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1.
S. J. Brown R. B. Child S. H. Day A. E. Donnelly 《European journal of applied physiology and occupational physiology》1997,75(4):369-374
Indirect indices of exercise-induced human skeletal muscle damage and connective tissue breakdown were studied following
a single bout of voluntary eccentric muscle contractions. Subjects (six female, two male), mean (SD) age 22 (2) years performed
a bout of 50 maximum voluntary eccentric contractions of the knee extensors of a single leg. The eccentric exercise protocol
induced muscle soreness (P < 0.05 Wilcoxon test), chronic force loss, and a decline in the 20:100 Hz percutaneous electrical myostimulation force ratio
[P < 0.01, repeated measures analysis of variance (ANOVA)]. Serum creatine kinase (CK) and lactate dehydrogenase (LDH) activities
were elevated (P < 0.01, repeated measures ANOVA) following the bout. The mean (SD) CK and LDH levels recorded 3 days post-exercise were 2815
(4144) IU · l–1 and 375 (198) IU · l–1, respectively. Serum alkaline phosphatase activity showed no changes throughout the study, and a non-significant increase
(P = 0.058, repeated measures ANOVA) in pyridinoline was recorded following the bout. Urinary hydroxyproline (HP) and hydroxylysine
(HL) excretion, expressed in terms of creatinine (Cr) concentration, increased after exercise (P < 0.05 and P < 0.01, respectively, repeated measures ANOVA). An increased HP:Cr was recorded 2 days post-exercise and HL:Cr was increased
above baseline on days 2, 5, and 9 post-exercise. This indirect evidence of exercise-induced muscle damage suggests that myofibre
disruption was caused by the eccentric muscle contractions. Elevated urine concentrations of indirect indices of collagen
breakdown following eccentric muscle contractions suggests an increased breakdown of connective tissue, possibly due to a
localised inflammatory response.
Accepted: 9 October 1996 相似文献
2.
J. M. Saxton A. E. Donnelly H. P. Roper 《European journal of applied physiology and occupational physiology》1994,68(3):189-193
This study monitored plasma and skeletal muscle markers of free-radical-mediated damage following maximum eccentric and concentric exercise, to examine the potential role of free radicals in exercise-induced muscle damage. Fourteen male volunteers performed either (1) a bout of 70 maximum eccentric and a bout of 70 maximum concentric muscle actions of the forearm flexors (the bouts being separated by 4 weeks; n = 8) or (2) a bout of 80 maximum eccentric and a bout of 80 maximum concentric muscle actions of the knee extensors (the bouts being separated by 1 week; n=6). Plasma markers of lipid peroxidation, thiobarbituric acid-reactive substances (TBARS) and diene-conjugated compounds (DCC) were monitored in the arm protocol and skeletal muscle markers of oxidative lipid and protein damage, malondialdehyde (MDA) and protein carbonyl derivatives (PCD) respectively, were monitored in the leg protocol. In both protocols, the contralateral limb was used for the second bout and the order of the bouts was randomised between limbs. Repeated measures ANOVA indicated significant changes from baseline following eccentric arm work on the measures of serum creatine kinase activity (P < 0.05), maximum voluntary torque production (P < 0.01) and relaxed arm angle (P < 0.01). Subjective muscle soreness peaked 2 days after eccentric arm work (P < 0.05, Wilcoxon test). However, there were no changes in the plasma levels of TBARS or DCC following the eccentric or concentric arm exercise. Immediately after concentric leg exercise, skeletal muscle PCD concentrations was significantly higher than that observed immediately after eccentric work (P < 0.05). However, no significant difference between the eccentric and concentric knee extensor bouts was observed on the measure of skeletal muscle MDA concentration. The results of this study offer no support for the involvement of oxygen free radicals in exercise-induced muscle damage. 相似文献
3.
