Perceived Pain is Associated with Cardiovascular Responsiveness During Metaboreflex Activation in Apparently Healthy Young Males and Females.

Stimuli that evoke pain stimulate the sympathetic nervous system leading to downstream vascular and hemodynamic adjustments. In clinical populations and older individuals, the perception of pain is associated with cardiovascular responses (e.g., heart rate, blood pressure, and arterial stiffness). However, there are extensive inter-individual differences in the perception of pain, pain perception may be influenced by age, and it's unclear if pain is associated with cardiovascular responses in younger adults. PURPOSE: Therefore, we sought to determine whether heart rate, blood pressure, and arterial stiffness responses to sympathoexcitatory stimuli were associated with perceived pain, in apparently healthy young adults METHODS: 17 young adults (21.6±3.9 yrs; BMI: 24.4±2.8 kg/m ;Mean±SD) participated in this investigation. Following 10-min of supine rest, we measured heart rate (HR) and mean arterial pressure (MAP), via pulse wave analysis (PWA), and arterial stiffness via carotid-femoral pulse wave velocity (cf-PWV). Measures were obtained in duplicate then averaged for analysis. Participants then performed a 3-min isometric handgrip exercise (HG) at 30% of maximum voluntary contraction, which was immediately followed by 3-min of brachial cuff-occlusion at 240mmHg. Perceived pain was assessed via visual analog scale (0-10; 0=no pain, 10=most pain) at the first minute of each stimulus. HR and MAP were assessed at minute two and arterial stiffness was acquired in the final minute of each stimulus. Associations between perceived pain scores during HG and cuff-occlusion with percent change in cardiovascular responses were assessed using Spearman's correlations (α=0.05) RESULTS: During HG, significant (P<0.01) increases in HR (pre: 63±6 vs. post: 78±11 bpm; 23±15 %), MAP (pre: 86±9 vs. post: 105±14 mmHg; 22±10 %), and cf-PWV (pre: 6.5±1.7 vs. post: 7.2±1.0 m/s; 13±26 %) were observed. During cuff-occlusion, relative to pre, significant (P<0.05) increases in MAP (post: 100±13 mmHg; 18±15%) and cf-PWV (post: 7.2±1.4 m/s; 14±13%), but not (P>0.05) HR (post: 64±7 bpm; 7±6%) were observed. Perceived pain during cuff-occlusion (3.73±1.79 A.U.) was significantly greater (P=0.01) than during HG (1.88±1.20 A.U.). While no relationships were observed between perceived pain and cardiovascular responsiveness during HG (P>0.05) with HR (r=0.28; P=0.28), BP (r=0.45; P=0.07), or cf-PVW (r=0.28; P=0.28), perceived pain was associated with increases in BP (r=0.57; P=0.02) and cf-PWV (r=0.55; P=0.02;), but not HR (r=0.19; P=0.47), during cuff-occlusion. CONCLUSIONS: While pain during HG was not associated with cardiovascular responses, significantly greater cuff-occlusion evoked pain was associated with cardiovascular responsiveness. Our data suggests that the relation between perceived pain and cardiovascular responsiveness to sympathoexcitatory stimuli exists in younger adults, although additional data in larger cohorts and using varied stimuli are warranted.