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White M, Bruce R. The role of muscle mechano and metaboreflexes in the control of ventilation: breathless with (over) excitement? Exp Physiol 2020; 105:2250-2253. [DOI: 10.1113/ep088460] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2020] [Revised: 08/27/2020] [Accepted: 09/02/2020] [Indexed: 11/08/2022]
Affiliation(s)
- Michael White
- School of Sport Exercise and Rehabilitation Sciences University of Birmingham Birmingham UK
| | - Richard Bruce
- Centre for Human and Applied Physiological Sciences School of Basic and Medical Sciences King's College London London UK
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Bruce RM, Jolley C, White MJ. Control of exercise hyperpnoea: Contributions from thin-fibre skeletal muscle afferents. Exp Physiol 2019; 104:1605-1621. [PMID: 31429500 DOI: 10.1113/ep087649] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2019] [Accepted: 08/16/2019] [Indexed: 12/16/2022]
Abstract
NEW FINDINGS What is the topic of this review? In this review, we examine the evidence for control mechanisms underlying exercise hyperpnoea, giving attention to the feedback from thin-fibre skeletal muscle afferents, and highlight the frequently conflicting findings and difficulties encountered by researchers using a variety of experimental models. What advances does it highlight? There has been a recent resurgence of interest in the role of skeletal muscle afferent involvement, not only as a mechanism of healthy exercise hyperpnoea but also in the manifestation of breathlessness and exercise intolerance in chronic disease. ABSTRACT The ventilatory response to dynamic submaximal exercise is immediate and proportional to metabolic rate, which maintains isocapnia. How these respiratory responses are controlled remains poorly understood, given that the most tightly controlled variable (arterial partial pressure of CO2 /H+ ) provides no error signal for arterial chemoreceptors to trigger reflex increases in ventilation. This review discusses evidence for different postulated control mechanisms, with a focus on the feedback from group III/IV skeletal muscle mechanosensitive and metabosensitive afferents. This concept is attractive, because the stimulation of muscle mechanoreceptors might account for the immediate increase in ventilation at the onset of exercise, and signals from metaboreceptors might be proportional to metabolic rate. A variety of experimental models have been used to establish the contribution of thin-fibre muscle afferents in ventilatory control during exercise, with equivocal results. The inhibition of afferent feedback via the application of lumbar intrathecal fentanyl during exercise suppresses ventilation, which provides the most compelling supportive evidence to date. However, stimulation of afferent feedback at rest has no consistent effect on respiratory output. However, evidence is emerging for synergistic interactions between muscle afferent feedback and other stimulatory inputs to the central respiratory neuronal pool. These seemingly hyperadditive effects might explain the conflicting findings encountered when using different experimental models. We also discuss the increasing evidence that patients with certain chronic diseases exhibit exaggerated muscle afferent activation during exercise, resulting in enhanced cardiorespiratory responses. This might provide a neural link between the well-established limb muscle dysfunction and the associated exercise intolerance and exertional dyspnoea, which might offer therapeutic targets for these patients.
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Affiliation(s)
- Richard M Bruce
- Centre for Human and Applied Physiological Sciences, School of Basic and Medical Sciences, King's College London, London, UK
| | - Caroline Jolley
- Centre for Human and Applied Physiological Sciences, School of Basic and Medical Sciences, King's College London, London, UK
| | - Michael J White
- School of Sport, Exercise and Rehabilitation Sciences, University of Birmingham, Birmingham, UK
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Francois ME, Graham MJ, Parr EB, Rehrer NJ, Lucas SJE, Stavrianeas S, Cotter JD. Similar metabolic response to lower- versus upper-body interval exercise or endurance exercise. Metabolism 2017; 68:1-10. [PMID: 28183441 DOI: 10.1016/j.metabol.2016.11.009] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/22/2016] [Revised: 10/25/2016] [Accepted: 11/22/2016] [Indexed: 01/04/2023]
Abstract
PURPOSE To compare energy use and substrate partitioning arising from repeated lower- versus upper-body sprints, or endurance exercise, across a 24-h period. METHODS Twelve untrained males (24±4 y) completed three trials in randomized order: (1) repeated sprints (five 30-s Wingate, 4.5-min recovery) on a cycle ergometer (SITLegs); (2) 50-min continuous cycling at 65% V̇O2max (END); (3) repeated sprints on an arm-crank ergometer (SITArms). Respiratory gas exchange was assessed before and during exercise, and at eight points across 22h of recovery. RESULTS Metabolic rate was elevated to greater extent in the first 8h after SITLegs than SITArms (by 0.8±1.1kJ/min, p=0.03), and tended to be greater than END (by 0.7±1.3kJ/min, p=0.08). Total 24-h energy use (exercise+recovery) was equivalent between SITLegs and END (p = 0.55), and SITLegs and SITArms (p=0.13), but 24-h fat use was higher with SITLegs than END (by 26±38g, p=0.04) and SITArms (by 27±43g, p=0.05), whereas carbohydrate use was higher with SITArms than SITLegs (by 32±51g, p=0.05). Plasma volume-corrected post-exercise and fasting glucose and lipid concentrations were unchanged. CONCLUSION Despite much lower energy use during five sprints than 50-min continuous exercise, 24-h energy use was not reliably different. However, (i) fat metabolism was greater after sprints, and (ii) carbohydrate metabolism was greater in the hours after sprints with arms than legs, while 24-h energy usage was comparable. Thus, sprints using arms or legs may be an important adjunct exercise mode for metabolic health.
