Electromechanical stimulation ameliorates inactivity-induced adaptations in the medial gastrocnemius of adult rats

2007 ◽  
Vol 103 (1) ◽  
pp. 195-205 ◽  
Author(s):  
Soo J. Kim ◽  
Roland R. Roy ◽  
Hui Zhong ◽  
Hideki Suzuki ◽  
Lusine Ambartsumyan ◽  
...  
Keyword(s):  
Rest Period ◽  
High Load ◽  
Medial Gastrocnemius ◽  
Isometric Contractions ◽  
Adult Rats ◽  
Functional Deficits ◽  
Fiber Size ◽  
Chain Composition ◽  
Myosin Heavy Chain Composition ◽  
Tetanic Tension

The efficacy of high-load, short-duration isometric contractions, delivered as one vs. two sessions per day, on blunting inactivity-induced adaptations in the medial gastrocnemius (MG) were compared. Adult rats were assigned to a control (Con) or spinal cord-isolated (SI) group where one limb was stimulated (SI-Stim) while the other served as a SI control (SI-C). One bout of stimulation (BION microstimulator) consisted of a 100-Hz, 1-s stimulus, delivered every 30 s for 5 min with a 5-min rest period. This bout was repeated six times consecutively (SI-Stim1) or with a 9-h rest interval after the third bout (SI-Stim2) for 30 consecutive days. MG weights (relative to body weight) were 63, 72, and 79% of Con in SI-C, SI-Stim1, and SI-Stim2, respectively. Mean fiber size was 56% smaller in SI-C than in Con, and it was 19 and 31% larger in SI-Stim1 and SI-Stim2, respectively, compared with SI-C. Maximum tetanic tension was 42, 60, and 73% of Con in SI-C, SI-Stim1, and SI-Stim2, respectively. Specific tension was 77% of Con in SI-C, and at Con levels in both SI-Stim groups. SI increased the percent IIb myosin heavy chain composition (from 49 to 77%) and IIb+ fibers (from 63 to 79%): these adaptations were prevented by both Stim paradigms. These results demonstrate that 1) brief periods of high-load isometric contractions are effective in reducing inactivity-induced atrophy, functional deficits, and phenotypic adaptations in a fast hindlimb extensor, and 2) the same amount of stimulation distributed in two compared with one session per day is more effective in ameliorating inactivity-related adaptations.

MYOSIN HEAVY CHAIN COMPOSITION AND FIBER SIZE IN HUMAN LEG MUSCLES UNDERGOING LIMB SUSPENSION

1998 ◽  
Vol 30 (Supplement) ◽  
pp. 38
Author(s):  
K. R. Short ◽  
M. Sheffield-Moore ◽  
A. C. Parcell ◽  
W. J. Fink ◽  
S. W. Trappe ◽  
...  
Keyword(s):  
Myosin Heavy Chain ◽  
Heavy Chain ◽  
Leg Muscles ◽  
Fiber Size ◽  
Chain Composition ◽  
Myosin Heavy Chain Composition

scholarly journals Gene expression during inactivity-induced muscle atrophy: effects of brief bouts of a forceful contraction countermeasure

2008 ◽  
Vol 105 (4) ◽  
pp. 1246-1254 ◽  
Author(s):  
Soo J. Kim ◽  
Roland R. Roy ◽  
Jung A. Kim ◽  
Hui Zhong ◽  
Fadia Haddad ◽  
...  
Keyword(s):  
High Resistance ◽  
Muscle Protein ◽  
Critical Role ◽  
Ring Finger ◽  
Specific Protein ◽  
Medial Gastrocnemius ◽  
Minor Role ◽  
Isometric Contractions ◽  
Adult Rats ◽  
A Minor

Anabolic and catabolic markers of muscle protein metabolism were examined in inactivity-induced atrophying muscles with and without daily short-duration, high-resistance isometric contractions. Inactivity was achieved via spinal cord isolation (SI), which results in near inactivity of the hindlimb musculature without compromising the motoneuron-muscle connectivity. Adult rats were assigned to a control (Con) or SI group in which one limb was stimulated (SI-Stim, 5 consecutive days of brief bouts of high-load isometric contractions) while the other served as a SI control (SI). Both the medial gastrocnemius (MG) and soleus weights (relative to body weight) were ∼71% of Con in the SI, but maintained at Con in the SI-Stim group. Activity of the IGF-1/phosphatidylinositol 3-kinase (PI3K)/Akt pathway of protein synthesis was similar among all groups in the MG. Expression of atrogin-1 and muscle RING finger-1 (MuRF-1), markers of protein degradation, were higher in the MG and soleus of the SI than Con and maintained at Con in the SI-Stim. Compared with Con, the anti-growth factor myostatin was unaffected in the MG and soleus in the SI but was lower in the MG of the SI-Stim. These results demonstrate that upregulation of specific protein catabolic pathways plays a critical role in SI-induced atrophy, while this response was blunted by 4 min of daily high-resistance electromechanical stimulation and was able to preserve most of the muscle mass. Although the protein anabolic pathway (IGF-1/PI3K/Akt) appears to play a minor role in regulating mass in the SI model, increased translational capacity may have contributed to mass preservation in response to isometric contractions.

