Research aim was to establish the peculiarities of control of the accuracy and the stability of continuous isometric muscle contractions. Objectives: 1) to establish and compare effect of visual feedback on the accuracy, stability and muscle activity of continuous isometric contractions performed with different strength; 2) to establish and compare effect of learning on the dependence of accuracy and stability of a continuous isometric contraction on muscle potentiation. The subjects studied were healthy, physically active men (n = 8; age 20.0 ± 1.5 m, height 182.4 ± 6.5 cm; body mass 73.0 ± 5.7 kg, body mass index 22.0 ± 1.7 kg/m2 ( ±SD).

In experiment 1, the subjects performed CIC at 20%, 50% and 70% force of MVC. The subjects performed two series of CIC – first with visual feedback information (VFI), second – without VFI. The duration of each series was 13 sec. In experiment 2, the subjects performed the same CIC at 20% force of MVC. The subjects after two series of CIC (first with VFI, second – without VFI), done potentiation load (PL), when they had to achieve maximal force and it maintain 10 sec. After 10 sec rest the subjects performed CIC without VFI. All the experiment was repeated after 9 training series. In training series, they were learning speeds – accuracy isometric contractions at 20% force of MVC.

Absence of visual feedback information worsening in the accuracy of performing CIC at all forces of MVC. We have established that there is a significant worsening in the accuracy and stability of performing CIC at 20% ir 70% force of MVC. Increasing of force increased the muscle electrical activity.

Second experimental the data show, that after different type (speeds – accuracy) isometric contractions learning at 20% force of MVC improves the same force performed continuous isometric contraction accuracy, whereas stability, although and significantly, however impair. Interestingly, after learning without VFI performed isometric contraction variability don’t change, what could follow then, when continuous isometric contraction were performed after learning. The data from 2 experimental indicate, that potentiation load impair performed CIC accuracy and stability before different type (speeds – accurate) isometric contraction learning and after it.

Keywords: isometric contractions, stability, accuracy, learning, potentiation load

Raktažodžiai: isometric contractions, stability, accuracy, learning, potentiation load