Correlation Between Drop in Synergy Index and Coincidence Anticipation Timing Performance Errors

Document Type : Original Article

Authors

1 Department of Sports Coaching, Faculty of Sports Sciences and Health, Unioversity of Tehran, Tehran, Iran.

2 Department of Cognitive and Behavioral Sciences, Faculty of Sport Sciences and Health, University of Tehran.

3 Department of Cognitive and Behavioral sciences, Faculty of sport sciences and Health, University of Tehran.

4 Department of Sport Biomechanics and Technology, Sport Science Research Institute

10.22034/mmbj.2026.67570.1194

Abstract

In order to execute rapid voluntary movements, a decrease in the synergy index occurs, which helps facilitate these movements by counteracting the synergy that stabilizes posture. This study aimed to investigate the relationship between anticipatory synergy adjustment (ASA) and errors in a coincidence anticipation timing task. To achieve this, 20 participants were randomly selected, and each performed 20 tennis forehand strokes with a 10-second interval between trials. Data were collected on muscle activity from 14 muscles, center of pressure, hand movement acceleration, as well as constant and variable errors. Principal component analysis was used to identify muscle modes, and multivariate regression was applied to obtain the Jacobian matrix. Finally, the synergy index was calculated using the uncontrolled manifold (UCM) method. The results indicated that ASA occurred approximately 114 milliseconds before the onset of movement, reflecting a feedforward adjustment by the central nervous system. Additionally, there was a significant positive correlation between the onset time and the amplitude of ASA; specifically, the earlier the ASA occurred, the greater the amplitude of the drop in the synergy index. However, Pearson correlation analysis showed no significant relationship between the onset time or amplitude of ASA and constant or variable errors in forehand stroke performance. These findings suggest that, for these participants, ASA does not necessarily indicate direct optimization of performance. Instead, the presence of ASA may signify the development of neuromuscular mechanisms in response to the task at hand.

Keywords

Main Subjects

Mind, Movement, and Behavior
Volume 5, Issue 1
April 2026
Pages 194-219

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History

  • Receive Date: 02 June 2025
  • Accept Date: 07 September 2025

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