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Terwoord JD, Hearon CM, Racine ML, Ketelhut NB, Luckasen GJ, Richards JC, Dinenno FA. K IR channel activation links local vasodilatation with muscle fibre recruitment during exercise in humans. J Physiol 2020; 598:2621-2636. [PMID: 32329892 DOI: 10.1113/jp279682] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2020] [Accepted: 04/17/2020] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS During exercise, blood flow to working skeletal muscle increases in parallel with contractile activity such that oxygen delivery is sufficient to meet metabolic demand. K+ released from active skeletal muscle fibres could facilitate vasodilatation in proportion to the degree of muscle fibre recruitment. Once released, K+ stimulates inwardly rectifying K+ (KIR ) channels on the vasculature to elicit an increase in blood flow. In the present study, we demonstrate that KIR channels mediate the rapid vasodilatory response to an increase in exercise intensity. We also show that KIR channels augment vasodilatation during exercise which demands greater muscle fibre recruitment independent of the total amount of work performed. These results suggest that K+ plays a key role in coupling the magnitude of vasodilatation to the degree of contractile activity. Ultimately, the findings from this study help us understand the signalling mechanisms that regulate muscle blood flow in humans. ABSTRACT Blood flow to active skeletal muscle is augmented with greater muscle fibre recruitment. We tested whether activation of inwardly rectifying potassium (KIR ) channels underlies vasodilatation with elevated muscle fibre recruitment when work rate is increased (Protocol 1) or held constant (Protocol 2). We assessed forearm vascular conductance (FVC) during rhythmic handgrip exercise under control conditions and during local inhibition of KIR channels (intra-arterial BaCl2 ). In Protocol 1, healthy volunteers performed mild handgrip exercise for 3 min, then transitioned to moderate intensity for 30 s. BaCl2 eliminated vasodilatation during the first contraction at the moderate workload (ΔFVC, BaCl2 : -1 ± 17 vs. control: 30 ± 28 ml min-1 100 mmHg-1 ; n = 9; P = 0.004) and attenuated the 30 s area under the curve by 56 ± 14% (n = 9; P < 0.0001). In Protocol 2, participants performed two exercise bouts in which muscle fibre recruitment was manipulated while total contractile work was held constant via reciprocal changes in contraction frequency: (1) low fibre recruitment, with contractions at 12.5% maximal voluntary contraction once every 4 s and (2) high fibre recruitment, with contractions at 25% maximal voluntary contraction once every 8 s. Under control conditions, steady-state FVC was augmented in high vs. low fibre recruitment (211 ± 90 vs. 166 ± 73 ml min-1 ⋅100 mmHg-1 ; n = 10; P = 0.0006), whereas BaCl2 abolished the difference between high and low fibre recruitment (134 ± 59 vs. 134 ± 63 ml min-1 100 mmHg-1 ; n = 10; P = 0.85). These findings demonstrate that KIR channel activation is a key mechanism linking local vasodilatation with muscle fibre recruitment during exercise.
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Affiliation(s)
- Janée D Terwoord
- Human Cardiovascular Physiology Laboratory, Department of Health and Exercise Science, Colorado State University, Fort Collins, CO, USA
| | - Christopher M Hearon
- Human Cardiovascular Physiology Laboratory, Department of Health and Exercise Science, Colorado State University, Fort Collins, CO, USA
| | - Matthew L Racine
- Human Cardiovascular Physiology Laboratory, Department of Health and Exercise Science, Colorado State University, Fort Collins, CO, USA
| | - Nathaniel B Ketelhut
- Human Cardiovascular Physiology Laboratory, Department of Health and Exercise Science, Colorado State University, Fort Collins, CO, USA
| | - Gary J Luckasen
- Medical Center of the Rockies Foundation, University of Colorado Health, Loveland, CO, USA
| | - Jennifer C Richards
- Human Cardiovascular Physiology Laboratory, Department of Health and Exercise Science, Colorado State University, Fort Collins, CO, USA
| | - Frank A Dinenno
- Human Cardiovascular Physiology Laboratory, Department of Health and Exercise Science, Colorado State University, Fort Collins, CO, USA
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Dillon GA, Shepherd JR, Casey DP, Dinenno FA, Curry TB, Joyner MJ, Ranadive SM. Rapid-onset vasodilator responses to exercise in humans: Effect of increased baseline blood flow. Exp Physiol 2020; 105:88-95. [PMID: 31762131 PMCID: PMC6938538 DOI: 10.1113/ep088227] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2019] [Accepted: 11/22/2019] [Indexed: 11/08/2022]
Abstract
NEW FINDINGS What is the central question of this study? What is the effect of an elevated baseline blood flow, induced by high-dose intra-arterial infusion of either adenosine or ATP, on the rapid-onset vasodilatory response to a single forearm muscle contraction? What is the main finding and its importance? The peak response to a single contraction is unaffected by augmented baseline blood flow, and thus, is likely to be attributable to a feedforward vasodilatory mechanism. ABSTRACT The hyperaemic responses to single muscle contractions are proportional to exercise intensity, which, in turn, is proportional to tissue metabolic demand. Hence, we tested the hypothesis that the rapid-onset vasodilatory response after a single muscle contraction would be unaffected when baseline blood flow was increased via high-dose intra-arterial infusion of either adenosine (ADO) or ATP. Twenty-four healthy young participants (28 ± 1 years) performed a single forearm contraction (20% maximal voluntary contraction) 75 min after commencement of a continuous infusion of ADO (n = 6), ATP (n = 8) or saline (control; n = 10). Brachial artery diameter and blood velocity were measured using Doppler ultrasound. Resting forearm vascular conductance (FVC; in millilitres per minute per 100 mmHg per decilitre of forearm volume) was significantly higher during ADO (33 ± 17) and ATP infusion (33 ± 17) compared with the control infusion (8 ± 3; P < 0.05). The peak FVCs post-contraction during ADO and ATP infusions were significantly greater than during the control infusion (P < 0.05), but not different from one another. The peak change in FVC from baseline was similar in all three conditions (control, 14 ± 1; ADO, 24 ± 2; and ATP, 23 ± 6; P = 0.15). Total FVC (area under the curve) did not differ significantly between ADO and ATP (333 ± 69 and 440 ± 125); however, total FVC during ATP infusion was significantly greater compared with the control value (150 ± 19; P < 0.05). We conclude that the peak response to a single contraction is unaffected by augmented baseline blood flow and is therefore likely to be attributable to a feedforward vasodilatory mechanism.
