Shortening of muscle relaxation time after creatine loading

The effect of creatine (Cr) supplementation on muscle isometric torque generation and relaxation was investigated in healthy male volunteers. Maximal torque (Tmax), contraction time (CT) from 0.25 to 0.75 of Tmax, and relaxation time (RT) from 0.75 to 0.25 of Tmax were measured during 12 maximal isometric 3-s elbow flexions interspersed by 10-s rest intervals. Between the pretest and the posttest, subjects ingested Cr monohydrate (4 × 5 g/day; n = 8) or placebo ( n = 8) for 5 days. Pretest Tmax, CT, and RT were similar in Cr and placebo groups. Also in the posttest, Tmax and CT were similar between groups. However, posttest RT was decreased consistently by ∼20% ( P < 0.05) in the Cr group from the first to the last of the 12 contractions. In addition, the mean decrease in RT after Cr loading was positively correlated with pretest RT ( r = 0.82). It is concluded that Cr loading facilitates the rate of muscle relaxation during brief isometric muscle contractions without affecting torque production.

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Repeatability of the Mean Power Frequency of the Endurance Level, During Fatiguing Isometric Muscle Contractions

11th Mediterranean Conference on Medical and Biomedical Engineering and Computing 2007 - IFMBE Proceedings ◽

10.1007/978-3-540-73044-6_261 ◽

2007 ◽

pp. 1009-1012

Author(s):

Igor Stirn ◽

T. Jarm ◽

V. Strojnik

Keyword(s):

Muscle Contractions ◽

Mean Power ◽

Mean Power Frequency ◽

Power Frequency ◽

The Mean ◽

Isometric Muscle

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Fatigue and recovery of power and isometric torque following isotonic knee extensions

Journal of Applied Physiology ◽

10.1152/japplphysiol.00452.2005 ◽

2005 ◽

Vol 99 (4) ◽

pp. 1446-1452 ◽

Cited By ~ 41

Author(s):

Arthur J. Cheng ◽

Charles L. Rice

Keyword(s):

Relaxation Time ◽

Voluntary Contraction ◽

Contractile Properties ◽

Task Failure ◽

Motor Unit Activation ◽

Isometric Torque ◽

Isotonic Function ◽

Isotonic Contractions ◽

Muscle Contractile ◽

Isometric Muscle

The purpose of this study was to assess fatigue and recovery of isotonic power and isometric contractile properties after a series of maximal isotonic contractions. Using a Biodex dynamometer, 13 men [26 yr (SD 3)] performed isotonic [50% of isometric maximal voluntary contraction (MVC) every 1.2 s through 75° range of motion] single-limb knee extensions at the fastest velocity they could achieve until velocity was reduced by 35%. Time to task failure was 38 s, and, compared with baseline, power declined by ∼42% [741.0 (SD 106.0) vs. 426.5 W (SD 60.3) at task failure], and MVC declined by ∼26% [267.3 (SD 42.5) vs. 198.4 N·m (SD 45.7) at task failure]. Power recovered by 5 min, whereas MVC did not recover, and at 10 min was only ∼85% of baseline. Isometric MVC motor unit activation was ∼95% at rest and was unchanged at task failure (∼96%), but a small amount of failure was apparent between 1.5 and 10 min of recovery (∼87 to ∼91%). Half relaxation time measured from a 50-Hz isometric tetanus was significantly prolonged by ∼33% immediately after task failure but recovered by 1.5 min. A decline in the 10- to 50-Hz ratio of the evoked isometric contractions was observed at 5 and 10 min of recovery, which suggests excitation-contraction coupling impairment. Changes in velocity and half relaxation time during the protocol were strongly and negatively correlated ( r = −0.85). Thus mainly peripheral mechanisms were implicated in the substantial depression but relatively fast recovery of isotonic power. Furthermore, isometric muscle contractile properties were related to some, but not all, changes in isotonic function.

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Pharmacokinetics and Inflammatory Fluid Penetration of Clinafloxacin

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.42.2.428 ◽

1998 ◽

Vol 42 (2) ◽

pp. 428-430 ◽

Cited By ~ 13

Author(s):

R. Wise ◽

S. Jones ◽

I. Das ◽

J. M. Andrews

Keyword(s):

Half Life ◽

Maximum Concentration ◽

Healthy Male ◽

Elimination Half Life ◽

Concentration Time ◽

Healthy Male Volunteers ◽

Elimination Half ◽

The Mean ◽

Fluid Penetration ◽

Mean Time

ABSTRACT A single 200-mg dose of clinafloxacin was given orally to each of nine healthy male volunteers, and the concentrations of the drug were measured in plasma, cantharidin-induced inflammatory fluid, and urine over the following 24 h (48 h in the case of urine). The mean maximum concentration in plasma was 1.34 μg/ml at a mean time of 1.8 h postdose. The mean maximum concentration in the inflammatory fluid was 1.3 μg/ml at 3.8 h postdose. The mean elimination half-life of clinafloxacin in plasma was 5.65 h. The overall penetration into the inflammatory fluid was 93.1%, as assessed by determining the ratio of area under the concentration-time curves. Recovery of clinafloxacin in urine was 58.8% by 24 h and 71.8% by 48 h postdose.

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Pharmacokinetics and metabolism of genaconazole, a potent antifungal drug, in men.

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.40.1.92 ◽

1996 ◽

Vol 40 (1) ◽

pp. 92-96 ◽

Cited By ~ 8

Author(s):

C Lin ◽

H Kim ◽

E Radwanski ◽

M Affrime ◽

M Brannan ◽

...

