Article Title



E. Flood1, I. Matthews1, L. Heenan1, K. Fisher1, B.J. Winn2, B.S. Kirby2, B.W. Wilkins1

1Gonzaga University, Spokane, WA.

2Nike Sport Research Lab, Nike Inc., Portland, OR.

Mental stress has a significant neuro-excitatory effect on the cardiovascular system and the maximal sustainable metabolic rate (critical intensity; CI) appears predicated on adequate oxygen supply to match demand. PURPOSE: To determine if mental stress alters the parameters of the power-duration relationship (CI) and if mental stress during exercise alters the balance between oxygen supply and demand. METHODS: 14 young (8 male, 6 female) participants completed five study days. Day 1: a three minute all out cycling (3MT) to determine baseline CI and maximal oxygen uptake. Days 2 & 3: a 3MT preceded by either a 2-min Color Word Stroop Test (Stroop) or a control test (counterbalanced order). Days 4 & 5: constant work-rate cycling trials at either 5% above or 5% below CI (counterbalanced order) as determined by the 3MT; a Stroop was performed while participants exercised at the prescribed work-rate. Oxygen uptake (VO2), heart rate (HR), and muscle oxygenation (%SmO2, thigh and shoulder sites) were assessed throughout exercise and venous blood lactate was determined before and after the 3MT’s and every 5 min during constant work-rate trials. Blood pressure was monitored continuously throughout the control and Stroop conditions which preceded the 3MT’s (Days 2 & 3). RESULTS: Blood pressure dynamics verified a robust pressor response to the Stroop, not observed in control (p<0.05). The pressor response increased the dynamic %SmO2 response (P<0.05) to the Stroop test. End test power (from 3MT) was similar following control (261±76 W) and Stroop (254±80 W) conditions. This was also true for maximal VO2 (50.7± 4.9 vs 50.9±3.8 ml/kg/min for control vs Stroop) and venous blood lactate (16.2±1.3 vs 17.2±1.9 mmol/L for control vs Stroop). There was a clear increase in %SmO2 to the Stroop (p<0.05), but only in the non-exercising muscle (shoulder site) and only during exercise at 5% below CI. CONCLUSIONS: Despite a clear pressor response leading to altered oxygen supply relative to demand, mental stress does not alter CI determined from a 3MT. However, there is a clear mismatch in oxygen supply relative to demand in non-exercising muscle during exercise below CI. This suggests a different exercise intensity and non-exercising muscle interaction in the control of blood flow during combined exercise and mental stress. Supported by Nike, Inc.

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