Controlled intermittent shortening contractions of a muscle–tendon complex: muscle fibre damage and effects on force transmission from a single head of rat EDL

Abstract

This study was performed to examine effects of prolonged (3 h) intermittent shortening (amplitude 2 mm) contractions (muscles were excited maximally) of head III of rat extensor digitorum longus muscle (EDL III) on indices of muscle damage and on force transmission within the intact anterior crural compartment. Three hours after the EDL III exercise, muscle fibre damage, as assessed by immunohistochemical staining of structural proteins (i.e. dystrophin, desmin, titin, laminin-2), was found in EDL, tibialis anterior (TA) and extensor hallucis longus (EHL) muscles. The damaged muscle fibres were not uniformly distributed throughout the muscle cross-sections, but were located predominantly near the interface of TA and EDL muscles as well as near intra-and extramuscular neurovascular tracts. In addition, changes were observed in desmin, muscle ankyrin repeat protein 1, and muscle LIM protein gene expression: significantly (P<0.01) higher (1.3, 45.5 and 2.3-fold, respectively) transcript levels compared to the contralateral muscles. Post-EDL III exercise, length-distal force characteristics of EDL III were altered significantly (P<0.05): at high EDL III lengths, active forces decreased and the length range between active slack length and optimum length increased. For all EDL III lengths tested, proximal passive and active force of EDL decreased. The slope of the EDL III length-TA+EHL force curve decreased, which indicates a decrease of the degree of intermuscular interaction between EDL III and TA+EHL. It is concluded that prolonged intermittent shortening contractions of a single head of multi-tendoned EDL muscle results in structural damage to muscle fibres as well as altered force transmission within the compartment. A possible role of myofascial force transmission is discussed.

Effects of fatiguing jumping exercise on mRNA expression of titin-complex proteins and calpains

“…MLP interacts with titin through T-cap. In rodents, increased mRNA expression of MLP has been observed 6 h after lengthening muscle actions (5) and 3 h after prolonged concentric contractions (34). In the present study, the increase in the mRNA levels of MLP was observed 2 days postexercise.…”

“…This is the first study to show increased CARP mRNA expression after physical exercise in human skeletal muscle. In rodents, increased mRNA expression CARP has been observed 6 h after lengthening muscle actions (5) and 3 h after prolonged concentric contractions (34). We observed increased CARP mRNA expression as early as 30 min postexercise, which can be regarded as an extremely rapid response.…”

Torque–EMG–velocity relationship in female workers with chronic neck muscle pain

“…However this resulted in significantly lower torque only during the latter. High shear forces of the muscle connective tissue has been suggested to occur especially during eccentric (Kjaer, 2004) but also concentric contraction (Maas et al, 2005). Together, this may explain that differences were more consistent during slow concentric and eccentric contraction.…”

“…Isokinetic dynamometry at various contraction modes and velocities as opposed to static contraction alone can be used to more completely evaluate strength capacity. Both concentric and eccentric contractions have been suggested to involve high shear forces of the muscle connective tissue (Maas et al, 2005;Kjaer, 2004). Furthermore, concentric compared with static contraction involves higher cross-bridge cycling rate, energy expenditure and fatigue (Woledge et al, 1985;Vedsted et al, 2003), and eccentric contraction has been associated with ultra-structural muscle damage (Proske and Allen, 2005).…”

A semiautomatic method for in vivo three-dimensional quantitative analysis of fascial layers mobility based on 3D ultrasound scans

“…Several studies have hypothesized the key role of deep fascia in coordinating muscular activity [42], and in the literature, there is growing evidence [43][44][45][46] that this tissue plays a role in "limb stability, force transmission, and elastic energy storage during locomotion." In the past years, many efforts have been made to develop biomechanical models to assist in deciphering the fascia function and help in understanding how alterations of the deep fascia can result in musculoskeletal disorders and pain [3,18,[46][47][48].…”