Circadian Force and EMG Activity in Hindlimb Muscles of Rhesus Monkeys

2001 ◽  
Vol 86 (3) ◽  
pp. 1430-1444 ◽  
Author(s):  
J. A. Hodgson ◽  
S. Wichayanuparp ◽  
M. R. Recktenwald ◽  
R. R. Roy ◽  
G. McCall ◽  
...  
Keyword(s):  
Vastus Lateralis ◽  
Medial Gastrocnemius ◽  
Emg Activity ◽  
Activity Levels ◽  
Hindlimb Muscles ◽  
Cage Activity ◽  
Wide Range ◽  
Postural Muscle ◽  
Low Levels ◽  
Antagonistic Muscles

Continuous intramuscular electromyograms (EMGs) were recorded from the soleus (Sol), medial gastrocnemius (MG), tibialis anterior (TA), and vastus lateralis (VL) muscles of Rhesus during normal cage activity throughout 24-h periods and also during treadmill locomotion. Daily levels of MG tendon force and EMG activity were obtained from five monkeys with partial datasets from three other animals. Activity levels correlated with the light-dark cycle with peak activities in most muscles occurring between 08:00 and 10:00. The lowest levels of activity generally occurred between 22:00 and 02:00. Daily EMG integrals ranged from 19 mV/s in one TA muscle to 3339 mV/s in one Sol muscle: average values were 1245 (Sol), 90 (MG), 65 (TA), and 209 (VL) mV/s. The average Sol EMG amplitude per 24-h period was 14 μV, compared with 246 μV for a short burst of locomotion. Mean EMG amplitudes for the Sol, MG, TA, and VL during active periods were 102, 18, 20, and 33 μV, respectively. EMG amplitudes that approximated recruitment of all fibers within a muscle occurred for 5–40 s/day in all muscles. The duration of daily activation was greatest in the Sol [151 ± 45 (SE) min] and shortest in the TA (61 ± 19 min). The results show that even a “postural” muscle such as the Sol was active for only ∼9% of the day, whereas less active muscles were active for ∼4% of the day. MG tendon forces were generally very low, consistent with the MG EMG data but occasionally reached levels close to estimates of the maximum force generating potential of the muscle. The Sol and TA activities were mutually exclusive, except at very low levels, suggesting very little coactivation of these antagonistic muscles. In contrast, the MG activity usually accompanied Sol activity suggesting that the MG was rarely used in the absence of Sol activation. The results clearly demonstrate a wide range of activation levels among muscles of the same animal as well as among different animals during normal cage activity.

scholarly journals A Preliminary Study of Dynamic Muscle Function in Hereditary Ataxia

1980 ◽  
Vol 7 (4) ◽  
pp. 367-377 ◽  
Author(s):  
C. Richards ◽  
J.P. Bouchard ◽  
R. Bouchard ◽  
H. Barbeau
Keyword(s):  
Muscle Function ◽  
Autosomal Recessive ◽  
Normal Values ◽  
Vastus Lateralis ◽  
Dynamic Strength ◽  
Knee Extension ◽  
Emg Activity ◽  
Isokinetic Contractions ◽  
Preliminary Study ◽  
Antagonistic Muscles

SUMMARY:Dynamic muscle function was evaluated in nine patients with Friedreich's ataxia (FA) and eight with autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS). The measurement of torque throughout maximum voluntary isokinetic knee movements was used to quantitatively describe muscle weakness in the ataxic patients. Both FA and ARSACS patients were shown to have decreased dynamic strength in comparison to normal values during knee extension and flexion movements at 30% /s. In the FA patients a lower torqueproducing capacity was seen in the older patients.The electromyographic (EMG) activity was recorded in lower extremity muscles during the movements. In the vastus lateralis (VL), deviations from the normal EMG activation pattern were described in both groups of patients. A reduced amplitude in the EMG activity in the medial hamstrings (MH) was seen in the majority of the patients. An index of coactivation was defined by comparing the EMG activity when a muscle lengthened (antagonistic) to the EMG activity when the same muscle shortened (agonistic) during the isokinetic contractions. In comparison to normal values increased coactivation indexes were present in the VL and MH in patients of both groups. The characteristics of dynamic muscle strength and the activation of agonistic and antagonistic muscles described in the present study will provide the basis of evaluation for the effects of therapy in these patients.