Jean Farup Stine Klejs Rahbek Inge Skovgaard Knudsen Frank de Paoli Abigail L. Mackey Kristian Vissing 《Amino acids》2014,46(11):2503-2516
Human skeletal muscle satellite cells (SCs) are essential for muscle regeneration and remodeling processes in healthy and clinical conditions involving muscle breakdown. However, the potential influence of protein supplementation on post-exercise SC regulation in human skeletal muscle has not been well investigated. In a comparative human study, we investigated the effect of hydrolyzed whey protein supplementation following eccentric exercise on fiber type-specific SC accumulation. Twenty-four young healthy subjects received either hydrolyzed whey protein + carbohydrate (whey, n = 12) or iso-caloric carbohydrate (placebo, n = 12) during post-exercise recovery from 150 maximal unilateral eccentric contractions. Prior to and 24, 48 and 168 h post-exercise, muscle biopsies were obtained from the exercise leg and analyzed for fiber type-specific SC content. Maximal voluntary contraction (MVC) and serum creatine kinase (CK) were evaluated as indices of recovery from muscle damage. In type II fiber-associated SCs, the whey group increased SCs/fiber from 0.05 [0.02; 0.07] to 0.09 [0.06; 0.12] (p < 0.05) and 0.11 [0.06; 0.16] (p < 0.001) at 24 and 48 h, respectively, and exhibited a difference from the placebo group (p < 0.05) at 48 h. The whey group increased SCs/myonuclei from 4?% [2; 5] to 10?% [4; 16] (p?0.05) at 48?h, whereas the placebo group increased from 5?% [2; 7] to 9?% [3; 16] (p?0.01) at 168?h. MVC decreased (p < 0.001) and muscle soreness and CK increased (p < 0.001), irrespective of supplementation. In conclusion, whey protein supplementation may accelerate SC proliferation as part of the regeneration or remodeling process after high-intensity eccentric exercise. 相似文献
4.
M. Gleeson N. P. Walsh A. K. Blannin P. J. Robson L. Cook A. E. Donnelly S. H. Day 《European journal of applied physiology and occupational physiology》1998,77(6):543-546
The aim of this study was to determine if severe exercise-induced muscle damage alters the plasma concentrations of glutamine
and zinc. Changes in plasma concentrations of glutamine, zinc and polymorphonuclear elastase (an index of phagocytic cell
activation) were examined for up to 10 days following eccentric exercise of the knee extensors of one leg in eight untrained
subjects. The exercise bout consisted of 20 repetitions of electrically stimulated eccentric muscle actions on an isokinetic
dynamometer. Subjects experienced severe muscle soreness and large increases in plasma creatine kinase activity indicative
of muscle fibre damage. Peak soreness occurred at 2 days post-exercise and peak creatine kinase activity [21714 (6416) U · l−1, mean (SEM)] occurred at 3 days post-exercise (P < 0.01 compared with pre-exercise). Plasma elastase concentration was increased at 3 days post-exercise compared with pre-exercise
(P < 0.05), and is presumably indicative of ongoing phagocytic leucocyte infiltration and activation in the damaged muscles.
There were no significant changes in plasma zinc and glutamine concentrations in the days following eccentric exercise. We
conclude that exercise-induced muscle damage does not produce changes in plasma glutamine or zinc concentrations despite evidence
of phagocytic neutrophil activation.
Accepted: 3 November 1997 相似文献
5.
N. P. Walsh A. K. Blannin A. M. Clark L. Cook P. J. Robson M. Gleeson 《European journal of applied physiology and occupational physiology》1998,77(5):434-438
Glutamine is an essential substrate for the proper functioning of cells of the immune system. Falls in plasma glutamine concentration
after exercise may have deleterious consequences for immune cell function and render the individual more susceptible to infection.
The purpose of the present study was to examine changes in plasma glutamine concentration (measured using a validated enzymatic
spectrophotometric method) following an acute bout of intermittent high-intensity exercise. Eight well-trained male games
players took part in the study. Subjects reported to the laboratory following an overnight fast and performed a 1-h cycle
exercise task consisting of 20 1-min periods at 100% maximal O2 consumption (V˙O2max) each separated by 2 min of recovery at 30% V˙O2max. Venous blood samples were taken before exercise and at 5 min, 1 h, 2.5 h, 5 h and 24 h post-exercise. Glutamine was measured
by enzymatic spectrophotometric determination of the ammonia concentration before and after treatment of the plasma with glutaminase
(EC 3.5.1.2). Plasma glutamine concentration did not fall in the immediate post-exercise period [pre-exercise 681 (23) μM
compared with 663 (46) μM at 5 min post-exercise, mean (SEM)], but fell to 572 (35) μM at 5 h post-exercise (P < 0.05 compared with pre-exercise). Plasma lactate concentration rose to 8.8 (1.0) mM at the end of exercise and fell to
1.8 (0.4) mM at 1 h post-exercise, but plasma concentrations of free fatty acids and β-hydroxybutyrate both rose substantially
in the post-exercise period (to 240% and 400% of pre-exercise levels, respectively). The circulating leucocyte count increased
significantly during exercise (P < 0.01), continued to increase in the hours following exercise and peaked at 2.5 h post-exercise (mainly due to a neutrophilia).
