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Journal ArticleDOI

Percutaneous Needle Biopsy of Skeletal Muscle in Physiological and Clinical Research

01 Nov 1975-Scandinavian Journal of Clinical & Laboratory Investigation (Scand J Clin Lab Invest)-Vol. 35, Iss: 7, pp 609-616
TL;DR: In this article, a percutaneous needle biopsy of skeletal muscle in Physiological and Clinical Research is described, and the authors present a detailed discussion of the procedure and the results.
Abstract: (1975). Percutaneous Needle Biopsy of Skeletal Muscle in Physiological and Clinical Research. Scandinavian Journal of Clinical and Laboratory Investigation: Vol. 35, No. 7, pp. 609-616.
Citations
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Journal ArticleDOI
TL;DR: The regulation of myocardial fatty acid beta-oxidation is reviewed and how alterations in fatty acid Beta-Oxidation can contribute to heart disease is discussed.
Abstract: There is a constant high demand for energy to sustain the continuous contractile activity of the heart, which is met primarily by the β-oxidation of long-chain fatty acids. The control of fatty acid β-oxidation is complex and is aimed at ensuring that the supply and oxidation of the fatty acids is sufficient to meet the energy demands of the heart. The metabolism of fatty acids via β-oxidation is not regulated in isolation; rather, it occurs in response to alterations in contractile work, the presence of competing substrates (i.e., glucose, lactate, ketones, amino acids), changes in hormonal milieu, and limitations in oxygen supply. Alterations in fatty acid metabolism can contribute to cardiac pathology. For instance, the excessive uptake and β-oxidation of fatty acids in obesity and diabetes can compromise cardiac function. Furthermore, alterations in fatty acid β-oxidation both during and after ischemia and in the failing heart can also contribute to cardiac pathology. This paper reviews the regulation of myocardial fatty acid β-oxidation and how alterations in fatty acid β-oxidation can contribute to heart disease. The implications of inhibiting fatty acid β-oxidation as a potential novel therapeutic approach for the treatment of various forms of heart disease are also discussed.

1,675 citations

Journal ArticleDOI
TL;DR: Given the markedly lower training volume in the SIT group, these data suggest that high‐intensity interval training is a time‐efficient strategy to increase skeletal muscle oxidative capacity and induce specific metabolic adaptations during exercise that are comparable to traditional ET.
Abstract: Low-volume ‘sprint’ interval training (SIT) stimulates rapid improvements in muscle oxidative capacity that are comparable to levels reached following traditional endurance training (ET) but no study has examined metabolic adaptations during exercise after these different training strategies. We hypothesized that SIT and ET would induce similar adaptations in markers of skeletal muscle carbohydrate (CHO) and lipid metabolism and metabolic control during exercise despite large differences in training volume and time commitment. Active but untrained subjects (23 ± 1 years) performed a constant-load cycling challenge (1 h at 65% of peak oxygen uptake ( ˙ VO2peak) before and after 6 weeks of either SIT or ET (n = 5 men and 5 women per group). SIT consisted of four to six repeats of a 30 s ‘all out’ Wingate Test (mean power output ∼500 W) with 4.5 min recovery between repeats, 3 days per week. ET consisted of 40‐60 min of continuous cycling at a workload that elicited ∼65% ˙ VO2peak (mean power output ∼150 W) per day, 5 days per week. Weekly time commitment (∼1.5 versus ∼4.5 h) and total training volume (∼225 versus ∼2250 kJ week −1 ) were substantially lower in SIT versus ET. Despite these differences, both protocols induced similar increases (P < 0.05) in mitochondrial markers for skeletal muscle CHO (pyruvate dehydrogenase E1α protein content) and lipid oxidation (3-hydroxyacyl CoA dehydrogenase maximal activity) and protein content of peroxisome proliferator-activated receptor-γ coactivator-1α. Glycogen and phosphocreatine utilization during exercise were reduced after training, and calculated rates of whole-body CHO and lipid oxidation were decreased and increased, respectively, with no differences between groups (all main effects, P < 0.05). Given the markedly lower training volume in the SIT group, these data suggest that high-intensity interval training is a time-efficient strategy to increase skeletal muscle oxidative capacity and induce specific metabolic adaptations during exercise that are comparable to traditional ET.

