scholarly journals Effect of xanthine oxidase-generated extracellular superoxide on skeletal muscle force generation

2010 ◽  
Vol 298 (1) ◽  
pp. R2-R8 ◽  
Author(s):  
M. C. Gomez-Cabrera ◽  
G. L. Close ◽  
A. Kayani ◽  
A. McArdle ◽  
J. Viña ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Polyethylene Glycol ◽  
Cytochrome C ◽  
Extracellular Space ◽  
Superoxide Anion ◽  
Skeletal Muscles ◽  
Muscle Force ◽  
Force Production ◽  
Force Generation ◽  
Isometric Contractions

Skeletal muscle contractions increase superoxide anion in skeletal muscle extracellular space. We tested the hypotheses that 1) after an isometric contraction protocol, xanthine oxidase (XO) activity is a source of superoxide anion in the extracellular space of skeletal muscle and 2) the increase in XO-derived extracellular superoxide anion during contractions affects skeletal muscle contractile function. Superoxide anion was monitored in the extracellular space of mouse gastrocnemius muscles by following the reduction of cytochrome c in muscle microdialysates. A 15-min protocol of nondamaging isometric contractions increased the reduction of cytochrome c in microdialysates, indicating an increase in superoxide anion. Mice treated with the XO inhibitor oxypurinol showed a smaller increase in superoxide anions in muscle microdialysates following contractions than in microdialysates from muscles of vehicle-treated mice. Intact extensor digitorum longus (EDL) and soleus muscles from mice were also incubated in vitro with oxypurinol or polyethylene glycol-tagged Cu,Zn-SOD. Oxypurinol decreased the maximum tetanic force produced by EDL and soleus muscles, and polyethylene glycol-tagged Cu,Zn-SOD decreased the maximum force production by the EDL muscles. Neither agent influenced the rate of decline in force production when EDL or soleus muscles were repeatedly electrically stimulated using a 5-min fatiguing protocol (stimulation at 40 Hz for 0.1 s every 5 s). Thus these studies indicate that XO activity contributes to the increased superoxide anion detected within the extracellular space of skeletal muscles during nondamaging contractile activity and that XO-derived superoxide anion or derivatives of this radical have a positive effect on muscle force generation during isometric contractions of mouse skeletal muscles.

Neuromuscular drive and force production are not altered during bilateral contractions

1998 ◽  
Vol 84 (1) ◽  
pp. 200-206 ◽  
Author(s):  
J. M. Jakobi ◽  
E. Cafarelli
Keyword(s):  
Motor Unit ◽  
Force Production ◽  
Young Male ◽  
Neuromuscular Control ◽  
Force Generation ◽  
Isometric Contractions ◽  
Firing Rates ◽  
Significant Limitation ◽  
Motor Unit Firing ◽  
Male Subjects

Jakobi, J. M., and E. Cafarelli. Neuromuscular drive and force production are not altered during bilateral contractions. J. Appl. Physiol. 84(1): 200–206, 1998.—Several investigators have studied the deficit in maximal voluntary force that is said to occur when bilateral muscle groups contract simultaneously. A true bilateral deficit (BLD) would suggest a significant limitation of neuromuscular control; however, some of the data from studies in the literature are equivocal. Our purpose was to determine whether there is a BLD in the knee extensors of untrained young male subjects during isometric contractions and whether this deficit is associated with a decreased activation of the quadriceps, increased activation of the antagonist muscle, or an alteration in motor unit firing rates. Twenty subjects performed unilateral (UL) and bilateral (BL) isometric knee extensions at 25, 50, 75, and 100% maximal voluntary contraction. Total UL and BL force (Δ3%) and maximal rate of force generation (Δ2.5%) were not significantly different. Total UL and BL maximal vastus lateralis electromyographic activity (EMG; 2.7 ± 0.28 vs. 2.6 ± 0.24 mV) and coactivation (0.17 ± 0.02 vs. 0.20 ± 0.02 mV) were also not different. Similarly, the ratio of force to EMG during submaximal UL and BL contractions was not different. Analysis of force production by each leg in UL and BL conditions showed no differences in force, rate of force generation, EMG, motor unit firing rates, and coactivation. Finally, assessment of quadriceps activity with the twitch interpolation technique indicated no differences in the degree of voluntary muscle activation (UL: 93.6 ± 2.51 Hz, BL: 90.1 ± 2.43 Hz). These results provide no evidence of a significant limitation in neuromuscular control between BL and UL isometric contractions of the knee extensor muscles in young male subjects.

Beetroot Juice Increases Skeletal Muscle Force Production in Recreationally Active Subjects.

2016 ◽  
Vol 48 ◽  
pp. 897
Author(s):  
Jamie Whitfield ◽  
George J. F. Heigenhauser ◽  
Lawrence L. Spriet ◽  
Graham P. Holloway ◽  
A. Russell Tupling
Keyword(s):  
Skeletal Muscle ◽  
Muscle Force ◽  
Force Production ◽  
Beetroot Juice ◽  
Muscle Force Production

scholarly journals Factors determining stress-reactivity of hemodynamics in the adolescents

2008 ◽  
Vol 14 (2) ◽  
pp. 165-171 ◽  
Author(s):  
A. Sumin ◽  
L. Sumina ◽  
N. Vasilyeva
Keyword(s):  
Blood Pressure ◽  
Skeletal Muscle ◽  
Body Weight ◽  
Mental Stress ◽  
Skeletal Muscles ◽  
Muscle Force ◽  
Stress Reactivity ◽  
Normal Reaction ◽  
Reducing Stress ◽  
Psychological Questionnaires

Resume In order to assess factors contributing to stress reactivity of blood pressure 66 adolescents (25 boys and 41 girles) form 14 to 17 yrs (15,2+0,1 yrs) were examined. Test with oral calculation, psychological (questionnaires of Bass-Darky, Kettle, Spielberg) as well as force of skeletal muscles and were assessed. Hyperreaction of blood pressure (BP) was observed in 27% of adolescents, normal reaction - in 47% cases, low reactivity - in 26%. In hyperreactive subjects lower parameters of skeletal muscle force were documented. Psychological discrepancies were insignificant between the groups. The BP raise during mental stress correlated with muscle force, body weight, baseline BP level and mental development. The data obtained can indicate that reducing stress reactivity can be important instrument in primary prevention of cardiovascular diseases in psychogenic rest groups.

The Effect of the Fascia on the Stress Distribution in Skeletal Muscle

2010 ◽  
Author(s):  
Angelica Maria Ramirez ◽  
Begoña Calvo Calzada ◽  
Jorge Grasa
Keyword(s):  
Skeletal Muscle ◽  
Connective Tissue ◽  
Skeletal Muscles ◽  
Body Force ◽  
Anatomical Structure ◽  
The Body ◽  
Force Generation ◽  
Fibre Bundles ◽  
Muscle Shortening ◽  
Whole Muscle

The human and vertebrate interaction with the environment is done primarily through the movement. This is possible due the skeletal muscle: anatomical structure able to contract voluntarily. The skeletal muscles are made up of contractile proteins which slide one over another allowing the muscle shortening and the body force generation. This protein structure of actin and myosin maintains its organization through the connective tissue that surrounds it (endomysium, perimysium and epimysium), creating arrays of myofibrils, fibre bundles, fascicles until conform the whole muscle. All this connective tissue extends to the ends of the muscle to form the tendon.

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