Search results for "soleus"

Joined effects of pennation angle and tendon compliance on fibre length in isometric contractions: a simulation study.

1998

The main purpose of this study was to investigate the joined behaviours of tendon and pennation angle during maximal isometric contractions. A musculotendon model of the human soleus muscle was simulated as a function of ankle joint position, which determines the soleus length. Analysis of the respective values of tendon length and pennation angle for various musculotendon lengths showed that the primary effects of tendon elasticity and pennation angle variation were to reduce the fibre length variations by absorption of the musculotendon lengthening. The efficiency of this reduction process was the highest at short soleus lengths and principally related to tendon length variations. Finally…

Mechanical and neural stretch responses of the human soleus muscle at different walking speeds

2009

During human walking, a sudden trip may elicit a Ia afferent fibre mediated short latency stretch reflex. The aim of this study was to investigate soleus (SOL) muscle mechanical behaviour in response to dorsiflexion perturbations, and to relate this behaviour to short latency stretch reflex responses. Twelve healthy subjects walked on a treadmill with the left leg attached to an actuator capable of rapidly dorsiflexing the ankle joint. Ultrasound was used to measure fascicle lengths in SOL during walking, and surface electromyography (EMG) was used to record muscle activation. Dorsiflexion perturbations of 6 deg were applied during mid-stance at walking speeds of 3, 4 and 5 km h(-1). At eac…

The Hoffmann reflex of human plantar foot muscles

1998

Electrical stimulation of the tibial nerve in the popliteal fossa evoked an M wave (10.9 ms) and a late reflex response (38.1 ms) in the plantar foot muscles of all 10 volunteers. The late response had a somewhat lower electrical threshold than the corresponding M wave (8.5 versus 9 mA), and reached a maximum of amplitude when the stimulus intensity was increased, but was strongly suppressed by further increased intensity. A more distal stimulation of the tibial nerve at the ankle shortened the onset latency of the M wave and lengthened that of the late response. The reflex was facilitated by activation of synergists and inhibited by activation of antagonists. We showed that the late respon…

The effects of immobilization on the quality of Achilles tendon in rats

2007

Immobilization of an Achilles tendon in a shortened position for 1 and 3 weeks did not change pyridinoline and mature collagen concentrations. Although a significant decrease in the biosynthesis of collagen was observed simultaneously in the soleus muscle of the same hindlimb, these results suggest that the stability of collagen provided by the nonreducible cross-link, pyridinoline, is not altered during this type of immobilization. The significance of stable cross-links for the known decrease in tensile strength during immobilization remains open.

Decreased motor unit firing rate and force control in older men

2006

Introduction Ageing is related to muscle atrophy that leads to decreases in muscle force. The largest changes are found in fast muscle fibres and fast force production, reducing the capability to recover from sudden balance disturbances. Also ageing-related decrease in force control has been found, as indicated by an increase in force fluctuations and motor unit (MU) firing variability (Galganski et al. 1993). Possibly due to differences in measurement protocols and muscles, the results concerning the effects of ageing on motor unit firing rate are, however, somewhat contradictory (for review, see Roos et al. 1997). The purpose of the present study was to investigate the age-related changes…

2020

Even though the acute effects of pre-exercise static stretching and dynamic muscle activity on muscular and functional performance have been largely investigated, their effects on the corticospinal pathway are still unclear. For that reason, this study examined the acute effects of 5×20 s of static stretching, dynamic muscle activity and a control condition on spinal excitability, corticospinal excitability and plantar flexor neuromuscular properties. Fifteen volunteers were randomly tested on separate days. Transcranial magnetic stimulation was applied to investigate corticospinal excitability by recording the amplitude of the motor-evoked potential (MEP) and the duration of the cortical s…

Synthesis and degradation of type IV collagen in rat skeletal muscle during immobilization in shortened and lengthened positions

2003

Aim:  Type IV collagen is a major protein in basement membranes surrounding and supporting skeletal muscle cells. In the present study, we tested the hypotheses that immobilization down-regulates synthesis and up-regulates degradation of type IV collagen in skeletal muscle. Methods:  mRNA level and concentration of type IV collagen as well as mRNA levels and activities of proteins involved in its degradation were analysed from soleus (SOL), gastrocnemius (GAS) and extensor digitorum longus muscles after immobilization in shortened and lengthened positions for 1, 3 and 7 days. Results:  Following immobilization, type IV collagen mRNA level was decreased in SOL and GAS suggesting down-regulat…

Effects of prolonged walking on neural and mechanical components of stretch responses in the human soleus muscle

2009

After repeated passive stretching, tendinous tissue compliance increases in the human soleus (SOL) muscle–tendon unit. During movement, such changes would have important consequences for neural and mechanical stretch responses. This study examined the existence of such effects in response to a 75 min walking intervention. Eleven healthy subjects walked on a treadmill at 4 km h−1 with a robotic stretch device attached to the left leg. Ultrasonography was used to measure SOL fascicle lengths, and surface EMG activity was recorded in the SOL and tibialis anterior (TA) muscles. Perturbations of 6 deg were imposed at three different measurement intervals: Pre (immediately before the walking inte…

Redox regulation of E3 ubiquitin ligases and their role in skeletal muscle atrophy

2015

Muscle atrophy is linked to reactive oxygen species (ROS) production during hindlimb-unloading due, at least in part, to the activation of xanthine oxidase (XO). The major aim of our study was to determine the mechanism by which ROS cause muscle atrophy and its possible prevention by allopurinol, a well-known inhibitor of XO widely used in clinical practice, and indomethacin, a nonsteroidal anti-inflammatory drug. We studied the activation of p38 MAP Kinase and NF-?B pathways, and the expression of two E3 ubiquitin ligases involved in proteolysis, the Muscle atrophy F-Box (MAFb) and Muscle RING Finger-1 (MuRF-1). Male Wistar rats (3 mold) conditioned by 14 days of hindlimb unloading (n=18),…

Age dependency of neuromuscular function and dynamic balance control

2010

Abstract The purpose of the present study was to examine whether static and dynamic balance control are related to neuromuscular function and ageing. For this purpose, we constructed a new dynamic balance measurement system that simulates natural falling. Ten young (age 21–31 years) and 20 elderly (age 60–70 years) men participated in the experiment. Maximal isometric torque (MVC) and activation level were measured from the quadriceps and plantar flexor muscles. The H-reflex, V-wave, and maximal M-wave were measured from the soleus muscle. In dynamic balance control, anterior-posterior centre-of-pressure swaying was 74±8.1 mm in the young men and 91.5±19.4 mm in the elderly men (P<0.05), wh…