Combined Cold Pressor Test And Rhythmic Handgrip Responses In Cold Pressor Test Hyperreactors Vs. Normoreactors

PURPOSE: Prior evidence indicates that the cold pressor test (CPT) opposes post-occlusive dilation response, but not the dilation response to voluntary handgrip exercise. However, whether this extends to individuals classified as hyperreactors to the CPT is unclear. This study tested the hypothesis that individuals classified as hyperreactors to the CPT would demonstrate attenuated increases in forearm blood flow (FBF) and vascular conductance (FVC) during rhythmic handgrip exercise (RHG) combined with CPT. METHODS: Beat by beat heart rate (HR; via electrocardiogram), blood pressure (via finger photoplethysmography), and femoral blood flow (FBF; via duplex Doppler ultrasound) were collected from 81 adults during 2 min of cold-water foot immersion (CPT), 2 min of RHG (performed at 25% MVC at a 1:1 work to rest ratio at 60 contractions per minute), and 2 min of combined CPT + RHG. Of these participants, 27 were classified as hyperreactors to the CPT based on increases in systolic [ΔSBP] or diastolic blood pressure [ΔDBP] >15 mmHg. Repeated measures analyses of variance examined the changes in HR (ΔHR), mean arterial pressure (ΔMAP), FBF (ΔFBF), and femoral vascular conductance (ΔFVC, calculated as the quotient of FBF and MAP) across conditions (CPT vs. RHG vs. RHG + CPT) and between groups. RESULTS: As expected, individuals classified as hyperreactors demonstrated significantly exaggerated ΔMAP (F = 16.96, p < 0.001) and ΔHR (F = 6.6, p = 0.002) responses across the CPT and CPT + HG conditions compared to the control group. However, no main effects of group (F < 0.786, p> 0.378) or group by condition interactions were observed for ΔFBF or ΔFVC (F< 0.87, p> 0.420). CONCLUSIONS: Despite significantly exaggerated blood pressure and HR responses, individuals classified as hyperreactors to the CPT do not demonstrate altered peripheral hemodynamic responses to exercise when performed in combination with the CPT. These findings support the notion that the exaggerated responses to the CPT in individuals classified as hyperreactors are likely due to generalized sympathetic overactivation rather than augmented peripheral vasoconstriction.