An Electromyographical Analysis of the Role of Dorsiflexors on the Gait Transition during Human Locomotion

2001 ◽  
Vol 17 (4) ◽  
pp. 287-296 ◽  
Author(s):  
Alan Hreljac ◽  
Alan Arata ◽  
Reed Ferber ◽  
John A. Mercer ◽  
Brandi S. Row
Keyword(s):  
Tibialis Anterior ◽  
Walking Speed ◽  
Vastus Lateralis ◽  
Human Locomotion ◽  
Medial Gastrocnemius ◽  
Energetic Cost ◽  
Emg Activity ◽  
Gait Transition ◽  
Transition Speed ◽  
Preferred Transition Speed

Previous research has demonstrated that the preferred transition speed during human locomotion is the speed at which critical levels of ankle angular velocity and acceleration (in the dorsiflexor direction) are reached, leading to the hypothesis that gait transition occurs to alleviate muscular stress on the dorsiflexors. Furthermore, it has been shown that the metabolic cost of running at the preferred transition speed is greater than that of walking at that speed. This increase in energetic cost at gait transition has been hypothesized to occur due to a greater demand being placed on the larger muscles of the lower extremity when gait changes from a walk to a run. This hypothesis was tested by monitoring electromyographic (EMG) activity of the tibialis anterior, medial gastrocnemius, vastus lateralis, biceps femoris, and gluteus maximus while participants (6 M, 3 F) walked at speeds of 70, 80, 90, and 100% of their preferred transition speed, and ran at their preferred transition speed. The EMG activity of the tibialis anterior increased as walking speed increased, then decreased when gait changed to a run at the preferred transition speed. Concurrently, the EMG activity of all other muscles that were monitored increased with increasing walking speed, and at a greater rate when gait changed to a run at the preferred transition speed. The results of this study supported the hypothesis presented.

Locomotor and Reflex Adaptation After Partial Denervation of Ankle Extensors in Chronic Spinal Cats

2008 ◽  
Vol 100 (3) ◽  
pp. 1513-1522 ◽  
Author(s):  
Alain Frigon ◽  
Serge Rossignol
Keyword(s):  
Spinal Cord ◽  
Vastus Lateralis ◽  
Knee Extensor ◽  
Mean Amplitude ◽  
Emg Activity ◽  
Nerve Lesion ◽  
Hindlimb Muscles ◽  
Reflex Pathways ◽  
Before And After ◽  
Spinal Section

This work investigates the capacity of the spinal cord to generate locomotion after a complete spinal section and its ability to adapt its locomotor pattern after a peripheral nerve lesion. To study this intrinsic adaptive capacity, the left lateral gastrocnemius-soleus (LGS) nerve was sectioned in three cats that expressed a stable locomotion following a complete spinal transection. The electromyograph (EMG) of multiple hindlimb muscles and reflexes, evoked by stimulating the left tibial (Tib) nerve at the ankle, were recorded before and after denervation during treadmill locomotion. Following denervation, the mean amplitude of EMG bursts of multiple hindlimb muscles increased during locomotion, similar to what is found after an identical denervation in otherwise intact cats. Reflex changes were noted in ipsilateral flexors, such as semitendinosus and tibialis anterior, but not in the ipsilateral knee extensor vastus lateralis following denervation. The present results demonstrate that the spinal cord possesses the circuitry necessary to mediate increased EMG activity in multiple hindlimb muscles and also to produce changes in reflex pathways after a muscle denervation. The similarity of changes following LGS denervation in cats with an intact and transected spinal cord suggests that spinal mechanisms play a major role in the locomotor adaptation.

scholarly journals Modularity of Endpoint Force Patterns Evoked Using Intraspinal Microstimulation in Treadmill Trained and/or Neurotrophin-Treated Chronic Spinal Cats

