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Oxidative stress and COPD: the effect of oral antioxidants on skeletal muscle fatigue.
Rossman, MJ, Groot, HJ, Reese, V, Zhao, J, Amann, M, Richardson, RS
Medicine and science in sports and exercise. 2013;(7):1235-43
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Abstract
PURPOSE Oxidative stress may contribute to exercise intolerance in patients with chronic obstructive pulmonary disease (COPD). This study sought to determine the effect of an acute oral antioxidant cocktail (AOC, vitamins C and E, and alpha-lipoic acid) on skeletal muscle function during dynamic quadriceps exercise in COPD. METHODS Ten patients with COPD performed knee extensor exercise to exhaustion and isotime trials after either the AOC or placebo (PL). Pre- to postexercise changes in quadriceps maximal voluntary contractions and potentiated twitch forces (Q(tw,pot)) quantified quadriceps fatigue. RESULTS Under PL conditions, the plasma electron paramagnetic resonance (EPR) spectroscopy signal was inversely correlated with the forced expiratory volume in 1 s to forced vital capacity ratio (FEV1/FVC), an index of lung dysfunction (r = -0.61, P = 0.02), and maximal voluntary contraction force (r = -0.56, P = 0.04). AOC consumption increased plasma ascorbate levels (10.1 ± 2.2 to 24.1 ± 3.8 μg · mL(-1), P < 0.05) and attenuated the area under the curve of the EPR spectroscopy free radical signal (11.6 ± 3.7 to 4.8 ± 2.2 AU, P < 0.05), but it did not alter the endurance time or quadriceps fatigue. The ability of the AOC to decrease the EPR spectroscopy signal, however, was prominent in those with high basal free radicals (n = 5, PL, 19.7 ± 5.8, to AOC, 5.8 ± 4.5 AU; P < 0.05) with minimal effects in those with low levels (n = 5, PL, 1.6 ± 0.5, to AOC, 3.4 ± 1.1 AU). DISCUSSION These data document a relation between directly measured free radicals and lung dysfunction and the ability of the AOC to decrease oxidative stress in COPD. Acute amelioration of free radicals, however, does not appear to affect dynamic quadriceps exercise performance.
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Repeated maximal eccentric actions causes long-lasting disturbances in movement control.
Bottas, R, Linnamo, V, Nicol, C, Komi, PV
European journal of applied physiology. 2005;(1-2):62-9
Abstract
This study examined acute and long-lasting effects of fatigue and muscle damage on fast and accurate elbow flexion and extension target movements (TM) with eight male students. An isokinetic machine was used to perform 100 maximal eccentric and concentric elbow flexions at 4-week intervals. Movement range was 40-170 degrees in eccentric exercise (ECCE) and 170-40 degrees in concentric exercise (CONE), with an angular velocity of 2 rad s(-1). TM was performed in sitting position with the right forearm fixed to lever arm above protractor. Subjects performed TM in horizontal plane (amplitude 60 degrees ) by visual feedback of movement from a television monitor. Surface EMG was recorded from the biceps brachii and triceps brachii muscles. TM measurements and serum creatine kinase (CK) determinations were conducted before, after, 0.5 h, 2 days, and 7 days after both exercises. Blood lactate was taken before, after, and 0.5 h after the exercises. Both ECCE and CONE led to a large decline in maximal voluntary contractions, but the recovery was slower after ECCE when it remained incomplete even until day 7 post-exercise. Lactate increased (P < 0.001) similarly after both exercises. Delayed-onset muscle soreness peaked on day 2 and CK peaked on day 7 after ECCE. Exhaustive eccentric exercise of agonistic muscles impaired the flexion TM performance, and had a long-duration modulation effect on the triphasic EMG activity pattern of flexion and extension TM. In the acute phase, the observed changes in performance and in the EMG patterns are suggested to be related to metabolic changes via III and IV muscle afferents. The delayed recovery, on the other hand, may be related to problems in the proprioceptive feedback caused by muscle damage.
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Prolonged exercise to fatigue in humans impairs skeletal muscle Na+-K+-ATPase activity, sarcoplasmic reticulum Ca2+ release, and Ca2+ uptake.
