Attenuated spontaneous postural sway enhances diastolic blood pressure during quiet standing
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ORIGINAL ARTICLE
Attenuated spontaneous postural sway enhances diastolic blood pressure during quiet standing Ryo Naruse1 · Chinami Taki1 · Masayuki Yaegashi1 · Yusuke Sakaue2 · Naruhiro Shiozawa3 · Tetsuya Kimura1 Received: 6 May 2020 / Accepted: 26 September 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Purpose Spontaneous postural sway during quiet standing has been considered a simple output error of postural control. However, as postural sway and inherent body orientation evoke compensatory activity of the plantar flexors, they might contribute to blood circulation under gravitational stress via the muscle pump. Hence, the present study employed an external support device to attenuate the plantar flexor activity in supported standing (SS), to experimentally identify its physiological impact on blood circulation. Methods Eight healthy young subjects performed two 5-min quiet standing trials (i.e., normal standing (NS) and SS), and the beat-to-beat interval (RRI) and blood pressure (BP) were compared between trials. We confirmed that postural sway and corresponding plantar flexor activity, quantified by the anteroposterior displacement of the foot center of pressure and lower back position with respect to the wall, and by the amplitude of electromyography and mechanomyography, respectively, were attenuated in SS, while mean body orientation angle and relative position of the BP sensor were comparable to NS. Results The 5-min averages of diastolic BP and mean arterial pressure during SS were significantly higher than during NS, while RRI and systolic BP did not change. These could be interpreted as an increase in peripheral vascular resistance; meanwhile, in NS, this effect was replaced by the muscle pump of the plantar flexors. Conclusion The muscle contractions related to spontaneous postural sway and body orientation produce substantial physiological impact on blood circulation during quiet standing. Keywords Postural control · Blood circulation control · Postural sway · Body orientation · Muscle pump · Plantar flexion Abbreviations BP Beat-by-beat blood pressure CoM Center of mass CoMy Anteroposterior coordinate of center of mass CoP Foot center of pressure CoPy Anteroposterior coordinate of foot center of pressure DBP Beat-by-beat diastolic blood pressure Communicated by I. Mark Olfert. * Tetsuya Kimura [email protected]‑u.ac.jp 1
Graduate School of Human Development and Environment, Kobe University, 3‑11 Tsurukabuto, Nada‑ku, Kobe 657‑8501, Japan
2
Ritsumeikan Global Innovation Research Organization, Ritsumeikan University, Kusatsu, Japan
3
Faculty of Sport and Health Science, Ritsumeikan University, Kusatsu, Japan
∆θbody Rotation angle of body orientation around ankle joint EA Right elbow joint angle ECG Electrocardiography EMG Electromyography HF High-frequency range LF Low-frequency range LG Lateral head of gastrocnemius muscle MAP Beat-by-beat mean arterial pressure MG Medial head of gastrocnemius muscle MMG Mechanomyography MPF Mean
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