Load-Specific Distribution of Muscle Activity in Human Triceps Surae Muscles

During human walking, muscle activation strategies are approximately constant across consecutive steps over a short time, but it is unknown whether they are maintained over a longer duration. Prolonged walking may increase tendinous tissue (TT) compliance, which can influence neural activation, but the neural responses of individual muscles have not been investigated. This study investigated the hypothesis that muscle activity is up- or down-regulated in individual triceps surae muscles during prolonged walking. Thirteen healthy subjects walked on a treadmill for 60 min at 4.5 km/h, while triceps surae muscle activity, maximal muscle compound action potentials, and kinematics were recorded every 5 min, and fascicle lengths were estimated at the beginning and end of the protocol using ultrasound. After 1 h of walking, soleus activity increased by 9.3 ± 0.2% ( P < 0.05) and medial gastrocnemius activity decreased by 9.3 ± 0.3% ( P < 0.01). Gastrocnemius fascicle length at ground contact shortened by 4.45 ± 0.99% ( P < 0.001), whereas soleus fascicle length was unchanged ( P = 0.988). Throughout the stance phase, medial gastrocnemius fascicle lengthening decreased by 44 ± 13% ( P < 0.001), whereas soleus fascicle lengthening amplitude was unchanged ( P = 0.650). The data suggest that a compensatory neural strategy exists between triceps surae muscles and that changes in muscle activation are generally mirrored by changes in muscle fascicle length. These findings also support the notion of muscle-specific changes in TT compliance after prolonged walking and highlight the ability of the CNS to maintain relatively constant movement patterns in spite of neuromechanical changes in individual muscles.

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Fatigue responses of human triceps surae muscles during repetitive maximal isometric contractions

Journal of Applied Physiology ◽

10.1152/jappl.2000.88.6.1969 ◽

2000 ◽

Vol 88 (6) ◽

pp. 1969-1975 ◽

Cited By ~ 69

Author(s):

Yasuo Kawakami ◽

Kenji Amemiya ◽

Hiroaki Kanehisa ◽

Shigeki Ikegawa ◽

Tetsuo Fukunaga

Keyword(s):

Plantar Flexion ◽

Triceps Surae ◽

Peripheral Fatigue ◽

Isometric Contractions ◽

Electromyographic Activity ◽

Full Extension ◽

Flexor Muscles ◽

Human Triceps Surae ◽

Triceps Surae Muscles ◽

Plantar Flexor Muscles

Nine healthy men (22–45 yr) completed 100 repetitive maximal isometric contractions of the ankle plantar flexor muscles in two knee positions of full extension (K0) and flexion at 90° (K90), positions that varied the contribution of the gastrocnemii. Electromyographic activity was recorded from the medial and lateral gastrocnemii and soleus muscles by using surface electrodes. Plantar flexion torque in K0 was greater and decreased more rapidly than in K90. The electromyographic amplitude decreased over time, and there were no significant differences between muscles and knee joint positions. The level of voluntary effort, assessed by a supramaximal electrical stimulation during every 10th contraction, decreased from 96 to 70% ( P < 0.05) with no difference between K0 and K90. It was suggested that a decrease in plantar flexion torque was attributable to both central and peripheral fatigue and that greater fatigability in K0 than in K90 would result from a greater contribution and hence more pronounced fatigue of the gastrocnemius muscle. Further support for this possibility was provided from changes in twitch torque.

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Strain distribution within human triceps surae muscles during isometric contraction: in vivo study by Tagging MRI

The FASEB Journal ◽

10.1096/fasebj.22.1_supplement.753.24 ◽

2008 ◽

Vol 22 (S1) ◽

Author(s):

Toshiaki Oda ◽

Ryuta Kinugasa ◽

Mayoran Rajendra ◽

Ryutaro Himeno ◽

Hiroyuki Kataoka ◽

...

Keyword(s):

Isometric Contraction ◽

Strain Distribution ◽

Triceps Surae ◽

In Vivo Study ◽

Human Triceps Surae ◽

Triceps Surae Muscles ◽

Tagging Mri

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Inhibition of electromyographic activity in human triceps surae muscles during sinusoidal rotation of the foot.

Journal of Neurology Neurosurgery & Psychiatry ◽

10.1136/jnnp.38.4.336 ◽

1975 ◽

Vol 38 (4) ◽

pp. 336-345 ◽

Cited By ~ 3

Author(s):

W Freedman ◽

R Herman

Keyword(s):

Triceps Surae ◽

Electromyographic Activity ◽

Human Triceps Surae ◽

Triceps Surae Muscles

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The mechanical effectiveness of short latency reflexes in human triceps surae muscles revealed by ischaemia and vibration

Experimental Brain Research ◽

10.1007/bf00239584 ◽

1982 ◽

Vol 48 (1) ◽

Cited By ~ 21

Author(s):

J.H.J. Allum ◽

K.-H. Mauritz ◽

H. V�gele

Keyword(s):

Short Latency ◽

Triceps Surae ◽

Human Triceps Surae ◽

Triceps Surae Muscles

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Architectural and functional features of human triceps surae muscles during contraction

Journal of Applied Physiology ◽

10.1152/jappl.1998.85.2.398 ◽

1998 ◽

Vol 85 (2) ◽

pp. 398-404 ◽

Cited By ~ 328

Author(s):

Yasuo Kawakami ◽

Yoshiho Ichinose ◽

Tetsuo Fukunaga

Keyword(s):

Plantar Flexion ◽

Triceps Surae ◽

Passive Condition ◽

Human Triceps Surae ◽

Functional Features ◽

The Subject ◽

Triceps Surae Muscles ◽

Ultrasonic Images ◽

Elastic Characteristics

Architectural properties of the triceps surae muscles were determined in vivo for six men. The ankle was positioned at 15° dorsiflexion (−15°) and 0, 15, and 30° plantar flexion, with the knee set at 0, 45, and 90°. At each position, longitudinal ultrasonic images of the medial (MG) and lateral (LG) gastrocnemius and soleus (Sol) muscles were obtained while the subject was relaxed (passive) and performed maximal isometric plantar flexion (active), from which fascicle lengths and angles with respect to the aponeuroses were determined. In the passive condition, fascicle lengths changed from 59, 65, and 43 mm (knee, 0°; ankle, −15°) to 32, 41, and 30 mm (knee, 90° ankle, 30°) for MG, LG, and Sol, respectively. Fascicle shortening by contraction was more pronounced at longer fascicle lengths. MG had greatest fascicle angles, ranging from 22 to 67°, and was in a very disadvantageous condition when the knee was flexed at 90°, irrespective of ankle positions. Different lengths and angles of fascicles, and their changes by contraction, might be related to differences in force-producing capabilities of the muscles and elastic characteristics of tendons and aponeuroses.

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