Variation in Repeated Handgrip Strength Testing Indicates Submaximal Force Production in Patients With Myalgic...

Area of Science:

• Neurology
• Biomarkers
• Chronic Fatigue Research

Background:

• Handgrip strength is proposed as a biomarker for myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS).
• This assumes peripheral neuromuscular dysfunction in ME/CFS.
• An alternative hypothesis suggests higher-order motor control alterations contribute to weakness.

Purpose of the Study:

• To analyze handgrip strength variation in ME/CFS patients and healthy controls.
• To investigate if altered motor control, rather than peripheral dysfunction, explains strength deficits in ME/CFS.

Main Methods:

• Post hoc analysis of serial handgrip strength measurements from 105 ME/CFS patients and 66 controls.
• Comparison of coefficient of variation (CV) in handgrip exertion.
• Subgroup analysis of participants with normal fatigability indexes.

Main Results:

• ME/CFS patients exhibited significantly higher CV compared to healthy controls.
• Elevated CV persisted in female ME/CFS patients even with normal fatigability.
• No significant difference in CV was found for male ME/CFS patients with normal fatigability.

Conclusions:

• Increased handgrip strength variation in ME/CFS suggests involvement of higher-order motor control deficits.
• This finding challenges the use of grip strength as a biomarker for peripheral dysfunction in ME/CFS.
• Functional weakness may stem from reduced self-efficacy within a context of chronic dysregulation.