Keyword(s):

Oral Dose ◽

Single Oral Dose ◽

Total Radioactivity ◽

Healthy Male ◽

Serum Samples ◽

Time Curve ◽

Concentration Time ◽

Healthy Male Volunteers ◽

Male Volunteers ◽

The Mean

The pharmacokinetics of genaconazole, a racemic triazole antifungal agent comprising 50% RR and 50% SS enantiomers, were studied in 12 healthy male volunteers after a single oral dose of 200 mg. The serum samples were analyzed for the two enantiomers by using a chiral high-pressure liquid chromatography assay. The concentrations of the RR and SS enantiomers in serum were virtually identical. The mean values for the maximum concentrations in serum (Cmax) (1.7 micrograms/ml), times to Cmax (4.0 to 4.2 h), half-lives (83 h), and areas under the concentration-time curve from 0 h to infinity (195 to 199 micrograms.h/ml) were similar for the two enantiomers. The results showed that the pharmacokinetic profiles of the two enantiomers were similar after a single oral dosing of the racemate. The pharmacokinetics of the RR enantiomer were also evaluated in 12 healthy male volunteers after a single oral dose of 100 or 200 mg. The ratios of the Cmaxs and of the areas under the concentration-time curves from 0 h to infinity for the two doses were about 2, indicating a dose proportionality. In a separate study, six healthy male volunteers received a single oral dose of 50 mg of 14C-labeled genaconazole. The Cmax values for total radioactivity (14C) and intact genaconazole were virtually identical (0.6 micrograms/ml). The mean half-lives in serum were about 73 h for both total radioactivity and genaconazole. The amounts of total radioactivity excreted in the 0 to 240-h interval (representing approximately three half-lives) in urine and feces were 66.6 and 9.3% of the dose, respectively; 64.4% of the dose was excreted in urine as parent drug. There were no detectable metabolites in either serum or urine. The data demonstrate that genaconazole (racemate) is well absorbed, undergoes negligible biotransformation, and is slowly excreted, primarily in the urine.

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Pharmacokinetics and Inflammatory-Fluid Penetration of Moxifloxacin following Oral or Intravenous Administration

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.43.6.1508 ◽

1999 ◽

Vol 43 (6) ◽

pp. 1508-1510 ◽

Cited By ~ 76

Author(s):

Richard Wise ◽

Jennifer M. Andrews ◽

Gill Marshall ◽

Giles Hartman

Keyword(s):

Intravenous Administration ◽

The Other ◽

Healthy Male ◽

Oral Dosing ◽

Healthy Male Volunteers ◽

Male Volunteers ◽

Elimination Half ◽

The Mean ◽

Fluid Penetration

ABSTRACT A single 400-mg oral or intravenous (i.v.) dose of moxifloxacin was given to each of eight healthy male volunteers, and 6 weeks later the dose was administered by the other route. The concentrations of the drug in plasma, cantharidin-induced inflammatory fluid, and urine were measured over the subsequent 24 h. The mean maximum concentrations observed in plasma were 4.98 μg/ml after oral dosing and 5.09 μg/ml after i.v. dosing. The mean maximum concentrations attained in the inflammatory fluid were 2.62 and 3.23 μg/ml, respectively. The mean elimination half-lives from plasma were 8.32 and 8.17 h, respectively. The overall penetration into the inflammatory fluid was 103.4 and 104.2%. Over 24 h 15% of the drug was recovered in the urine when administered by either route.

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Effects of FMO3 Polymorphisms on Pharmacokinetics of Sulindac in Chinese Healthy Male Volunteers

BioMed Research International ◽

10.1155/2017/4189678 ◽

2017 ◽

Vol 2017 ◽

pp. 1-7 ◽

Cited By ~ 2

Author(s):

Yong-Jun Tang ◽

Kai Hu ◽

Wei-Hua Huang ◽

Chong-Zhi Wang ◽

Zhi Liu ◽

...

Keyword(s):

Plasma Concentrations ◽

Pharmacokinetic Parameters ◽

Healthy Male ◽

Mean Values ◽

Healthy Male Volunteers ◽

Male Volunteers ◽

Pcr Rflp ◽

Hardy Weinberg Equilibrium ◽

Sulindac Sulfide ◽

The Mean

Sulindac is a nonsteroidal anti-inflammatory drug, which is clinically used for the ailments of various inflammations. This study investigated the allele frequencies of FMO3 E158K and E308G and evaluated the influences of these two genetic polymorphisms on the pharmacokinetics of sulindac and its metabolites in Chinese healthy male volunteers. Eight FMO3 wild-type (FMO3 HHDD) subjects and seven FMO3 homozygotes E158K and E308G mutant (FMO3 hhdd) subjects were recruited from 247 healthy male volunteers genotyped by PCR-RFLP method. The plasma concentrations of sulindac, sulindac sulfide, and sulindac sulfone were determined by UPLC, while the pharmacokinetic parameters of the two different FMO3 genotypes were compared with each other. The frequencies of FMO3 E158K and E308G were 20.3% and 20.1%, respectively, which were in line with Hardy-Weinberg equilibrium (D′ = 0.977, r2 = 0.944). The mean values of Cmax, AUC0–24, and AUC0–∞ of sulindac were significantly higher in FMO3 hhdd group than those of FMO3 HHDD group (P<0.05), while the pharmacokinetic parameters except Tmax of sulindac sulfide and sulindac sulfone showed no statistical difference between the two groups. The two FMO3 mutants were in close linkage disequilibrium and might play an important role in the pharmacokinetics of sulindac in Chinese healthy male volunteers.

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