The fall in the plasma glutamine concentration at 5 h post-exercise could be due to increased renal uptake of glutamine, which
generally occurs in conditions of metabolic acidosis or due to a greater removal of glutamine from the plasma resulting from
the elevated circulating leucocyte count.
Accepted: 22 October 1997 相似文献
6.
《Somatosensory & motor research》2013,30(2):45-54
Eccentric exercise has been extensively used as a model to study muscle damage-induced neuromuscular impairment, adopting mainly a bilateral matching task between the reference (unexercised) arm and the indicator (exercised) arm. However, little attention has been given to the muscle proprioceptive function when the exercised arm acts as its own reference. This study investigated muscle proprioception and motor control, with the arm acting both as reference and indicator, following eccentric exercise and compared them with those observed after isometric exercise. Fourteen young male volunteers were equally divided into two groups and performed an eccentric or isometric exercise protocol with the elbow flexors of the non-dominant arm on an isokinetic dynamometer. Both exercise protocols induced significant changes in indicators of muscle damage, that is, muscle soreness, range of motion and maximal isometric force post-exercise (p < 0.05–0.001), and neuromuscular function was similarly affected following both protocols. Perception of force was impaired over the 4-day post-exercise period (p < 0.001), with the applied force being systematically overestimated. Perception of joint position was significantly disturbed (i.e., target angle was underestimated) only at one elbow angle on day 4 post-exercise (p < 0.05). The misjudgements and disturbed motor output observed when the exercised arm acted as its own reference concur with the view that they could be a result of a mismatch between the central motor command and an impaired motor control after muscle damage. 相似文献
7.
The effect of a 120-day 6° head-down tilt (HDT) bed rest with and without countermeasures on the mechanical properties of
the human triceps surae muscle was studied in eight healthy young women subjects. One group [n = 4, mean age 31.5 (SEM 1.7) years] underwent a 120-day HDT only and a second group [n = 4; mean age 28.0 (SEM 1.1) years] underwent HDT with countermeasures (physical training). The results showed that the contractile
properties of the skeletal muscle studied changed considerably. After HDT without countermeasures the maximal voluntary contraction
(MVC) had decreased by 36% (P < 0.05), and the electrically evoked tetanic tension at 150 Hz (P
o) and isometric twitch contraction (P
t) had decreased by 24% (P < 0.02) and 12% (P < 0.05), respectively. Time- to-peak tension (TPT) of the twitch had significantly increased by 14% (P<0.05), but half-relaxation time (1/2RT), and total contraction time (TCT) had decreased by 19% (P<0.05) and 18% (P<0.05), respectively. The difference between P
o and MVC expressed as a percentage of P
o and referred to as force deficiency (FD), was also calculated. The FD had increased by 40% (P<0.001). The rate of increase of voluntary contractions calculated according to a relative scale had significantly reduced,
but for the electrically evoked contraction no substantial changes were observed. After HDT with countermeasures TPT, 1/2RT
and TCT of the twitch had decreased by 4%, 7%, 19%, respectively in relation to the control condition. Training had caused
a decrease of 3% (P>0.05) in MVC, and P
t, and in P
o of 14%, and of 9% (P>0.05), respectively. The FD had decreased significantly by 10% (P<0.02). The rate of increase of electrically evoked tetanic tension did not change significantly during HDT with countermeasures
but the rate of increase in isometric voluntary tension development was increased. Physical training provided a reserve of
neuromuscular function, which attenuated the effect of bed rest. The experimental findings indicated that neural as well as
muscle adaptation occurred in response to HDT with countermeasures.
Accepted: 7 November 1997 相似文献
8.
Jane A. Kent-Braun 《European journal of applied physiology and occupational physiology》1999,80(1):57-63
The purpose of this study was to estimate the relative contributions of central and peripheral factors to the development of human muscle fatigue. Nine healthy subjects [five male, four female; age = 30 (2) years, mean (SE)] sustained a maximum voluntary isometric contraction (MVC) of the ankle dorsiflexor muscles for 4 min. Fatigue was quantitated as the fall in MVC. Three measures of central activation and one measure of peripheral activation (compound muscle action potential, CMAP) were made using electromyography (EMG) and electrical stimulation. Measures of intramuscular metabolism were made using magnetic resonance spectroscopy. After exercise, MVC and electrically stimulated tetanic contraction (50 Hz, 500 ms) forces were 22.2 (3.7)% and 37.3 (7.1)% of pre-exercise values, respectively. The measures of central activation suggested some central fatigue during exercise: (1) the central activation ratio [MVC/(MVC + superimposed tetanic force)] fell from 0.94 (0.03) to 0.78 (0.09), (2) the MVC/tetanic force ratio fell from 2.3 (0.7) to 1.3 (0.7), and (3) the integral of the EMG (iEMG) signal decreased to 72.6 (9.1)% of the initial value, while the CMAP amplitude was unchanged. Intramuscular pH was associated by regression with the decline in MVC force (and therefore fatigue) and iEMG. The results indicate that central factors, which were not associated with altered peripheral excitability, contributed approximately 20% to the muscle fatigue developed, with the remainder being attributable to intramuscular (i.e., metabolic) factors. The association between pH and iEMG is consistent with proton concentration as a feedback mechanism for central motor drive during maximal effort. 相似文献
9.
