Hand grip strength and fatigability: correlation with clinical parameters and diagnostic suitability in ME/CFS.

Abstract

BACKGROUND: Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) is a complex and debilitating disease accompanied by muscular fatigue and pain. A  functional measure to assess muscle fatigability of ME/CFS patients is, however,  not established in clinical routine. The aim of this study is to evaluate by  assessing repeat maximum handgrip strength (HGS), muscle fatigability as a  diagnostic tool and its correlation with clinical parameters. METHODS: We  assessed the HGS of 105 patients with ME/CFS, 18 patients with Cancer related  fatigue (CRF) and 66 healthy controls (HC) using an electric dynamometer  assessing maximal (Fmax) and mean force (Fmean) of ten repetitive measurements.  Results were correlated with clinical parameters, creatinine kinase (CK) and  lactate dehydrogenase (LDH). Further, maximum isometric quadriceps strength  measurement was conducted in eight ME/CFS patients and eight HC. RESULTS: ME/CFS  patients have a significantly lower Fmax and Fmean HGS compared to HC  (p < 0.0001). Further, Fatigue Ratio assessing decline in strength during repeat  maximal HGS measurement (Fmax/Fmean) was higher (p ≤ 0.0012). The Recovery Ratio  after an identical second testing 60 min later was significantly lower in ME/CFS  compared to HC (Fmean2/Fmean1; p ≤ 0.0020). Lower HGS parameters correlated with  severity of disease, post-exertional malaise and muscle pain and with higher CK  and LDH levels after exertion. CONCLUSION: Repeat HGS assessment is a sensitive  diagnostic test to assess muscular fatigue and fatigability and an objective  measure to assess disease severity in ME/CFS.