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Seow KN, Seow CY. Molecular Events of the Crossbridge Cycle Reflected in the Force–Velocity Relationship of Activated Muscle. Front Physiol 2022; 13:846284. [PMID: 35360243 PMCID: PMC8960716 DOI: 10.3389/fphys.2022.846284] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2021] [Accepted: 02/15/2022] [Indexed: 11/13/2022] Open
Abstract
Muscles convert chemical energy to mechanical work. Mechanical performance of a muscle is often assessed by the muscle’s ability to shorten and generate power over a range of loads or forces, characterized by the force–velocity and force–power relationships. The hyperbolic force–velocity relationship of muscle, for a long time, has been regarded as a pure empirical description of the force–velocity data. Connections between mechanical manifestation in terms of force–velocity properties and the kinetics of the crossbridge cycle have only been established recently. In this review, we describe how the model of Huxley’s crossbridge kinetics can be transformed to the hyperbolic Hill equation, and link the changes in force–velocity properties to molecular events within the crossbridge cycle driven by ATP hydrolysis. This allows us to reinterpret some findings from previous studies on experimental interventions that altered the force–velocity relationship and gain further insight into the molecular mechanisms of muscle contraction under physiological and pathophysiological conditions.
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Affiliation(s)
- Kathryn N. Seow
- Faculty of Land and Food Systems, University of British Columbia, Vancouver, BC, Canada
| | - Chun Y. Seow
- Department of Pathology and Laboratory Medicine, University of British Columbia, Vancouver, BC, Canada
- Centre for Heart Lung Innovation, Providence Health Care/St. Paul’s Hospital, University of British Columbia, Vancouver, BC, Canada
- *Correspondence: Chun Y. Seow,
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2
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Olesen JH, Herskind J, Pedersen KK, Overgaard K. Potassium-induced potentiation of subtetanic force in rat skeletal muscles: influences of β 2-activation, lactic acid, and temperature. Am J Physiol Cell Physiol 2021; 321:C884-C896. [PMID: 34613841 DOI: 10.1152/ajpcell.00120.2021] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2021] [Accepted: 09/28/2021] [Indexed: 02/04/2023]
Abstract
Moderate elevations of extracellular K+ concentration ([K+]o) occur during exercise and have been shown to potentiate force during contractions elicited with subtetanic frequencies. Here, we investigated whether lactic acid (reduced chloride conductance), β2-adrenoceptor activation, and increased temperature would influence the potentiating effect of potassium in slow- and fast-twitch muscles. Isometric contractions were elicited by electrical stimulation at various frequencies in isolated rat soleus and extensor digitorum longus (EDL) muscles incubated at normal (4 mM) or elevated K+, in combination with salbutamol (5 μM), lactic acid (18.1 mM), 9-anthracene-carboxylic acid (9-AC; 25 μM), or increased temperature (30-35°C). Elevating [K+]o from 4 mM to 7 mM (soleus) and 10 mM (EDL) potentiated isometric twitch and subtetanic force while slightly reducing tetanic force. In EDL, salbutamol further augmented twitch force (+27 ± 3%, P < 0.001) and subtetanic force (+22 ± 4%, P < 0.001). In contrast, salbutamol reduced subtetanic force (-28 ± 6%, P < 0.001) in soleus muscles. Lactic acid and 9-AC had no significant effects on isometric force of muscles already exposed to moderate elevations of [K+]o. The potentiating effect of elevated [K+]o was still well maintained at 35°C. Addition of salbutamol exerts a further force-potentiating effect in fast-twitch but not in slow-twitch muscles already potentiated by moderately elevated [K+]o, whereas lactic acid, 9-AC, or increased temperature does not exert any further augmentation. However, the potentiating effect of elevated [K+]o was still maintained in the presence of these, thus emphasizing the positive influence of moderately elevated [K+]o for contractile performance during exercise.
