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KATO T, MUROGA S, YAMASHIRO SM, MATSUMOTO T. Effect of 3% CO2 inhalation on pulmonary gas exchange kinetics during constant work-rate exercise. GAZZETTA MEDICA ITALIANA ARCHIVIO PER LE SCIENZE MEDICHE 2022. [DOI: 10.23736/s0393-3660.20.04529-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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Meng Z, Gao H, Li T, Ge P, Xu Y, Gao B. Effects of Eight Weeks Altitude Training on the Aerobic Capacity and Microcirculation Function in Trained Rowers. High Alt Med Biol 2021; 22:24-31. [PMID: 33719550 DOI: 10.1089/ham.2020.0059] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Meng, Zhijun, Huan Gao, Tao Li, Peng Ge, Yixiao Xu, and Binghong Gao. Effects of eight weeks altitude training on the aerobic capacity and microcirculation function in trained rowers. High Alt Med Biol. 22:24-31, 2021. Background: The mechanism of aerobic improvement after altitude training (AT) has not been resolved yet. Few studies have looked at microcirculation changes after AT in athletes. Materials and Methods: Thirty-three male rowers were recruited and divided into either the AT (n = 18, altitude 2,280 m) or the sea level training (ST group, n = 15, altitude 50 m) for 8 weeks training. Microcirculation function was monitored using a laser Doppler flowmeter. VO2peak and ergometer 5 km time trial (Er5k) were conducted. Results: Within the AT group there was an 8.8% increment in VO2peak from pre- to post-training (4,708.9 ± 455.2 vs. 5,123.3 ± 391.2 ml/min, p < 0.01), whereas in ST group there was a 3.1% increase of VO2peak from pre- to post-training (4,975.4 ± 501.1 vs. 5,128.0 ± 499.3 m/min, p = 0.125). Er5k performance in AT group was significantly improved (1,040.3 ± 26.3 vs. 1,033.2 ± 27.5 seconds, p = 0.038), whereas in ST group Er5k performance was not improved (1,059.6 ± 30.9 vs. 1,060.4 ± 33.2 seconds, p = 0.819). Postocclusive reactive hyperemia reserve and heat reserve in the forearm of AT subjects increased significantly after 8 weeks. Meanwhile, the AT group's resting blood flow and cutaneous vascular conductance (CVC) of the thigh were higher after AT. For the ST group, resting blood flow and CVC in the thigh decreased significantly at third week post-training. There was a low correlation between the change of VO2peak and blood flow of the thigh (r = 0.45, p = 0.01). Conclusions: Trained rowers benefit more from 8 weeks of AT than from 8 weeks ST in terms of aerobic capacity. We have found that 8 weeks of AT increases thigh blood flow and improves endothelial function.
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Affiliation(s)
- Zhijun Meng
- Center of Laboratory, School of Kinesiology, Shanghai University of Sport, Shanghai, China.,The Research Institute of Sports Science of Yunnan Province, Kunming, China
| | - Huan Gao
- The First Research Center of Competitive Sports, Shanghai Research Institute of Sports Science, Shanghai, China
| | - Tao Li
- The First Research Center of Competitive Sports, Shanghai Research Institute of Sports Science, Shanghai, China
| | - Peng Ge
- Center of Laboratory, School of Kinesiology, Shanghai University of Sport, Shanghai, China
| | - Yixiao Xu
- Center of Laboratory, School of Kinesiology, Shanghai University of Sport, Shanghai, China
| | - Binghong Gao
- School of Physical Education and Sport Training, Shanghai University of Sport, Shanghai, China
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Miura K, Kashima H, Namura S, Morimoto M, Endo MY, Oue A, Fukuba Y. Effects of cooling or warming of the distal upper limb on skin vascular conductance and brachial artery shear profiles during cycling exercise. Res Sports Med 2021; 30:308-324. [PMID: 33472421 DOI: 10.1080/15438627.2021.1872573] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
The relative influence of skin vascular conductance in glabrous (G; palm) and non-glabrous (NG; dorsal and forearm) regions to upstream brachial artery-shear stress (BA-SS) profile are unknown. This study aimed to elucidate the effects of G and/or NG skin vascular conductance (VC), which were modulated by warming or cooling manipulation, on BA-shear rate (SR, an estimate of SS) during cycling exercise. Seven healthy subjects performed 60-min exercise. Between 20 and 50 min of the exercise, the NG+G or G skin region were warmed to 42°C or cooled to 15°C using a water bath. Throughout the protocol, diameter and blood velocity in BA and skin VCs in forearm and palm were measured. All measurements showed that a steady-state response was reached after 20 min of exercise. Subsequently, during cooling manipulation, forearm VC was significantly decreased, and the concomitant BA-SR profile was revealed (primarily characterized by decreased antegrade SR and increased retrograde SR) in the NG+G. Such changes were not observed in G alone. During warming manipulation, forearm VC and mean BA-SR significantly increased only in the NG+G. In conclusion, vascular response in NG skin possibly plays a major role in the modulation of BA-SS profile during cycling exercise.
