Abstract
Exercise recovery index (ERI; heart rate/oxygen consumption plateau), has been positively associated with body fat and is thought to be a minimally invasive method to assess sympathetic dysfunction within individuals at risk of cardiovascular disease. PURPOSE: To examine differences in sympathetic activity (SA), assessed by ERI and catecholamine release between obese and lean males. An additional aim was to determine the association of ERI with resting microvascular vasodilatory capacity (MVC), utilizing forearm blood flow (FBF). METHODS: Twenty apparently healthy (Obese: n=10, 36.7 ± 4.2 kg/m2; Lean: n=10, 21.6 ± 1.7 kg/m2) volunteers participated in a treadmill exercise test to exhaustion in which ERI was calculated during an immediate 5-min passive recovery. FBF measures, before and during reactive hyperemia (RH), were obtained prior to exercise. Blood samples were collected prior to the exercise (PRE) and again after the recovery period (POST). Epinephrine (EPI) and norepinephrine (NE) were quantified via enzyme-linked immunosorbent assay. RESULTS: The ERI was significantly greater in obese compared to lean males (18.5 ± 2.1 vs 12.2 ± 2.8 bpm · mLO2-1, P < 0.001). Although, no measures of MVC were significantly different between the two groups, the duration of FBF during RH was significantly correlated to ERI in obese males (r = 0.719, P = 0.019) only. EPI and NE were not significantly different prior to exercise between the two groups. In addition, EPI was significantly elevated following exercise (69.25 ± 34.86 vs. 152.78 ± 81.79 pg/mL, P < 0.001) in both groups, whereas NE was demonstrated an increase following exercise in only the lean males (417.91 ± 211.12 vs. 1468.77 ± 481.10 pg/mL, P < 0.001). Although exercise induced changes in NE was not related to ERI, elevated EPI was related to a lower ERI index (r = -0.654, P = 0.002). CONCLUSIONS: These results suggest that obese males may have an impaired sympathetic function (greater ERI), possibly due to less EPI uptake following exercise. Impaired sympathetic function may result in greater vascular tone, resulting in an increased duration of FBF during RH. Supported by VCU Presidential Research Incentive Program.
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