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Affiliation(s)
- Gabrielle A. Dillon
- Department of Anesthesiology, Mayo Clinic, Rochester, MN 55905 United States
| | - John R.A. Shepherd
- Department of Anesthesiology, Mayo Clinic, Rochester, MN 55905 United States
| | - Darren P. Casey
- Department of Physical Therapy and Rehabilitation Science, University of Iowa, Iowa City, IA 52242 United States
| | - Frank A. Dinenno
- Department of Health and Exercise Science, and Center for Cardiovascular Research, Colorado State University, Fort Collins, CO 80523 United States
| | - Timothy B. Curry
- Department of Anesthesiology, Mayo Clinic, Rochester, MN 55905 United States
| | - Michael J. Joyner
- Department of Anesthesiology, Mayo Clinic, Rochester, MN 55905 United States
| | - Sushant M. Ranadive
- Department of Anesthesiology, Mayo Clinic, Rochester, MN 55905 United States
- Department of Kinesiology, University of Maryland, College Park, MD 20742 United States
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Garten RS, Hogwood AC, Weggen J, Decker K, Darling A, Maniyar R, Michael A. Examining Arm Vascular Function and Blood Flow Regulation in Row-trained Males. Med Sci Sports Exerc 2019; 51:2058-2066. [PMID: 31009422 DOI: 10.1249/mss.0000000000002014] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Vascular function and blood flow responses to upper limb exercise are differentially altered in response to different exercise training modalities. Rowing is a unique exercise modality that incorporates the upper limbs and can significantly augment upper limb endurance, strength, and power capacity. PURPOSE This study sought to determine whether vascular function and blood flow regulation during handgrip exercise are altered in row-trained males. METHODS Nine young row-trained males (ROW, 20 ± 1 yr; V˙O2peak = 51 ± 2 mL·kg·min) and 14 recreationally active male controls (C: 22 ± 1 yr; V˙O2peak = 37 ± 2 mL·kg·min) were recruited for this study. Subjects performed multiple bouts of progressive rhythmic handgrip exercise. Brachial artery (BA) diameter, blood flow, shear rate, and mean arterial pressure were measured at rest and during the last minute of each exercise workload. RESULTS Resting values for BA diameter, blood flow, shear rate, and mean arterial pressure were not different between groups. During handgrip exercise, the ROW group reported significantly lower BA blood flow (ROW vs C: 4 kg [146 ± 21 vs 243 ± 13 mL·min], 8 kg [248 ± 29 vs 375 ± 17 mL·min], 12 kg [352 ± 43 vs 490 ± 22 mL·min]) across all workloads when compared with controls. The examination of BA dilation, when controlled for the shear rate stimulus and evaluated across all workloads, was revealed to be significantly greater in ROW group versus controls. CONCLUSION This study revealed that vascular function and blood flow regulation were significantly different in row-trained males when compared with untrained controls evidenced by greater shear-induced BA dilation and lower arm blood flow during progressive handgrip exercise.
