scholarly journals ATP2A2 rs3026468 does not associate with quadriceps contractile properties and acute muscle potentiation in humans

2019 ◽  
Vol 51 (1) ◽  
pp. 10-11
Author(s):  
Eric A. Kirk ◽  
Shiva M. Singh ◽  
Charles L. Rice
Keyword(s):  
Contractile Properties ◽  
Voluntary Activation ◽  
Contractile Property ◽  
Healthy Men ◽  
Twitch Response ◽  
Atp2a2 Gene ◽  
Active Calcium ◽  
Slow Twitch ◽  
Muscle Potentiation ◽  
Voluntary Strength

The ATP2A2 gene encodes the SERCA protein required for active calcium reuptake to the sarcoplasmic reticulum in cardiac and slow-twitch skeletal muscle. The ATP2A2 rs3026468 variant has been associated with voluntary strength phenotypes in humans but requires further validation. Here we investigated a homogenous cohort of 80 young, healthy, active Caucasian males who were assessed for maximal isometric strength, voluntary activation, stimulated contractile properties, and muscle potentiation in the quadriceps. A dynamometer was used to record knee extensions, and electrical stimulation was applied to the thigh to elicit a twitch response. DNA was isolated from cheek swabs, and the rs3026468 genotypes were assessed by TaqMan primer quantitative PCR. The results show no association between ATP2A2 rs3026468 variants and muscle strength measures. We conclude there is no effect of the rs3026468 variant in our cohort and that functional influences do not likely contribute to contractile property differences in young healthy men.

Recovery in skeletal muscle contractile function after prolonged hindlimb immobilization

1985 ◽  
Vol 59 (3) ◽  
pp. 916-923 ◽  
Author(s):  
R. H. Fitts ◽  
C. J. Brimmer
Keyword(s):  
Contractile Function ◽  
Vastus Lateralis ◽  
Weight Ratio ◽  
Contractile Properties ◽  
Shortening Velocity ◽  
Slow Twitch ◽  
Isometric Twitch ◽  
Fast Twitch ◽  
Muscle Contractile

Contractile properties of slow-twitch soleus (SOL), fast-twitch extensor digitorum longus (EDL), and fast-twitch superficial region of the vastus lateralis were determined in vitro (22 degrees C) in rats remobilized after prolonged (3 mo) hindlimb immobilization (IM). For all muscles the muscle-to-body weight ratio was significantly depressed by IM, and the ratios failed to completely recover even after 90 days. The contractile properties of the fast-twitch muscles were less affected by IM than the slow-twitch SOL. The IM shortened the SOL isometric twitch duration due to a reduced contraction and half-relaxation time. These parameters returned to control levels by the 14th day of recovery. Peak tetanic tension (Po, g/cm2) declined with IM by 46% in the SOL but showed no significant change in the fast-twitch muscles. After IM the SOL Po (g/cm2) recovered to control values by 28 days. The recovery of Po in absolute units (g) was considerably slower and did not return to control levels until 60 (SOL) to 90 (EDL) days. The maximum shortening velocity was not altered by IM in any of the muscles studied. These results demonstrate that both fast- and slow-twitch skeletal muscles possess the ability to completely recover normal contractile function following prolonged periods of hindlimb IM.

Contractile properties of muscle: control by pattern of muscle activity in the rat

1974 ◽  
Vol 187 (1086) ◽  
pp. 99-103 ◽  
Keyword(s):  
Soleus Muscle ◽  
Muscle Activity ◽  
Stimulation Frequency ◽  
Contractile Properties ◽  
Fast Muscle ◽  
Muscle Control ◽  
Rat Soleus Muscle ◽  
The Mean ◽  
Slow Twitch

The denervated slow twitch rat soleus muscle was stimulated electrically for 3-6 weeks with brief trains of stimuli at 100 Hz or long trains at 10 Hz. In both cases the mean stimulation frequency was 2 Hz. Muscles stimulated at 100 Hz acquired several properties characteristic of fast muscle, whereas muscles stimulated at 10 Hz remained slow. The results demonstrate the importance of pattern of muscle activity in determining the contractile properties of muscle.

