Grip strength measurement: Towards a standardized approach in sarcopenia research and practice

Abstract

Introduction

Grip strength is a well-accepted measure of muscle strength. A standardized protocol for the measurement of grip strength has been proposed in 2011 to enable consistent measurement of grip strength and comparisons between studies. It is unknown whether this protocol has been adopted in sarcopenia research and practice. The aim of the study was to provide insight into current measurement practice, including the use of cut-off values for low muscle strength.

Methods

A systematic review of the literature was conducted, followed by a methodological quality assessment and extraction of relevant data. Inclusion criteria included a description of the grip strength protocol, EWGSOP standards were used to define sarcopenia, data was collected after 2010 and participants were 65 years and older.

Results

Twenty-seven observational papers were included in the review. The methodological quality was acceptable/good. Overall, information about the protocol was limited with a large variability in measurement approach. Most non-Asian studies used cut-off values for low grip strength of 30 kg for men and 20 kg for women. Asian studies showed more variability in choice of cut-off values.

Discussion

The proposed grip strength measurement protocol has been poorly adopted since its publication. Although there seems to be some agreement on cut-off values in non-Asian studies, proposed cut-off values need to be evaluated in specific diseases and settings and its predictive abilities regarding outcomes such as mobility limitations and falls needs to be determined. Asian research on cut-off values is still ongoing.

Introduction

Isometric handgrip strength has gained growing acceptance as a simple, inexpensive, clinical marker of well-being among older healthy and unwell populations [1], [2]. In studies across many older cohorts, including the very old, institutionalized with advanced dementia [3], grip strength is reported to be associated with markers of disability and morbidity [4], [5], [6]. In addition, research has shown that below normal grip strength is predictive of hospital length of stay, low vitamin D status, higher risk of institutionalization and mortality [4], [7], [8], [9]. In 2010, the European Working Group on Sarcopenia in Older People (EWGSOP) reported grip strength as the preferred measure of muscle strength in the defined assessment criteria for sarcopenia [10]. Supporting this, a recent systematic review has demonstrated grip strength as valid and reliable measure within the diagnosis of sarcopenia [11]. However, questions still exist on the protocol of assessment and cut-off value appropriateness across varied populations [12].

In 2010, based on a comprehensive review of the literature, Roberts et al. [1] proposed 12 equipment and protocol recommendations to standardize the approach for grip strength collection. This “Southampton protocol” included utilization of a Jamar hydraulic hand held dynamometer, with the participant seated, elbow at side and 90°, and the hand in a neutral position. Six measurements (three on each hand) should be performed and the maximal strength out of the six measurements should be used in statistical analyses [1]. To date, an investigation of whether these recommendations have been embraced and adhered to has not been undertaken. A consensus assessment protocol would enable the comparison between studies, and, for sarcopenia, could reduce the assessment and tool based disparity reported within current prevalence publications [13]. Moreover, with an established protocol for assessment and more consistent population data would come more effective treatment and prevention strategies.

As with the assessment protocol, muscle strength cut-off values based on maximal grip strength are also varied. The EWGSOP has suggested muscle strength cut-off values of < 20 kilograms (kg) for women and < 30 kg for men in the diagnosis of sarcopenia [14]. Similarly, the FNIH Sarcopenia Study reported men and women with a grip strength of 26–30 kg and 16–20 kg, respectively, as having “intermediate” muscle weakness, or being “weak” with measures below 26 kg for men and 16 kg for women [15]. Complicating this further is that the Asian population is reported as having normative grip strength 26% (male 25%, female 27%) weaker than their Caucasian counterparts [16]. In contrast, some researchers have adhered to muscle strength cut-off values specific to the participant BMI or set at 2.5 standard deviations below the mean from UK-based epidemiology studies [17], [18]. While cut-off values may be selected for statistical, theoretical or practical reasons, difficulties arise in the accurate establishment of the investigated population muscle strength status and in the promotion of a clear-cut definition of sarcopenia.

Given the growing acknowledgment of the financial and personal implications of sarcopenia for older adults [19], it is important to identify which grip strength cut-off values and protocols are being employed. In addition, how comorbidities such as osteoarthritis may affect assessment modification is also an important consideration. The aim of this review is to provide insight into the current practices of grip strength assessment in research among older adults aged 65 and over and specific to the diagnosis of sarcopenia. This will include the identification of the protocol and cut-off points being most commonly used and whether the protocol is reflective of that proposed by Roberts et al. [1]. Cut-off values will be reported specific to the diagnosis of sarcopenia and consideration given to ethic background, gender and other common comorbidities and geriatric syndromes. Subsequently, this review will provide insight into current research practice and lead to well-considered recommendations concerning the measurement of grip strength in research and clinical practice.