Effects of Weakness on Symmetrical Bilateral Grip Force Exertion in Subjects With Hemiparesis

Abstract

It has been shown that, in a bilateral force-matching task, subjects presenting weakness in one limb produce a lower force in the weakened limb even though they subjectively perceive that they are exerting the same force. The aim of this study was to verify whether subjects with hemiparesis produced asymmetrical forces during a bilateral submaximal grip task and whether this asymmetry is related to weakness of the paretic limb. Fifteen subjects with hemiparesis and 15 healthy subjects were recruited. First, the maximal voluntary force was measured for each hand. Then, subjects were asked to exert equal forces with both hands simultaneously at three submaximal force levels using two dynamometers. In the bilateral task, the force ratios (paretic/nonparetic or nondominant/dominant) differed between groups. Severely weak hemiparetic subjects produced lower force ratios than mildly weak hemiparetic subjects and healthy subjects (P < 0.000), whereas there was no difference between the force ratios produced by mildly weak hemiparetic subjects and those produced by healthy subjects. In subjects with hemiparesis, the force ratios in the bilateral task were related to the ratios of maximal voluntary forces (R2 = 0.39-0.66, P < or = 0.013) and the presence of somatosensory impairment did not affect these relationships. These results suggest that the strategy used is to compare the intensity of the motor commands on both sides and then perform the force-matching task. The use of such a strategy by subjects who have had paresis for 1 year reflects a lack of adaptation to their weakness.

Perception of Weight-Bearing Distribution During Sit-to-Stand Tasks in Hemiparetic and Healthy Individuals

“…According to previous studies, the asymmetries observed in hemiparetic subjects seem to be related to the desire to produce symmetrical levels of effort. 21,22 Bertrand et al 22 proposed the principle of bilateral matching effort to explain the strategy chosen by hemiparetic individuals when performing bilateral matching tasks at the upper limbs. Also, Simon and Ferris 21 demonstrated in hemiparetic subjects that, during an isometric force-matching task on a leg press machine, there was no significant difference between limbs when normalizing the forces produced by those obtained in bilateral maximum voluntary contractions.…”

Bilateral Level of Effort of the Plantar Flexors, Hip Flexors, and Extensors During Gait in Hemiparetic and Healthy Individuals

“…One possible explanation for this observation is that the hemiparetic participants scaled their effort to their maximal strength, as shown in single or multiarticulated efforts. 21,22 The idea of using the sense of effort in hemiparetic gait was first presented in a previous work by the authors. 9 The presence of similar levels of effort between affected and unaffected sides can also provide a new explanation for the asymmetrical gait pattern observed in stroke individuals.…”

Motor dysfunction of the “non-affected” lower limb: a kinematic comparative study between hemiparetic stroke and total knee prosthesized patients

“…On the contrary, reduced motility and proprioceptive impairments are themes of discussion which involve both groups of patients. Motor impairment of the ''other side leg'' may be a consequence of abnormal postural stabilization [3,16]. In HS patients, the force produced by the ''ipsilateral limb'' is reduced because of the difficulty in supplying contralateral stabilization using the paretic side owing to weakness, spasticity and abnormal postures [19].…”

“…About this topic, there is a reduced number of studies underlining the role of peripheral mechanisms [2]. For instance, an abnormal postural stabilization too may play a role in ipsilateral motor impairment [3,16].…”