• M. Walsh
  • A. Strang
  • M. Hieronymus
  • J. Haworth
Keywords: balance, fatigue, nonlinear dynamics


Recently, researchers have begun to use nonlinear measures such as the Lyapunovexponent (LyE) and Approximate Entropy (ApEn) to examine temporal structure in the continuous behavior of biological systems. When using these measures a higher score indicates lesser periodicity and greater chaotic behavior. A decrease in LyE and ApEn values have been shown in some cases to indicate pathological conditions. Studies of postural control have found that after a cerebral concussion, an athlete’s center of pressure oscillations measured by ApEn are significantly decreased even up to 96 hours post-injury as compared with their preseason ApEn scores, even when the athlete appears steady (Cavanaugh, 2006). In regards to walking gate, local dynamic stability showed decreased variability when assessed amongst ACL reconstruction patients (Stergiou, 2004). The purpose of the current experiment ıs to use ApEn versus a set of traditional postural measure to evaluate a postural sway during upright stance prior to and following a bout of exhaustive running. In published balance studies only about 50% report significant improvements, possibly because traditional measures aren’t capturing the improvements in postural control. Promising results from the above cited studies indicate that nonlinear measures may be measuring elements that the traditional measures don’t detect.
Coaching and Sports Activities