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Affiliation(s)
- Monique E Francois
- School of Physical Education, Sport and Exercise Sciences, University of Otago, Dunedin, New Zealand
| | - Matthew J Graham
- School of Physical Education, Sport and Exercise Sciences, University of Otago, Dunedin, New Zealand
| | - Evelyn B Parr
- School of Physical Education, Sport and Exercise Sciences, University of Otago, Dunedin, New Zealand
| | - Nancy J Rehrer
- School of Physical Education, Sport and Exercise Sciences, University of Otago, Dunedin, New Zealand
| | - Samuel J E Lucas
- Department of Physiology, University of Otago, Dunedin, New Zealand
| | | | - James D Cotter
- School of Physical Education, Sport and Exercise Sciences, University of Otago, Dunedin, New Zealand.
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Abstract
NEW FINDINGS What is the topic of this review? This brief review describes the work of Professor John Coote and colleagues at the University of Birmingham, which has contributed to understanding of the role of muscle afferent involvement in cardiorespiratory control in exercise. What advances does it highlight? The seminal findings of John Coote's early work are highlighted, as well as more recent developments in the field, especially the role of muscle afferents in the control of human ventilation during exercise. Through the work of John Coote, research into the role of muscle afferent involvement in cardiorespiratory control has had strong links with Birmingham since the late 1960s. This brief review gives an historical background to John's early work and how his research and mentorship of colleagues continues to have a profound influence on the field today.
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Affiliation(s)
- Michael J White
- * School of Sport, Exercise & Rehabilitation Sciences, College of Life and Environmental Sciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK.
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Effects of the intensity of leg isometric training on the vasculature of trained and untrained limbs and resting blood pressure in middle-aged men. Int J Vasc Med 2012; 2012:964697. [PMID: 22991668 PMCID: PMC3443998 DOI: 10.1155/2012/964697] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2012] [Revised: 07/20/2012] [Accepted: 07/26/2012] [Indexed: 11/17/2022] Open
Abstract
The purpose of this study was to establish whether changes in resting blood pressure and the vasculature of trained and untrained limbs are dependent on training intensity, following isometric-leg training. Thirty middle-aged males undertook an 8 week training programme (4 × 2 min bilateral-leg isometric contractions 3 times per week). Two groups trained at either high (HI; 14%MVC) or low (LO; 8%MVC) intensity a third group (CON) acted as controls. All parameters were measured at baseline, 4-weeks and post-training. Resting SBP (−10.8 ± 7.9 mmHg), MAP (−4.7 ± 6.8 mmHg) and HR (−4.8 ± 5.9 b·min−1) fell significantly in the HI group post-training with concomitant significant increases in resting femoral mean artery diameter (FMAD; 1.0 ± 0.4 mm), femoral mean blood velocity (FMBV; 0.68 ± 0.83 cm·s−1), resting femoral artery blood flow (FABF; 82.06 ± 31.92 ml·min−1) and resting femoral vascular conductance (FVC, 45%). No significant changes occurred in any brachial artery measure nor in any parameters measured in the LO or CON groups. These findings show that training-induced reductions in resting blood pressure after isometric-leg training in healthy middle-aged men are associated with concomitant adaptations in the local vasculature, that appear to be dependent on training intensity and take place in the later stages of training.