K. S. M. T. Mudambo G. P. Leese M. J. Rennie 《European journal of applied physiology and occupational physiology》1997,75(2):109-114
The effects of exercise on gastric emptying remain controversial, with some workers reporting that heavy exercise inhibits
it to varying degrees whereas others report no effects up to an intensity of 70% maximal oxygen consumption (O2max). The state of hydration of the subjects and the environmental conditions may influence the rate of gastric emptying during
exercise. To understand further the effects of a 3-h, 16-km walk/run carrying 30 kg of equipment under field conditions at
39°C, we estimated gastric emptying using a [13C]acetate breath test method. Breath samples were collected at intervals after giving 150 mg of [13C]acetate. The effects of giving a standard volume (530 ml) of water or dextrose (7.5 g · 100 ml−1) with electrolytes or fructose/corn solids (7.5 g · 100 ml−1) at rest before exercise were compared with those of exercise and of recovery after exercise with or without extra fluids
(400 ml each 20 min). At rest, after a standard 530-ml load, gastric emptying times [mean (SE)] were: 37 (2) min (water),
46 (3) min (dextrose/electrolytes) and 47 (5) min (fructose/corn solids) and were significantly slower (P < 0.05) than those occurring after extra fluid ingestion, i.e. 32 (3), 39 (2) and 41 (3) min respectively. After a standard
530-ml load, emptying times during exercise were almost identical to those at rest but, during exercise, extra fluid speeded
up gastric emptying more than at rest to 24 (2), 26 (1) and 27 (5) min (P < 0.05) respectively. During resting recovery without extra fluids, gastric emptying was significantly slowed to 60 (2),
71 (5) and 78 (3) min, respectively. Although emptying times during recovery from exercise with extra fluid were faster [49
(6), 55 (2) and 58 (4) min, respectively], they were still slower than before exercise. The results suggest that: (1) extra
fluid increases gastric emptying more during exercise than at rest, and (2) gastric emptying during resting recovery from
exercise is slower than at rest before exercise whether or not fluid has previously been taken.
Accepted: 17 June 1996 相似文献
10.
Jay R. Hoffman Nicholas A. Ratamess Christopher P. Tranchina Stefanie L. Rashti Jie Kang Avery D. Faigenbaum 《Amino acids》2010,38(3):771-778
The effect of 42 g of protein ingested pre- and post-exercise on recovery from an acute resistance exercise session was examined
in 15 male strength/power athletes who were randomly divided into a supplement (SUP) or placebo (PL) group. Subjects reported
to the Human Performance Laboratory (HPL) on four separate occasions (T1–T4). Maximal strength [one repetition-maximum (1-RM)]
testing was performed during T1. During T2 subjects performed four sets of ten repetitions at 80% of their 1-RM in the squat,
dead lift and barbell lunge exercises with 90 s of rest between each set. Blood draws occurred at baseline (BL), immediate
and 15 min post-exercise to determine testosterone, cortisol and creatine kinase (CK) concentrations. Subjects reported back
to the HPL 24 (T3) and 48 h (T4) post-exercise for a BL blood draw and to perform four sets of ten repetitions with 80% of
1-RM for the squat exercise only. No differences in the number of repetitions performed in the squat exercise were seen between
the groups at T2. Relative to T2, PL performed significantly (P < 0.05) fewer repetitions than SUP at T3 and T4 (−9.5 ± 5.5 repetitions vs. −3.3 ± 3.6 during T3, respectively, and −10.5 ± 8.2
repetitions vs. −2.3 ± 2.9 repetitions during T4, respectively). No differences in hormonal measures were seen between the
groups. CK concentrations were significantly (P < 0.05) elevated at T3 for both groups, but continued to elevate (P < 0.05) at T4 for PL only. No significant group differences were noted for CK at any time point. Results indicate that a
proprietary protein SUP consumed before and after a resistance training session significantly contributes to improvements
in exercise recovery 24 and 48 h post-exercise. 相似文献
11.