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Affiliation(s)
- Ryan S Garten
- Department of Kinesiology and Health Sciences, Virginia Commonwealth University, Richmond, VA
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4
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Liu W, Kuang H, Xia Y, Pope ZC, Wang Z, Tang C, Yin D. Regular aerobic exercise-ameliorated troponin I carbonylation to mitigate aged rat soleus muscle functional recession. Exp Physiol 2019; 104:715-728. [PMID: 30820991 DOI: 10.1113/ep087564] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2018] [Accepted: 02/27/2019] [Indexed: 12/23/2022]
Abstract
NEW FINDINGS What is the central question of this study? What is the biological role of carbonylation in muscle age-related functional decline and how might exercise affect the carbonylation process differently compared to habitual sedentary behaviour? What is the main finding and its importance? The carbonylation of troponin I (TNNI1), tropomyosin α-1 chain and α-actinin-1 demonstrated a relationship with muscle age-related functional decline. Exercise attenuated the decline by slowing the rate of carbonylation and promoting antioxidant reactions within the muscle. As exercise demonstrated the greatest effect on TNNI1, quantification of protein carbonyls in TNNI1 may be used as a potential biomarker of muscle age-related functional decline. ABSTRACT This study investigated the biological role of carbonylation in muscle age-related functional decline and how regular aerobic exercise may affect the carbonylation process differently from habitual sedentary behaviour. Twenty-four healthy male Sprague-Dawley (SD) rats (mean age: 23 months) were randomly divided into an old-aged sedentary control group (O-SED) and an old-aged aerobic exercise group (O-EX). The O-EX group participated in regular aerobic exercise - treadmill running - with exercise intensity increased gradually from 50-55% to 65-70% of maximum oxygen consumption ( V ̇ O 2 max ) over 10 weeks. Rats' body weight, exercise behaviour index, morphology and oxidative stress were monitored. Avidin magnetic beads and electrospray ionization quadrupole time-of-flight mass spectrometry were used for gathering and separating carbonylated proteins while western blot tested for molecular targets. O-SED and O-EX rats both had 19 oxidative modification sites for protein carbonylation. In the O-SED group, 16 specific carbonylated proteins were identified, while 16 additional specific species were also found in the O-EX group, with all 28 species demonstrating oxidative modifications. The carbonylated proteins included troponin I (TNNI1; slow skeletal muscle), tropomyosin α1 and α-actinin 1. In particular, TNNI1 carbonylation modifications were found only in sedentary rats. Aerobic exercise increased TNNI1 and Ca2+ /calmodulin-dependent protein kinase IIα expression significantly. Observations suggested that quantification of TNNI1 carbonylation may be a potential biomarker of muscle age-related functional decline. Importantly, regular aerobic exercise appeared to have antioxidant effects in the muscle that reduced TNNI1 slow carbonylation and promoted Ca2+ /calmodulin-dependent protein kinase IIα (CAMK2) and TNNI1 expression for skeletal muscle contraction regulation, thus attenuating possible age-related skeletal muscle functional decline.
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Affiliation(s)
- Wenfeng Liu
- Hunan Provincial Key Laboratory of Physical Fitness and Sports Rehabilitation, Hunan Normal University, Changsha, Hunan, 410012, China.,Department of Experimental and Clinical Pharmacology, University of Minnesota, Minneapolis, MN, 55455, USA
| | - Heyu Kuang
- Hunan Provincial Key Laboratory of Physical Fitness and Sports Rehabilitation, Hunan Normal University, Changsha, Hunan, 410012, China
| | - Yan Xia
- Hunan Provincial Key Laboratory of Physical Fitness and Sports Rehabilitation, Hunan Normal University, Changsha, Hunan, 410012, China
| | - Zachary C Pope
- School of Public Health, University of Minnesota, Minneapolis, MN, 55455, USA
| | - Zhiyuan Wang
- Hunan Provincial Key Laboratory of Physical Fitness and Sports Rehabilitation, Hunan Normal University, Changsha, Hunan, 410012, China
| | - Changfa Tang
- Hunan Provincial Key Laboratory of Physical Fitness and Sports Rehabilitation, Hunan Normal University, Changsha, Hunan, 410012, China
| | - Dazhong Yin
- Hunan Provincial Key Laboratory of Physical Fitness and Sports Rehabilitation, Hunan Normal University, Changsha, Hunan, 410012, China.,Qingyuan People's Hospital, the Sixth Affiliated Hospital, Guangzhou Medical University, Guangzhou, Guangdong, 511500, China
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Ranadive SM, Shepherd JRA, Curry TB, Dinenno FA, Joyner MJ. Sustained exercise hyperemia during prolonged adenosine infusion in humans. Physiol Rep 2019; 7:e14009. [PMID: 30806018 PMCID: PMC6389741 DOI: 10.14814/phy2.14009] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2019] [Accepted: 01/28/2019] [Indexed: 11/24/2022] Open
Abstract
The contribution of Adenosine (ADO) to exercise hyperemia remains controversial and it is unknown whether ADO can evoke the prolonged vasodilation seen during exercise bouts. Therefore, we tested hypotheses in the human forearm during 3 h of intra-arterial high dose ADO infusion: (1) skeletal muscle blood flow would wane over time; (2) exercise hyperemic responses during ADO administration would be unaffected compared to baseline. Using sodium nitroprusside (SNP), we tested parallel hypotheses regarding nitric oxide (NO) in a separate group of participants. Seventeen young healthy participants (ADO: n = 9; SNP: n = 8) performed multiple rhythmic handgrip exercise bouts (20% of maximum), two during saline and five during 3 h of continuous drug infusion. Five minutes of ADO infusion resulted in a ~5-fold increase in forearm vascular conductance (FVC; 4.8 ± 0.6 vs. 24.2 ± 3.2 mL/min/100 mmHg, P < 0.05). SNP caused a ~4-fold increase (4.4 ± 0.6 vs. 16.6 ± 2 mL/min/100 mmHg, P < 0.05). FVC did not wane over time with ADO (24.2 ± 3.2 and 22 ± 1.2 mL/min/100 mmHg [P > 0.05]) or SNP (16.6 ± 2 and 14.1 ± 2.4 mL/min/ 100 mmHg [P > 0.05]) at 5 versus 150 min. Superimposed exercise during ADO or SNP infusions evoked marked and consistent additional dilation over the course of the infusions. Our findings demonstrate that in humans there is no reduction in endothelial or vascular smooth muscle responsiveness to the exogenous vasodilatory metabolites ADO and NO. Additionally, even in the presence of an exogenous vasodilator, superimposed exercise can cause significant hyperemia.