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Leprêtre PM, Lopes P, Thomas C, Hanon C. Changes in cardiac tone regulation with fatigue after supra-maximal running exercise. ScientificWorldJournal 2012; 2012:281265. [PMID: 22666098 PMCID: PMC3361189 DOI: 10.1100/2012/281265] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2011] [Accepted: 12/11/2011] [Indexed: 11/17/2022] Open
Abstract
To investigate the effects of fatigue and metabolite accumulation on the postexercicse parasympathetic reactivation, 11 long-sprint runners performed on an outdoor track an exhaustive 400 m long sprint event and a 300 m with the same 400 m pacing strategy. Time constant of heart rate recovery (HRRτ), time (RMSSD), and frequency (HF, and LF) varying vagal-related heart rate variability indexes were assessed during the 7 min period immediately following exercise. Biochemical parameters (blood lactate, pH, PO₂, PCO₂, SaO₂, and HCO₃⁻) were measured at 1, 4 and 7 min after exercise. Time to perform 300 m was not significantly different between both running trials. HHRτ measured after the 400 m running exercise was longer compared to 300 m running bouts (183.7 ± 11.6 versus 132.1 ± 9.8 s, P < 0.01). Absolute power density in the LF and HF bands was also lower after 400 m compared to the 300 m trial (P < 0.05). No correlation was found between biochemical and cardiac recovery responses except for the PO₂ values which were significantly correlated with HF levels measured 4 min after both bouts. Thus, it appears that fatigue rather than metabolic stresses occurring during a supramaximal exercise could explain the delayed postexercise parasympathetic reactivation in longer sprint runs.
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Affiliation(s)
- Pierre-Marie Leprêtre
- Laboratoire de Recherche Adaptations Physiologiques à l'Exercice et Réadaptations à l'Effort, EA 3300, UFR-STAPS, Université de Picardie Jules Verne, 80025 Amiens Cedex 1, France.
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Liang N, Nakamoto T, Mochizuki S, Matsukawa K. Differential contribution of central command to the cardiovascular responses during static exercise of ankle dorsal and plantar flexion in humans. J Appl Physiol (1985) 2011; 110:670-80. [DOI: 10.1152/japplphysiol.00740.2010] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
To examine whether central command contributes differently to the cardiovascular responses during voluntary static exercise engaged by different muscle groups, we encouraged healthy subjects to perform voluntary and electrically evoked involuntary static exercise of ankle dorsal and plantar flexion. Each exercise was conducted with 25% of the maximum voluntary force of the right ankle dorsal and plantar flexion, respectively, for 2 min. Heart rate (HR) and mean arterial blood pressure (MAP) were recorded, and stroke volume, cardiac output (CO), and total peripheral resistance were calculated. With voluntary exercise, HR, MAP, and CO significantly increased during dorsal flexion (the maximum increase, HR: 12 ± 2.3 beats/min; MAP: 14 ± 2.0 mmHg; CO: 1 ± 0.2 l/min), whereas only MAP increased during plantar flexion (the maximum increase, 6 ± 2.0 mmHg). Stroke volume and total peripheral resistance were unchanged throughout the two kinds of voluntary static exercise. With involuntary exercise, there were no significant changes in all cardiovascular variables, irrespective of dorsal or plantar flexion. Furthermore, before the force onset of voluntary static exercise, HR and MAP started to increase without muscle contraction, whereas they had no significant changes with involuntary exercise at the moment. The present findings indicate that differential contribution of central command is responsible for the different cardiovascular responses to static exercise, depending on the strength of central control of the contracting muscle.