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Affiliation(s)
- Kohei Miura
- Department of Exercise Science and Physiology, School of Health Sciences, Prefectural University of Hiroshima, Hiroshima, Japan.,Department of Health and Nutrition, Faculty of Health Sciences, University of Hiroshima Shudo, Hiroshima, Japan
| | - Hideaki Kashima
- Department of Exercise Science and Physiology, School of Health Sciences, Prefectural University of Hiroshima, Hiroshima, Japan
| | - Saki Namura
- Department of Exercise Science and Physiology, School of Health Sciences, Prefectural University of Hiroshima, Hiroshima, Japan
| | - Marina Morimoto
- Department of Exercise Science and Physiology, School of Health Sciences, Prefectural University of Hiroshima, Hiroshima, Japan
| | - Masako Y Endo
- Department of Exercise Science and Physiology, School of Health Sciences, Prefectural University of Hiroshima, Hiroshima, Japan
| | - Anna Oue
- Faculty of Food and Nutritional Sciences, Toyo University, Gunma, Japan
| | - Yoshiyuki Fukuba
- Department of Exercise Science and Physiology, School of Health Sciences, Prefectural University of Hiroshima, Hiroshima, Japan
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Boussana A, Galy O, Le Gallais D, Hue O. The effect of an Olympic distance triathlon on the respiratory muscle strength and endurance in triathletes. J Exerc Rehabil 2020; 16:356-362. [PMID: 32913841 PMCID: PMC7463066 DOI: 10.12965/jer.2040518.259] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2020] [Accepted: 07/17/2020] [Indexed: 11/22/2022] Open
Abstract
High-intensity exercise, marathons, and long distances triathlons have been shown to induce the fatigue of respiratory muscles (RMs). Never-theless, fatigue and the recovery period have not been studied in re-sponse of an Olympic distance triathlon (1.5-km swim, 40-km bike, 10-km run: short-distance triathlon). The aim of this study was to evaluate the RM fatigue induced by an Olympic distance triathlon. Nine male triath-letes (24±1.1 years) underwent spirometric testing and the assessment of RM performance. Respiratory function tests were conducted in sit-ting position. Spirometric parameters, maximal inspiratory and expirato-ry pressures, and RM endurance assessed by measuring the time limit were evaluated before (pre-T), after (post-T), and the day following the triathlon (post-T-24 hr). Residual volume increased: pre-T vs. post-T (P<0.002), maximal inspiratory pressure significantly decreased from 127.4±17.2 (pre-T) to 121.6±18.5 cmH2O (post-T) (P<0.001) and returned to the pre-T value 24 hr after the race (125.0±18.6). RM endurance sig-nificantly decreased from 4:51±0:8 (pre-T) to 3:13±0:7 min (post-T, P< 0.001) and then remained decreased for 24 hr after the race from 4:51± 0:8 (pre-T) to 3:39±0:4 min 24 hr after (P<0.002). Both, strength and en-durance of inspiratory muscles decrease after Olympic distance triath-lon. Furthermore, the impaired of inspiratory muscle endurance 24 hr after the race suggested a slow recovery and persistence of inspiratory muscle fatigue.
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Affiliation(s)
- Alain Boussana
- Department Higher Institute of Physical and Sports Education, University Marien Ngouabi, Brazzaville, Congo.,Department Sciences and Techniques of Physical and Sports Activities, University Antilles Guyane, Pointe à Pitre Cedex, France
| | - Olivier Galy
- Department Higher School of Professorship and Education, University of New-Caledonia, Noumea CEDEX, New-Caledonia, France
| | - Daniel Le Gallais
- Department Sciences and Techniques of Physical and Sports Activities, University of Montpellier, Montpellier, France
| | - Olivier Hue
- Department Sciences and Techniques of Physical and Sports Activities, University Antilles Guyane, Pointe à Pitre Cedex, France
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5
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Smith JR, Bruhn EJ, Berg JD, Nur AA, Villarraga N, Olson TP. Combined influence of inspiratory loading and locomotor subsystolic cuff inflation on cardiovascular responses during submaximal exercise. J Appl Physiol (1985) 2020; 128:1338-1345. [PMID: 32240016 DOI: 10.1152/japplphysiol.00781.2019] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
It is unknown if simultaneous stimulation of the respiratory and locomotor muscle afferents via inspiratory loading (IL) and locomotor subsystolic cuff inflation (CUFF) influences the cardiovascular responses during exercise. We hypothesized that combined IL and CUFF (IL + CUFF) will result in greater increases in blood pressure (MAP) and systemic vascular resistance (SVR) than IL and CUFF alone during exercise. Eight adults (6 males/2 females) were enrolled and performed four 10-min bouts of constant-load cycling eliciting 40% maximal oxygen uptake on a single day. For each exercise bout, the first 5 min consisted of spontaneous breathing. The second 5 min consisted of voluntary hyperventilation (i.e., breathing frequency of 40 breaths/min) with IL (30% maximum inspiratory pressure), CUFF (80 mmHg), IL + CUFF, or no intervention (CTL) in randomized order. During exercise, cardiac output and MAP were determined via open-circuit acetylene wash-in and manual sphygmomanometry, respectively, and SVR was calculated. Across CTL, IL, CUFF, and IL + CUFF, MAP was greater with each condition (CTL: 97 ± 14; IL: 106 ± 13; CUFF: 114 ± 14; IL + CUFF: 119 ± 15 mmHg, all P < 0.02). Furthermore, SVR was greater with IL + CUFF compared with IL, CUFF, and CTL (CTL: 6.6 ± 1.1; IL: 7.5 ± 1.4; CUFF: 7.5 ± 1.3; IL + CUFF: 8.2 ± 1.4 mmHg·L-1·min-1, all P < 0.02). Cardiac output was not different across conditions (CTL: 15.2 ± 3.8; IL: 14.8 ± 3.7; CUFF: 15.6 ± 3.5; IL + CUFF: 14.7 ± 4.3 L/min, all P > 0.05). These data demonstrate that simultaneous stimulation of respiratory and locomotor muscle afferent feedback results in additive MAP and SVR responses than IL and CUFF alone during submaximal exercise. These findings have important clinical implications for populations with exaggerated locomotor and respiratory muscle reflex feedbacks.NEW & NOTEWORTHY Reflexes arising from the respiratory and locomotor muscles influence cardiovascular regulation during exercise. However, it is unclear how the respiratory and locomotor muscle reflexes interact when simultaneously stimulated. Herein, we demonstrate that stimulation of the respiratory and locomotor muscle reflexes yielded additive cardiovascular responses during submaximal exercise.
