Improvement in Hemodynamic Responses to Metaboreflex Activation after One Year of Training in Spinal Cord Injured Humans

Abstract

Spinal cord injured (SCI) individuals show an altered hemodynamic response to metaboreflex activation due to a reduced capacity to vasoconstrict the venous and arterial vessels below the level of the lesion. Exercise training was found to enhance circulating catecholamines and to improve cardiac preload and venous tone in response to exercise in SCI subjects. Therefore, training would result in enhanced diastolic function and capacity to vasoconstrict circulation. The aim of this study was to test the hypothesis that one year of training improves hemodynamic response to metaboreflex activation in these subjects. Nine SCI individuals were enrolled and underwent a metaboreflex activation test at the beginning of the study (T0) and after one year of training (T1). Hemodynamics were assessed by impedance cardiography and echocardiography at both T0 and T1. Results show that there was an increment in cardiac output response due to metaboreflex activity at T1 as compared to T0 (545.4 ± 683.9 mL·min−1 versus 220.5 ± 745.4 mL·min−1, P < 0.05). Moreover, ventricular filling rate response was higher at T1 than at T0. Similarly, end-diastolic volume response was increased after training. We concluded that a period of training can successfully improve hemodynamic response to muscle metaboreflex activation in SCI subjects.

Differences in hemodynamic response to metaboreflex activation between obese patients with metabolic syndrome and healthy subjects with obese phenotype

“…The response in this parameter was higher in the CTL than in the OMS group, whereas no difference was present between the two groups with obesity, with the MHO group showing a behavior in the medium between those of the CTL and of the OMS group. The increase in VFR occurring in the CTL and in the MHO group is similar to what has been reported in previous human research with similar experimental settings (13,14,29) and confirms that an increase in diastolic flow takes place during the metaboreflex in normal individuals, probably because of a sympathetic-mediated venous and splanchnic constriction (32,53,54). The lack of VFR response in the OMS group appears to suggest that, in subjects with complicated obesity, certain phenomena likely prevented the normal increase in venous return and cardiac preload.…”

Cardiovascular Reflexes Activity and Their Interaction during Exercise

“…This phenomenon facilitates venous return and produces a sort of blood volume “centralization” in order to support SV and CO [ 36 , 41 , 49 ]. In particular, a reduction in ventricular filling rate, a measure of diastolic function, has been reported to impair the metaboreflex-induced SV response [ 36 , 38 , 49 , 50 ]. Moreover, it has been recently reported that healthy, elderly subjects show an impaired SV response via the metaboreflex as compared to young individuals because of their reduction in cardiac compliance which impaired diastolic filling [ 43 ].…”

Low Frequencies of Physical Activity in Patients with Spinal Cord Injury

“…However, some improvement was observed on pre-loading due to increased venous tone and more effective operation of the muscle pump after training. Milia et al (2014)34 examined haemodynamic response to muscle activation in SCI with a one-year training period. They found that mean blood pressure response was significantly increased after the period of training, enhancement of HR, cardiac output, ventricular filling rate, and end diastolic volume responses.…”