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Affiliation(s)
- Nan Liang
- Department of Physiology, Graduate School of Health Sciences, and
- Center for Advanced Practice and Research of Rehabilitation, Hiroshima University, Minami-ku, Hiroshima, Japan
| | - Tomoko Nakamoto
- Department of Physiology, Graduate School of Health Sciences, and
| | - Seina Mochizuki
- Department of Physiology, Graduate School of Health Sciences, and
| | - Kanji Matsukawa
- Department of Physiology, Graduate School of Health Sciences, and
- Center for Advanced Practice and Research of Rehabilitation, Hiroshima University, Minami-ku, Hiroshima, Japan
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Green JG, Stannard SR. Active recovery strategies and handgrip performance in trained vs. untrained climbers. J Strength Cond Res 2010; 24:494-501. [PMID: 20072048 DOI: 10.1519/jsc.0b013e3181c06af3] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Isometric contractions, such as occurring during rock climbing, occlude blood flow to the active musculature. The ability to maximize forearm blood flow between such contractions is a likely determinant of intermittent handgrip performance. This study aimed to test the hypothesis that intermittent isometric handgrip performance is improved by 2 common active recovery strategies suggested to increase muscle blood flow. On 6 separate occasions, 9 trained indoor rock climbers and 9 untrained participants undertook a fatiguing, intermittent, isometric handgrip exercise bout consisting of sets of 6 contractions (approximately 33% of maximal voluntary contraction [MVC] force), each 3-second long separated by a 1-second rest. Between sets, participants were allowed 9-second recovery performing passive rest, "shaking out" (vigorously shaking the hand), or grasping a handgrip vibration machine, each with or without forearm occlusion. Performance was assessed by pre- and post-exercise MVC trials and a 20-contraction post-exercise handgrip time trial (TT20). Trained climbers exhibited significantly greater handgrip MVC force and intermittent exercise capacity than untrained (p < 0.01). There was no effect of recovery strategy on any measure (p > 0.05). Trained climbers were more affected by occlusion than untrained in MVC (p < 0.05) and TT20 (p < 0.01). Shaking out and low-frequency vibration are unlikely to affect rock climbing performance. It is recommended that rock climbers and their coaches focus on optimizing body position rather than compromising body position to allow for shaking out.
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Affiliation(s)
- Jackson G Green
- Institute of Food, Nutrition and Human Health, Massey University, Palmerston, New Zealand.
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TILLIN NEALEA, JIMENEZ-REYES PEDRO, PAIN MATTHEWTG, FOLLAND JONATHANP. Neuromuscular Performance of Explosive Power Athletes versus Untrained Individuals. Med Sci Sports Exerc 2010; 42:781-90. [DOI: 10.1249/mss.0b013e3181be9c7e] [Citation(s) in RCA: 156] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Vianna L, Ricardo D, Araújo C. Training-related changes in the R-R interval at the onset of passive movements in humans. Braz J Med Biol Res 2008; 41:825-32. [DOI: 10.1590/s0100-879x2008000900014] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2007] [Accepted: 08/18/2008] [Indexed: 11/21/2022] Open
Affiliation(s)
| | | | - C.G.S. Araújo
- Universidade Gama Filho, Brasil; 3Clínica de Medicina do Exercício (CLINIMEX), Brasil
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Fisher JP, White MJ. Muscle afferent contributions to the cardiovascular response to isometric exercise. Exp Physiol 2004; 89:639-46. [PMID: 15364880 DOI: 10.1113/expphysiol.2004.028639] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The cardiovascular response to isometric exercise is governed by both central and peripheral mechanisms. Both metabolic and mechanical stresses on the exercising skeletal muscle produce cardiovascular change, yet it is often overlooked that the afferent signal arising from the muscle can be modified by factors other than exercise intensity. This review discusses research revealing that muscle fibre type, muscle mass and training status are important factors in modifying this peripheral feedback from the active muscles. Studies in both animals and humans have shown that the pressor response resulting from exercise of muscle with a faster contractile character and isomyosin content is greater than that from a muscle of slower contractile character. Athletic groups participating in training programmes that place a high anaerobic load on skeletal muscle groups show attenuated muscle afferent feedback. Similarly, longitudinal studies have shown that specific local muscle training also blunts the pressor response to isometric exercise. Thus it appears that training may decrease the metabolic stimulation of muscle afferents and in some instances chronic exposure to the products of anaerobic metabolism may blunt the sensitivity of the muscle metaboreflex. There may be surprising parallels between the local muscle conditions induced in athletes training for longer sprint events (e.g. 400 m) and by the low-flow conditions in, for example, the muscles of chronic heart failure patients. Whether their similar attenuations in muscle afferent feedback during exercise are due to decreased metabolite accumulation or to a desensitization of the muscle afferents is not yet known.
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Affiliation(s)
- James P Fisher
- School of Sport and Exercise Sciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK.
