Large postural fluctuations but unchanged postural sway dynamics during tiptoe standing compared to quiet standing

• Published in: Journal of electromyography and kinesiology Vol. 22; no. 6; pp. 975 - 982
• Main Authors: Tanabe, Hiroko, Fujii, Keisuke, Kouzaki, Motoki
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.12.2012
• Subjects: Adult; Analysis of Variance; Center of pressure; Coherence spectrum; Electromyography; Humans; Lower Extremity - physiology; Male; Muscle, Skeletal - physiology; Physical Medicine and Rehabilitation; Postural Balance - physiology; Posture - physiology; Power spectrum density; Stabilogram-diffusion analysis; Center of pressure; Coherence spectrum; Power spectrum density; Stabilogram-diffusion analysis
• DOI: 10.1016/j.jelekin.2012.05.006
• ISSN: 1050-6411; 1873-5711

The purpose of this study was to detect the characteristics of center of pressure (COP) movement during tiptoe standing (TS) compared to quiet standing (QS). Eight healthy subjects were asked to perform QS and TS on a force platform. During standing, surface electromyograms (EMGs) were recorded from the soleus (SOL), flexor hallucis brevis (FHB), medial gastrocnemius (MG), lateral gastrocnemius (LG), and tibialis anterior (TA) muscles. The path length and rectangular area of the COP trajectory were significantly larger during TS than during QS. In contrast, irrespective of standing condition, the scaling coefficients in the short and long regions were above and below 0.5, respectively. The coherence spectrum between the COP and EMG from the SOL and FHB muscles was statistically significant during TS at frequencies up to 17Hz, while that for the QS was only significant below 1Hz. In conclusion, the control of COP movement during TS was similar to that during QS despite large COP fluctuations during TS. Our results suggest that unstable posture during TS is compensated for by the activities of the SOL and FHB muscles, which enhance postural control.