Leppik, JA, Aughey, RJ, Medved, I, Fairweather, I, Carey, MF, McKenna, MJ
Journal of applied physiology (Bethesda, Md. : 1985). 2004;(4):1414-23
Abstract
Prolonged exhaustive submaximal exercise in humans induces marked metabolic changes, but little is known about effects on muscle Na+-K+-ATPase activity and sarcoplasmic reticulum Ca2+ regulation. We therefore investigated whether these processes were impaired during cycling exercise at 74.3 +/- 1.2% maximal O2 uptake (mean +/- SE) continued until fatigue in eight healthy subjects (maximal O2 uptake of 3.93 +/- 0.69 l/min). A vastus lateralis muscle biopsy was taken at rest, at 10 and 45 min of exercise, and at fatigue. Muscle was analyzed for in vitro Na+-K+-ATPase activity [maximal K+-stimulated 3-O-methylfluorescein phosphatase (3-O-MFPase) activity], Na+-K+-ATPase content ([3H]ouabain binding sites), sarcoplasmic reticulum Ca2+ release rate induced by 4 chloro-m-cresol, and Ca2+ uptake rate. Cycling time to fatigue was 72.18 +/- 6.46 min. Muscle 3-O-MFPase activity (nmol.min(-1).g protein(-1)) fell from rest by 6.6 +/- 2.1% at 10 min (P <0.05), by 10.7 +/- 2.3% at 45 min (P <0.01), and by 12.6 +/- 1.6% at fatigue (P <0.01), whereas 3[H]ouabain binding site content was unchanged. Ca2+ release (mmol.min(-1).g protein(-1)) declined from rest by 10.0 +/- 3.8% at 45 min (P <0.05) and by 17.9 +/- 4.1% at fatigue (P < 0.01), whereas Ca2+ uptake rate fell from rest by 23.8 +/- 12.2% at fatigue (P=0.05). However, the decline in muscle 3-O-MFPase activity, Ca2+ uptake, and Ca2+ release were variable and not significantly correlated with time to fatigue. Thus prolonged exhaustive exercise impaired each of the maximal in vitro Na+-K+-ATPase activity, Ca2+ release, and Ca2+ uptake rates. This suggests that acutely downregulated muscle Na+, K+, and Ca2+ transport processes may be important factors in fatigue during prolonged exercise in humans.
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Post-exercise vitamin C supplementation and recovery from demanding exercise.
Thompson, D, Williams, C, Garcia-Roves, P, McGregor, SJ, McArdle, F, Jackson, MJ
European journal of applied physiology. 2003;(3-4):393-400
Abstract
The aim of this study was to investigate whether post-exercise vitamin C supplementation influences recovery from an unaccustomed bout of exercise. Sixteen male subjects were allocated to either a placebo (P; n=8) or vitamin C (VC) group ( n=8). Subjects performed a prolonged (90-min) intermittent shuttle-running test, and supplementation began after the cessation of exercise. Immediately after exercise the VC group consumed 200 mg of VC dissolved in a 500 ml drink, whereas the subjects in the P group consumed the drink alone. Later on the same day and then in the morning and evening of the following 2 days, subjects consumed additional identical drinks. Plasma VC concentrations in the VC group increased above those in the P group 1 h after exercise and remained above P values for the 3 days after exercise. Nevertheless, post-exercise VC supplementation was not associated with improved recovery. Post-exercise serum creatine kinase activities and myoglobin concentrations were unaffected by supplementation. Muscle soreness and the recovery of muscle function in the leg flexors and extensors were not different in VC and P groups. Furthermore, although plasma concentrations of interleukin-6 and malondialdehyde increased following exercise, there was no difference between VC and P groups. These results suggest that either free radicals are not involved in delaying the recovery process following a bout of unaccustomed exercise, or that the consumption of VC wholly after exercise is unable to deliver this antioxidant to the appropriate sites with sufficient expediency to improve recovery.
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Oral creatine supplementation and upper extremity anaerobic response in females.
