. While isokinetic dynamometry is the gold standard for limb strength measurement, it requires a considerable amount of space, an expensive apparatus, and technical expertise. It can only test specific muscles [15]. Sit-to-stand (STS) and heel-raise tests are widely used to assess muscle strength [10]

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Discussion

Conclusion