Response to sudden torques about ankle in man. IV. A functional role of alpha-gamma linkage.

Gottlieb, G. L.; Agarwal, Gyan C.; Jaeger, Robert J.

doi:10.1152/jn.1981.46.1.179

Cited by 40 publications

(26 citation statements)

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“…In the landing activity, such as occurred in DJ, it is thought that pre-activity is involved in the centrally preprogrammed motor commands of the required motor task (Melvill Jones and Watt 1971;Dietz et al 1981;Dyhre-Poulsen et al 1991;Gollhofer and Kyro¨la¨inen 1991) as well as the compensation for local muscular failure after fatigue (Horita et al 1996). Another function of the pre-activation is assumed to be an increased sensitivity of the muscle spindle via enhanced a-c coactivation to enhance the stretch reflexes, as suggested earlier (Gottlieb et al 1981). The stretch reflex has a compensatory role, enhancing muscle stiffness after yielding during stretch (Nichols and Houk 1976;Hoffer and Andreassen 1981;Allum and Mauritz 1984).…”

Section: Discussionmentioning

confidence: 91%

Interaction between pre-landing activities and stiffness regulation of the knee joint musculoskeletal system in the drop jump: implications to performance

Horita

Nicol

et al. 2002

European Journal of Applied Physiology

134

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The purpose of the present study was to investigate the interaction between the pre-landing activities and the stiffness regulation of the knee joint musculoskeletal system and the takeoff speed during a drop jump (DJ). Nine healthy male subjects performed a DJ test from the height of 50 cm. The surface electromyographic (EMG) activity of the vastus lateralis (VL) muscle was recorded to evaluate both the pre-landing and post-landing muscle activation levels. Simultaneous recording of the jumping motion and ground reaction force was performed by a high-speed video camera (100 frames x s(-1)), and a force platform was employed to allow joint moment analysis. Joint stiffness was calculated by a linear regression of the knee joint moment/angle relationship. Elasticity of the knee extensor muscle during DJ was estimated by means of a four-element muscle model consisting of a parallel elastic component, a series elastic component (SEC), a viscous damper, and a contractile element. DJ performance correlated positively with the positive peak power of the knee joint (P < 0.01) and with the moment of the knee joint at the end of stretch (P < 0.01). However, there was no significant relationship between DJ performance and the positive peak power of the ankle joint. The knee joint moment at the end of stretch correlated with the SEC stiffness during the transmission phase from the end of the initial impact to the onset of the concentric action (P < 0.01) and with the maximum rate of isometric force development of the knee extensors (P < 0.01). Multiple regression analysis showed that the SEC stiffness during the transmission phase of the knee joint can be explained by a combination of the pre-activity of the VL muscle and the knee joint angular velocity at touchdown (F = 5.76, P < 0.05). These results seem to emphasize the functional significance of the pre-programmed activity for controlling the subsequent stiffness regulation and then contributing to the performance in DJ. Thus, it can be suggested that the centrally pre-programmed activity and the associated elastic behavior of the SEC in the knee extensor muscle in conjunction with the muscle contractile property play a major role in regulating the performance in DJ.

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Section: Discussionmentioning

confidence: 91%

Interaction between pre-landing activities and stiffness regulation of the knee joint musculoskeletal system in the drop jump: implications to performance

Horita

Nicol

et al. 2002

European Journal of Applied Physiology

134

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“…As a further important aspect, muscle pre-activity is assumed to increase the sensitivity of muscle spindles (Matthews and Stein 1969) by enhancing the alpha-gamma co-activation, causing a potentiation of stretch-reflexes in the subsequent joint flexion phase (Gottlieb et al 1981). The higher sensitivity of muscle spindles leads to an increase in the excitation of type Ia afferents (Matthews 1984) and consequently to a facilitation of a-motoneurones, finally producing increased EMG activation in the involved extensor muscles.…”

Section: Discussionmentioning

confidence: 99%

Changes in upper body muscle activity with increasing double poling velocities in elite cross-country skiing

et al. 2009

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The purpose of this study was to investigate whether the stretch-shortening cycle (SSC) contraction is integrated in neuromuscular activation in upper body muscles during double poling in cross-country skiing. Thirteen elite skiers performed double poling roller-skiing at increasing treadmill velocities of 9, 15, 21, 27 km h(-1) and their individual maximal velocity. Elbow angle, axial pole force and surface EMG in the triceps brachii, pectoralis major, latissimus dorsi and teres major muscle were recorded. Increases in peak pole force, rate of force development and elbow flexion angular velocities were identified (P < 0.05). The mean MVC-normalized EMG amplitudes increased during the pre-activation phase before pole plant, elbow flexion and the reflex-mediated phase between 30 and 120 ms after pole plant due to velocity increases (P < 0.05). It is thus suggested that elite cross-country skiers use SSC during double poling, particularly in the triceps muscle in order to generate high forces.

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“…Horita et al, 1996). Furthermore, pre-activity is assumed to increase the sensitivity of the muscle spindle through enhanced alpha± gamma coactivation, thus potentiating stretch re¯exes (Gottlieb et al, 1981) and enhancing tendomuscular stiþ ness and performance (Nichols and Houk, 1976;Gollhofer et al, 1984;Kyr"l"inen et al, 1989).…”

Section: Discussionmentioning

confidence: 99%

Biomechanical loading in the triple jump

Perttunen¹,

Kyröläinen²,

Komi³

et al. 2000

Journal of Sports Sciences

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The triple jump is a demanding ® eld event in which a jumper must tolerate extremely high impact forces while maintaining high horizontal speed. The present study was designed to clarify the mechanical loading characteristics and the role of neuromuscular function in the triple jump. Seven national triple jumpers (4 males, 3 females) volunteered to perform 3± 6 jumps. The mean best performances were 14.32 ± 0.45 m and 11.90 ± 0.28 m for males and females, respectively. The three longest triple jumps for each jumper were selected for ® nal analysis. The mean contact times were 0.139 s (hop), 0.157 s (step) and 0.177 s (jump). The largest ground reaction forces were observed in the step (15.2 times body weight), while the highest peak pressures were recorded under the heel and forefoot. The plantar pressure of the lateral side of the forefoot was highly related to the length of the triple jump (P < 0.05± 0.01). In addition, electromyograms of both legs suggested that mechanical loading places high demands on the neuromuscular system, as characterized by the high rate of activation in the pre-activity phase followed by high eccentric activity. Thus, the high activities of the gastrocnemius, vastus lateralis and hip extensor muscles seem to play an important role in preventing unnecessary yielding of the jumper during the braking phase.

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Response to sudden torques about ankle in man. IV. A functional role of alpha-gamma linkage.

Cited by 40 publications

References 0 publications

Interaction between pre-landing activities and stiffness regulation of the knee joint musculoskeletal system in the drop jump: implications to performance

Interaction between pre-landing activities and stiffness regulation of the knee joint musculoskeletal system in the drop jump: implications to performance

Changes in upper body muscle activity with increasing double poling velocities in elite cross-country skiing

Biomechanical loading in the triple jump

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