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Affiliation(s)
- Sushant M. Ranadive
- Department of AnesthesiologyMayo ClinicRochesterMinnesota
- Department of KinesiologySchool of Public HealthUniversity of MarylandCollege ParkMaryland
| | | | | | - Frank A. Dinenno
- Department of Health and Exercise Science and Center for Cardiovascular ResearchColorado State UniversityFort CollinsColorodo
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6
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Caldwell JT, Sutterfield SL, Post HK, Lovoy GM, Banister HR, Hammer SM, Ade CJ. Vasoconstrictor responsiveness through alterations in relaxation time and metabolic rate during rhythmic handgrip contractions. Physiol Rep 2018; 6:e13933. [PMID: 30511427 PMCID: PMC6277543 DOI: 10.14814/phy2.13933] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2018] [Revised: 10/29/2018] [Accepted: 10/31/2018] [Indexed: 11/24/2022] Open
Abstract
Increasing the relaxation phase of the contraction-relaxation cycle will increase active skeletal muscle blood flow ( Q ˙ m ). However, it remains unknown if this increase in Q ˙ m alters the vasoconstriction responses in active skeletal muscle. This investigation determined if decreasing mechanical impedance would impact vasoconstriction of the active skeletal muscle. Eight healthy men performed rhythmic handgrip exercise under three different conditions; "low" duty cycle at 20% maximal voluntary contraction (MVC), "low" duty cycle at 15% MVC, and "high" duty cycle at 20% MVC. Relaxation time between low and high duty cycles were 2.4 sec versus 1.5 sec, respectively. During steady-state exercise lower body negative pressure (LBNP) was used to evoke vasoconstriction. Finger photoplethysmography and Doppler ultrasound derived diameters and velocities were used to measure blood pressure, forearm blood flow (FBF: mL min-1 ) and forearm vascular conductance (FVC: mL min-1 mmHg) throughout testing. The low duty cycle increased FBF and FVC versus the high duty cycle under steady-state conditions at 20% MVC (P < 0.01). The high duty cycle had the greatest attenuation in %ΔFVC (-1.9 ± 3.8%). The low duty cycle at 20% (-13.3 ± 1.4%) and 15% MVC (-13.1 ± 2.5%) had significantly greater vasoconstriction than the high duty cycle (both: P < 0.01) but were not different from one another (P = 0.99). When matched for work rate and metabolic rate ( V ˙ O 2 ), the high duty cycle had greater functional sympatholysis than the low duty cycle. However, despite a lower V ˙ O 2 , there was no difference in functional sympatholysis between the low duty cycle conditions. This may suggest that increases in Q ˙ m play a role in functional sympatholysis when mechanical compression is minimized.
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Affiliation(s)
| | | | - Hunter K. Post
- Department of KinesiologyKansas State UniversityManhattanKansas
| | | | | | - Shane M. Hammer
- Department of KinesiologyKansas State UniversityManhattanKansas
| | - Carl J. Ade
- Department of KinesiologyKansas State UniversityManhattanKansas
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7
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Terwoord JD, Hearon CM, Luckasen GJ, Richards JC, Joyner MJ, Dinenno FA. Elevated extracellular potassium prior to muscle contraction reduces onset and steady-state exercise hyperemia in humans. J Appl Physiol (1985) 2018; 125:615-623. [PMID: 29722620 DOI: 10.1152/japplphysiol.00183.2018] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The increase in interstitial potassium (K+) during muscle contractions is thought to be a vasodilatory signal that contributes to exercise hyperemia. To determine the role of extracellular K+ in exercise hyperemia, we perfused skeletal muscle with K+ before contractions, such that the effect of any endogenously-released K+ would be minimized. We tested the hypothesis that local, intra-arterial infusion of potassium chloride (KCl) at rest would impair vasodilation in response to subsequent rhythmic handgrip exercise in humans. In 11 young adults, we determined forearm blood flow (FBF) (Doppler ultrasound) and forearm vascular conductance (FVC) (FBF/mean arterial pressure) during 4 min of rhythmic handgrip exercise at 10% of maximal voluntary contraction during 1) control conditions, 2) infusion of KCl before the initiation of exercise, and 3) infusion of sodium nitroprusside (SNP) as a control vasodilator. Infusion of KCl or SNP elevated resting FVC similarly before the onset of exercise (control: 39 ± 6 vs. KCl: 81 ± 12 and SNP: 82 ± 13 ml·min-1·100 mmHg-1; both P < 0.05 vs. control). Infusion of KCl at rest diminished the hyperemic (ΔFBF) and vasodilatory (ΔFVC) response to subsequent exercise by 22 ± 5% and 30 ± 5%, respectively (both P < 0.05 vs. control), whereas SNP did not affect the change in FBF ( P = 0.74 vs. control) or FVC ( P = 0.61 vs. control) from rest to steady-state exercise. These findings implicate the K+ ion as an essential vasodilator substance contributing to exercise hyperemia in humans. NEW & NOTEWORTHY Our findings support a significant and obligatory role for potassium signaling in the local vasodilatory and hyperemic response to exercise in humans.