C. Jones T. Allen J. Talbot D. L. Morgan U. Proske 《European journal of applied physiology and occupational physiology》1997,76(1):21-31
Following a series of eccentric contractions, that is stretching of the muscle while generating active tension, the length-tension
relationship of isolated amphibian muscle has been shown to shift towards longer muscle lengths (Katz 1939; Wood et al. 1993).
Here we report observations of electrically stimulated ankle extensor muscles of nine human subjects, demonstrating a similar
shift in optimum angle for torque generation [3.9 (1.5)°] following exercise on an inclined treadmill that involved eccentric
contractions in one leg. (All values are means with the SEMs in parentheses.) The shift in the unexercised, control leg was
significantly less [mean 0.4 (0.7)°P < 0.05]. Correlated with this shift was a drop in torque [25.1 (5.6)% for the experimental leg; 1.6 (0.7)% for the control
leg, P < 0.002]. Optimum angles returned to pre-exercise values by 2 days post-exercise, while torque took a week to recover. A
similar shift in optimum length [12 (1.3)% of rest length] was obtained for five toad (Bufo marinus) sartorius muscles subjected to 25 eccentric contractions. Isometrically contracted control muscles showed a smaller shift
[3.5 (1.6)%, n = 5]. Accompanying the shift was a drop in tension of 46 (3)% after the eccentric contractions [control isometric, 23 (6)%,
P < 0.0001]. By 5 h after the eccentric contractions the shift had returned to control values, while tension had not recovered.
When viewed with an electron microscope, sartorius muscles fixed immediately after the eccentric contractions exhibited many
small, and a few larger, regions of myofilament disruption. In muscles fixed 5 h after the contractions, no small regions
of disruption were visible, and the number of large regions was no greater than in those muscles fixed immediately after the
eccentric contractions. These disruptions are interpreted as the cause of the shift in length-tension relationship.
Accepted: 9 January 1997 相似文献
12.
Richards JG Heigenhauser GJ Wood CM 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2003,173(6):463-474
We examined the effects of exhaustive exercise and post-exercise recovery on white muscle substrate depletion and metabolite distribution between white muscle and blood plasma in the Pacific spiny dogfish, both in vivo and in an electrically stimulated perfused tail-trunk preparation. Measurements of arterial-venous lactate, total ammonia, -hydroxybutyrate, glucose, and l-alanine concentrations in the perfused tail-trunk assessed white muscle metabolite fluxes. Exhaustive exercise was fuelled primarily by creatine phosphate hydrolysis and glycolysis as indicated by 62, 71, and 85% decreases in ATP, creatine phosphate, and glycogen, respectively. White muscle lactate production during exercise caused a sustained increase (~12 h post-exercise) in plasma lactate load and a short-lived increase (~4 h post-exercise) in plasma metabolic acid load during recovery. Exhaustive exercise and recovery did not affect arterial
PO2,
PCO2, or PNH3 but the metabolic acidosis caused a decrease in arterial HCO3–
immediately after exercise and during the first 8 h recovery. During recovery, lactate was retained in the white muscle at higher concentrations than in the plasma despite increased lactate efflux from the muscle. Pyruvate dehydrogenase activity was very low in dogfish white muscle at rest and during recovery (0.53±0.15 nmol g wet tissue–1 min–1; n=40) indicating that lactate oxidation is not the major fate of lactate during post-exercise recovery. The lack of change in white muscle free-carnitine and variable changes in short-chain fatty acyl-carnitine suggest that dogfish white muscle does not rely on lipid oxidation to fuel exhaustive exercise or recovery. These findings support the notion that extrahepatic tissues cannot utilize fatty acids as an oxidative fuel. Furthermore, our data strongly suggest that ketone body oxidation is important in fuelling recovery metabolism in dogfish white muscle and at least 20% of the ATP required for recovery could be supplied by uptake and oxidation of -hydroxybutyrate from the plasma.Abbreviations CoA-SH
free coenzyme A
- CPT-1
carnitine palmitoyltransferase-1
- CrP
creatine phosphate
- H+m
metabolic proton load
- Lac
lactate load
- PDH
pyruvate dehydrogenase
- PVP
polyvinylpyrrolidone
- SCFA-carnitine
short-chain fatty acyl-carnitine
- TAG
triacylglycerol
- TENS
trancutaneous electrical nerve stimulator
Communicated by: L.C.-H. Wang 相似文献
13.
