Good hand function is a vital component of functional independence, and a strong barometer of how individuals may execute activities of daily living after stroke. Patients working to recover from stroke may find sustained finger flexor muscle activity prevents a paretic hand from releasing an object without a delay. This type of deficit can leave patients feeling frustrated and possibly lead them to abandon use of the arm. A study led by a scientist from Northwestern University affiliated with the Rehabilitation Institute of Chicago (RIC) suggests there is at least one way to improve grip release function post-stroke. The findings spark new thinking about how to help patients minimize frustration and boost ability among stroke-affected hands.
Na Jin Seo, PhD, adjunct assistant professor at Northwestern, led the investigation that pursued two goals: the first was to quantify the time necessary for a patient to initiate and terminate grip muscular activity after a stroke. The second objective was to learn how variables such as arm support, grip location and active muscle stretch might affect delays in a patient’s paretic hand. Seo’s team believed patients would be able to release their grips faster with hands nearer their torsos compared to when their hands were positioned at a distance. The researchers also hypothesized upper extremity muscle stretches would decrease delays in grip termination for a paretic hand.
The study focused on comparisons between 10 chronic hemiparetic stroke subjects and five subjects who were neurologically intact. Among the stroke subjects, an electromyographic (EMG) signal recorded data about grip initiation and termination from both the paretic hand and nonparetic hand. A vertical cylinder was used for each of the test subject’s hands to test grip characteristics through a repeated grip-and-relax task. One of the curiosities shared among the investigators was how the use of an arm support—a gravity-compensating orthosis—and active muscle stretch would affect results of the grip-and-relax task. The answer to that question is wrapped in an encouraging statistic: the arm support reduced grip termination delay in the paretic hand by 37%.
“This study demonstrated that subjects could instantly decrease delay in grip termination by using the arm orthosis,”1 Seo and her team note in their report. “Because the basic role of the arm orthosis is to support the weight of the arm, it is conceivable that simply supporting the affected arm’s elbow using the stronger hand or against a table may help shorten the delay in grip termination for the paretic hand, especially when one cannot let go of grasped objects in the hand.”
Seo’s team also discovered that repeated active muscle stretch in the paretic hand caused a decrease in the delay of grip initiation but lengthened the delay of grip termination. Researchers left an open door for further research to determine whether passive muscle stretch would create a different response for grip termination. They further acknowledged a possibility pharmacological intervention may offer a positive effect on grip termination delays.
Seo, who is also an associate professor at the University of Wisconsin, Milwaukee, College of Engineering and Applied Science, points out there are several other therapies that may benefit hand function for stroke patients. Active-passive bilateral therapy, for example, works to restore the imbalance between the brain’s hemispheres caused by stroke. This therapy is based on a patient’s use of the paretic hand and nonparetic hand performing together tasks designed to retrain the balance between hemispheres.
Brain stimulation is another approach that may help improve hand function. This therapy calls for repeated trans-cranial magnetic stimulation or trans-cranial direct current stimulation that reduces overactivity among neurons. Application of stimulation under this method works to restore a degree of balance between the stroke-affected hemisphere and healthy hemisphere by reducing the healthy hemisphere’s dominance over the injured hemisphere.
A final therapy Seo suggests can help stroke patients is biofeedback. This method, she says, may make stroke patients more aware of muscle contractions, and the heightened awareness can foster relaxation in hand muscles or offer greater coordination for hand movements.
While Seo’s study leaves room for further investigation, such as the long-term effect of active muscle stretch on delayed grip termination, it spotlights important steps forward in this area of stroke rehabilitation. More importantly, it brings into clearer view therapies that may shorten the distance from where patients are on the recovery continuum and where they want to be.
- Seo NJ, Rymer WZ, Kamper DG. Delays in grip initiation and termination in persons with stroke: effects of arm support and active muscle stretch exercise. Neurophysiology. 2009:101(6);3108-3115.