Effects of increased occlusal vertical dimension on daily activity and myosin heavy chain composition in rat jaw muscle

2009 ◽  
Vol 54 (8) ◽  
pp. 783-789 ◽  
Author(s):  
Yoshiki Ohnuki ◽  
Nobuhiko Kawai ◽  
Eiji Tanaka ◽  
Geerling E.J. Langenbach ◽  
Kazuo Tanne ◽  
...  
Keyword(s):  
Myosin Heavy Chain ◽  
Heavy Chain ◽  
Daily Activity ◽  
Vertical Dimension ◽  
Jaw Muscle ◽  
Chain Composition ◽  
Occlusal Vertical Dimension ◽  
Myosin Heavy Chain Composition

scholarly journals Absence of lateral gastrocnemius activity and differential motor unit behavior in soleus and medial gastrocnemius during standing balance

2014 ◽  
Vol 116 (2) ◽  
pp. 140-148 ◽  
Author(s):  
Martin E. Héroux ◽  
Christopher J. Dakin ◽  
Billy L. Luu ◽  
John Timothy Inglis ◽  
Jean-Sébastien Blouin
Keyword(s):  
Firing Rate ◽  
Motor Unit ◽  
Standing Position ◽  
Standing Balance ◽  
Triceps Surae ◽  
Medial Gastrocnemius ◽  
Isometric Contractions ◽  
Functional Requirements ◽  
Vertical Projection ◽  
Lateral Gastrocnemius

In a standing position, the vertical projection of the center of mass passes in front of the ankle, which requires active plantar-flexor torque from the triceps surae to maintain balance. We recorded motor unit (MU) activity in the medial (MG) and lateral (LG) gastrocnemius muscle and the soleus (SOL) in standing balance and voluntary isometric contractions to understand the effect of functional requirements and descending drive from different neural sources on motoneuron behavior. Single MU activity was recorded in seven subjects with wire electrodes in the triceps surae. Two 3-min standing balance trials and several ramp-and-hold contractions were performed. Lateral gastrocnemius MU activity was rarely observed in standing. The lowest thresholds for LG MUs in ramp contractions were 20–35 times higher than SOL and MG MUs ( P < 0.001). Compared with MUs from the SOL, MG MUs were intermittently active ( P < 0.001), had higher recruitment thresholds ( P = 0.022), and greater firing rate variability ( P < 0.001); this difference in firing rate variability was present in standing balance and isometric contractions. In SOL and MG MUs, both recruitment of new MUs ( R2 = 0.59–0.79, P < 0.01) and MU firing rates ( R2 = 0.05–0.40, P < 0.05) were associated with anterior-posterior and medio-lateral torque in standing. Our results suggest that the two heads of the gastrocnemius may operate in different ankle ranges with the larger MG being of primary importance when standing, likely due to its fascicle orientation. These differences in MU discharge behavior were independent of the type of descending neural drive, which points to a muscle-specific optimization of triceps surae motoneurons.

scholarly journals Neuromuscular Control of the Knee during a Resisted Single-Limb Squat Exercise

2005 ◽  
Vol 33 (10) ◽  
pp. 1520-1526 ◽  
Author(s):  
Richard K. Shields ◽  
Sangeetha Madhavan ◽  
Emy Gregg ◽  
Jennifer Leitch ◽  
Ben Petersen ◽  
...  
Keyword(s):  
Body Weight ◽  
Knee Joint ◽  
Knee Flexion ◽  
Neuromuscular Control ◽  
Biceps Femoris ◽  
Medial Gastrocnemius ◽  
Isometric Contractions ◽  
Low Resistance ◽  
Squat Exercise ◽  
Flexion And Extension

Background Closed kinetic chain exercises such as single-limb squats are preferred for knee rehabilitation. A complete understanding of the neuromuscular control of the knee during the single-limb squat is essential to increase the efficiency of rehabilitation programs. Hypothesis Performing a controlled single-limb squat with resistance to knee flexion and extension will increase the coactivation of the hamstring muscle group, thus reducing the quadriceps/hamstrings ratio. Study Design Descriptive laboratory study. Methods A total of 15 healthy human subjects (7 women, 8 men) performed controlled single-limb squats in a custom mechanical device that provided resistance to both flexion and extension. Subjects performed the task at 3 levels of resistance, set as a percentage of body weight. Surface electromyographic recordings from 7 muscles (gluteus medius, rectus femoris, vastus medialis oblique, vastus lateralis, biceps femoris, semitendinosus, and medial gastrocnemius) were collected during the task. Results Biceps femoris activity during knee flexion increased from approximately 12% maximum voluntary isometric contractions during low resistance (0% body weight) to approximately 27% maximum voluntary isometric contractions during high resistance (8% body weight). Although the quadriceps had greater activity than the hamstrings at all levels of resistance, the quadriceps/hamstrings ratio declined significantly with resistance (F2,27 = 29.05; P=. 012) from 3.0 at low resistance to 2.32 at the highest resistance. Conclusions Performing controlled resisted single-limb squats may help to simultaneously strengthen the quadriceps and facilitate coactivation of the hamstrings, thus reducing anterior tibial shear forces. The coactivation may also increase the dynamic control of the knee joint. Clinical Relevance The typical single-limb squat exercise performed in the clinic does not usually control for bidirectional resistance and knee joint excursion. As seen in this study, controlled single-limb squats at increased levels of resistance help to increase the coactivation of the hamstring muscles, which is essential to optimize neuromuscular control of the knee.

Effects of inactivity on myosin heavy chain composition and size of rat soleus fibers

1998 ◽  
Vol 21 (3) ◽  
pp. 375-389 ◽  
Author(s):  
Elena J. Grossman ◽  
Roland R. Roy ◽  
Robert J. Talmadge ◽  
Hui Zhong ◽  
V. Reggie Edgerton
Keyword(s):  
Myosin Heavy Chain ◽  
Heavy Chain ◽  
Chain Composition ◽  
Myosin Heavy Chain Composition
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