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Edgell H.,University of Alberta | Stickland M.K.,University of Alberta | Stickland M.K.,Center for Lung Health Covenant Health | Stickland M.K.,Mazankowski Alberta Heart Institute
American Journal of Physiology - Regulatory Integrative and Comparative Physiology | Year: 2014

Recent work has shown that the carotid chemoreceptor (CC) contributes to sympathetic control of cardiovascular function during exercise, despite no evidence of increased circulating CC stimuli, suggesting enhanced CC activity/sensitivity. As interactions between metaboreceptors and chemoreceptors have been previously observed, the purpose of this study was to isolate the metaboreflex while acutely stimulating or inhibiting the CC to determine whether the metaboreflex increased CC activity/sensitivity. Fourteen young healthy men (height: 177.0 ± 2.1 cm, weight: 85.8 ± 5.5 kg, age: 24.6 ± 1.1 yr) performed three trials of 40% maximal voluntary contraction handgrip for 2 min, followed by 3 min of postexercise circulatory occlusion (PECO) to stimulate the metaboreflex. In random order, subjects either breathed room air, hypoxia (target SPO2 = 85%), or hyperoxia (FIO2 = 1.0) during the PECO to modulate the chemoreflex. After these trials, a resting hypoxia trial was conducted without handgrip or PECO. Ventilation (V̇E), heart rate (HR), blood pressure, and muscle sympathetic nervous activity (MSNA) data were continuously obtained. Relative to normoxic PECO, inhibition of the CC during hyperoxic PECO resulted in lower MSNA (P = 0.038) and HR (P = 0.021). Relative to normoxic PECO, stimulation of the CC during hypoxic PECO resulted in higher HR (P < 0.001) and V̇E (P < 0.001). The ventilatory and MSNA responses to hypoxic PECO were not greater than the sum of the responses to hypoxia and PECO individually, indicating that the CC are not sensitized during metaboreflex activation. These results demonstrate that stimulation of the metaboreflex activates, but does not sensitize the CC, and help explain the enhanced CC activity with exercise. © 2014 the American Physiological Society. Source

Stickland M.K.,University of Alberta | Stickland M.K.,Center for Lung Health Covenant Health | Fuhr D.P.,University of Alberta | Haykowsky M.J.,University of Alberta | And 4 more authors.
Journal of Physiology | Year: 2011

Carotid chemoreceptor (CC) inhibition reduces sympathetic nervous outflow in exercising dogs and humans. We sought to determine if CC suppression increases muscle blood flow in humans during exercise and hypoxia. Healthy subjects (N= 13) were evaluated at rest and during constant-work leg extension exercise while exposed to either normoxia or hypoxia (inspired O 2 tension, ≈ 0.12, target arterial O 2 saturation = 85%). Subjects breathed hyperoxic gas (≈ 1.0) and/or received intravenous dopamine to inhibit the CC while femoral arterial blood flow data were obtained continuously with pulsed Doppler ultrasound. Exercise increased heart rate, mean arterial pressure, femoral blood flow and conductance compared to rest. Transient hyperoxia had no significant effect on blood flow at rest, but increased femoral blood flow and conductance transiently during exercise without changing blood pressure. Similarly, dopamine had no effect on steady-state blood flow at rest, but increased femoral blood flow and conductance during exercise. The transient vasodilatory response observed by CC inhibition with hyperoxia during exercise could be blocked with simultaneous CC inhibition with dopamine. Despite evidence of dopamine reducing ventilation during hypoxia, no effect on femoral blood flow, conductance or mean arterial pressure was observed either at rest or during exercise with CC inhibition with dopamine while breathing hypoxia. These findings indicate that the carotid chemoreceptor contributes to skeletal muscle blood flow regulation during normoxic exercise in healthy humans, but that the influence of the CC on blood flow regulation in hypoxia is limited. © 2011 The Authors. Journal compilation © 2011 The Physiological Society. Source

Stickland M.K.,University of Alberta | Stickland M.K.,Center for Lung Health Covenant Health | Vogan N.,University of Alberta | Petersen S.R.,University of Alberta | And 2 more authors.
Respiratory Physiology and Neurobiology | Year: 2013

Arterial stiffness is predictive of cardiovascular events and is elevated in chronic obstructive pulmonary disease (COPD). As physical inactivity and exercise intolerance are associated with elevated arterial stiffness in health, we hypothesized that lower physical activity would be related to increased arterial stiffness in COPD; and that active COPD patients would have reduced arterial stiffness compared to sedentary counterparts. Arterial stiffness was evaluated using pulse wave velocity (PWV) in 33 COPD patients (FEV1=65% predicted) and 10 controls. FEV1%pred, peak oxygen consumption (VO2peak), and physical activity data were obtained. The inactive COPD group had higher PWV than controls (9.6 vs. 8.3ms-1, p<0.05); while there was no difference in PWV between the active COPD group and controls. Within the COPD patients, V̇O2peak (r=-0.44, p=0.01) and physical activity (r=-0.38, p=0.03) were the best predictors of PWV. Physical inactivity and exercise intolerance appear to be related to arterial stiffness in COPD, and may contribute to increased cardiovascular disease risk in COPD. © 2013 Published by Elsevier B.V. Source

Ramadi A.,University of Alberta | Stickland M.K.,University of Alberta | Stickland M.K.,Center for Lung Health Covenant Health | Rodgers W.M.,University of Alberta | Haennel R.G.,University of Alberta
Heart and Lung: Journal of Acute and Critical Care | Year: 2015

Objectives: The purpose of this study was to assess the impact of exercise rehabilitation (ER) on the daily physical activity (PA) of cardiopulmonary patients. Background: The impact of ER programs on the objectively measured quantity and quality of daily PA in cardiopulmonary patients is not completely understood. Methods: Participants' exercise capacity and PA were measured at baseline and at the end of the ER program (. n=37). Results: Exercise capacity was higher at the end of the ER. Participants' sedentary time decreased while time spent in light PA increased; however, time spent in moderate-vigorous PA (MVPA) did not change. There was an increase in steps/day (>1.5 METs) and PA energy expenditure (PAEE) (>1.5 METs); whereas steps/day (≥3METs) and PAEE (≥3 METs) remained unchanged. Conclusions: Findings imply that changes in daily PA in patients participating in ER occur in activities where the EE is in light intensity rather than in MVPA. © 2015 Elsevier Inc. Source

Rodgers W.M.,University of Alberta | Selzler A.-M.,University of Alberta | Haennel R.G.,University of Alberta | Holm S.,University of Alberta | And 3 more authors.
Journal of Behavioral Medicine | Year: 2014

Techniques to increase physical activity among pulmonary rehabilitation patients outside of the rehabilitation context are warranted. Implementation intentions are a strategy used to initiate goal-directed behaviour, and have been found to be useful in other populations. This study compared the long-term effects of exercise and social implementation intentions interventions on objectively measured physical activity in 40 pulmonary rehabilitation patients randomly assigned to condition. Repeated measures ANOVAs found that those in the exercise implementation intentions group took more steps (p =.007) at the end of pulmonary rehabilitation than those in the social implementation intentions group. Improvements attained by the exercise group during the intervention were not maintained 6-months following rehabilitation. Implementation intentions targeting physical activity appear to have positive short term effects on physical activity, although the long term effects are less consistent. This may be due in part to methods used to assess physical activity behaviour. © 2013 Springer Science+Business Media New York. Source

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