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Affiliation(s)
- Jonas H Olesen
- Exercise Biology, Department of Public Health, Aarhus University, Aarhus, Denmark
| | - Jon Herskind
- Exercise Biology, Department of Public Health, Aarhus University, Aarhus, Denmark
| | - Katja K Pedersen
- Exercise Biology, Department of Public Health, Aarhus University, Aarhus, Denmark
| | - Kristian Overgaard
- Exercise Biology, Department of Public Health, Aarhus University, Aarhus, Denmark
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3
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Hostrup M, Cairns SP, Bangsbo J. Muscle Ionic Shifts During Exercise: Implications for Fatigue and Exercise Performance. Compr Physiol 2021; 11:1895-1959. [PMID: 34190344 DOI: 10.1002/cphy.c190024] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Exercise causes major shifts in multiple ions (e.g., K+ , Na+ , H+ , lactate- , Ca2+ , and Cl- ) during muscle activity that contributes to development of muscle fatigue. Sarcolemmal processes can be impaired by the trans-sarcolemmal rundown of ion gradients for K+ , Na+ , and Ca2+ during fatiguing exercise, while changes in gradients for Cl- and Cl- conductance may exert either protective or detrimental effects on fatigue. Myocellular H+ accumulation may also contribute to fatigue development by lowering glycolytic rate and has been shown to act synergistically with inorganic phosphate (Pi) to compromise cross-bridge function. In addition, sarcoplasmic reticulum Ca2+ release function is severely affected by fatiguing exercise. Skeletal muscle has a multitude of ion transport systems that counter exercise-related ionic shifts of which the Na+ /K+ -ATPase is of major importance. Metabolic perturbations occurring during exercise can exacerbate trans-sarcolemmal ionic shifts, in particular for K+ and Cl- , respectively via metabolic regulation of the ATP-sensitive K+ channel (KATP ) and the chloride channel isoform 1 (ClC-1). Ion transport systems are highly adaptable to exercise training resulting in an enhanced ability to counter ionic disturbances to delay fatigue and improve exercise performance. In this article, we discuss (i) the ionic shifts occurring during exercise, (ii) the role of ion transport systems in skeletal muscle for ionic regulation, (iii) how ionic disturbances affect sarcolemmal processes and muscle fatigue, (iv) how metabolic perturbations exacerbate ionic shifts during exercise, and (v) how pharmacological manipulation and exercise training regulate ion transport systems to influence exercise performance in humans. © 2021 American Physiological Society. Compr Physiol 11:1895-1959, 2021.
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Affiliation(s)
- Morten Hostrup
- Section of Integrative Physiology, Department of Nutrition, Exercise and Sports, University of Copenhagen, Copenhagen, Denmark
| | - Simeon Peter Cairns
- SPRINZ, School of Sport and Recreation, Auckland University of Technology, Auckland, New Zealand.,Health and Rehabilitation Research Institute, Auckland University of Technology, Auckland, New Zealand
| | - Jens Bangsbo
- Section of Integrative Physiology, Department of Nutrition, Exercise and Sports, University of Copenhagen, Copenhagen, Denmark
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Ríos DCZ, Miramar AJM, Paz YM, Padilla ICR. LACTATE: A BIOLOGICAL MARKER OF PHYSICAL ACTIVITY IN COLOMBIAN WEIGHTLIFTING ATHLETES. REV BRAS MED ESPORTE 2021. [DOI: 10.1590/1517-8692202127012019_0047] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/03/2023] Open
Abstract
ABSTRACT Introduction Blood biomarkers are measurable metabolic products that allow objective monitoring of the training process, and their analysis provides an opportunity to improve athletic performance. Objective To evaluate blood lactate concentrations in a group of the Valle League weightlifting athletes as a tool to determine the effects of training and its direct relationship to performance during competition. Methods This is an observational cross-sectional study. Lactate levels of 32 weightlifting athletes belonging to the Valle Weightlifting League were evaluated. Blood samples were taken from the ear lobe to quantify the lactate concentration, using a Scout Lactate analyzer. Samples were taken before and after a high intensity training section consisting of four maximum repetition (MR) sports gestures, in which 5 series and 15 repetitions were performed for each sports gesture, with a rest period of 40 seconds between each exercise. The software program SPSS, version 25, was used to determine the lactate concentrations. Results An average lactate concentration 22.46 mg/dL was obtained for the athletes at rest, and an average of 98.30 mg/dL in the final lactate concentration, after high intensity exercise. Significant differences were found between the initial and final lactate concentrations. Conclusion Lactate concentration increases with physical activity; it varies from one individual to another; and it can be used as a biomarker of intensity of physical activity in the field of sports. Level of evidence; II type of study: Prognostic Studies Investigating the Effect of a Patient Characteristic on a disease outcome.