Hamilton, KL, Meyers, MC, Skelly, WA, Marley, RJ
International journal of sport nutrition and exercise metabolism. 2000;(3):277-89
Abstract
The purpose of this study was to investigate the influence of creatine monohydrate (CrH2O) on upper extremity anaerobic response in strength-trained females involved in overhand sports. Two movements were utilized in this evaluation: elbow flexion (EF) and shoulder internal rotation (IR). Subjects were pair-matched and assigned to receive placebo (n = 13) or 25 g CrH2O (n = 11) for 7 days. Pre- and post-treatment measurements included peak concentric and eccentric isokinetic torque, isotonic 1RM, and fatigue (FAT) during EF; isotonic 1RM, FAT, and peak velocity during IR; and body weight. MANOVAs revealed significant interaction between treatment and trial for EF (p <.05) but not for IR or weight. Univariate analysis indicated a significantly greater change in EFFAT following CrH2O than following placebo. Thus, CrH2O did not influence peak EF or IR strength, IR work to fatigue, or IR velocity, but was associated with greater work capacity during fatiguing EF. These data suggest that CrH2O may enhance upper extremity work capacity, but this enhancement may not extend to the muscles primarily responsible for overhand sports performance.
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Contractile properties, fatigue and recovery are not influenced by short-term creatine supplementation in human muscle.
Jakobi, JM, Rice, CL, Curtin, SV, Marsh, GD
Experimental physiology. 2000;(4):451-60
Abstract
There have been several studies on the effect of short-term creatine (Cr) supplementation on exercise performance, but none have investigated both voluntary and stimulated muscle contractions in the same experiment. Fourteen moderately active young men (19-28 years) were randomly assigned, in a double blind manner, to either a creatine (Cr) or placebo (P) group. The subjects supplemented their regular diet 4 times a day for 5 days with either 5 g Cr + 5 g maltodextrin (Cr group), or 5 g maltodextrin (P group). Isometric maximal voluntary contraction (MVC), muscle activation, as assessed using the modified twitch interpolation technique, electrically stimulated contractile properties, electromyography (EMG), endurance time and recovery from fatigue were measured in the elbow flexors. The fatigue protocol involved both voluntary and stimulated contractions. Following supplementation there was a significant weight gain in the Cr group (1.0 kg), whereas the P group did not change. For each group, pre-supplementation measures were not significantly different from post-supplementation for MVC, twitch and tetanic tensions at rest, time to peak tension, half-relaxation time and contraction duration. Prior to Cr supplementation time to fatigue was 10 +/- 4 min (mean +/- S.E.M.) for both groups, and following supplementation there was a non-significant increase of 1 min in each group. MVC force, muscle activation, EMG, stimulated tensions and durations were similar for the Cr and P groups over the course of the fatigue protocol and did not change after supplementation. Furthermore, recovery of MVC, stimulated tensions and contractile speeds did not differ as a result of Cr supplementation. These results indicate that short-term Cr supplementation does not influence isometric elbow flexion force, muscle activation, stimulated contractile properties, or delay time to fatigue or improve recovery.
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7.
Acute creatine supplementation in older men.
Rawson, ES, Clarkson, PM
International journal of sports medicine. 2000;(1):71-5
Abstract
The hypothesis of this study was that short term creatine (Cr) ingestion in older individuals would increase body mass and exercise performance, as has been shown in younger subjects. Seventeen males 60-78 years old were randomly placed into two groups, Cr and placebo (P), and supplemented in double-blind fashion for 5 days. Subjects ingested either 5 g of Cr plus 1 g of sucrose 4x per day or 6 g of a sucrose placebo 4x per day. Isometric strength of the elbow flexors was assessed using a modified preacher bench attached to a strain gauge. Isokinetic exercise performance was assessed using an intermittent fatigue test of the knee extensors. Subjects performed 3 sets of 30 repetitions with 60 sec rest between sets. There was a small (0.5 kg) but statistically significant increase in body mass (p < 0.05) in the Cr group after supplementation. There was a significant overall interaction between groups in isokinetic performance from pre to post supplementation (group x time x set, p < 0.05). However, analysis of the groups separately revealed that the subjects in the Cr group demonstrated a small non-significant increase in isokinetic performance while subjects in the P group demonstrated a small non-significant performance decrement. There was no significant difference in isometric strength between groups from pre to post supplementation. These data suggest that acute oral Cr supplementation does not increase isometric strength and only produces small increases in isokinetic performance and body mass in men over the age of 60.