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Affiliation(s)
- Joshua R Smith
- Department of Cardiovascular Medicine, Mayo Clinic, Rochester Minnesota
| | - Eric J Bruhn
- Department of Cardiovascular Medicine, Mayo Clinic, Rochester Minnesota
| | - Jessica D Berg
- Department of Cardiovascular Medicine, Mayo Clinic, Rochester Minnesota
| | - Amran A Nur
- Department of Cardiovascular Medicine, Mayo Clinic, Rochester Minnesota
| | | | - Thomas P Olson
- Department of Cardiovascular Medicine, Mayo Clinic, Rochester Minnesota
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Miura K, Kashima H, Oue A, Kondo A, Watanabe S, Endo MY, Fukuba Y. Effect of sinusoidal leg cycling exercise period on brachial artery blood flow dynamics in humans. J Physiol Sci 2020; 70:23. [PMID: 32312251 PMCID: PMC7170823 DOI: 10.1186/s12576-020-00750-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2020] [Accepted: 04/10/2020] [Indexed: 11/17/2022]
Abstract
Purpose To quantify the dynamics of blood flow in brachial artery (BF-BA) in response to sinusoidal work rate (WR) leg cycling exercises of 2-, 4-, and 6-min periods and to examine their relationship with the forearm skin blood flow (SBF). Methods Seven healthy young male subjects performed upright leg ergometer exercise with a constant WR (mean sinusoidal WR) for 30 min followed by sinusoidal WR exercise of three different periods (number of repetitions): 2 min (7), 4 min (4), and 6 min (3). The WR fluctuated from 20 W to a peak WR corresponding to 60% peak oxygen uptake (VO2). We continuously measured pulmonary gas exchange, heart rate (HR), blood velocity and cross-sectional area of BA, and forearm SBF and sweating rate (SR). Results All variables were followed by the sinusoidal WR. The phases of the variables for gas exchange and central circulation, such as VO2 and HR with WR forcing were similar (e.g., phase shift (θ) in HR [°]: 2 min, 60 ± 7; 4 min, 45 ± 10; 6 min, 37 ± 8; mean ± SD) to previous study results, that is, a longer period showed a shorter θ and larger amplitude of responses. Contrarily, the BF-BA response showed anti-phase (approximately 180°) regardless of the period, whereas the θ of forearm SBF and SR were similar to gas exchange and central circulation. Conclusions Inactive limb BF-BA during sinusoidal leg cycling exercise was out of phase relative to the regulation of O2-delivery to active muscles and thermoregulation. The response of BF-BA seems to not always reflect the response of forearm SBF in the downstream area.
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Affiliation(s)
- Kohei Miura
- Department of Exercise Science and Physiology, School of Health Sciences, Prefectural University of Hiroshima, Hiroshima, 734-8558, Japan.,Department of Health and Nutrition, Faculty of Health Sciences, University of Hiroshima Shudo, Hiroshima, 731-3195, Japan
| | - Hideaki Kashima
- Department of Exercise Science and Physiology, School of Health Sciences, Prefectural University of Hiroshima, Hiroshima, 734-8558, Japan
| | - Anna Oue
- Faculty of Food and Nutritional Sciences, Toyo University, Gunma, 374-0193, Japan
| | - Ayaka Kondo
- Department of Exercise Science and Physiology, School of Health Sciences, Prefectural University of Hiroshima, Hiroshima, 734-8558, Japan
| | - Sachiko Watanabe
- Department of Exercise Science and Physiology, School of Health Sciences, Prefectural University of Hiroshima, Hiroshima, 734-8558, Japan
| | - Masako Y Endo
- Department of Exercise Science and Physiology, School of Health Sciences, Prefectural University of Hiroshima, Hiroshima, 734-8558, Japan
| | - Yoshiyuki Fukuba
- Department of Exercise Science and Physiology, School of Health Sciences, Prefectural University of Hiroshima, Hiroshima, 734-8558, Japan.
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El Assar M, Angulo J, Rodríguez-Mañas L. Frailty as a phenotypic manifestation of underlying oxidative stress. Free Radic Biol Med 2020; 149:72-77. [PMID: 31422077 DOI: 10.1016/j.freeradbiomed.2019.08.011] [Citation(s) in RCA: 56] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/12/2019] [Revised: 08/09/2019] [Accepted: 08/11/2019] [Indexed: 02/08/2023]
Abstract
Oxidative stress plays a key role in the aging process. Lifestyle behaviours including low physical activity and inadequate nutritional habits in addition to genetic susceptibility and some chronic diseases compromise physiological response to free radicals and promote oxidative damage. Reduced resilience (referred to the ability to respond to stressors or adverse conditions) or functional reserve in isolated organs or systems determines clinical manifestations as the age-related chronic diseases while multisystemic dysfunction results in the frailty phenotype. In older adults, frailty, but not age, is associated with elevation of oxidative stress markers and reduction of antioxidant parameters. Mitochondrial dysfunction related to oxidative stress plays a prominent role in this process affecting not only skeletal muscle but also other potential tissues and organs. Increasing endogenous antioxidant capacity in different systems by exercise outstand among therapeutic interventions with potential ability to prevent or delay frailty phenotype and to promote healthy aging.
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Affiliation(s)
- Mariam El Assar
- Fundación para la Investigación Biomédica del Hospital Universitario de Getafe, Getafe, Spain; Centro de Investigación Biomédica en Red de Fragilidad y Envejecimiento Saludable (CIBERFES), Instituto de Salud Carlos III, Madrid, Spain
| | - Javier Angulo
- Centro de Investigación Biomédica en Red de Fragilidad y Envejecimiento Saludable (CIBERFES), Instituto de Salud Carlos III, Madrid, Spain; Servicio de Histología-Investigación, Unidad de Investigación Traslacional en Cardiología, Hospital Universitario Ramón y Cajal, IRYCIS, Madrid, Spain
| | - Leocadio Rodríguez-Mañas
- Centro de Investigación Biomédica en Red de Fragilidad y Envejecimiento Saludable (CIBERFES), Instituto de Salud Carlos III, Madrid, Spain; Servicio de Geriatría, Hospital Universitario de Getafe, Getafe, Spain.