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Affiliation(s)
| | | | - Yecid Mina Paz
- Institución Universitaria Escuela Nacional del Deporte, Colombia
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5
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Pedersen KK, Cheng AJ, Westerblad H, Olesen JH, Overgaard K. Moderately elevated extracellular [K+] potentiates submaximal force and power in skeletal muscle via increased [Ca2+]i during contractions. Am J Physiol Cell Physiol 2019; 317:C900-C909. [DOI: 10.1152/ajpcell.00104.2019] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The extracellular K+ concentration ([K+]o) increases during physical exercise. We here studied whether moderately elevated [K+]o may increase force and power output during contractions at in vivo-like subtetanic frequencies and whether such potentiation was associated with increased cytosolic free Ca2+ concentration ([Ca2+]i) during contractions. Isolated whole soleus and extensor digitorum longus (EDL) rat muscles were incubated at different levels of [K+]o, and isometric and dynamic contractility were tested at various stimulation frequencies. Furthermore, [Ca2+]i at rest and during contraction was measured along with isometric force in single mouse flexor digitorum brevis (FDB) fibers exposed to elevated [K+]o. Elevating [K+]o from 4 mM up to 8 mM (soleus) and 11 mM (EDL) increased isometric force at subtetanic frequencies, 2–15 Hz in soleus and up to 50 Hz in EDL, while inhibition was seen at tetanic frequency in both muscle types. Elevating [K+]o also increased peak power of dynamic subtetanic contractions, with potentiation being more pronounced in EDL than in soleus muscles. The force-potentiating effect of elevated [K+]o was transient in FDB single fibers, reaching peak after ~4 and 2.5 min in 9 and 11 mM [K+]o, respectively. At the time of peak potentiation, force and [Ca2+]i during 15-Hz contractions were significantly increased, whereas force was slightly decreased and [Ca2+]i unchanged during 50-Hz contractions. Moderate elevation of [K+]o can transiently potentiate force and power during contractions at subtetanic frequencies, which can be explained by a higher [Ca2+]i during contractions.
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Affiliation(s)
- Katja K. Pedersen
- Department of Public Health, Section of Sport Science, Aarhus University, Aarhus, Denmark
| | - Arthur J. Cheng
- Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden
| | - Håkan Westerblad
- Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden
| | - Jonas H. Olesen
- Department of Public Health, Section of Sport Science, Aarhus University, Aarhus, Denmark
| | - Kristian Overgaard
- Department of Public Health, Section of Sport Science, Aarhus University, Aarhus, Denmark
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6
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Kristensen AM, Nielsen OB, Pedersen TH, Overgaard K. Fatiguing stimulation increases curvature of the force-velocity relationship in isolated fast-twitch and slow-twitch rat muscles. ACTA ACUST UNITED AC 2019; 222:jeb.204545. [PMID: 31292165 DOI: 10.1242/jeb.204545] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2019] [Accepted: 07/04/2019] [Indexed: 01/14/2023]
Abstract
In skeletal muscles, the ability to generate power is reduced during fatigue. In isolated muscles, maximal power can be calculated from the force-velocity relationship. This relationship is well described by the Hill equation, which contains three parameters: (1) maximal isometric force, (2) maximum contraction velocity and (3) curvature. Here, we investigated the hypothesis that a fatigue-induced loss of power is associated with changes in curvature of the force-velocity curve in slow-twitch muscles but not in fast-twitch muscles during the development of fatigue. Isolated rat soleus (slow-twitch) and extensor digitorum longus (EDL; fast-twitch) muscles were incubated in Krebs-Ringer solution at 30°C and stimulated electrically at 60 Hz (soleus) and 150 Hz (EDL) to perform a series of concentric contractions to fatigue. Force-velocity data were fitted to the Hill equation, and curvature was determined as the ratio of the curve parameters a/F 0 (inversely related to curvature). At the end of the fatiguing protocol, maximal power decreased by 58±5% in the soleus and 69±4% in the EDL compared with initial values in non-fatigued muscles. At the end of the fatiguing sequence, curvature increased as judged from the decrease in a/F 0 by 81±20% in the soleus and by 31±12% in the EDL. However, during the initial phases of fatiguing stimulation, we observed a small decrease in curvature in the EDL, but not in the soleus, which may be a result of post-activation potentiation. In conclusion, fatigue-induced loss of power is strongly associated with an increased curvature of the force-velocity relationship, particularly in slow-twitch muscles.