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Affiliation(s)
- Janée D Terwoord
- Human Cardiovascular Physiology Laboratory, Department of Health and Exercise Science, Colorado State University , Fort Collins, Colorado
| | - Christopher M Hearon
- Human Cardiovascular Physiology Laboratory, Department of Health and Exercise Science, Colorado State University , Fort Collins, Colorado.,Institute for Exercise and Environmental Medicine, University of Texas Southwestern Medical Center , Dallas, Texas
| | - Gary J Luckasen
- Medical Center of the Rockies Foundation, University of Colorado Health, Loveland, Colorado
| | - Jennifer C Richards
- Human Cardiovascular Physiology Laboratory, Department of Health and Exercise Science, Colorado State University , Fort Collins, Colorado
| | - Michael J Joyner
- Department of Anesthesiology, Mayo Clinic , Rochester, Minnesota
| | - Frank A Dinenno
- Human Cardiovascular Physiology Laboratory, Department of Health and Exercise Science, Colorado State University , Fort Collins, Colorado
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8
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Kruse NT, Hughes WE, Ueda K, Casey DP. Vasoconstrictor responsiveness in contracting human muscle: influence of contraction frequency, contractile work, and metabolic rate. Eur J Appl Physiol 2017. [PMID: 28624852 DOI: 10.1007/s00421-017-3660-7] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
PURPOSE The aim of this study was to examine whether independent effects exist between contractile work and metabolic demand (VO2m) on vasoconstrictor responsiveness (i.e., functional sympatholysis) under different contraction durations matched for total contractile work in exercising human skeletal muscle. METHODS Ten young men performed rhythmic forearm contractions at 10 and 15% of maximum voluntary contraction (MVC) which consisted of muscle contractions using the same duty cycle but altering the duration of the contraction-relaxation cycles of exercise and included: 1) fast frequency contractions at 10% MVC (FFC10%) using a contraction relaxation cycle at 1:2 s; 2) slow frequency contractions at 10% MVC (SFC10%) at 2:4 s; and 3) SFC at 15% MVC (SFC15%) at 2:4 s. Lower body negative pressure (LBNP) was applied to increase sympathetic vasoconstriction during forearm exercise. Brachial artery diameter and blood velocities (measured via Doppler ultrasound) determined forearm blood flow (FBF), and forearm vascular conductance (FVC) was calculated from FBF (ml min-1) and mean arterial blood pressure. RESULTS Results revealed that steady-state indices of FBF, FVC, and VO2m were greater (P < 0.05) in FFC10% and SFC15% vs. SFC10%. In addition, the magnitude of vasoconstriction (percent reduction in FVC) in response to reflex increases in sympathetic activity during LBNP was greater with SFC10% vs. FFC10% (-20.6 ± 3.0 vs. -11.1 ± 2.0%; P < 0.05), whereas there was no difference with FFC10% vs. SFC15% (-11.1 ± 2.0 vs. -11.8 ± 1.8%; P = 0.91). CONCLUSIONS Our data indicate that faster work-matched muscle contractions increase blood flow and metabolism, leading to improved functional sympatholysis as compared to slower work-matched muscle contractions in humans.
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Affiliation(s)
- Nicholas T Kruse
- Department of Physical Therapy and Rehabilitation Science, Carver College of Medicine, University of Iowa, Iowa, IA, 52242, USA. .,Abboud Cardiovascular Research Center, Iowa, IA, USA.
| | - William E Hughes
- Department of Physical Therapy and Rehabilitation Science, Carver College of Medicine, University of Iowa, Iowa, IA, 52242, USA
| | - Kenichi Ueda
- Department of Anesthesia, Carver College of Medicine, University of Iowa, Iowa, IA, USA
| | - Darren P Casey
- Department of Physical Therapy and Rehabilitation Science, Carver College of Medicine, University of Iowa, Iowa, IA, 52242, USA.,Abboud Cardiovascular Research Center, Iowa, IA, USA.,Fraternal Order of Eagles Diabetes Research, Iowa, IA, USA
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9
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Bentley RF, Poitras VJ, Hong T, Tschakovsky ME. Characteristics and effectiveness of vasodilatory and pressor compensation for reduced relaxation time during rhythmic forearm contractions. Exp Physiol 2017; 102:621-634. [PMID: 28397384 DOI: 10.1113/ep086069] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2016] [Accepted: 03/30/2017] [Indexed: 11/08/2022]
Abstract
NEW FINDINGS What is the central question of this study? Reduced relaxation time between contractions in exercise requires increased vasodilatation and/or pressor response to prevent hypoperfusion and potential compromise to exercise tolerance. However, it remains unknown whether and to what extent local vasodilatation and/or systemic pressor compensation occurs and whether the efficacy of compensation is exercise intensity dependent. What is the main finding and its importance? We demonstrate that in a forearm exercise model vasodilatory but not pressor compensation occurs and is adequate to prevent hypoperfusion below but not above ∼40% peak work rate. Inadequate compensation occurs with exercise still well inside the submaximal domain, despite a vasodilatory reserve, and compromises exercise performance. During muscle contraction in rhythmic exercise, muscle blood flow is significantly impeded by microvascular compression. The purpose of this study was to establish the nature and magnitude of vasodilatory and/or pressor compensatory responses during forearm exercise in the face of an increased duration of mechanical microvascular compression, and whether the effectiveness of such compensation was exercise intensity dependent. Seven healthy males (21.0 ± 1.8 years old) completed progressive forearm exercise (24.5 N every 3 min; 2 s contraction-4 s relaxation duty cycle) in two conditions: control (CON), 2 s 100 mmHg forearm cuff inflation during contraction; and impedance (IMP), extension of cuff inflation 2 s beyond contraction. Forearm blood flow (in millilitres per minute); brachial artery Doppler and echo ultrasound), mean arterial blood pressure (in millimetres of mercury; finger photoplethysmography) and exercising forearm venous effluent (antecubital vein catheter) measurements revealed an exercise intensity-dependent compensatory vasodilatation effectiveness whereby increased vasodilatation fully protected forearm blood flow up to the 30% exercise intensity in IMP. Above this exercise intensity, forearm blood flow was defended only in part, although submaximal oxygen uptake was not compromised for any completed work rate. As a result, peak exercise intensity (175 ± 22 versus 196 ± 28 N, P = 0.04) and oxygen delivery (76 ± 14 versus 112 ± 22 ml O2 min-1 , P = 0.01) were significantly reduced in IMP compared with CON. In conclusion, reducing relaxation time compromised exercise capacity without compromise to oxygen uptake. Vasodilatory compensation was complete at lower but not higher exercise intensities, whereas pressor compensation was absent. The reasons for the exercise intensity dependence of the efficacy of vasodilatory compensation remain to be determined.