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8
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Fukuba Y, Endo MY, Kondo A, Kikugawa Y, Miura K, Kashima H, Fujimoto M, Hayashi N, Fukuoka Y, Koga S. Brachial artery blood flow dynamics during sinusoidal leg cycling exercise in humans. Physiol Rep 2018; 5:5/19/e13456. [PMID: 28989117 PMCID: PMC5641938 DOI: 10.14814/phy2.13456] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2017] [Accepted: 08/29/2017] [Indexed: 01/16/2023] Open
Abstract
To explore the control of the peripheral circulation of a nonworking upper limb during leg cycling exercise, blood flow (BF) dynamics in the brachial artery (BA) were determined using a sinusoidal work rate (WR) exercise. Ten healthy subjects performed upright leg cycling exercise at a constant WR for 30 min, followed by 16 min of sinusoidal WR consisting of 4‐min periods of WR fluctuating between a minimum output of 20 W and a maximum output corresponding to ventilatory threshold (VT). Throughout the protocol, pulmonary gas exchange, heart rate (HR), mean arterial blood pressure (MAP), blood velocity (BV), and cross‐sectional area of the BA, forearm skin BF (SBF), and sweating rate (SR) were measured. Each variable was fitted to a sinusoidal model with phase shift (θ) and amplitude (A). Nearly all variables closely fit a sinusoidal model. Variables relating to oxygen transport, such as VO2 and HR, followed the sinusoidal WR pattern with certain delays (θ: VO2; 51.4 ± 4.0°, HR; 41.8 ± 5.4°, mean ± SD). Conversely, BF response in the BA was approximately in antiphase (175.1 ± 28.9°) with a relatively large A, whereas the phase of forearm SBF was dissimilar (65.8 ± 35.9°). Thus, the change of BF through a conduit artery to the nonworking upper limb appears to be the reverse when WR fluctuates during sinusoidal leg exercise, and it appears unlikely that this could be ascribed exclusively to altering the downstream circulation to forearm skin.
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Affiliation(s)
- Yoshiyuki Fukuba
- Department of Exercise Science & Physiology, School of Health Sciences, Prefectural University of Hiroshima, Hiroshima, Japan
| | - Masako Y Endo
- Department of Exercise Science & Physiology, School of Health Sciences, Prefectural University of Hiroshima, Hiroshima, Japan
| | - Ayaka Kondo
- Department of Exercise Science & Physiology, School of Health Sciences, Prefectural University of Hiroshima, Hiroshima, Japan
| | - Yuka Kikugawa
- Department of Exercise Science & Physiology, School of Health Sciences, Prefectural University of Hiroshima, Hiroshima, Japan
| | - Kohei Miura
- Department of Exercise Science & Physiology, School of Health Sciences, Prefectural University of Hiroshima, Hiroshima, Japan
| | - Hideaki Kashima
- Department of Exercise Science & Physiology, School of Health Sciences, Prefectural University of Hiroshima, Hiroshima, Japan
| | - Masaki Fujimoto
- Department of Exercise Science & Physiology, School of Health Sciences, Prefectural University of Hiroshima, Hiroshima, Japan
| | - Naoyuki Hayashi
- Graduate School of Decision Science and Technology, Tokyo Institute of Technology, Tokyo, Japan
| | - Yoshiyuki Fukuoka
- Faculty of Health and Sports Science, Doshisha University, Kyoto, Japan
| | - Shunsaku Koga
- Applied Physiology Laboratory, Kobe Design University, Kobe, Japan
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Respiratory muscle strength is decreased after maximal incremental exercise in trained runners and cyclists. Respir Physiol Neurobiol 2017; 248:25-30. [PMID: 29155334 DOI: 10.1016/j.resp.2017.11.005] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2017] [Revised: 11/14/2017] [Accepted: 11/14/2017] [Indexed: 01/11/2023]
Abstract
The respiratory muscle fatigue seems to be able to limit exercise performance and may influence the determination of maximal oxygen uptake (V̇O2max) or maximum aerobic work rate during maximal incremental test. The aim of this study was therefore to investigate whether maximal incremental exercise decreases respiratory muscle strength. We hypothesized that respiratory muscle strength (maximal pressure) will decrease after maximal incremental exercise to exhaustion. 36 runners and 23 cyclists completed a maximal incremental test on a treadmill or a cycle ergometer with continuous monitoring of expired gases. Maximal inspiratory (MIP) and expiratory (MEP) pressure measurements were taken at rest and post- exercise. At rest, the MIP and MEP were 140±25 and 172±27 in runners vs. 115±26 and 146±33 in cyclists (p<0.05 between groups, respectively). The rest values of MIP and MEP were correlated to the V̇O2peak in all athletes, r=0.34, p<0.01 and r=0.36, p<0.01, respectively. At exhaustion, the MIP and MEP decreased significantly post- test by 13±7% and 13±5% in runners vs. 17±11% and 15±10% in cyclists (p>0.05), respectively. Our results suggest that respiratory muscle strength is decreased following maximal incremental exercise in trained runners and cyclists.
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Smith JR, Didier KD, Hammer SM, Alexander AM, Kurti SP, Copp SW, Barstow TJ, Harms CA. Effect of cyclooxygenase inhibition on the inspiratory muscle metaboreflex-induced cardiovascular consequences in men. J Appl Physiol (1985) 2017; 123:197-204. [PMID: 28522759 DOI: 10.1152/japplphysiol.00165.2017] [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] [Received: 02/21/2017] [Revised: 05/03/2017] [Accepted: 05/10/2017] [Indexed: 12/25/2022] Open
Abstract
Inspiratory muscle metaboreflex activation increases mean arterial pressure (MAP) and limb vascular resistance (LVR) and decreases limb blood flow (Q̇L). Cyclooxygenase (COX) inhibition has been found to attenuate limb skeletal muscle metaboreflex-induced increases in muscle sympathetic nerve activity. We hypothesized that compared with placebo (PLA), COX inhibition would attenuate inspiratory muscle metaboreflex-induced 1) increases in MAP and LVR and 2) decreases in Q̇L Seven men (22 ± 1 yr) were recruited and orally consumed ibuprofen (IB; 10 mg/kg) or PLA 90 min before performing the cold pressor test (CPT) for 2 min and inspiratory resistive breathing task (IRBT) for 14.9 ± 2.0 min at 65% of maximal inspiratory pressure. Breathing frequency was 20 breaths/min with a 50% duty cycle during the IRBTs. MAP was measured via automated oscillometry, Q̇L was determined via Doppler ultrasound, and LVR was calculated as MAP divided by Q̇L Electromyography was recorded on the leg to ensure no muscle contraction occurred. The 65% IRBT led to greater increases (P = 0.02) in 6-keto-prostaglandin-F1α with PLA compared with IB. IB, compared with PLA, led to greater (P < 0.01) increases in MAP (IB: 17 ± 7 mmHg vs. PLA: 8 ± 5 mmHg) and LVR (IB: 69 ± 28% vs. PLA: 52 ± 22%) at the final minute of the 65% IRBT. The decrease in Q̇L was not different (P = 0.72) between IB (-28 ± 11%) and PLA (-27 ± 9%) at the final minute. The increase in MAP during the CPT was not different (P = 0.87) between IB (25 ± 11 mmHg) and PLA (24 ± 6 mmHg). Contrary to our hypotheses, COX inhibition led to greater inspiratory muscle metaboreflex-induced increases in MAP and LVR.NEW & NOTEWORTHY Cyclooxygenase (COX) products play a role in activating the muscle metaboreflex. It is not known whether COX products contribute to the inspiratory muscle metaboreflex. Herein, we demonstrate that COX inhibition led to greater increases in blood pressure and limb vascular resistance compared with placebo during inspiratory muscle metaboreflex activation.