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Affiliation(s)
| | - Ole B Nielsen
- Department of Public Health, Aarhus University, DK-8000 Aarhus C, Denmark
| | - Thomas H Pedersen
- Department of Biomedicine, Aarhus University, DK-8000 Aarhus C, Denmark
| | - Kristian Overgaard
- Department of Public Health, Aarhus University, DK-8000 Aarhus C, Denmark
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7
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Cunha VCR, Aoki MS, Zourdos MC, Gomes RV, Barbosa WP, Massa M, Moreira A, Capitani CD. Sodium citrate supplementation enhances tennis skill performance: a crossover, placebo-controlled, double blind study. J Int Soc Sports Nutr 2019; 16:32. [PMID: 31370896 PMCID: PMC6676531 DOI: 10.1186/s12970-019-0297-4] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2018] [Accepted: 07/08/2019] [Indexed: 11/25/2022] Open
Abstract
Background The efficacy of sodium citrate supplementation (SC) in exercise performance is unclear. Therefore, the aim of this study was to investigate the effect of SC on skilled tennis performance. Methods Ten Brazilian nationally-ranked young male tennis players (age: 17 ± 1 yrs.; stature: 176.7 ± 5.2 cm; body mass: 68.4 ± 7.9 kg) participated in this crossover, placebo-controlled, double-blind study. Upon arrival, at baseline, in both experimental sessions blood was collected, then subjects ingested either sodium citrate (SC - 0.5 g.kg−1BM in capsules of 500 mg) or a placebo (PLA). Two hours later, pre-match blood was collected then skills tests (skill tennis performance test - STPT, repeated-sprint ability shuttle test - RSA) were performed followed by a 1-h simulated match. Immediately following the match, blood was again collected, and STPT, and RSA were administered. Results All metabolic parameters (i.e. base excess, pH, bicarbonate, and blood lactate) increased (p < 0.001) from baseline to pre-match and post-match in SC condition. Each metabolic parameter was greater (p < 0.001) in SC compared to PLA condition at both pre- and post-match. The SC condition elicited a greater (p < 0.01) shot consistency at post-match in the STPT vs. PLA condition (SC: 58.5 ± 14.8% vs. PLA: 40.4 ± 10.4%). A greater (p < 0.001) amount of games won was observed in the simulated match for SC condition vs. PLA condition (SC: 8.0 ± 1.6 vs. PLA: 6.0 ± 1.7). Additionally, the games won during the simulated match in SC condition was positively correlated with percentage shot consistency (r = 0.67, p < 0.001). Conclusions The current findings suggest that SC supplementation is an effective ergogenic aid to enhance skilled tennis performance.
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Affiliation(s)
- Vivian C R Cunha
- School of Applied Sciences, University of Campinas, Rua Pedro Zaccaria 1300, Limeira, 13484-350, Sao Paulo, Brazil
| | - Marcelo S Aoki
- School of Arts, Sciences and Humanities, University of Sao Paulo, Sao Paulo, Sao Paulo, Brazil
| | - Michael C Zourdos
- Department of Exercise Science and Health Promotion, Muscle Physiology Laboratory, Florida Atlantic University, Kissimme, Florida, USA
| | - Rodrigo V Gomes
- School of Arts, Sciences and Humanities, University of Sao Paulo, Sao Paulo, Sao Paulo, Brazil
| | - Wesley P Barbosa
- School of Arts, Sciences and Humanities, University of Sao Paulo, Sao Paulo, Sao Paulo, Brazil
| | - Marcelo Massa
- School of Arts, Sciences and Humanities, University of Sao Paulo, Sao Paulo, Sao Paulo, Brazil
| | - Alexandre Moreira
- School of Physical Education and Sport, University of Sao Paulo, Sao Paulo, Sao Paulo, Brazil
| | - Caroline D Capitani
- School of Applied Sciences, University of Campinas, Rua Pedro Zaccaria 1300, Limeira, 13484-350, Sao Paulo, Brazil.
