Muscle metabolism during isometric exercise performed at constant force.

Ahlborg, Björn; Bergström, Jonas; Ekelund, Lars‐Göran; Guarnieri, Giulia; Harris, Roger C.; Hultman, E.; Nordesjö, Lars‐Olof

doi:10.1152/jappl.1972.33.2.224

Cited by 81 publications

(48 citation statements)

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“…The increase in intramuscular pressure at 45% MVIC results in occlusion of muscle blood flow, allowing only minimal loss of lactate anions and H + from the contracting muscle. The estimated increase in H + production (estimated from the known rate of lactate plus pyruvate production at this intensity (Ahlborg et al, 1972) was closely matched with the theoretical increase in H + buffering capacity from the estimated increase in muscle carnosine which occurs with this supplementation protocol. Given these findings, we suggest that the most plausible explanation for the very likely improvement to 2,000-m rowing performance shown following 4 weeks of beta-alanine supplementation at 6.4 g·d -1 in the current study is via an increase in intracellular buffering capacity as the result of an elevation in muscle carnosine.…”

Section: Discussionsupporting

confidence: 65%

Effect of Beta-Alanine With and Without Sodium Bicarbonate on 2,000-m Rowing Performance

Hobson¹,

Harris²,

Martin³

et al. 2013

International Journal of Sport Nutrition and Exercise Metabolism

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Purpose:To examine the effect of beta-alanine only and beta-alanine with sodium bicarbonate supplementation on 2,000-m rowing performance. Methods: Twenty well-trained rowers (age 23 ± 4 y; height 1.85 ± 0.08 m; body mass 82.5 ± 8.9 kg) were assigned to either a placebo or beta-alanine (6.4 g·d -1 for 4 weeks) group. A 2,000-m rowing time trial (TT) was performed before supplementation (Baseline) and after 28 and 30 days of supplementation. The post supplementation trials involved supplementation with either maltodextrin or sodium bicarbonate in a double-blind, crossover design, creating four study conditions (placebo with maltodextrin; placebo with sodium bicarbonate; beta-alanine with maltodextrin; beta-alanine with sodium bicarbonate). Blood lactate, pH, bicarbonate, and base excess were measured pre-TT, immediately post-TT and at TT+5 min. Performance data were analyzed using magnitude based inferences. Results: Beta-alanine supplementation was very likely to be beneficial to 2,000-m rowing performance (6.4 ± 8.1 s effect compared with placebo), with the effect of sodium bicarbonate having a likely benefit (3.2 ± 8.8 s). There was a small (1.1 ± 5.6 s) but possibly beneficial additional effect when combining chronic beta-alanine supplementation with acute sodium bicarbonate supplementation compared with chronic beta-alanine supplementation alone. Sodium bicarbonate ingestion led to increases in plasma pH, base excess, bicarbonate, and lactate concentrations. Conclusions: Both chronic beta-alanine and acute sodium bicarbonate supplementation alone had positive effects on 2,000-m rowing performance. The addition of acute sodium bicarbonate to chronic beta-alanine supplementation may further enhance rowing performance.

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Section: Discussionsupporting

confidence: 65%

Effect of Beta-Alanine With and Without Sodium Bicarbonate on 2,000-m Rowing Performance

Hobson¹,

Harris²,

Martin³

et al. 2013

International Journal of Sport Nutrition and Exercise Metabolism

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“…Fatigue from isometric contraction in human muscle has mostly been studied during ischaemic or high-force contractions, where the decline in maximal force is associated with an accumulation of Pi and H+ ions (Ahlborg et al 1972;Sahlin et al 1975;Harris et al 1977; . The (V0llestad et al 1988), as well as little release of lactate from the muscle (V0llestad et al 1990;Sahlin et al 1992).…”

Section: Discussionmentioning

confidence: 99%

“…Fatigue during isometric contraction in human muscle has generally been associated with ischaemia, leading to rapid phosphocreatine (PCr) depletion and accumulation of metabolites (Ahlborg, Bergstrom, Ekelund, Guarnieri, Harris, Hultman & Nordesjo, 1972;Edwards, Harris, Hultman & Nordesjo, 1972a;Sahlin, Harris & Hultman, 1975;Harris, Sahlin & Hultman, 1977). Within this protocol, fatigue, defined as a decline in maximal force (BiglandRitchie, Furbush & Woods, 1986b;V0llestad, Sejersted, Bahr, Woods & Bigland-Ritchie, 1988) is explained at the cellular level, where the inhibiting effect of high inorganic phosphate (Pi) and H' levels on maximal Ca2+-activated force is well documented (reviewed by Westerblad, Lee, Liinnergren & Allen, 1991;Fitts, 1994).…”

