Relationship between in vivo muscle force at different speeds of isokinetic movements and myosin isoform expression in men and women

Abstract

In an attempt to explore the relationship between force production during voluntary contractions at different speeds of isokinetic movement and the myofibrillar protein isoform expression in humans, an improved isokinetic dynamometer that corrects for gravitation, controls for acceleration and deceleration, and identifies a maximum voluntary activation was used. Muscle torque recordings were compared at the same muscle length (knee angle) and the torque was calculated as the average torque at each angle over a large knee angle range (75 degrees -25 degrees ) to reduce the influence of small torque oscillation on the calculated torque. Muscle torque at fast (240 degrees s(-1)) versus slow (30 degrees s(-1)) speeds of movement, torque normalized to muscle cross-sectional area (specific tension), and absolute torque at fast speeds of movement were measured in 34 young healthy male and female short-, middle-, and long-distance runners. The relationship between the different measures of muscle function and the expression of myosin heavy chain (MyHC) isoforms using enzyme-histochemical and electrophoretic protein separation techniques were investigated. A significant correlation between the 240 degrees s(-1) vs 30 degrees s(-1) torque ratio and the relative area of the type II fibers and type II MyHC isoforms were observed in both the men (r=0.74; P<0.001) and the women (r=0.81; P<0.05). Thus, the present results confirm a significant relationship between in vivo human muscle function and the MyHC isoform expression in the contracting muscle.

Torque, myoeletric sygnal and heart rate responses during concentric and eccentric exercises in older men

“…The present results are very important because contribute to the knowledge regarding the influence of the muscular activity on the magnitude of the HR responses during eccentric and concentric exercises which has implications for rehabilitation and training, leading to a safer prescription of exercise from the cardiovascular point of view. In relation to the type of contraction, our results are in accordance with the literature, which reports that during eccentric action, higher torque values were observed 2,[4][5][6][7][8][9][10][11][12]19 despite the lower EMG values 5,9,11 when compared to concentric action. These results could be attributed to the additional contribution of the elastic components to force generation during eccentric contraction 19 and the higher unit motor activation during the concentric contraction 9 .…”

“…This reduction is more accentuated in type II fibers, which is considered a direct cause of decreased muscular strength and power 1 , mainly during muscular concentric action 2,3 . Although the eccentric action produces greater force than the concentric 2,[4][5][6][7][8][9][10][11][12] , some electromyographic evidence suggests that during eccentric activity neural inhibition occurs (i.e., the muscular fibers are not totally activated) and, consequently, there is a lower myoelectrical activity 10,11,13 . The literature reports that torque magnitude is also influenced by angular velocity, since during concentric exercise, a decrease in maximum voluntary torque is observed as consequence of higher angle acceleration for young 2,[6][7][8][14][15][16][17] and older subjects 18 .…”

“…Although the eccentric action produces greater force than the concentric 2,[4][5][6][7][8][9][10][11][12] , some electromyographic evidence suggests that during eccentric activity neural inhibition occurs (i.e., the muscular fibers are not totally activated) and, consequently, there is a lower myoelectrical activity 10,11,13 . The literature reports that torque magnitude is also influenced by angular velocity, since during concentric exercise, a decrease in maximum voluntary torque is observed as consequence of higher angle acceleration for young 2,[6][7][8][14][15][16][17] and older subjects 18 . On the other hand, there are conflicting results about angular velocity during eccentric action as different studies have found that torque development during eccentric actions remains similar 2 or increases from slow to fast angular velocities 5,19,20 .…”

Physiological role of myosin light and heavy chain isoforms in fast- and slow-twitch muscles: effect of exercise

“…It has been shown that exercise, depending on its character, induces differential expression of myosin protein isoforms in skeletal muscle [2]. Most exercise studies focus on the assessment of the composition of MyHC, because of its regulatory role in myosin ATPase activity and therefore in the velocity of muscle fiber shortening [5,9]. Only in a few studies has attention been paid to the simultaneous effect of exercise on the composition of MyHC and MyLC isoforms [23,27].…”

Análise comparativa da força, potência e fadiga muscular de crianças e adolescentes saudáveis e com mielomeningocele

“…O TR é utilizado principalmente para analisar grupos heterogêneos, uma vez que, permite minimizar as diferenças entre os indivíduos em relação à orientação e posicionamento das fibras musculares, às alavancas mecânicas formadas pela anatomia articular, à elasticidade dos músculos e tendões e ao recrutamento das unidades motoras (GÜR et al, 2003;BACK et al, 2008).…”