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8
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Pedersen KK, Nielsen OB, Overgaard K. Contractile benefits of doublet-initiated low-frequency stimulation in rat extensor digitorum longus muscle exposed to high extracellular [K +] or fatiguing contractions. Am J Physiol Cell Physiol 2019; 317:C39-C47. [PMID: 30969780 DOI: 10.1152/ajpcell.00519.2018] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
During dynamic contractions, high-frequency muscle activation is needed to achieve optimal power. This must be balanced against an increased excitation-induced accumulation of extracellular K+, which can reduce excitability and ultimately may prevent adequate responses to high-frequency activation. Mean activation frequencies in vivo are often low (subtetanic), but activation patterns contain bursts of high (supratetanic) frequencies known as doublets, which enhance dynamic contraction in rested muscles at normal extracellular K+ concentration ([K+]o). Here, we examine how dynamic contractions in fast-twitch fibers stimulated by high frequency/doublets are affected during exposure to 11 mM [K+]o and during fatigue. Dynamic contractions were elicited by electrical stimulation in isolated rat extensor digitorum longus muscles incubated at 4 or 11 mM K+. When stimulation frequency was maintained constant, an increase from 150 to 300 Hz enhanced maximal power (Pmax), maximal velocity (Vmax), and rate of force development (RFD) at 4 mM K+ but only Vmax at 11 mM K+. With the use of subtetanic frequency trains (50 Hz) with or without an initiating doublet (300 Hz), the addition of a doublet increased maximal force, Pmax, Vmax, and RFD at both 4 and 11 mM K+. Furthermore, a work-matched fatiguing protocol was performed comparing a doublet-initiated subtetanic train (DT) of 60 Hz with a constant-frequency train (CFT) of 71 Hz during 100 dynamic contractions. We found that DT produced higher power, velocity, and RFD than CFT throughout the fatiguing protocol. The results indicate that doublets enhance dynamic contraction in fast-twitch muscles stimulated at subtetanic frequency during both normal and fatiguing conditions.
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Affiliation(s)
| | - Ole Bækgaard Nielsen
- Department of Public Health, Aarhus University , Aarhus , Denmark.,Department of Biomedicine, Aarhus University , Aarhus , Denmark
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9
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Kristensen AM, Nielsen OB, Overgaard K. Effects of manipulating tetanic calcium on the curvature of the force-velocity relationship in isolated rat soleus muscles. Acta Physiol (Oxf) 2018; 222. [PMID: 28972685 DOI: 10.1111/apha.12977] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2017] [Revised: 09/25/2017] [Accepted: 09/25/2017] [Indexed: 01/03/2023]
Abstract
AIM In dynamically contracting muscles, increased curvature of the force-velocity relationship contributes to the loss of power during fatigue. It has been proposed that fatigue-induced reduction in [Ca++ ]i causes this increased curvature. However, earlier studies on single fibres have been conducted at low temperatures. Here, we investigated the hypothesis that curvature is increased by reductions in tetanic [Ca++ ]i in isolated skeletal muscle at near-physiological temperatures. METHODS Rat soleus muscles were stimulated at 60 Hz in standard Krebs-Ringer buffer, and contraction force and velocity were measured. Tetanic [Ca++ ]i was in some experiments either lowered by addition of 10 μmol/L dantrolene or use of submaximal stimulation (30 Hz) or increased by addition of 2 mmol/L caffeine. Force-velocity curves were constructed by fitting shortening velocity at different loading forces to the Hill equation. Curvature was determined as the ratio a/F0 with increased curvature reflecting decreased a/F0 . RESULTS Compared to control levels, lowering tetanic [Ca++ ]i with dantrolene or reduced stimulation frequency decreased the curvature slightly as judged from increase in a/F0 of 13 ± 1% (P = < .001) and 20 ± 2% (P = < .001) respectively. In contrast, increasing tetanic [Ca++ ]i with caffeine increased the curvature (a/F0 decreased by 17 ± 1%; P = < .001). CONCLUSION Contrary to our hypothesis, interventions that reduced tetanic [Ca++ ]i caused a decrease in curvature, while increasing tetanic [Ca++ ]i increased the curvature. These results reject a simple causal relation between [Ca++ ]i and curvature of the force-velocity relation during fatigue.