2009 ◽  
Vol 101 (3) ◽  
pp. 1309-1320 ◽  
Author(s):  
Vanessa S. Boyce ◽  
Michel A. Lemay
Keyword(s):  
Muscle Activity ◽  
Vastus Lateralis ◽  
Biceps Femoris ◽  
Motor Output ◽  
Medial Gastrocnemius ◽  
Lumbar Spinal Cord ◽  
Intraspinal Microstimulation ◽  
Hindlimb Muscles ◽  
Spinal Motor ◽  
Lumbar Spinal

Chronic spinal cats with neurotrophin-secreting fibroblasts (NTF) transplants recover locomotor function. To ascertain possible mechanisms, intraspinal microstimulation was used to examine the lumbar spinal cord motor output of four groups of chronic spinal cats: untrained cats with unmodified-fibroblasts graft (Op-control) or NTF graft and locomotor-trained cats with unmodified-fibroblasts graft (Trained) or NTF graft (Combination). Forces generated via intraspinal microstimulation at different hindlimb positions were recorded and interpolated, generating representations of force patterns at the paw. Electromyographs (EMGs) of hindlimb muscles, medial gastrocnemius, tibialis anterior, vastus lateralis, and biceps femoris posterior, were also collected to examine relationships between activated muscles and force pattern types. The same four force pattern types obtained in spinal-intact cats were found in chronic spinal cats. Proportions of force patterns in spinal cats differed significantly from those in intact cats, but no significant differences in proportions were observed among individual spinal groups (Op-control, NTF, Trained, and Combination). However, the proportions of force patterns differed significantly between trained (Trained and Combination) and untrained groups (Op-control and NTF). Thus the frequency of expression of some response types was modified by injury and to a lesser extent by training. Force pattern laminar distribution differed in spinal cats compared with intact, with more responses obtained dorsally (0–1,000 μm) and fewer ventrally (3,200–5,200 μm). EMG analysis demonstrated that muscle activity highly predicted some force pattern types and was independent of hindlimb position. We conclude that spinal motor output modularity is preserved after injury.

scholarly journals Phase-Dependent Modulation of Percutaneously Elicited Multisegmental Muscle Responses After Spinal Cord Injury

2010 ◽  
Vol 103 (5) ◽  
pp. 2808-2820 ◽  
Author(s):  
Christine J. Dy ◽  
Yury P. Gerasimenko ◽  
V. Reggie Edgerton ◽  
Poul Dyhre-Poulsen ◽  
Grégoire Courtine ◽  
...  
Keyword(s):  
Spinal Cord ◽  
Spinal Cord Injury ◽  
Vastus Lateralis ◽  
Medial Gastrocnemius ◽  
Emg Activity ◽  
Step Cycle ◽  
Human Spinal Cord ◽  
Lumbosacral Spinal Cord ◽  
Weight Support ◽  
Cord Injury

Phase-dependent modulation of monosynaptic reflexes has been reported for several muscles of the lower limb of uninjured rats and humans. To assess whether this step-phase-dependent modulation can be mediated at the level of the human spinal cord, we compared the modulation of responses evoked simultaneously in multiple motor pools in clinically complete spinal cord injury (SCI) compared with noninjured (NI) individuals. We induced multisegmental responses of the soleus, medial gastrocnemius, tibialis anterior, medial hamstring, and vastus lateralis muscles in response to percutaneous spinal cord stimulation over the Th11–Th12 vertebrae during standing and stepping on a treadmill. Individuals with SCI stepped on a treadmill with partial body-weight support and manual assistance of leg movements. The NI group demonstrated phase-dependent modulation of evoked potentials in all recorded muscles with the modulation of the response amplitude corresponding with changes in EMG amplitude in the same muscle. The SCI group demonstrated more variation in the pattern of modulation across the step cycle and same individuals in the SCI group could display responses with a magnitude as great as that of modulation observed in the NI group. The relationship between modulation and EMG activity during the step cycle varied from noncorrelated to highly correlated patterns. These findings demonstrate that the human lumbosacral spinal cord can phase-dependently modulate motor neuron excitability in the absence of functional supraspinal influence, although with much less consistency than that in NI individuals.