1,151 citations

Journal ArticleDOI
TL;DR: It is concluded that short sprint interval training (approximately 15 min of intense exercise over 2 wk) increased muscle oxidative potential and doubled endurance capacity during intense aerobic cycling in recreationally active individuals.
Abstract: Parra et al. (Acta Physiol. Scand 169: 157–165, 2000) showed that 2 wk of daily sprint interval training (SIT) increased citrate synthase (CS) maximal activity but did not change “anaerobic” work c...

811 citations

Journal ArticleDOI
TL;DR: It is concluded that the most likely mechanism for the reduction in fat oxidation during high‐intensity exercise is a downregulation of carnitine palmitoyltransferase I, either by this marked decline in free carnitines availability or by a decrease in intracellular pH.
Abstract: 1. Contemporary stable isotope methodology was applied in combination with muscle biopsy sampling to accurately quantify substrate utilisation and study the regulation of muscle fuel selection during exercise. 2. Eight cyclists were studied at rest and during three consecutive 30 min stages of exercise at intensities of 40, 55 and 75 % maximal workload (W(max)). A continuous infusion of [U-(13)C]palmitate and [6,6-(2)H(2)]glucose was administered to determine plasma free fatty acid (FFA) oxidation and estimate plasma glucose oxidation, respectively. Biopsy samples were collected before and after each exercise stage. 3. Muscle glycogen and plasma glucose oxidation rates increased with every increment in exercise intensity. Whole-body fat oxidation increased to 32 +/- 2 kJ min(-1) at 55 % W(max), but declined at 75 % W(max) (19 +/- 2 kJ min(-1)). This decline involved a decrease in the oxidation rate of both plasma FFA and triacylglycerol fat sources (sum of intramuscular plus lipoprotein-derived triacylglycerol), and was accompanied by increases in muscle pyruvate dehydrogenase complex activation and acetylation of the carnitine pool, resulting in a decline in muscle free carnitine concentration. 4. We conclude that the most likely mechanism for the reduction in fat oxidation during high-intensity exercise is a downregulation of carnitine palmitoyltransferase I, either by this marked decline in free carnitine availability or by a decrease in intracellular pH.

789 citations

Journal ArticleDOI
TL;DR: The purpose of this document is to update the 1999 ATS/ERS statement on limb muscle dysfunction in COPD with important advances in the understanding of the extent and nature of the structural alterations in limb muscles in patients with COPD.
Abstract: Background: Limb muscle dysfunction is prevalent in chronic obstructive pulmonary disease (COPD) and it has important clinical implications, such as reduced exercise tolerance, quality of life, and even survival. Since the previous American Thoracic Society/European Respiratory Society (ATS/ERS) statement on limb muscle dysfunction, important progress has been made on the characterization of this problem and on our understanding of its pathophysiology and clinical implications.Purpose: The purpose of this document is to update the 1999 ATS/ERS statement on limb muscle dysfunction in COPD.Methods: An interdisciplinary committee of experts from the ATS and ERS Pulmonary Rehabilitation and Clinical Problems assemblies determined that the scope of this document should be limited to limb muscles. Committee members conducted focused reviews of the literature on several topics. A librarian also performed a literature search. An ATS methodologist provided advice to the committee, ensuring that the methodological ...