Contractile properties, structure and fiber phenotype of intact and regenerating slow-twitch muscles of mice treated with cyclosporin A

2002 ◽  
Vol 308 (1) ◽  
pp. 143-156 ◽  
Author(s):  
Andrey Irintchev ◽  
Margit Zweyer ◽  
Racquel Cooper ◽  
Gillian Butler-Browne ◽  
Anton Wernig
Keyword(s):  
Cyclosporin A ◽  
Contractile Properties ◽  
Slow Twitch

scholarly journals Nonlinear summation of contractions in cat muscles. I. Early depression.

1981 ◽  
Vol 78 (3) ◽  
pp. 277-293 ◽  
Author(s):  
R B Stein ◽  
F Parmiggiani
Keyword(s):  
Motor Units ◽  
Repetitive Stimulation ◽  
Actin Binding ◽  
Linear Summation ◽  
First Order ◽  
Twitch Response ◽  
Single Motor Units ◽  
Sodium Hydrate ◽  
Slow Twitch ◽  
Stimulation Of

Nerves to fast- and slow-twitch cat muscles were stimulated with various numbers of supramaximal pulses under isometric conditions. By subtracting the force produced by j - 1 pulses from that produced by j pulses, the contribution of the j th pulse could be compared with the response to one pulse (twitch response). A less-than-linear summation (depression) was observed during the rising phase of the twitch. This depression became increasingly prominent and longer in duration with repetitive stimulation. A more-than-linear summation (facilitation) was observed during the falling phase of the twitch, which became increasingly delayed and smaller in amplitude with repetitive stimulation. The early depression could be abolished for the first few pulses by Dantrolene [1-(5-p-nitrophenyl) furfurilidene amino hydantoin sodium hydrate], which reduced Ca++ release from the sarcoplasmic reticulum. The depression was less prominent at short muscle lengths or with stimulation of single motor units. A first-order, saturable reaction such as Ca++ binding to troponin or actin binding to myosin can quantitatively account for the early depression.

Mechanical properties of muscle units in the cat diaphragm

1988 ◽  
Vol 59 (3) ◽  
pp. 1055-1066 ◽  
Author(s):  
M. Fournier ◽  
G. C. Sieck
Keyword(s):  
Contractile Properties ◽  
Fatigue Properties ◽  
Tetanic Force ◽  
Wide Range ◽  
The Mean ◽  
Slow Twitch ◽  
The Right ◽  
Fast Twitch ◽  
Tetanic Tension

1. Muscle units in the right sternocostal region of the cat diaphragm (DIA) were isolated in situ by dissecting filaments of the C5 ventral root. Isometric contractile and fatigue properties of DIA units were then measured. Contractile properties included: twitch contraction time (CT), peak twitch tension (Pt), maximum tetanic tension (P0), and the frequency dependence of tension production. Muscle-unit fatigue resistance was estimated using a 2-min fatigue test. 2. DIA muscle units were classified as fast (F) or slow (S) based on the presence or absence of sag in their unfused tetanic force responses. Muscle-unit fatigue indices (FI) were used to further classify DIA units as slow-twitch fatigue-resistant (S), fast-twitch fatigue-resistant (FR) fast-twitch fatigue-intermediate (FInt), or fast-twitch fatigable (FF) types. 3. Based on a total of 47 completely characterized DIA muscle units, 21% were classified as S, 4% as FR, 28% as FInt, and 47% as FF. In contrast to the distribution of unit types in other mixed appendicular muscles, the DIA was composed of a very low proportion of FR units and a relatively high proportion of FInt units. An interval of FIs between 0.50 and 0.75 separated units into fatigue-resistant and fatigable groups. The distribution of FIs for FF and most FInt units was continuous, indicating that they formed a single fatigable group. Relatively few FF units in the DIA had FIs less than 0.10. 4. A wide range of contractile properties was observed for DIA muscle units. Type S units had longer CTs and lower Pt and P0 values than type F units. The mean Pt and P0 of FF and FInt units were comparable, whereas the mean Pt and P0 of the two FR units were lower. Type S units produced a greater proportion of their P0 at lower frequencies of activation than type F units. The lower P0S produced by type F units in the DIA indicated that they were smaller than similar units in appendicular muscles. It was concluded that in meeting most normal ventilatory requirements, adequate force could be generated by the recruitment of only type S and FR units. The recruitment of the more fatigable FF and FInt units may occur only during more forceful respiratory and nonrespiratory behaviors of the DIA.

scholarly journals Altered contractile properties of the gastrocnemius muscle poststroke