Section: Introductionmentioning

confidence: 99%

“…Due to the restriction of blood flow during isometric contraction (Edwards, Hill, Jones & Merton. 1972b; Hargens, Kardel, Blom, Jensen & Hermansen, 1984;Saugen & V0llestad, 1995 b), exhaustion from sustained activity is associated with high levels of Pi and H+ ions (Ahlborg et al 1972;Edwards et al 1972a;Sahlin et al 1975;Harris et al 1977), and possibly also with a decline in the free energy of ATP hydrolysis (Dawson, Gadian & Wilkie, 1980). During RIE the vastus lateralis muscle is rapidly reperfused between contractions (V0llestad, Wesche & Sejersted, 1990).…”

Section: Introductionmentioning

confidence: 99%

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Dissociation between metabolic and contractile responses during intermittent isometric exercise in man

Saugen

Vøllestad²,

Gibson³

et al. 1997

Experimental Physiology

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SUMMARYThis study examines the temporal changes in high-energy phosphate and metabolite levels, and in force-generating capacity, during and after voluntary submaximal repetitive isometric exercise (RIE). Eight male subjects performed one-legged RIE with the knee extensors at 40 % maximum voluntary contraction (MVC) target force (duty cycle: 6 s contraction, 4 s rest) in a 48 cm bore whole body 1-5 T superconducting magnet. Phosphocreatine (PCr), inorganic phosphate (Pi), ATP and pH were measured every 9 s. Force-generating capacity was repeatedly measured using MVC force and electrically stimulated contractions (sequential train of impulses of 1-100 Hz). During RIE, MVC declined gradually by 56 + 5 % (mean + S.E.M.). Electrically stimulated force also declined, with a disproportionally large drop in low-frequency force, seen as a decline from 0-76 + 0-02 to 0-33 + 0-02 in 20:50 Hz force ratio. The PCr decline during RIE was 65 + 9 %, in most subjects seen as a rapid initial drop followed by less or no further decline to exhaustion. pH declined in parallel by 0 18 + 0.04 units, whilst ATP levels remained unchanged throughout the exercise. PCr, Pi and pH recovered to near control values within 5 min of exhaustion. Force, however, was not fully restored after 30 min recovery. The results support the hypothesis that fatigue from submaximal RIE is unrelated to changes in Pi and H' levels. The decline in 20:50 Hz force ratio implies that fatigue may be associated with excitation-contraction coupling impairment. No sudden changes were observed in mechanical or metabolic factors at exhaustion. Exhaustion was probably not caused by lack of substrates for ATP resynthesis, since pH had decreased only marginally.

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“…The accumulation of metabolic by-products during a sustained contraction could be due to an increase in their pro duction [12] and/or a decrease in their removal due to dimin ished blood flow during forceful contractions [13]- [ 15]. The accumulation of lactic acid and the subsequent lowering of muscle pH has long been associated with localized muscular fatigue [16], [17] and muscle pain [18].…”

Section: Introductionmentioning

confidence: 99%

Muscle Fatigue Monitor: A Noninvasive Device for Observing Localized Muscular Fatigue

Stulen

Luca

1982

IEEE Trans. Biomed. Eng.

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Abstract-As a muscular contraction is sustained, the spectrum of the myoelectric signal is compressed into lower frequencies. This spectral compression has been associated with localized muscular fatigue by several investigators. A device is presented that implements a technique to track the spectral compression by calculating the median frequency and two other parameters of the spectrum. The device is referred to as the muscle fatigue monitor (MFM) and is built with analog circuitry so that parameters are calculated and displayed in real-time and on-line. The technique is based on modulated filters which are implemented by using periodically-controlled switches to effectively vary the cutoff frequencies of the filters, The median frequency of a myoelectric signal obtained during a sustained, constant-force, isometric contraction was calculated by the MFM and digital computation. The results obtained by the two techniques were essentiaIIy the same, verifying the opera tion of the MFM.Several other techniques to quantify the spectral compression are discussed and compared to the MFM. While most of the other tech niques do track spectral compression, the features of the MFM make it appropriate and accurate for clinical and industrial applications.

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Muscle metabolism during isometric exercise performed at constant force.

Cited by 81 publications

References 0 publications

Effect of Beta-Alanine With and Without Sodium Bicarbonate on 2,000-m Rowing Performance

Effect of Beta-Alanine With and Without Sodium Bicarbonate on 2,000-m Rowing Performance

Dissociation between metabolic and contractile responses during intermittent isometric exercise in man

Muscle Fatigue Monitor: A Noninvasive Device for Observing Localized Muscular Fatigue

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