Introduction: Abnormalities in the autonomic nervous system in the presence of insulin resistance may be involved in the pathophysiology of obesity-associated hypertension. We evaluated the association between exercise-induced exaggerated blood pressure (BP) response [exercise-induced hypertension (EIH)] and heart rate variability (HRV) and insulin resistance in men with metabolic syndrome (MetS).
Materials and methods: Ninety-eight resting normotensive men with MetS underwent a maximal symptom-limited treadmill test. BP was measured after a 5-min rest (anticipatory BP) every 3 min during exercise and during the recovery period. EIH was defined as maximum systolic BP of 220 mmHg or higher and/or maximum diastolic BP of 100 mmHg or higher. Insulin resistance was estimated using HOMA-IR. Each participant underwent a 3-h oral glucose tolerance test (OGTT). HRV was derived from a 24-h Holter.
Results: About half of the participants (52%) presented EIH. Resting BPs at baseline were 125 ± 10/83 ± 7 mmHg in participants with EIH and 120 ± 9/80 ± 6 mmHg (P = 0.01) in the group with normal BP response to exercise. OGTT glucose levels were higher in the group with EIH (all P < 0.04) as well as HOMA-IR compared with participants with normal BP response to exercise (P = 0.03). In terms of HRV, 24-h standard deviation of the RR intervals (SDNN) was lower in participants with EIH (P = 0.04) as well as 24-h daytime and night-time high frequency and low frequency (P < 0.05).
Conclusion: Normotensive men with MetS but with EIH have greater insulin resistance as well as lower HRV parasympathetic and sympathetic indices. These features may be involved in the pathophysiology of EIH.