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Affiliation(s)
- Joshua R Smith
- Department of Kinesiology, Kansas State University, Manhattan Kansas
| | - Kaylin D Didier
- Department of Kinesiology, Kansas State University, Manhattan Kansas
| | - Shane M Hammer
- Department of Kinesiology, Kansas State University, Manhattan Kansas
| | | | - Stephanie P Kurti
- Department of Kinesiology, Kansas State University, Manhattan Kansas
| | - Steven W Copp
- Department of Kinesiology, Kansas State University, Manhattan Kansas
| | - Thomas J Barstow
- Department of Kinesiology, Kansas State University, Manhattan Kansas
| | - Craig A Harms
- Department of Kinesiology, Kansas State University, Manhattan Kansas
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11
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Smith JR, Alexander AM, Hammer SM, Didier KD, Kurti SP, Broxterman RM, Barstow TJ, Harms CA. Cardiovascular consequences of the inspiratory muscle metaboreflex: effects of age and sex. Am J Physiol Heart Circ Physiol 2017; 312:H1013-H1020. [DOI: 10.1152/ajpheart.00818.2016] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/12/2016] [Revised: 02/22/2017] [Accepted: 02/23/2017] [Indexed: 01/15/2023]
Abstract
With inspiratory muscle metaboreflex activation, we hypothesized that, compared with their younger counterparts, older men and women would exhibit greater 1) increases in mean arterial pressure (MAP) and limb vascular resistance (LVR) and 2) decreases in limb blood flow (Q̇L) but 3) no sex differences would be present in older adults. Sixteen young adults [8 young men (YM) and 8 young women (YW), 18–24 yr] and 16 older adults [8 older men (OM) and 8 older women (OW), 60–73 yr] performed inspiratory resistive breathing tasks (IRBTs) at 2% and 65% of their maximal inspiratory pressure. During the IRBTs, breathing frequency was 20 breaths/min with a 50% duty cycle. At baseline and during the IRBTs, MAP was measured via automated oscillometry, Q̇L was determined via Doppler ultrasound, and LVR was calculated. The 65% IRBT led to significantly greater increases in MAP in OW (15.9 ± 8.1 mmHg) compared with YW (6.9 ± 1.4 mmHg) but not ( P > 0.05) between OM (12.3 ± 5.7 mmHg) and YM (10.8 ± 5.7 mmHg). OW (−20.2 ± 7.2%) had greater ( P < 0.05) decreases in Q̇L compared with YW (−9.4 ± 10.2%), but no significant differences were present between OM (−22.8 ± 9.7%) and YM (−22.7 ± 11.3%) during the 65% IRBT. The 65% IRBT led to greater ( P < 0.05) increases in LVR in OW (48.2 ± 25.5%) compared with YW (19.7 ± 15.0%), but no differences ( P > 0.05) existed among OM (54.4 ± 17.8%) and YM (47.1 ± 23.3%). No significant differences were present in MAP, Q̇L, or LVR between OM and OW. These data suggest that OW exhibit a greater inspiratory muscle metaboreflex compared with YW, whereas no differences between OM and YM existed. Finally, sex differences in the inspiratory muscle metaboreflex are not present in older adults. NEW & NOTEWORTHY Premenopausal women exhibit an attenuated inspiratory muscle metaboreflex compared with young men; however, it is unknown whether these sex differences are present in older adults. Older women exhibited a greater inspiratory muscle metaboreflex compared with premenopausal women, whereas no differences were present between older and younger men.