2008 ◽  
Vol 105 (6) ◽  
pp. 1802-1808 ◽  
Author(s):  
Fan Gao ◽  
Li-Qun Zhang
Keyword(s):  
Muscle Weakness ◽  
Gastrocnemius Muscle ◽  
Contractile Properties ◽  
Medial Gastrocnemius ◽  
Contractile Property ◽  
Stroke Survivors ◽  
Motor Impairments ◽  
Fascicle Length ◽  
Length Relationship ◽  
Muscle Fascicles

Spasticity, contracture and muscle weakness often occur together poststroke and cause considerable motor impairments to stroke survivors. The underlying changes in contractile properties of muscle fascicles are still not clear. The purpose of this study was to investigate the contractile property changes of the medial gastrocnemius muscle fascicles poststroke. Ten stroke survivors and ten healthy subjects participated in the study. The medial gastrocnemius fascicular length was measured at various combinations of ankle and knee positions using ultrasonography, with the muscle activated selectively using electrical stimulation. The stimulation intensity was kept constant across different ankle and knee positions to establish the active force-length relationship of the muscle fascicles. It was found that stroke survivors showed a shift of the force-length curve with a significantly shorter optimal fascicle length (33.2 ± 3.2 mm) compared with that of healthy controls (47.4 ± 2.7 mm) with P < 0.001. Furthermore, the width span of the fascicular force-length curve of stroke survivors was significantly narrower with steeper slopes than that of controls ( P ≤ 0.001), suggesting reduced number of sarcomeres along the fascicles and/or reduced sarcomere length poststroke. Regression analysis showed that the medial gastrocnemius fascicular length of stroke survivors varied significantly less with ankle and knee flexions ( P ≤ 0.001) than that of controls, suggesting shorter and stiffer muscle fascicles poststroke, which might be attributed to muscle architectural adaptation. This study showed that there are considerable changes in the contractile properties of muscle fascicles poststroke, which may contribute directly to the joint-level changes of decreased range of motion, increased stiffness, muscle weakness, and impaired motor functions in stroke survivors.

scholarly journals Skeletal muscle morphology and contractile function in relation to muscle denervation in diabetic neuropathy

2014 ◽  
Vol 116 (5) ◽  
pp. 545-552 ◽  
Author(s):  
Matti D. Allen ◽  
Brendan Major ◽  
Kurt Kimpinski ◽  
Timothy J. Doherty ◽  
Charles L. Rice
Keyword(s):  
Tibialis Anterior ◽  
Contractile Function ◽  
Relative Proportion ◽  
Magnetic Resonance Images ◽  
Contractile Properties ◽  
Voluntary Activation ◽  
Muscle Quality ◽  
Functional Impairments ◽  
Muscle Morphology ◽  
Voluntary Contractions

The objective of the study was to assess the effects of diabetic polyneuropathy (DPN) on muscle contractile properties in humans, and how these changes are related to alterations in muscle morphology and denervation. Patients with DPN ( n = 12) were compared with age- and sex-matched controls ( n = 12). Evoked and voluntary contractile properties, including stimulated twitch responses and maximal voluntary contractions, of the dorsiflexor muscles were assessed using an isometric ankle dynamometer. Motor unit number estimates (MUNE) of the tibialis anterior (TA) were performed via quantitative electromyography and decomposition-enhanced spike-triggered averaging. Peak tibialis anterior (TA) cross-sectional area (CSA; cm2), and relative proportion of contractile to noncontractile tissue (%) was determined from magnetic resonance images. Patients with DPN demonstrated decreased strength (−35%) and slower (−45%) dorsiflexion contractile properties for both evoked and voluntary contractions ( P < 0.05). These findings were not accounted for by differences in voluntary activation ( P > 0.05) or antagonist coactivation ( P > 0.05). Additionally, patients with DPN were weaker when strength was normalized to TA total CSA (−30%; P < 0.05) or contractile tissue CSA (−26%; P < 0.05). In the DPN patient group, TA MUNEs were negatively related to both % noncontractile tissue ( P < 0.05; r = 0.72) and twitch half-relaxation time ( P < 0.05; r = 0.60), whereas no relationships were found between these variables in controls ( P > 0.05). We conclude that patients with DPN demonstrated reduced strength and muscle quality as well as contractile slowing. This process may contribute to muscle power loss and functional impairments reported in patients with DPN, beyond the loss of strength commonly observed.

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