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Affiliation(s)
- A. M. Kristensen
- Department of Public Health; Aarhus University; Aarhus C Denmark
| | - O. B. Nielsen
- Department of Biomedicine; Aarhus University; Aarhus C Denmark
| | - K. Overgaard
- Department of Public Health; Aarhus University; Aarhus C Denmark
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10
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Fan C, Mao N, Lehmann-Horn F, Bürmann J, Jurkat-Rott K. Effects of S906T polymorphism on the severity of a novel borderline mutation I692M in Na v 1.4 cause periodic paralysis. Clin Genet 2016; 91:859-867. [PMID: 27714768 DOI: 10.1111/cge.12880] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2016] [Revised: 09/29/2016] [Accepted: 09/30/2016] [Indexed: 11/29/2022]
Abstract
Hyperkalemic periodic paralysis (HyperPP) is a dominantly inherited muscle disease caused by mutations in SCN4A gene encoding skeletal muscle voltage gated Nav 1.4 channels. We identified a novel Nav 1.4 mutation I692M in 14 families out of the 104 genetically identified HyperPP families in the Neuromuscular Centre Ulm and is therefore as frequent as I693T (13 families out of 14 HyperPP families) in Germany. Surprisingly, in 13 families, a known polymorphism S906T was also present. It was on the affected allele in at least 10 families compatible with a possible founder effect in central Europe. All affected members suffered from episodic weakness; myotonia was also common. Compared with I692M patients, I692M-S906T patients had longer weakness episodes, more affected muscles, CK elevation and presence of permanent weakness. Electrophysiological investigation showed that both mutants had incomplete slow inactivation and a hyperpolarizing shift of activation which contribute to membrane depolarization and weakness. Additionally, I692M-S906T significantly enhanced close-state fast inactivation compared with I692M alone, suggesting a higher proportion of inactivated I692M-S906T channels upon membrane depolarization which may facilitate the initiation of weakness episodes and therefore clinical manifestation. Our results suggest that polymorphism S906T has effects on the clinical phenotypic and electrophysiological severity of a novel borderline Nav 1.4 mutation I692M, making the borderline mutation fully penetrant.
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Affiliation(s)
- C Fan
- Division of Neurophysiology, Ulm University, Ulm, Germany
| | - N Mao
- Division of Neurophysiology, Ulm University, Ulm, Germany.,Human Oncology & Pathogenesis Program, Memorial Sloan Kettering Cancer Center, New York, NY, USA
| | - F Lehmann-Horn
- Division of Neurophysiology, Ulm University, Ulm, Germany
| | - J Bürmann
- Department of Neurology, University Hospital of the Saarland, Homburg, Germany
| | - K Jurkat-Rott
- Dept. of Neurosurgery, Ulm University, Albert-Einstein-Allee 23,89081 Ulm, Germany
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11
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Siegler JC, Marshall PWM, Bishop D, Shaw G, Green S. Mechanistic Insights into the Efficacy of Sodium Bicarbonate Supplementation to Improve Athletic Performance. SPORTS MEDICINE-OPEN 2016; 2:41. [PMID: 27747796 PMCID: PMC5059234 DOI: 10.1186/s40798-016-0065-9] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/13/2016] [Accepted: 09/20/2016] [Indexed: 01/13/2023]
Abstract
A large proportion of empirical research and reviews investigating the ergogenic potential of sodium bicarbonate (NaHCO3) supplementation have focused predominately on performance outcomes and only speculate about underlying mechanisms responsible for any benefit. The aim of this review was to critically evaluate the influence of NaHCO3 supplementation on mechanisms associated with skeletal muscle fatigue as it translates directly to exercise performance. Mechanistic links between skeletal muscle fatigue, proton accumulation (or metabolic acidosis) and NaHCO3 supplementation have been identified to provide a more targeted, evidence-based approach to direct future research, as well as provide practitioners with a contemporary perspective on the potential applications and limitations of this supplement. The mechanisms identified have been broadly categorised under the sections ‘Whole-body Metabolism’, ‘Muscle Physiology’ and ‘Motor Pathways’, and when possible, the performance outcomes of these studies contextualized within an integrative framework of whole-body exercise where other factors such as task demand (e.g. large vs. small muscle groups), cardio-pulmonary and neural control mechanisms may outweigh any localised influence of NaHCO3. Finally, the ‘Performance Applications’ section provides further interpretation for the practitioner founded on the mechanistic evidence provided in this review and other relevant, applied NaHCO3 performance-related studies.
