Hemodynamic responses to vibration in human calf muscle

Kurzfassung

HEMODYNAMIC RESPONSES TO VIBRATION IN HUMAN CALF MUSCLE Zange, J.1; Illbruck, A.1,2; Molitor, S.1; Kohl-Bareis, M.2; Rittweger, J.1 1: DLR, Institute of Aerospace Medicine, (Cologne, Germany); 2: University of Applied Technology Koblenz, Rhein-Ahr-Campus (Remagen, Germany) Introduction During whole body vibration training leg muscles moderately increase their energy turn-over (Zange et al. 2009) and absorb part of the kinetic energy by conversion into heat (Cochrane et al. 2008). This entails the need for appropriate blood supply. The present study focuses on the hemodynamic response to passive vibration in terms of blood content and blood oxygenation in the unloaded calf muscle exploring the relative contribution of the arterial and the venous compartment. The hypothesis was that venous restriction would prevail over arterial vasodilatation. Methods The subjects (n=12, male) sat in front of a vibration platform with their bare right foot affixed to the platform. The test included 2 intervals of 3 min vibration at either 15Hz or 25Hz (permutated order, ±2.5 mm amplitude), followed by 3 min recovery. Near infra-red spectroscopy (Geraskin, 2009) was used for measuring hemoglobin oxygen saturation (SmO2 in %) and the concentrations of oxygenated, desoxygenated, and total hemoglobin (HbO2, HbH, tHb) in the m. gastrocnemius medialis. EMG was recorded for the detection of reflex responses. Results Within the first 30s of vibration SmO2 increased from 56±7% to 68±4%. After having reached this maximum, SmO2 slowly decreased until it reached a steady state at 63±5% after almost 1.5 min of vibration. In the recovery phase SmO2 linearly decreased back to base line. No significant differences were found for frequency and the order of vibration intervals. The initial increase of SmO2 corresponded to a large decrease in HbH, a small increase in HbO2, and a decrease in tHb. The EMG was super-imposed by artefacts at the vibration frequency and its harmonics and did not reveal any evidence of muscular activity. Furthermore, there was no evidence for a reflex contraction by visual observation or subjects’ sensation. Discussion These observations suggest that in the unloaded calf muscle 15 and 25 Hz vibration initially cause a mechanical removal of predominantly desoxygenated blood from the capillaries and venules. Afterwards a moderate mismatch between oxygen supply and consumption was indicated by the decrease in SmO2 followed by a steady state indicating a balance. After vibration full recovery was reached within 3 min without indications of a reactive hyperemia. Of note, all these very clear changes occurred in the absence of EMG activity. The responsible mechanisms could e.g. be related to vasomotor responses or to basic muscle tone and need to be established by further studies. Reference Cochrane DJ, Stannard SR, Sargeant AJ, Rittweger J (2008) Eur J Appl Physiol 103: 441-448 Geraskin D, Boeth H, Kohl-Bareis M (2009) J Biomed Opt 14(4): 044017 Zange J, Haller T, Müller K, Liphardt AM, Mester J (2009) Eur J Appl Physiol 105: 265-270