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Affiliation(s)
- Joshua R. Smith
- Department of Kinesiology, Kansas State University, Manhattan, Kansas
| | | | - Shane M. Hammer
- Department of Kinesiology, Kansas State University, Manhattan, Kansas
| | - Kaylin D. Didier
- Department of Kinesiology, Kansas State University, Manhattan, Kansas
| | | | | | - Thomas J. Barstow
- Department of Kinesiology, Kansas State University, Manhattan, Kansas
| | - Craig A. Harms
- Department of Kinesiology, Kansas State University, Manhattan, Kansas
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Black MI, Jones AM, Blackwell JR, Bailey SJ, Wylie LJ, McDonagh STJ, Thompson C, Kelly J, Sumners P, Mileva KN, Bowtell JL, Vanhatalo A. Muscle metabolic and neuromuscular determinants of fatigue during cycling in different exercise intensity domains. J Appl Physiol (1985) 2016; 122:446-459. [PMID: 28008101 PMCID: PMC5429469 DOI: 10.1152/japplphysiol.00942.2016] [Citation(s) in RCA: 158] [Impact Index Per Article: 19.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2016] [Revised: 12/12/2016] [Accepted: 12/16/2016] [Indexed: 01/15/2023] Open
Abstract
The gas exchange threshold and the critical power demarcate discrete exercise intensity domains. For the first time, we show that the limit of tolerance during whole body exercise within these domains is characterized by distinct metabolic and neuromuscular responses. Fatigue development during exercise greater than critical power is associated with the attainment of consistent “limiting” values of muscle metabolites, whereas substrate availability and limitations to muscle activation may constrain performance at lower intensities. Lactate or gas exchange threshold (GET) and critical power (CP) are closely associated with human exercise performance. We tested the hypothesis that the limit of tolerance (Tlim) during cycle exercise performed within the exercise intensity domains demarcated by GET and CP is linked to discrete muscle metabolic and neuromuscular responses. Eleven men performed a ramp incremental exercise test, 4–5 severe-intensity (SEV; >CP) constant-work-rate (CWR) tests until Tlim, a heavy-intensity (HVY; <CP but >GET) CWR test until Tlim, and a moderate-intensity (MOD; <GET) CWR test until Tlim. Muscle biopsies revealed that a similar (P > 0.05) muscle metabolic milieu (i.e., low pH and [PCr] and high [lactate]) was attained at Tlim (approximately 2–14 min) for all SEV exercise bouts. The muscle metabolic perturbation was greater at Tlim following SEV compared with HVY, and also following SEV and HVY compared with MOD (all P < 0.05). The normalized M-wave amplitude for the vastus lateralis (VL) muscle decreased to a similar extent following SEV (−38 ± 15%), HVY (−68 ± 24%), and MOD (−53 ± 29%), (P > 0.05). Neural drive to the VL increased during SEV (4 ± 4%; P < 0.05) but did not change during HVY or MOD (P > 0.05). During SEV and HVY, but not MOD, the rates of change in M-wave amplitude and neural drive were correlated with changes in muscle metabolic ([PCr], [lactate]) and blood ionic/acid-base status ([lactate], [K+]) (P < 0.05). The results of this study indicate that the metabolic and neuromuscular determinants of fatigue development differ according to the intensity domain in which the exercise is performed. NEW & NOTEWORTHY The gas exchange threshold and the critical power demarcate discrete exercise intensity domains. For the first time, we show that the limit of tolerance during whole-body exercise within these domains is characterized by distinct metabolic and neuromuscular responses. Fatigue development during exercise greater than critical power is associated with the attainment of consistent “limiting” values of muscle metabolites, whereas substrate availability and limitations to muscle activation may constrain performance at lower intensities.
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Affiliation(s)
- Matthew I Black
- College of Life and Environmental Sciences, St. Luke's Campus, University of Exeter, Exeter, United Kingdom.,School of Sport, Exercise and Health Sciences, Loughborough University, United Kingdom; and
| | - Andrew M Jones
- College of Life and Environmental Sciences, St. Luke's Campus, University of Exeter, Exeter, United Kingdom
| | - Jamie R Blackwell
- College of Life and Environmental Sciences, St. Luke's Campus, University of Exeter, Exeter, United Kingdom
| | - Stephen J Bailey
- College of Life and Environmental Sciences, St. Luke's Campus, University of Exeter, Exeter, United Kingdom.,School of Sport, Exercise and Health Sciences, Loughborough University, United Kingdom; and
| | - Lee J Wylie
- College of Life and Environmental Sciences, St. Luke's Campus, University of Exeter, Exeter, United Kingdom
| | - Sinead T J McDonagh
- College of Life and Environmental Sciences, St. Luke's Campus, University of Exeter, Exeter, United Kingdom
| | - Christopher Thompson
- College of Life and Environmental Sciences, St. Luke's Campus, University of Exeter, Exeter, United Kingdom
| | - James Kelly
- College of Life and Environmental Sciences, St. Luke's Campus, University of Exeter, Exeter, United Kingdom
| | - Paul Sumners
- Sport and Exercise Science Research Centre, School of Applied Sciences, London South Bank University, London, United Kingdom
| | - Katya N Mileva
- Sport and Exercise Science Research Centre, School of Applied Sciences, London South Bank University, London, United Kingdom
| | - Joanna L Bowtell
- College of Life and Environmental Sciences, St. Luke's Campus, University of Exeter, Exeter, United Kingdom
| | - Anni Vanhatalo
- College of Life and Environmental Sciences, St. Luke's Campus, University of Exeter, Exeter, United Kingdom;
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Skutnik BC, Smith JR, Johnson AM, Kurti SP, Harms CA. The Effect of Low Volume Interval Training on Resting Blood Pressure in Pre-hypertensive Subjects: A Preliminary Study. PHYSICIAN SPORTSMED 2016; 44:177-83. [PMID: 26918846 DOI: 10.1080/00913847.2016.1159501] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
OBJECTIVES Clinically pre-hypertensive adults are at a greater risk of developing hypertension, stiffened arteries, and other cardiovascular risks. Endurance exercise training has been shown to improve elevated resting blood pressure and C-reactive protein (CRP) levels. However, a primary barrier preventing individuals from engaging in regular physical activity is a lack of time. The purpose of our study was to determine if a high-intensity interval training (HIIT) protocol would be as effective as continuous aerobic endurance training (ET) on resting blood pressure in pre-hypertensive participants. Additionally, this study investigated the effects of HIIT vs. ET on CRP. METHODS Twelve pre-hypertensive participants (33.3±6.1 yrs; 3M/9W) participated in 8 weeks of cycle ergometer exercise training. The ET exercised for 30 continuous min/day, 4 days/week at 40% VO2max reserve. The HIIT exercised at a 1:1 work-to-rest for 20 min/day, 3 days/week at 60% peak power. Resting mean arterial pressure and CRP were compared throughout the study. RESULTS Both groups showed decreases (p<0.001) in mean arterial pressure (ET: -11.5 ± 5.9 mmHg; HIIT: -8.6 ± 4.8 mmHg) following the 8 weeks. For CRP, there was a significant decrease (p=0.014) as a main effect of time. VO2max increased (p<0.001) approximately 25% for both HIIT and ET. CONCLUSION These preliminary data suggest HIIT and ET similarly decreased resting blood pressure and increased VO2max.