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Carrington CA, Fisher JP, Davies MK, White MJ. Muscle afferent inputs to cardiovascular control during isometric exercise vary with muscle group in patients with chronic heart failure. Clin Sci (Lond) 2004; 107:197-204. [PMID: 15089744 DOI: 10.1042/cs20040038] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2004] [Revised: 03/25/2004] [Accepted: 04/19/2004] [Indexed: 11/17/2022]
Abstract
It is not known whether the contribution of the muscle metaboreflex to the cardiovascular response to isometric exercise varies between different muscles in patients with CHF (chronic heart failure) or whether this depends upon muscle fibre type and training status. To resolve these issues BP (blood pressure) and HR (heart rate) responses were recorded in seven stable CHF patients (ejection fraction 30–40%; age 67±3 years) and in six healthy AMA (age-matched active) subjects. The experimental protocol consisted of 2 min of ischaemic isometric exercise at 30% maximum voluntary force, performed in separate trials by the calf plantar flexors (CALF) and handgrip muscles (FOREARM). To isolate the muscle metaboreflex a subsequent period of PECO (post-exercise circulatory occlusion) was performed following exercise. FOREARM and CALF produced similar increases in BP in both the AMA subjects and CHF patients. CHF patients elicited a significantly lower diastolic BP during PECO following CALF in comparison with that following FOREARM (5±5 compared with 12±3 mmHg respectively). A similar result was seen in AMA subjects. It may be that even the limited weight-bearing locomotor role of the calf muscles constitutes a conditioning stimulus in CHF patients, which leads to desensitization of the muscle metaboreflex, thus producing an attenuated BP elevation. We conclude that it would be incorrect to make general statements about muscle chemoreflex inputs to cardiovascular control in CHF patients based upon measurements made on only one muscle group and without reference to muscle fibre type and training status.
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Ross A, Leveritt M. Long-term metabolic and skeletal muscle adaptations to short-sprint training: implications for sprint training and tapering. Sports Med 2002; 31:1063-82. [PMID: 11735686 DOI: 10.2165/00007256-200131150-00003] [Citation(s) in RCA: 144] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
The adaptations of muscle to sprint training can be separated into metabolic and morphological changes. Enzyme adaptations represent a major metabolic adaptation to sprint training, with the enzymes of all three energy systems showing signs of adaptation to training and some evidence of a return to baseline levels with detraining. Myokinase and creatine phosphokinase have shown small increases as a result of short-sprint training in some studies and elite sprinters appear better able to rapidly breakdown phosphocreatine (PCr) than the sub-elite. No changes in these enzyme levels have been reported as a result of detraining. Similarly, glycolytic enzyme activity (notably lactate dehydrogenase, phosphofructokinase and glycogen phosphorylase) has been shown to increase after training consisting of either long (>10-second) or short (<10-second) sprints. Evidence suggests that these enzymes return to pre-training levels after somewhere between 7 weeks and 6 months of detraining. Mitochondrial enzyme activity also increases after sprint training, particularly when long sprints or short recovery between short sprints are used as the training stimulus. Morphological adaptations to sprint training include changes in muscle fibre type, sarcoplasmic reticulum, and fibre cross-sectional area. An appropriate sprint training programme could be expected to induce a shift toward type IIa muscle, increase muscle cross-sectional area and increase the sarcoplasmic reticulum volume to aid release of Ca(2+). Training volume and/or frequency of sprint training in excess of what is optimal for an individual, however, will induce a shift toward slower muscle contractile characteristics. In contrast, detraining appears to shift the contractile characteristics towards type IIb, although muscle atrophy is also likely to occur. Muscle conduction velocity appears to be a potential non-invasive method of monitoring contractile changes in response to sprint training and detraining. In summary, adaptation to sprint training is clearly dependent on the duration of sprinting, recovery between repetitions, total volume and frequency of training bouts. These variables have profound effects on the metabolic, structural and performance adaptations from a sprint-training programme and these changes take a considerable period of time to return to baseline after a period of detraining. However, the complexity of the interaction between the aforementioned variables and training adaptation combined with individual differences is clearly disruptive to the transfer of knowledge and advice from laboratory to coach to athlete.
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Affiliation(s)
- A Ross
- School of Human Movement Studies, University of Queensland, St Lucia, Queensland, Australia.