scholarly journals Fracture risk across a wide range of physical activity levels, from sedentary individuals to elite athletes

Bone ◽  
2021 ◽  
pp. 116128
Author(s):  
Karl Stattin ◽  
Jonas Höijer ◽  
Ulf Hållmarker ◽  
John A. Baron ◽  
Susanna C. Larsson ◽  
...  
Keyword(s):  
Physical Activity ◽  
Fracture Risk ◽  
Elite Athletes ◽  
Activity Levels ◽  
Wide Range ◽  
Physical Activity Levels

scholarly journals Specific modulation of corticomuscular coherence during submaximal voluntary isometric, shortening and lengthening contractions

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Dorian Glories ◽  
Mathias Soulhol ◽  
David Amarantini ◽  
Julien Duclay
Keyword(s):  
H Reflex ◽  
Medial Gastrocnemius ◽  
Emg Activity ◽  
Beta Band ◽  
Lengthening Contractions ◽  
Time Frequency ◽  
Corticomuscular Coherence ◽  
Emg Signal ◽  
Voluntary Contractions ◽  
Spinal Excitability

AbstractDuring voluntary contractions, corticomuscular coherence (CMC) is thought to reflect a mutual interaction between cortical and muscle oscillatory activities, respectively measured by electroencephalography (EEG) and electromyography (EMG). However, it remains unclear whether CMC modulation would depend on the contribution of neural mechanisms acting at the spinal level. To this purpose, modulations of CMC were compared during submaximal isometric, shortening and lengthening contractions of the soleus (SOL) and the medial gastrocnemius (MG) with a concurrent analysis of changes in spinal excitability that may be reduced during lengthening contractions. Submaximal contractions intensity was set at 50% of the maximal SOL EMG activity. CMC was computed in the time–frequency domain between the Cz EEG electrode signal and the unrectified SOL or MG EMG signal. Spinal excitability was quantified through normalized Hoffmann (H) reflex amplitude. The results indicate that beta-band CMC and normalized H-reflex were significantly lower in SOL during lengthening compared with isometric contractions, but were similar in MG for all three muscle contraction types. Collectively, these results highlight an effect of contraction type on beta-band CMC, although it may differ between agonist synergist muscles. These novel findings also provide new evidence that beta-band CMC modulation may involve spinal regulatory mechanisms.

scholarly journals Non-Coding RNAs in the Transcriptional Network That Differentiates Skeletal Muscles of Sedentary from Long-Term Endurance- and Resistance-Trained Elderly

2021 ◽  
Vol 22 (4) ◽  
pp. 1539
Author(s):  
Paola De Sanctis ◽  
Giuseppe Filardo ◽  
Provvidenza Maria Abruzzo ◽  
Annalisa Astolfi ◽  
Alessandra Bolotta ◽  
...  
Keyword(s):  
Exercise Training ◽  
High Intensity ◽  
Vastus Lateralis ◽  
Mammalian Target Of Rapamycin ◽  
Differentially Expressed ◽  
Transcriptional Networks ◽  
Vastus Lateralis Muscle ◽  
Age Related ◽  
Wide Range ◽  
Non Coding Rnas

In a previous study, the whole transcriptome of the vastus lateralis muscle from sedentary elderly and from age-matched athletes with an exceptional record of high-intensity, life-long exercise training was compared—the two groups representing the two extremes on a physical activity scale. Exercise training enabled the skeletal muscle to counteract age-related sarcopenia by inducing a wide range of adaptations, sustained by the expression of protein-coding genes involved in energy handling, proteostasis, cytoskeletal organization, inflammation control, and cellular senescence. Building on the previous study, we examined here the network of non-coding RNAs participating in the orchestration of gene expression and identified differentially expressed micro- and long-non-coding RNAs and some of their possible targets and roles. Unsupervised hierarchical clustering analyses of all non-coding RNAs were able to discriminate between sedentary and trained individuals, regardless of the exercise typology. Validated targets of differentially expressed miRNA were grouped by KEGG analysis, which pointed to functional areas involved in cell cycle, cytoskeletal control, longevity, and many signaling pathways, including AMP-activated protein kinase (AMPK) and mammalian target of rapamycin (mTOR), which had been shown to be pivotal in the modulation of the effects of high-intensity, life-long exercise training. The analysis of differentially expressed long-non-coding RNAs identified transcriptional networks, involving lncRNAs, miRNAs and mRNAs, affecting processes in line with the beneficial role of exercise training.