Unaccustomed high-intensity eccentric exercise (ECC) can provoke muscle damage including several days of muscle force loss. Post-exercise dietary supplementation may provide a strategy to accelerate rate of force regain by affecting mechanisms related to muscle protein turnover. The aim of the current study was to investigate if protein signaling mechanisms involved in muscle protein turnover would be differentially affected by supplementation with either whey protein hydrolysate and carbohydrate (WPH+CHO) versus isocaloric carbohydrate (CHO) after muscle-damaging ECC. Twenty-four young healthy participants received either WPH+CHO (n = 12) or CHO supplements (n = 12) during post-exercise recovery from 150 maximal unilateral eccentric contractions. Prior to, at 3 h and at 24, 48, 96 and/or 168 h post-exercise, muscle strength, muscle soreness, and Akt-mTOR and FOXO signaling proteins, were measured in an ECC exercising leg and in the contralateral non-exercise control leg (CON). After ECC, muscle force decreased by 23–27 % at 24 h post-exercise, which was followed by gradual, although not full recovery at 168 h post-exercise, with no differences between supplement groups. Phosphorylation of mTOR, p70S6K and rpS6 increased and phosphorylation of FOXO1 and FOXO3 decreased in the ECC leg, with no differences between supplement groups. Phosphorylation changes were also observed for rpS6, FOXO1 and FOXO3a in the CON leg, suggesting occurrence of remote tissue effects. In conclusion, divergent dietary supplementation types did not produce differences in signaling for muscle turnover during recovery from muscle-damaging exercise. 相似文献
14.
G. P. Leese J. Bowtell S. Mudambo N. Reynolds J. Thompson C. M. Scrimgeour M. J. Rennie 《European journal of applied physiology and occupational physiology》1995,71(4):306-310
In an attempt to measure gastric emptying of carbohydrate solutions after exercise, we used the 13C acetate breath test to differentiate the gastric emptying of three approximately isoenergetic carbohydrate solutions (i.e. glucose, glucose polymer and sucrose) from each other and from water. On four separate occasions, six post-absorptive subjects walked on an inclined treadmill at 70% maximum oxygen uptake for 1 h and were then given 330 ml of one of the solutions in which 150 mg of sodium 1-[13C] acetate had been dissolved. Breath samples were collected at regular (2–30 min) intervals over the next 3.5 h for analysis of expired 13CO2 by isotope ratio mass spectrometry. When water was given, all subjects reached peak breath enrichment after 30 min, and had a mean (SE) gastric emptying time of 33.2 (1.6) min. Peak breath enrichment occurred later for sucrose and glucose polymer at 54.3 (3.1) min and 59.0 (2.1) min respectively (P < 0.01), and for glucose this was even later, at 62.3 (1.0) min (P < 0.05). Calculated gastric emptying times for sucrose and glucose polymer were almost identical [66.5 (2.5) and 69.8 (2.9) min respectively], whereas that for glucose was significantly slower [76.8 (3.2) min; P < 0.02], probably reflecting the effects of increased osmolality. The gastric emptying of all carbohydrates were significantly longer than for water (P < 0.01). These results show that in the post-exercise state the 13C acetate breath test can be used to differentiate the gastric emptying rates of water and carbohydrate solutions of different properties. 相似文献
15.
The origin of the well-documented discrepancy between maximum voluntary and in vitro tetanic eccentric strength has yet to be fully understood. This study aimed to determine whether surface EMG measurements can be used to reproduce the in vitro tetanic force–velocity relationship from maximum voluntary contractions. Five subjects performed maximal knee extensions over a range of eccentric and concentric velocities on an isovelocity dynamometer whilst EMG from the quadriceps were recorded. Maximum voluntary (MVC) force–length–velocity data were estimated from the dynamometer measurements and a muscle model. Normalised amplitude–length–velocity data were obtained from the EMG signals. Dividing the MVC forces by the normalised amplitudes generated EMG corrected force–length–velocity data. The goodness of fit of the in vitro tetanic force–velocity function to the MVC and EMG corrected forces was assessed. Based on a number of comparative scores the in vitro tetanic force–velocity function provided a significantly better fit to the EMG corrected forces compared to the MVC forces (p?0.05), Furthermore, the EMG corrected forces generated realistic in vitro tetanic force–velocity profiles. A 58±19% increase in maximum eccentric strength is theoretically achievable through eliminating neural factors. In conclusion, EMG amplitude can be used to estimate in vitro tetanic forces from maximal in vivo force measurements, supporting neural factors as the major contributor to the difference between in vitro and in vivo maximal force. 相似文献
16.