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Affiliation(s)
- Benjamin C Skutnik
- a Department of Kinesiology , Kansas State University , Manhattan , KS , USA
| | - Joshua R Smith
- a Department of Kinesiology , Kansas State University , Manhattan , KS , USA
| | - Ariel M Johnson
- a Department of Kinesiology , Kansas State University , Manhattan , KS , USA
| | - Stephanie P Kurti
- a Department of Kinesiology , Kansas State University , Manhattan , KS , USA
| | - Craig A Harms
- a Department of Kinesiology , Kansas State University , Manhattan , KS , USA
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15
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Reid MB. Redox interventions to increase exercise performance. J Physiol 2016; 594:5125-33. [PMID: 26584644 PMCID: PMC5023705 DOI: 10.1113/jp270653] [Citation(s) in RCA: 57] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2015] [Accepted: 10/21/2015] [Indexed: 11/08/2022] Open
Abstract
Skeletal muscle continually produces reactive oxygen species (ROS) and nitric oxide (NO) derivatives. Both oxidant cascades have complex effects on muscle contraction, metabolic function and tissue perfusion. Strenuous exercise increases oxidant production by muscle, limiting performance during endurance exercise tasks. Conversely, redox interventions that modulate ROS or NO activity have the potential to improve performance. Antioxidants have long been known to buffer ROS activity and lessen oxidative perturbations during exercise. The capacity to enhance human performance varies among antioxidant categories. Vitamins, provitamins and nutriceuticals often blunt oxidative changes at the biochemical level but do not enhance performance. In contrast, reduced thiol donors have been shown to delay fatigue or increase endurance under a variety of experimental conditions. Dietary nitrate supplementation has recently emerged as a second redox strategy for increasing endurance. Purified nitrate salts and nitrate-rich foods, notably beetroot and beetroot juice, are reported to lessen the oxygen cost of exercise, increase efficiency, and enhance performance during endurance tasks. These findings are exciting but enigmatic since nitrate per se has little bioactivity and cannot be converted to NO by mammalian cells. Overall, the available data suggest exercise endurance can be augmented by redox-active supplements, either reduced thiol donors or dietary nitrates. These findings have clear implications for athletes seeking a competitive edge. More importantly, interventions that increase endurance may benefit individuals whose physical activity is limited by illness, ageing, or frailty.
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Affiliation(s)
- Michael B Reid
- College of Health and Human Performance, University of Florida, Gainesville, FL, 32611, USA.
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Smith JR, Broxterman RM, Ade CJ, Evans KK, Kurti SP, Hammer SM, Barstow TJ, Harms CA. Acute supplementation of N-acetylcysteine does not affect muscle blood flow and oxygenation characteristics during handgrip exercise. Physiol Rep 2016; 4:4/7/e12748. [PMID: 27044854 PMCID: PMC4831322 DOI: 10.14814/phy2.12748] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2016] [Accepted: 03/02/2016] [Indexed: 11/24/2022] Open
Abstract
N‐acetylcysteine (NAC; antioxidant and thiol donor) supplementation has improved exercise performance and delayed fatigue, but the underlying mechanisms are unknown. One possibility is NAC supplementation increases limb blood flow during severe‐intensity exercise. The purpose was to determine if NAC supplementation affected exercising arm blood flow and muscle oxygenation characteristics. We hypothesized that NAC would lead to higher limb blood flow and lower muscle deoxygenation characteristics during severe‐intensity exercise. Eight healthy nonendurance trained men (21.8 ± 1.2 years) were recruited and completed two constant power handgrip exercise tests at 80% peak power until exhaustion. Subjects orally consumed either placebo (PLA) or NAC (70 mg/kg) 60 min prior to handgrip exercise. Immediately prior to exercise, venous blood samples were collected for determination of plasma redox balance. Brachial artery blood flow (BABF) was measured via Doppler ultrasound and flexor digitorum superficialis oxygenation characteristics were measured via near‐infrared spectroscopy. Following NAC supplementaiton, plasma cysteine (NAC: 47.2 ± 20.3 μmol/L vs. PLA: 9.6 ± 1.2 μmol/L; P = 0.001) and total cysteine (NAC: 156.2 ± 33.9 μmol/L vs. PLA: 132.2 ± 16.3 μmol/L; P = 0.048) increased. Time to exhaustion was not significantly different (P = 0.55) between NAC (473.0 ± 62.1 sec) and PLA (438.7 ± 58.1 sec). Resting BABF was not different (P = 0.79) with NAC (99.3 ± 31.1 mL/min) and PLA (108.3 ± 46.0 mL/min). BABF was not different (P = 0.42) during exercise or at end‐exercise (NAC: 413 ± 109 mL/min; PLA: 445 ± 147 mL/min). Deoxy‐[hemoglobin+myoglobin] and total‐[hemoglobin+myoglobin] were not significantly different (P = 0.73 and P = 0.54, respectively) at rest or during exercise between conditions. We conclude that acute NAC supplementation does not alter oxygen delivery during exercise in men.
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Affiliation(s)
- Joshua R Smith
- Department of Kinesiology, Kansas State University, Manhattan, Kansas
| | - Ryan M Broxterman
- Department of Kinesiology, Kansas State University, Manhattan, Kansas
| | - Carl J Ade
- Department of Health and Exercise Science, University of Oklahoma, Norman, Oklahoma
| | - Kara K Evans
- Department of Kinesiology, Kansas State University, Manhattan, Kansas
| | - Stephanie P Kurti
- Department of Kinesiology, Kansas State University, Manhattan, Kansas
| | - Shane M Hammer
- Department of Kinesiology, Kansas State University, Manhattan, Kansas
| | - Thomas J Barstow
- Department of Kinesiology, Kansas State University, Manhattan, Kansas
| | - Craig A Harms
- Department of Kinesiology, Kansas State University, Manhattan, Kansas
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Smith JR, Broxterman RM, Hammer SM, Alexander AM, Didier KD, Kurti SP, Barstow TJ, Harms CA. Sex differences in the cardiovascular consequences of the inspiratory muscle metaboreflex. Am J Physiol Regul Integr Comp Physiol 2016; 311:R574-81. [DOI: 10.1152/ajpregu.00187.2016] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2016] [Accepted: 07/30/2016] [Indexed: 11/22/2022]
Abstract
It is currently unknown whether sex differences exist in the cardiovascular consequences of the inspiratory muscle metaboreflex. We hypothesized that the activation of the inspiratory muscle metaboreflex will lead to less of an increase in mean arterial pressure (MAP) and limb vascular resistance (LVR) and less of a decrease in limb blood flow (Q̇L) in women compared with men. Twenty healthy men ( n = 10, 23 ± 2 yr) and women ( n = 10, 22 ± 3 yr) were recruited for this study. Subjects performed inspiratory resistive breathing tasks (IRBTs) at 2% or 65% of their maximal inspiratory mouth pressure (PIMAX). During the IRBTs, the breathing frequency was 20 breaths/min with a 50% duty cycle. At rest and during the IRBTs, MAP was measured via automated oscillometry, Q̇L was measured via Doppler ultrasound, and LVR was calculated. EMG was recorded on the leg to ensure no muscle contraction occurred. The 65% IRBT led to attenuated increases ( P < 0.01) from baseline in women compared with men for MAP (W: 7.3 ± 2.0 mmHg; M: 11.1 ± 5.0 mmHg) and LVR (W: 17.7% ± 14.0%; M: 47.9 ± 21.0%), as well as less of a decrease ( P < 0.01) in Q̇L (W: −7.5 ± 9.9%; M: −23.3 ± 10.2%). These sex differences in MAP, Q̇L, and LVR were still present in a subset of subjects matched for PIMAX. The 2% IRBT resulted in no significant changes in MAP, Q̇L, or LVR across time or between men and women. These data indicate premenopausal women exhibit an attenuated inspiratory muscle metaboreflex compared with age-matched men.