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Affiliation(s)
- Jason C Siegler
- School of Science and Health, Sport and Exercise Science, Western Sydney University, Locked Bag 1792, Penrith, NSW, Australia.
| | - Paul W M Marshall
- School of Science and Health, Sport and Exercise Science, Western Sydney University, Locked Bag 1792, Penrith, NSW, Australia
| | - David Bishop
- Institute of Sport, Exercise and Active Living (ISEAL), Victoria University, Melbourne, Australia
| | - Greg Shaw
- Australian Institute of Sport, Canberra, Australia
| | - Simon Green
- School of Science and Health, Sport and Exercise Science, Western Sydney University, Locked Bag 1792, Penrith, NSW, Australia.,School of Medicine, Western Sydney University, Sydney, Australia
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12
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The effect of pH on fatigue during submaximal isometric contractions of the human calf muscle. Eur J Appl Physiol 2014; 115:565-77. [DOI: 10.1007/s00421-014-3027-2] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2014] [Accepted: 10/15/2014] [Indexed: 01/03/2023]
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13
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Siegler JC, Marshall PWM, Raftry S, Brooks C, Dowswell B, Romero R, Green S. The differential effect of metabolic alkalosis on maximum force and rate of force development during repeated, high-intensity cycling. J Appl Physiol (1985) 2013; 115:1634-40. [DOI: 10.1152/japplphysiol.00688.2013] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The purpose of this investigation was to assess the influence of sodium bicarbonate supplementation on maximal force production, rate of force development (RFD), and muscle recruitment during repeated bouts of high-intensity cycling. Ten male and female ( n = 10) subjects completed two fixed-cadence, high-intensity cycling trials. Each trial consisted of a series of 30-s efforts at 120% peak power output (maximum graded test) that were interspersed with 30-s recovery periods until task failure. Prior to each trial, subjects consumed 0.3 g/kg sodium bicarbonate (ALK) or placebo (PLA). Maximal voluntary contractions were performed immediately after each 30-s effort. Maximal force (Fmax) was calculated as the greatest force recorded over a 25-ms period throughout the entire contraction duration while maximal RFD (RFDmax) was calculated as the greatest 10-ms average slope throughout that same contraction. Fmax declined similarly in both the ALK and PLA conditions, with baseline values (ALK: 1,226 ± 393 N; PLA: 1,222 ± 369 N) declining nearly 295 ± 54 N [95% confidence interval (CI) = 84–508 N; P < 0.006]. RFDmax also declined in both trials; however, a differential effect persisted between the ALK and PLA conditions. A main effect of condition was observed across the performance time period, with RFDmax on average higher during ALK (ALK: 8,729 ± 1,169 N/s; PLA: 7,691 ± 1,526 N/s; mean difference between conditions 1,038 ± 451 N/s, 95% CI = 17–2,059 N/s; P < 0.048). These results demonstrate a differential effect of alkalosis on maximum force vs. maximum rate of force development during a whole body fatiguing task.
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Affiliation(s)
| | | | - Sean Raftry
- Sport and Exercise Science, School of Science and Health, and
| | - Cristy Brooks
- Sport and Exercise Science, School of Science and Health, and
| | - Ben Dowswell
- Sport and Exercise Science, School of Science and Health, and
| | - Rick Romero
- Sport and Exercise Science, School of Science and Health, and
| | - Simon Green
- Sport and Exercise Science, School of Science and Health, and
- School of Medicine, University of Western Sydney Campbelltown Campus, Sydney, Australia
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14
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Abstract
Skeletal muscle fatigue is defined as the fall of force or power in response to contractile activity. Both the mechanisms of fatigue and the modes used to elicit it vary tremendously. Conceptual and technological advances allow the examination of fatigue from the level of the single molecule to the intact organism. Evaluation of muscle fatigue in a wide range of disease states builds on our understanding of basic function by revealing the sources of dysfunction in response to disease.
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Affiliation(s)
- Jane A Kent-Braun
- Department of Kinesiology, University of Massachusetts-Amherst, Amherst, Massachusetts, USA.
