The impact of grip strength recovery on grip force accuracy in chronic stroke
Date
2020
Authors
Alam, Tasnuva, author
Lodha, Neha, advisor
Hickey, Matthew, committee member
Yu, Yawen, committee member
Journal Title
Journal ISSN
Volume Title
Abstract
Decreased grip force accuracy and grip strength are two well-documented grip impairments that impede upper extremity function after stroke. Grip force accuracy is essential to perform precise motor actions in everyday life. Further, grip strength represents the ability to produce maximal grip force in a short duration of time and constitutes as a hallmark of upper extremity recovery in chronic stroke. Adequate grip strength and grip force accuracy are both important for regaining motor function after stroke. Despite this, no study has investigated whether the recovery of grip strength influences improvements in force accuracy. Purpose: Therefore, the purpose of the study was to investigate the impact of grip strength recovery on grip force accuracy in chronic stroke patients. Methods: We recruited two distinct stroke groups with low (less than 60%) and high (60% or more) grip strength recovery. The grip strength recovery was computed as the percent of paretic grip strength relative to nonparetic grip. A total of thirty-three participants, eleven in low strength recovery group (age 64 ±14.8 years; 6 females and 5 males), eleven in high strength recovery group (age 65.9 ± 9.9 years, 7 females and 4 males) and eleven age matched controls (age 69.6 ± 9.8 years, 4 females and 7 males) participated in the study. To examine the impact of grip strength recovery on grip force accuracy, all participants performed two tasks; 1) maximum voluntary contraction (MVC) and 2) dynamic force tracking task, using each hand. We quantified grip strength as the maximum force produced in the MVC task. Further, we assessed force accuracy by measuring root mean square error relative to the absolute target force. Result: The grip strength recovery in low strength recovery stroke group (27.1 ± 17.7)% was lower compared to the high strength recovery group (92.4 ± 24.9)% and controls (94.9 ±18.9)%. A significant main effect of Group [F (2, 30) = 34.53, p < 0.05, partial ղ2 = 0.69] revealed the grip strength recovery in low strength recovery group was significantly less than the high strength recovery stroke group (p < 0.05) and control (p < 0.05) whereas, the high strength recovery group was not significantly different than the control group (p > 0.05). A significant interaction between Group×Hand, [F (2, 30) = 7.21, p < 0.05, partial ղ2 = 0.33] demonstrated that the relative RMSE of paretic hand was significantly increased in low strength recovery stroke group compared to the high strength recovery (p < 0.05). Importantly, the relative RMSE of paretic hand in high strength recovery group was significantly greater than the control group's non-dominant hand (p < 0.05). Overall, a significant negative relationship between grip strength recovery and paretic relative RMSE (r = -0.598, p = 0.003) was found when investigating correlations in both groups together. In low strength recovery group, we found a negative association between the grip strength recovery and paretic relative RMSE, (r = -0.552, p = 0.078). However, in high strength recovery group, we found no association between the grip strength recovery (r = 0.308, p = 0.357). Conclusion: Grip strength recovery and force accuracy follow differential patterns of improvement for low and high strength recovery stroke groups. In chronic stroke survivors with strength recovery less than 60%, grip strength recovery is associated with grip force accuracy. However, in chronic stroke survivors with strength recovery more than 60%, the grip force accuracy may still be impaired despite near-normal grip strength recovery. After substantial gain in grip strength recovery, interventions that enhance grip force accuracy may be needed to improve the upper-extremity function. Our study results suggest, after improvement in strength, patients need additional interventions such as exergaming that will train force accuracy, to help them use this regained strength more meaningfully.