Prophylactic supplementation of N-acetyl-cysteine (NAC) and epigallocatechin gallate (EGCG) was studied for physiological and cellular changes in skeletal
muscle after eccentric muscle contractions. Thirty healthy, active males (20.0 ± 1.8 years, 160 ± 7.1 cm, 76.1 ± 17.0 kg)
ingested for 14 days either 1,800 mg of NAC, 1,800 mg of EGCG, or 1,000 mg of fiber (glucomannan) placebo (PLC) in a double
blind, prophylactic fashion. Subjects completed one eccentric exercise bout (100 repetitions at 30°/s) using the dominant
knee extensors. Strength and soreness were assessed, and blood and muscle samples obtained before and 6, 24, 48, and 72 h
with no muscle sample being collected at 72 h. Separate mixed factorial repeated measures ANOVA (P < 0.05) were used for all statistical analysis. All groups experienced significantly reduced peak torque production after
6 and 24 h, increased soreness at all time points from baseline [with even greater soreness levels 24 h after exercise in
PLC when compared to EGCG and NAC (P < 0.05)], increased lactate dehydrogenase at 6 h, and increased creatine kinase 6, 24 and 48 h after exercise. No significant
group × time interaction effects were found for serum cortisol, neutrophil counts, and the neutrophil:lymphocyte ratio; although,
all values experienced significant changes 6 h after exercise (P < 0.05), but at no other time points. At 48 h after the exercise bout the Neu:Lym ratio in EGCG was significantly less than
NAC (P < 0.05), whereas there was a trend (P = 0.08) for the EGCG values to be less when compared to PLC at this time point. Markers of intramuscular mitochondrial and
cytosolic apoptosis were assessed (e.g., bax, bcl-2, cytochrome C, caspase-3 content/enzyme activity, and total DNA content).
Significant increases (P < 0.05) in muscle levels of bax and bcl-2 were observed in all groups with no significant differences between groups, whereas
no changes (P > 0.05) were reported for cytochrome C, caspase-3 content, caspase-3 enzyme activity, and total DNA. Caspase-3 enzyme activity
was significantly greater in all groups 48 h after exercise when compared to baseline (P < 0.05) and 6 h (P < 0.05) after exercise. An eccentric bout of muscle contractions appears to significantly increase muscle damage, markers
of mitochondrial apoptosis, apoptotic enzyme activity, and whole-blood cell markers of inflammation with no changes in oxidative
stress. While soreness ratings were blunted in the two supplementation groups 24 h after exercise when compared to PLC values,
more research is needed to determine the potential impact of EGCG and NAC supplementation on changes related to oxidative
stress, apoptosis, and eccentric exercise. 相似文献
17.
Facioscapulohumeral muscular dystrophy (FSHD) is an autosomal dominant disease characterized by progressive weakness and atrophy of specific skeletal muscles. As growing evidence suggests that oxidative stress may contribute to FSHD pathology, antioxidants that might modulate or delay oxidative insults could help in maintaining FSHD muscle function. Our primary objective was to test whether oral administration of vitamin C, vitamin E, zinc gluconate, and selenomethionine could improve the physical performance of patients with FSHD. Adult patients with FSHD (n=53) were enrolled at Montpellier University Hospital (France) in a randomized, double-blind, placebo-controlled pilot clinical trial. Patients were randomly assigned to receive 500 mg vitamin C, 400 mg vitamin E, 25 mg zinc gluconate and 200 μg selenomethionine (n=26), or matching placebo (n=27) once a day for 17 weeks. Primary outcomes were changes in the two-minute walking test (2-MWT), maximal voluntary contraction, and endurance limit time of the dominant and nondominant quadriceps (MVCQD, MVCQND, TlimQD, and TlimQND, respectively) after 17 weeks of treatment. Secondary outcomes were changes in the antioxidant status and oxidative stress markers. Although 2-MWT, MVCQ, and TlimQ were all significantly improved in the supplemented group at the end of the treatment compared to baseline, only MVCQ and TlimQ variations were significantly different between groups (MVCQD: P=0.011; MVCQND: P=0.004; TlimQD: P=0.028; TlimQND: P=0.011). Similarly, the vitamin C (P<0.001), vitamin E as α-tocopherol (P<0.001), vitamin C/vitamin E ratio (P=0.017), vitamin E γ/α ratio (P=0.022) and lipid peroxides (P<0.001) variations were significantly different between groups. In conclusion, vitamin E, vitamin C, zinc, and selenium supplementation has no significant effect on the 2-MWT, but improves MVCQ and TlimQ of both quadriceps by enhancing the antioxidant defenses and reducing oxidative stress. This trial was registered at clinicaltrials.gov (number: NCT01596803). 相似文献
18.