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Affiliation(s)
- Joshua R. Smith
- Department of Kinesiology, Kansas State University, Manhattan, Kansas
| | | | - Shane M. Hammer
- Department of Kinesiology, Kansas State University, Manhattan, Kansas
| | | | - Kaylin D. Didier
- Department of Kinesiology, Kansas State University, Manhattan, Kansas
| | | | - Thomas J. Barstow
- Department of Kinesiology, Kansas State University, Manhattan, Kansas
| | - Craig A. Harms
- Department of Kinesiology, Kansas State University, Manhattan, Kansas
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McEntire SJ, Smith JR, Ferguson CS, Brown KR, Kurti SP, Harms CA. The effect of exercise training with an additional inspiratory load on inspiratory muscle fatigue and time-trial performance. Respir Physiol Neurobiol 2016; 230:54-9. [PMID: 27195511 DOI: 10.1016/j.resp.2016.05.001] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2016] [Revised: 03/31/2016] [Accepted: 05/02/2016] [Indexed: 10/21/2022]
Abstract
The purpose was to determine the effect of moderate-intensity exercise training (ET) on inspiratory muscle fatigue (IMF) and if an additional inspiratory load during ET (ET+IL) would further improve inspiratory muscle strength, IMF, and time-trial performance. 15 subjects were randomly divided to ET (n=8) and ET+IL groups (n=7). All subjects completed six weeks of exercise training three days/week at ∼70%V̇O2peak for 30min. The ET+IL group breathed through an inspiratory muscle trainer (15% PImax) during exercise. 5-mile, and 30-min time-trials were performed pre-training, weeks three and six. Inspiratory muscle strength increased (p<0.05) for both groups to a similar (p>0.05) extent. ET and ET+IL groups improved (p<0.05) 5-mile time-trial performance (∼10% and ∼18%) and the ET+IL group was significantly faster than ET at week 6. ET and ET+IL groups experienced less (p<0.05) IMF compared to pre-training following the 5-mile time-trial. In conclusion, these data suggest ET leads to less IMF, ET+IL improves inspiratory muscle strength and IMF, but not different than ET alone.
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Affiliation(s)
- Serina J McEntire
- Department of Kinesiology, Kansas State University, Manhattan, KS, USA
| | - Joshua R Smith
- Department of Kinesiology, Kansas State University, Manhattan, KS, USA.
| | | | - Kelly R Brown
- Department of Kinesiology, Kansas State University, Manhattan, KS, USA
| | - Stephanie P Kurti
- Department of Kinesiology, Kansas State University, Manhattan, KS, USA
| | - Craig A Harms
- Department of Kinesiology, Kansas State University, Manhattan, KS, USA
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Kurti SP, Smith JR, Emerson SR, Castinado KM, Harms CA. Absence of Respiratory Muscle Fatigue in High-Intensity Continuous or Interval Cycling Exercise. J Strength Cond Res 2015; 29:3171-6. [DOI: 10.1519/jsc.0000000000000974] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Exercise Tolerance Can Be Enhanced through a Change in Work Rate within the Severe Intensity Domain: Work above Critical Power Is Not Constant. PLoS One 2015; 10:e0138428. [PMID: 26407169 PMCID: PMC4583487 DOI: 10.1371/journal.pone.0138428] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2015] [Accepted: 08/29/2015] [Indexed: 01/04/2023] Open
Abstract
INTRODUCTION The characterization of the hyperbolic power-time (P-tlim) relationship using a two-parameter model implies that exercise tolerance above the asymptote (Critical Power; CP), i.e. within the severe intensity domain, is determined by the curvature (W') of the relationship. PURPOSES The purposes of this study were (1) to test whether the amount of work above CP (W>CP) remains constant for varied work rate experiments of high volatility change and (2) to ascertain whether W' determines exercise tolerance within the severe intensity domain. METHODS Following estimation of CP (208 ± 19 W) and W' (21.4 ± 4.2 kJ), 14 male participants (age: 26 ± 3; peak VO2: 3708 ± 389 ml.min(-1)) performed two experimental trials where the work rate was initially set to exhaust 70% of W' in 3 ('THREE') or 10 minutes ('TEN') before being subsequently dropped to CP plus 10 W. RESULTS W>CP for TEN (104 ± 22% W') and W' were not significantly different (P>0.05) but lower than W>CP for THREE (119 ± 17% W', P<0.05). For both THREE (r = 0.71, P<0.01) and TEN (r = 0.64, P<0.01), a significant bivariate correlation was found between W' and tlim. CONCLUSION W>CP and tlim can be greater than predicted by the P-tlim relationship when a decrement in the work rate of high-volatility is applied. Exercise tolerance can be enhanced through a change in work rate within the severe intensity domain. W>CP is not constant.
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