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Affiliation(s)
- Robert F Bentley
- School of Kinesiology and Health Studies, Queen's University, Kingston, Ontario, Canada, K7L 3N6
| | - Veronica J Poitras
- School of Kinesiology and Health Studies, Queen's University, Kingston, Ontario, Canada, K7L 3N6
| | - Terrence Hong
- School of Kinesiology and Health Studies, Queen's University, Kingston, Ontario, Canada, K7L 3N6
| | - Michael E Tschakovsky
- School of Kinesiology and Health Studies, Queen's University, Kingston, Ontario, Canada, K7L 3N6
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10
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Shepherd JRA, Joyner MJ, Dinenno FA, Curry TB, Ranadive SM. Prolonged adenosine triphosphate infusion and exercise hyperemia in humans. J Appl Physiol (1985) 2016; 121:629-35. [PMID: 27445304 DOI: 10.1152/japplphysiol.01034.2015] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2015] [Accepted: 07/15/2016] [Indexed: 11/22/2022] Open
Abstract
In humans, intra-arterial ATP infusion in limbs mimics many features of exercise hyperemia. However, it remains unknown whether ATP can evoke the prolonged vasodilation seen during exercise. Therefore, we addressed two questions during a continuous 3-h brachial artery infusion of ATP [20 μg·100 ml forearm volume (FAV)(-1)·min(-1)]: 1) would skeletal muscle blood flow remain robust or wane over time (tachyphylaxis); and 2) would the hyperemic response to moderate-intensity exercise performed during the ATP administration be blunted compared with that during control (saline) infusion. Nine participants (25 ± 1 yr) performed one trial consisting of seven bouts of rhythmic handgrip exercise (20 contractions/min at 20% of maximum), two bouts during saline (control), and five bouts during 180 min of continuous ATP infusion. Five minutes of ATP infusion resulted in a 710% increase in forearm vascular conductance (FVC) from control (4.8 ± 0.77 vs. 35.0 ± 5.7 ml·min(-1)·100 mmHg(-1)·dl FAV(-1), P < 0.05). Contrary to our expectations, FVC did not wane over time with values of 35.0 ± 5.7 and 36.0 ± 7.7 ml·min(-1)·100 mmHg(-1)·dl FAV(-1) (P > 0.05), seen prior to the exercise bouts at 5 vs. 150 min, respectively. During superimposed exercise, FVC increased from 35.0 ± 5.7 to 49.6 ± 5.4 ml·min(-1)·100 mmHg(-1)·dl FAV(-1) at 5 min and 36.0 ± 7.7 to 54.5 ± 5.0 at 150 min (P < 0.05). Our findings demonstrate ATP vasodilation is prolonged over time without tachyphylaxis; however, exercise hyperemia responses remain intact. Our results challenge the metabolic theory of exercise hyperemia, suggesting a disconnect between matching of blood flow and metabolic demand.
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Affiliation(s)
- John R A Shepherd
- Department of Anesthesiology, Mayo Clinic, Rochester, Minnesota; and
| | - Michael J Joyner
- Department of Anesthesiology, Mayo Clinic, Rochester, Minnesota; and
| | - Frank A Dinenno
- Department of Health and Exercise Science, and Center for Cardiovascular Research, Colorado State University, Fort Collins, Colorado
| | - Timothy B Curry
- Department of Anesthesiology, Mayo Clinic, Rochester, Minnesota; and
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11
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Broxterman RM, Craig JC, Ade CJ, Wilcox SL, Barstow TJ. The effect of resting blood flow occlusion on exercise tolerance and W'. Am J Physiol Regul Integr Comp Physiol 2015. [PMID: 26224689 DOI: 10.1152/ajpregu.00283.2015] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
It has previously been postulated that the anaerobic work capacity (W') may be utilized during resting blood flow occlusion in the absence of mechanical work. We tested the hypothesis that W' would not be utilized during an initial range of time following the onset of resting blood flow occlusion, after which W' would be utilized progressively more. Seven men completed blood flow occlusion constant power severe intensity handgrip exercise to task failure following 0, 300, 600, 900, and 1,200 s of resting blood flow occlusion. The work performed above critical power (CP) was not significantly different between the 0-, 300-, and 600-s conditions and was not significantly different from the total W' available. Significantly less work was performed above CP during the 1,200-s condition than the 900-s condition (P < 0.05), while both conditions were significantly less than the 0-, 300-, and 600-s conditions (P < 0.05). The work performed above CP during these conditions was significantly less than the total W' available (P < 0.05). The utilization of W' during resting blood flow occlusion did not begin until 751 ± 118 s, after which time W' was progressively utilized. The current findings demonstrate that W' is not utilized during the initial ∼751 s of resting blood flow occlusion, but is progressively utilized thereafter, despite no mechanical work being performed. Thus, the utilization of W' is not exclusive to exercise, and a constant amount of work that can be performed above CP is not the determining mechanism of W'.