787 citations

References
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Journal ArticleDOI
TL;DR: It has been shown that the glycogen content and, consequently, the long-term work capacity can be appreciably varied by instituting different diets after glycogen depletion.
Abstract: The muscle glycogen content of the quadriceps femoris muscle was determined in 9 healthy subjects with the aid of the needle biopsy technique. The glycogen content could be varied in the individual subjects by instituting different diets after exhaustion of the glycogen store by hard exercise. Thus, the glycogen content after a fat ± protein (P) and a carbohydrate-rich (C) diet varied maximally from 0.6 g/100g muscle to 4.7 g. In all subjects, the glycogen content after the C diet was higher than the normal range for muscle glycogen, determined after the mixed (M) diet. After each diet period, the subjects worked on a bicycle ergometer at a work load corresponding to 75 per cent of their maximal O2 uptake, to complete exhaustion. The average work time was 59, 126 and 189 min after diets P, M and C, and a good correlation was noted between work time and the initial muscle glycogen content. The total carbohydrate utilization during the work periods (54–798 g) was well correlated to the decrease in glycogen content. It is therefore concluded that the glycogen content of the working muscle is a determinant for the capacity to perform long-term heavy exercise. Moreover, it has been shown that the glycogen content and, consequently, the long-term work capacity can be appreciably varied by instituting different diets after glycogen depletion.

1,601 citations

Journal ArticleDOI
TL;DR: Variation in muscle content of ATP, ATP + ADP + AMP, phosphorylcreatine (PC), creatine (Cr), PC + Cr, and glycogen, between legs, between sites on the same muscle, or as a result of error introduced during analysis, was small compared with the between-individuals variance.
Abstract: Methods are described for the determination of glycogen, glycolytic intermediates, and high-energy phosphates in muscle biopsy samples. Initial freezedrying of samples and extraction of metabolites with relatively weak acid are preferred. Normal values in muscle are similar to those found by other workers. Variation in muscle content of ATP, ATP + ADP + AMP, phosphorylcreatine (PC), creatine (Cr), PC + Cr, and glycogen, between legs, between sites on the same muscle, or as a result of error introduced during analysis, was small compared with the between-individuals variance. The importance of the different sources of variance on taking a biopsy is discussed.

953 citations

Journal ArticleDOI
TL;DR: Glycogen depletion pattern in human skeletal muscle fibres was studied after bicycle exercise of varying intensity performed at different pedalling rates.
Abstract: 1. Glycogen depletion pattern in human skeletal muscle fibres was studied after bicycle exercise of varying intensity performed at different pedalling rates. Work intensities studied were equivalent to 30-150% of V(O) (2) max. with pedalling rates of 30-120 rev/min.2. Glycogen depletion increased dramatically with increasing exercise intensity; depletion was 2.7 and 7.4 times greater respectively at workloads demanding 64 and 84% V(O) (2) max. than at workloads calling for 31% V(O) (2) max. Even greater rates of glycogen utilization occurred at supramaximal loads.3. Slow twitch, high oxidative (ST) fibres were the first to lose glycogen (reduced PAS staining) at all workloads below V(O) (2) max. Progressive glycogen depletion occurred in fast twitch (FT) fibres as work continued. Large quantities of glycogen remained in the muscle after 3 hr of exercise at low exercise intensity. This was almost exclusively found in FT fibres. At workloads exceeding maximal aerobic power, there was an initial depletion of glycogen in both fibre types. Varying the pedalling rate and, thus, the total force exerted in each pedal thrust had no effect on the pattern of glycogen depletion in the fibres.4. Results point to primary reliance upon ST fibres during submaximal endurance exercise, FT fibres being recruited after ST fibres are depleted of glycogen. During exertion requiring energy expenditure greater than the maximal aerobic power, both fibre types appeared to be continuously involved in carrying out the exercise.

642 citations

Journal ArticleDOI
16 Apr 1966-Nature
TL;DR: Goldstein1 has shown that a humoral factor, which decreases the blood glucose concentration, is released during exercise and it is known that the insulin requirement decreases in diabetic subjects during exercise.
Abstract: IT is well known that glycogen is utilized during muscular work, but there is very little information available about the resynthesis of glycogen after exhaustive exercise. Goldstein1 has shown that a humoral factor, which decreases the blood glucose concentration, is released during exercise. Furthermore, it is known that the insulin requirement decreases in diabetic subjects during exercise.

460 citations