Michael Gleeson Andrew K. Blannin Neil P. Walsh Christine N. E. Field Jeanette C. Pritchard 《European journal of applied physiology and occupational physiology》1998,77(3):292-295
Eccentric muscle actions are known to induce temporary muscle damage, delayed onset muscle soreness (DOMS) and muscle weakness
that may persist for several days. The purpose of the present study was to determine whether DOMS-inducing exercise affects
blood lactate responses to subsequent incremental dynamic exercise. Physiological and metabolic responses to a standardised
incremental exercise task were measured two days after the performance of an eccentric exercise bout or in a control (no prior
exercise) condition. Ten healthy recreationally active subjects (9 male, 1 female), aged 20 (SD 1) years performed repeated
eccentric muscle actions during 40 min of bench stepping (knee high step; 15 steps · min−1). Two days after the eccentric exercise, while the subjects experienced DOMS, they cycled on a basket loaded cycle ergometer
at a starting work rate of 150 W, with increments of 50 W every 2 min until fatigue. The order of the preceding treatments
(eccentric exercise or control) was randomised and the treatments were carried out 2 weeks apart. Two days after the eccentric
exercise, all subjects reported leg muscle soreness and exhibited elevated levels of plasma creatine kinase activity (P < 0.05). Endurance time and peak V˙O2 during cycling were unaffected by the prior eccentric exercise. Minute volume, respiratory exchange ratio and heart rate
responses were similar but venous blood lactate concentration was higher (P < 0.05) during cycling after eccentric exercise compared with the control condition. Peak blood lactate concentration, observed
at 2 min post-exercise was also higher [12.6 (SD 1.4) vs 10.9 SD (1.3) mM; P < 0.01]. The higher blood lactate concentration during cycling exercise after prior eccentric exercise may be attributable
to an increased rate of glycogenolysis possibly arising from an increased recruitment of Type II muscle fibres. It follows
that determination of lactate thresholds for the purpose of fitness assessment in subjects experiencing DOMS is not appropriate.
Accepted: 27 September 1997 相似文献
19.
C T Davies K Young 《European journal of applied physiology and occupational physiology》1985,54(3):301-305
The effects of sustained and rhythmically performed isometric contractions on electrically evoked twitch and tetanic force generation of the triceps surae have been investigated in 4 healthy male subjects. The isometric contractions were performed separately and on different occasions at 30%, 60% and 100% of the force of maximal voluntary contraction (MVC). The area under the maximal voluntary contraction (MVC) force/time curve during the rhythmic and sustained contractions was the same for each experiment. The results showed that following rhythmic isometric exercise there was a small decrease in low (10 and 20 Hz) and high (40 Hz) frequency tetanic tension which was associated with % MVC. However, there was no change in the 20/40 ratio of tetanic forces, MVC or the contraction times and force of the maximal twitch. In contrast, following sustained isometric exercise tetanic forces were markedly reduced, particularly at low frequencies of stimulation. The 20/40 ratio decreased and the induced muscle weakness was greater at 30% than 60% or 100% MVC. The performance of sustained isometric contractions also effected a decrease in contraction time of the twitch and MVC. The results are in accord with previous findings for dynamic work (Davies and White 1982), and show that if isometric exercise is performed rhythmically the effect on tetanic tensions is small and there is no evidence of a preferential loss of electrically evoked force at either high or low frequencies of stimulation following the contractions. For sustained contractions, however, the opposite is true, the ratio of 20/40 Hz forces is markedly reduced and following 30% sustained MVC there is a significant (p less than 0.05) change in the time to peak tension (TPT) of the maximal twitch. 相似文献
20.
Theophylline does not increase maximal tetanic force or diaphragm endurance in vitro 总被引:2,自引:0,他引:2
These experiments tested the capacity of theophylline to improve diaphragm strength (maximal force development) and endurance (maintenance of force output during repeated contractions). Rodent diaphragm strips were mounted at optimal length in oxygenated Krebs-Ringer solution (37 degrees C, pH 7.37). Direct stimuli used supramaximal current density, 0.2-ms pulses, and 250-ms tetanic trains. Theophylline (500 mg/ml) increased force development at low stimulation frequencies but did not increase maximal force [25.7 +/- 0.5 for theophylline vs. 26.0 +/- 0.4 (SE) N/cm2 for control (n = 34)]. During repeated submaximal (25-36 Hz) tetanic contractions, theophylline did not affect endurance. During repeated maximal (160 Hz) tetanic contractions theophylline reduced endurance, accelerating the fall of developed force. Theophylline also inhibited recovery of force after endurance trials ended. We conclude that theophylline does not increase maximal tetanic force and can reduce diaphragm endurance in vitro. 相似文献