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Affiliation(s)
- Ryan M Broxterman
- Department of Kinesiology, Kansas State University, Manhattan, Kansas; Department of Anatomy and Physiology, Kansas State University, Manhattan, Kansas; and
| | - Jesse C Craig
- Department of Kinesiology, Kansas State University, Manhattan, Kansas
| | - Carl J Ade
- Department of Health and Exercise Science, University of Oklahoma, Norman, Oklahoma
| | - Samuel L Wilcox
- Department of Kinesiology, Kansas State University, Manhattan, Kansas
| | - Thomas J Barstow
- Department of Kinesiology, Kansas State University, Manhattan, Kansas
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12
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Richards JC, Crecelius AR, Larson DG, Dinenno FA. Acute ascorbic acid ingestion increases skeletal muscle blood flow and oxygen consumption via local vasodilation during graded handgrip exercise in older adults. Am J Physiol Heart Circ Physiol 2015; 309:H360-8. [PMID: 25980023 DOI: 10.1152/ajpheart.00209.2015] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/20/2015] [Accepted: 05/12/2015] [Indexed: 02/07/2023]
Abstract
Human aging is associated with reduced skeletal muscle perfusion during exercise, which may be a result of impaired endothelium-dependent dilation and/or attenuated ability to blunt sympathetically mediated vasoconstriction. Intra-arterial infusion of ascorbic acid (AA) increases nitric oxide-mediated vasodilation and forearm blood flow (FBF) during handgrip exercise in older adults, yet it remains unknown whether an acute oral dose can similarly improve FBF or enhance the ability to blunt sympathetic vasoconstriction during exercise. We hypothesized that 1) acute oral AA would improve FBF (Doppler ultrasound) and oxygen consumption (V̇o2) via local vasodilation during graded rhythmic handgrip exercise in older adults (protocol 1), and 2) AA ingestion would not enhance sympatholysis in older adults during handgrip exercise (protocol 2). In protocol 1 (n = 8; 65 ± 3 yr), AA did not influence FBF or V̇o2 during rest or 5% maximal voluntary contraction (MVC) exercise, but increased FBF (199 ± 13 vs. 248 ± 16 ml/min and 343 ± 24 vs. 403 ± 33 ml/min; P < 0.05) and V̇o2 (26 ± 2 vs. 34 ± 3 ml/min and 43 ± 4 vs. 50 ± 5 ml/min; P < 0.05) at both 15 and 25% MVC, respectively. The increased FBF was due to elevations in forearm vascular conductance (FVC). In protocol 2 (n = 10; 63 ± 2 yr), following AA, FBF was similarly elevated during 15% MVC (∼ 20%); however, vasoconstriction to reflex increases in sympathetic activity during -40 mmHg lower-body negative pressure at rest (ΔFVC: -16 ± 3 vs. -16 ± 2%) or during 15% MVC (ΔFVC: -12 ± 2 vs. -11 ± 4%) was unchanged. Our collective results indicate that acute oral ingestion of AA improves muscle blood flow and V̇o2 during exercise in older adults via local vasodilation.
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Affiliation(s)
- Jennifer C Richards
- Human Cardiovascular Physiology Laboratory, Department of Health and Exercise Science, Colorado State University, Fort Collins, Colorado; and
| | - Anne R Crecelius
- Human Cardiovascular Physiology Laboratory, Department of Health and Exercise Science, Colorado State University, Fort Collins, Colorado; and
| | - Dennis G Larson
- Medical Center of the Rockies Foundation, University of Colorado Health System, Loveland, Colorado
| | - Frank A Dinenno
- Human Cardiovascular Physiology Laboratory, Department of Health and Exercise Science, Colorado State University, Fort Collins, Colorado; and
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13
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Crecelius AR, Luckasen GJ, Larson DG, Dinenno FA. KIR channel activation contributes to onset and steady-state exercise hyperemia in humans. Am J Physiol Heart Circ Physiol 2014; 307:H782-91. [PMID: 24973385 DOI: 10.1152/ajpheart.00212.2014] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We tested the hypothesis that activation of inwardly rectifying potassium (KIR) channels and Na(+)-K(+)-ATPase, two pathways that lead to hyperpolarization of vascular cells, contributes to both the onset and steady-state hyperemic response to exercise. We also determined whether after inhibiting these pathways nitric oxide (NO) and prostaglandins (PGs) are involved in the hyperemic response. Forearm blood flow (FBF; Doppler ultrasound) was determined during rhythmic handgrip exercise at 10% maximal voluntary contraction for 5 min in the following conditions: control [saline; trial 1 (T1)]; with combined inhibition of KIR channels and Na(+)-K(+)-ATPase alone [via barium chloride (BaCl2) and ouabain, respectively; trial 2 (T2)]; and with additional combined nitric oxide synthase (N(G)-monomethyl-l-arginine) and cyclooxygenase inhibition [ketorolac; trial 3 (T3)]. In T2, the total hyperemic responses were attenuated ~50% from control (P < 0.05) at exercise onset, and there was minimal further effect in T3 (protocol 1; n = 11). In protocol 2 (n = 8), steady-state FBF was significantly reduced during T2 vs. T1 (133 ± 15 vs. 167 ± 17 ml/min; Δ from control: -20 ± 3%; P < 0.05) and further reduced during T3 (120 ± 15 ml/min; -29 ± 3%; P < 0.05 vs. T2). In protocol 3 (n = 8), BaCl2 alone reduced FBF during onset (~50%) and steady-state exercise (~30%) as observed in protocols 1 and 2, respectively, and addition of ouabain had no further impact. Our data implicate activation of KIR channels as a novel contributing pathway to exercise hyperemia in humans.