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15
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Pedersen KK, Nielsen OB, Overgaard K. Effects of high-frequency stimulation and doublets on dynamic contractions in rat soleus muscle exposed to normal and high extracellular [K(+)]. Physiol Rep 2013; 1:e00026. [PMID: 24303113 PMCID: PMC3831922 DOI: 10.1002/phy2.26] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2013] [Revised: 05/28/2013] [Accepted: 06/13/2013] [Indexed: 12/04/2022] Open
Abstract
The development of maximal velocity and power in muscle depends on the ability to transmit action potentials (AP) at very high frequencies up to about 400 Hz. However, for every AP there is a small loss of K+ to the interstitium, which during intense exercise, may build up to a point where excitability is reduced, thus limiting the intensity of further exercise. It is still unknown how the muscle responds to high-frequency stimulation when exposed to high [K+]. Contractile parameters of the muscles (force [F], velocity [V], power [P], rate of force development [RFD], and work) were examined during dynamic contractions, performed in vitro using rat soleus muscles incubated in buffers containing 4 or 8 mmol/L K+ and stimulated with constant trains of tetanic or supratetanic frequency or with trains initiated by a high-frequency doublet, followed by tetanic or subtetanic trains. At 4 mmol/L K+, an increase in frequency increased Pmax when using constant train stimulation. When stimulating with trains containing high-frequency doublets an increase in 120-msec work was seen, however, no increase in Pmax was observed. At 8 mmol/L K+, no differences were seen for either Pmax or 120-msec work when increasing frequency or introducing doublets. In all experiments where the frequency was increased or doublets applied, an increase in RFD was seen in both normal and high [K+]. The results indicate that stimulation with supratetanic frequencies can improve dynamic muscle contractility, but improvements are attenuated when muscles are exposed to high extracellular [K+].
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Affiliation(s)
- Katja K Pedersen
- Department of Public Health, Section of Sport Science, Aarhus University Aarhus, Denmark
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16
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Cairns SP. Holistic approaches to understanding mechanisms of fatigue in high-intensity sport. FATIGUE-BIOMEDICINE HEALTH AND BEHAVIOR 2013. [DOI: 10.1080/21641846.2013.765086] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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17
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Carnosine: from exercise performance to health. Amino Acids 2013; 44:1477-91. [PMID: 23479117 DOI: 10.1007/s00726-013-1476-2] [Citation(s) in RCA: 76] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2013] [Accepted: 02/16/2013] [Indexed: 12/27/2022]
Abstract
Carnosine was first discovered in skeletal muscle, where its concentration is higher than in any other tissue. This, along with an understanding of its role as an intracellular pH buffer has made it a dipeptide of interest for the athletic population with its potential to increase high-intensity exercise performance and capacity. The ability to increase muscle carnosine levels via β-alanine supplementation has spawned a new area of research into its use as an ergogenic aid. The current evidence base relating to the use of β-alanine as an ergogenic aid is reviewed here, alongside our current thoughts on the potential mechanism(s) to support any effect. There is also some emerging evidence for a potential therapeutic role for carnosine, with this potential being, at least theoretically, shown in ageing, neurological diseases, diabetes and cancer. The currently available evidence to support this potential therapeutic role is also reviewed here, as are the potential limitations of its use for these purposes, which mainly focusses on issues surrounding carnosine bioavailability.
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18
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Billaut F, Gore CJ, Aughey RJ. Enhancing team-sport athlete performance: is altitude training relevant? Sports Med 2013; 42:751-67. [PMID: 22845561 DOI: 10.1007/bf03262293] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Field-based team sport matches are composed of short, high-intensity efforts, interspersed with intervals of rest or submaximal exercise, repeated over a period of 60-120 minutes. Matches may also be played at moderate altitude where the lower oxygen partial pressure exerts a detrimental effect on performance. To enhance run-based performance, team-sport athletes use varied training strategies focusing on different aspects of team-sport physiology, including aerobic, sprint, repeated-sprint and resistance training. Interestingly, 'altitude' training (i.e. living and/or training in O(2)-reduced environments) has only been empirically employed by athletes and coaches to improve the basic characteristics of speed and endurance necessary to excel in team sports. Hypoxia, as an additional stimulus to training, is typically used by endurance athletes to enhance performance at sea level and to prepare for competition at altitude. Several approaches have evolved in the last few decades, which are known to enhance aerobic power and, thus, endurance performance. Altitude training can also promote an increased anaerobic fitness, and may enhance sprint capacity. Therefore, altitude training may confer potentially-beneficial adaptations to team-sport athletes, which have been overlooked in contemporary sport physiology research. Here, we review the current knowledge on the established benefits of altitude training on physiological systems relevant to team-sport performance, and conclude that current evidence supports implementation of altitude training modalities to enhance match physical performances at both sea level and altitude. We hope that this will guide the practice of many athletes and stimulate future research to better refine training programmes.
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Affiliation(s)
- François Billaut
- School of Sport and Exercise Science, Institute of Sport, Exercise and Active Living (ISEAL), Victoria University, Melbourne, VIC, Australia.
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