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Carrington CA, Fisher WJ, Davies MK, White MJ. Is there a relationship between muscle fatigue resistance and cardiovascular responses to isometric exercise in mild chronic heart failure? Eur J Heart Fail 2001; 3:53-8. [PMID: 11163736 DOI: 10.1016/s1388-9842(00)00112-4] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
BACKGROUND Exercise intolerance in chronic heart failure (CHF) may be due to altered fatigue resistance and muscle afferent input to the cardiovascular system from dysfunctional skeletal muscle. AIM To determine whether calf muscle fatigue resistance was associated with the magnitude of a muscle afferent driven cardiovascular response to isometric exercise. METHODS AND RESULTS Cardiovascular responses were recorded in eight stable CHF patients (ejection fraction 20-40%) and nine healthy, age-matched controls during voluntary and electrically evoked isometric plantar flexion and post-exercise circulatory occlusion. The force developed by the plantar flexors during a 2-min submaximal electrically evoked fatigue test was measured. There was no relationship between ischaemic muscle fatigue and cardiovascular changes during and after voluntary contraction in either group nor evoked contraction in the CHF group. In the control group, the change in diastolic blood pressure (DBP) at the end of evoked contraction was related to the severity of fatigue at 90 s and 120 s (FI=0.01DeltaDBP+0.3, r=0.81, P<0.05 and FI=0.02DeltaDBP+0.8, r=0.84, P<0.01, respectively). CONCLUSION Muscle fatigue resistance did not relate to the magnitude of the cardiovascular stress generated by isometric exercise of the same muscle in these patients.
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Affiliation(s)
- C A Carrington
- School of Sport and Exercise Sciences, University of Birmingham, Edgbaston, Birmingham, UK.
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O'Sullivan SE, Bell C. The effects of exercise and training on human cardiovascular reflex control. JOURNAL OF THE AUTONOMIC NERVOUS SYSTEM 2000; 81:16-24. [PMID: 10869695 DOI: 10.1016/s0165-1838(00)00148-x] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
During physical activity, there is a graded withdrawal of vagal cardiac tone and a graded increase in sympathetic cardiac and vasomotor tone, initiated through both central command from the somatic motor cortex and muscle chemoreceptive and mechanoreceptive inputs. In parallel, there is an upward resetting of the operating point of the arterial baroreflex, with preserved reflex sensitivity. In contrast to the traditional interpretation that blood flow through exercising muscle is independent of vasomotor neural influences because of the dominance of local dilator metabolites, recent evidence suggests that both constrictor and dilator sympathetic neural influences may be involved in determining absolute levels of perfusion. Post-exercise, there is a period of relative hypotension that is associated with decreased peripheral resistance. Some, but not all, evidence indicates a causal role for reduced sympathetic drive. Chronic exercise training appears to reduce resting sympathetic activity, with parallel changes in the gain of a variety of cardiovascular autonomic reflexes initiated from cardiovascular sites. These changes may be attributable at least partly to masking of arterial baroreflexes by the impact of elevated blood volume on low-pressure baroreceptors. The reductions in sympathetic drive that follow training are more pronounced in patients with essential hypertension than in normotensive individuals and are likely to underlie the anti-hypertensive effect of exercise.
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Affiliation(s)
- S E O'Sullivan
- Department of Physiology, Trinity College Dublin, 2, Dublin, Ireland.
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Fisher WJ, White MJ. Training-induced adaptations in the central command and peripheral reflex components of the pressor response to isometric exercise of the human triceps surae. J Physiol 1999; 520 Pt 2:621-8. [PMID: 10523427 PMCID: PMC2269582 DOI: 10.1111/j.1469-7793.1999.00621.x] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
1. The effect of calf raise training of the dominant limb on the pressor response to isometric exercise of the triceps surae was examined in the trained dominant limb and the contralateral untrained limb. Blood pressure and heart rate responses to electrically evoked and voluntary exercise at 30 % maximum voluntary contraction (MVC), followed by post-exercise circulatory occlusion (PECO), were compared before and after a 6 week training period. 2. In the trained limb the diastolic blood pressure rise seen during electrically evoked exercise was reduced by 27 % after training. However, the response during PECO was not significantly affected. 3. During voluntary exercise of the trained limb, diastolic blood pressure rise was reduced by 28 %, and heart rate rise was significantly attenuated after training. During PECO no significant effects of training were observed. 4. Voluntary exercise of the untrained limb resulted in a 24 % reduction in diastolic blood pressure rise after the training period, and a significant attenuation of the heart rate increase during exercise. Responses to electrically evoked exercise and PECO of the untrained limb remained unaltered after training. 5. Attenuation of blood pressure and heart rate responses, in the contralateral untrained limb, during voluntary but not electrically evoked exercise, indicates a training-induced alteration in central command.
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Affiliation(s)
- W J Fisher
- School of Sport and Exercise Sciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK
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