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Affiliation(s)
- Anne R Crecelius
- Human Cardiovascular Physiology Laboratory, Department of Health and Exercise Science, Colorado State University, Fort Collins, Colorado
| | - Gary J Luckasen
- Medical Center of the Rockies Foundation, University of Colorado Health, Loveland, Colorado
| | - Dennis G Larson
- Medical Center of the Rockies Foundation, University of Colorado Health, Loveland, Colorado
| | - Frank A Dinenno
- Human Cardiovascular Physiology Laboratory, Department of Health and Exercise Science, Colorado State University, Fort Collins, Colorado; Vascular Physiology Research Group, Department of Biomedical Sciences, Colorado State University, Fort Collins, Colorado; and
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14
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Influence of duty cycle on the power-duration relationship: observations and potential mechanisms. Respir Physiol Neurobiol 2013; 192:102-11. [PMID: 24361503 DOI: 10.1016/j.resp.2013.11.010] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2013] [Revised: 11/27/2013] [Accepted: 11/28/2013] [Indexed: 11/22/2022]
Abstract
The highest sustainable rate of aerobic metabolism [critical power (CP)] and the finite amount of work that can be performed above CP (W' [curvature constant]) were determined under two muscle contraction duty cycles. Eight men completed at least three constant-power handgrip tests to exhaustion to determine CP and W' for 50% and 20% duty cycles, while brachial artery blood flow (Q̇BA) and deoxygenated-[hemoglobin + myoglobin] (deoxy-[Hb+Mb]) were measured. CP was lower for the 50% duty cycle (3.9 ± 0.9 W) than the 20% duty cycle (5.1 ± 0.8 W; p < 0.001), while W' was not significantly different (50% duty cycle: 452 ± 141 J vs. 20% duty cycle: 432 ± 130 J; p > 0.05). At the same power output, Q̇BA and deoxy-[Hb + Mb] achieved higher end-exercise values for the 20% duty cycle (9.87 ± 1.73 ml·s(-1); 51.7 ± 4.7 μM) than the 50% duty cycle (7.37 ± 1.76 ml·s(-1), p < 0.001; 44.3 ± 2.4 μM, p < 0.03). These findings indicate that blood flow influences CP, but not W'.
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15
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Crecelius AR, Kirby BS, Richards JC, Dinenno FA. Mechanical effects of muscle contraction increase intravascular ATP draining quiescent and active skeletal muscle in humans. J Appl Physiol (1985) 2013; 114:1085-93. [PMID: 23429876 PMCID: PMC3633434 DOI: 10.1152/japplphysiol.01465.2012] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2012] [Accepted: 02/13/2013] [Indexed: 11/22/2022] Open
Abstract
Intravascular adenosine triphosphate (ATP) evokes vasodilation and is implicated in the regulation of skeletal muscle blood flow during exercise. Mechanical stresses to erythrocytes and endothelial cells stimulate ATP release in vitro. How mechanical effects of muscle contractions contribute to increased plasma ATP during exercise is largely unexplored. We tested the hypothesis that simulated mechanical effects of muscle contractions increase [ATP](venous) and ATP effluent in vivo, independent of changes in tissue metabolic demand, and further increase plasma ATP when superimposed with mild-intensity exercise. In young healthy adults, we measured forearm blood flow (FBF) (Doppler ultrasound) and plasma [ATP](v) (luciferin-luciferase assay), then calculated forearm ATP effluent (FBF×[ATP](v)) during rhythmic forearm compressions (RFC) via a blood pressure cuff at three graded pressures (50, 100, and 200 mmHg; Protocol 1; n = 10) and during RFC at 100 mmHg, 5% maximal voluntary contraction rhythmic handgrip exercise (RHG), and combined RFC + RHG (Protocol 2; n = 10). [ATP](v) increased from rest with each cuff pressure (range 144-161 vs. 64 ± 13 nmol/l), and ATP effluent was graded with pressure. In Protocol 2, [ATP](v) increased in each condition compared with rest (RFC: 123 ± 33; RHG: 51 ± 9; RFC + RHG: 96 ± 23 vs. Mean Rest: 42 ± 4 nmol/l; P < 0.05), and ATP effluent was greatest with RFC + RHG (RFC: 5.3 ± 1.4; RHG: 5.3 ± 1.1; RFC + RHG: 11.6 ± 2.7 vs. Mean Rest: 1.2 ± 0.1 nmol/min; P < 0.05). We conclude that the mechanical effects of muscle contraction can 1) independently elevate intravascular ATP draining quiescent skeletal muscle without changes in local metabolism and 2) further augment intravascular ATP during mild exercise associated with increases in metabolism and local deoxygenation; therefore, it is likely one stimulus for increasing intravascular ATP during exercise in humans.
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Affiliation(s)
- Anne R Crecelius
- Human Cardiovascular Physiology Laboratory, Department of Health and Exercise Science, Vascular Physiology Research Group, Department of Biomedical Sciences, Colorado State University, Fort Collins, CO, USA
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