A new device that measures handgrip strength in people with fibromyalgia has the potential to overcome some of the limitations of current hand-held dynamometers, researchers in Italy that developed the device reported.
The cylindrical-shape tool also confirmed weaker handgrip strength in these patients, directly correlating it with disease severity.
The study, “Force-time curve features of handgrip strength in fibromyalgia syndrome,” was published in the journal Scientific Reports.
Fibromyalgia patients often see their physical fitness lessen at their disease progresses, including a loss in muscle strength, balance, and flexibility. Previous studies have reported that women with fibromyalgia have 20% to 36% less strength compared to healthy women.
Handgrip strength is defined as the maximum amount of force a person can generate with each hand. In addition to assessing the status of a patient’s hand, this parameter can be used as a measure of overall muscle strength, which is related to physical fitness.
“In healthy subjects, HGs [handgrip strength] is correlated to knee extension strength and can therefore be a surrogate for the strength of other muscle groups,” the researchers wrote. “From this point of view, a relative simple measurement of the HGs can reflect a general assessment of muscle fitness in FM patients.”
Traditional methods of measuring the maximum (peak) handgrip force use devices called dynamometers. However, these devices fall short when it comes to evaluate several characteristics of hand strength, including force generation speed, sustainability, and force variability over time.
“The force evaluated by … dynamometers is essentially unidirectional since the handle only allows a movement from the fingers to the proximal palm and thumb. This type of force measurement may not adequately represent the activities that the hand must perform to handle a cylindrical object,” they added.
Researchers at the Università Politecnica delle Marche in Italy developed and tested a cylindrical-shape grip device that can determine handgrip strength within 30 seconds by making measurements every five seconds.
It can be used to obtain a graph representing the total amount of force exerted over the test’s 30-second time frame, called a force-time curve, which can then be analyzed.
Their study enrolled 110 women with fibromyalgia (mean age of 53.8) and 111 healthy women as controls (mean age of 55.2). Measures of hangrip strength using the dominant hand were taken on all participants while seated.
Findings showed both the total amount of force and the peak handgrip force were lower in patients than controls. Women with fibromyalgia also took longer (nearly four seconds) to achieve their maximal handgrip force compared to healthy women.
Women with severe fibromyalgia scored lower in both handgrip force parameters compared to women with milder forms of the disease, the researchers reported.
To investigate the impact of certain features of fibromyalgia on handgrip test results, the team evaluated disease severity using two questionnaires — the revised Fibromyalgia Impact Questionnaire (FIQR) and the Fibromyalgia Assessment Status (FAS) — and pain using the Widespread Pain Index (WPI).
Higher WPI, FIQR and FAS scores, indicative of greater disease severity and pain, were linked to lower peak handgrip force. Higher WPI and FIQR scores also associated with lower overall handgrip force in fibromyalgia patients.
“Our results showed that HGs is reduced by about 30% in women with FM [fibromyalgia] versus healthy controls. This reduction correlates with WPI and disease severity,” the researchers wrote.
“[T]his study proposes a new method (using a cylindrical-shape grip device) of evaluating HGs based on force-time curve analysis, trying to overcome some limitations of the dynamometers available today,” they added. “The device is currently not available on a large scale. However, considering the low production costs, we believe it will be widely available in the coming years.”
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