Impaired oxygen delivery to muscle in chronic fatigue syndrome

1999 ◽  
Vol 97 (5) ◽  
pp. 603-608 ◽  
Author(s):  
Kevin K. MCCULLY ◽  
Benjamin H. NATELSON
Keyword(s):  
Chronic Fatigue Syndrome ◽  
Time Constant ◽  
Oxidative Metabolism ◽  
Oxygen Delivery ◽  
Specific Effect ◽  
Chronic Fatigue ◽  
Medial Gastrocnemius ◽  
Resonance Spectroscopy ◽  
Activity Levels ◽  
Fatigue Syndrome

The purpose of this study was to determine if chronic fatigue syndrome (CFS) is associated with reduced oxygen delivery to muscles. Patients with CFS according to CDC (Center for Disease Control) criteria (n = 20) were compared with normal sedentary subjects (n = 12). Muscle oxygen delivery was measured as the rate of post-exercise and post-ischaemia oxygen-haem resaturation. Oxygen-haem resaturation was measured in the medial gastrocnemius muscle using continuous-wavelength near-IR spectroscopy. Phosphocreatine resynthesis was measured simultaneously using 31P magnetic resonance spectroscopy. The time constant of oxygen delivery was significantly reduced in CFS patients after exercise (46.5±16 s; mean±S.D.) compared with that in controls (29.4±6.9 s). The time constant of oxygen delivery was also reduced (20.0±12 s) compared with controls (12.0±2.8 s) after cuff ischaemia. Oxidative metabolism was also reduced by 20% in CFS patients, and a significant correlation was found between oxidative metabolism and recovery of oxygen delivery. In conclusion, oxygen delivery was reduced in CFS patients compared with that in sedentary controls. This result is consistent with previous studies showing abnormal autonomic control of blood flow. Reduced oxidative delivery in CFS patients could be specifically related to CFS, or could be a non-specific effect of reduced activity levels in these patients. While these results suggest that reduced oxygen delivery could result in reduced oxidative metabolism and muscle fatigue, further studies will be needed to address this issue.

scholarly journals Energy cost and muscular activity required for propulsion during walking

2003 ◽  
Vol 94 (5) ◽  
pp. 1766-1772 ◽  
Author(s):  
Jinger S. Gottschall ◽  
Rodger Kram
Keyword(s):  
Body Weight ◽  
Muscular Activity ◽  
Metabolic Cost ◽  
Medial Gastrocnemius ◽  
Emg Activity ◽  
Horizontal Force ◽  
Normal Walking ◽  
The Mean ◽  
The Cost ◽  
Muscle Actions

We reasoned that with an optimal aiding horizontal force, the reduction in metabolic rate would reflect the cost of generating propulsive forces during normal walking. Furthermore, the reductions in ankle extensor electromyographic (EMG) activity would indicate the propulsive muscle actions. We applied horizontal forces at the waist, ranging from 15% body weight aiding to 15% body weight impeding, while subjects walked at 1.25 m/s. With an aiding horizontal force of 10% body weight, 1) the net metabolic cost of walking decreased to a minimum of 53% of normal walking, 2) the mean EMG of the medial gastrocnemius (MG) during the propulsive phase decreased to 59% of the normal walking magnitude, and yet 3) the mean EMG of the soleus (Sol) did not decrease significantly. Our data indicate that generating horizontal propulsive forces constitutes nearly half of the metabolic cost of normal walking. Additionally, it appears that the MG plays an important role in forward propulsion, whereas the Sol does not.

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