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Biomedical subjects

F Goubel

Publications and source records attributed to F Goubel.

At least 19 recordsLinked to original sources
PubMed2000

Changes in stiffness induced by hindlimb suspension in rat Achilles tendon.

The aim of this study was to measure the effects of hindlimb suspension on mechanical properties of the rat Achilles tendon. Adult male Wistar rats were randomly assigned to groups to be either suspended, or a control. After 21 days, Achilles tendons were removed for mechanical analysis. Classical tests of tensile performance were made, and mechanical parameters were derived from a stress-strain relationship. The tendons of animals that had been suspended presented values for maximal stress and tangent modulus which were 37.5% (P < 0.01) and 41% (P < 0.01), respectively, lower than the tendons of the control rats. In a similar way, the energy absorption capacity had largely decreased in animals that had been suspended. However, the maximal strain was similar in the two groups. These results showed that hindlimb suspension in rats has an important detrimental effect on mechanical properties of the Achilles tendon. Differences in tendon stiffness obtained here, along with those found by other investigators, encourage the hypothesis that homeostatic responses of soft tissues are due to changes in limb loadings. This study may be useful in providing a better understanding of the adaptation of human skeletal muscle when exposed to microgravity.

Achilles Tendon↗
PubMed1999

The rat suspension model is also a good tool for inducing muscle hyperactivity.

The aim of the present study was to investigate changes in the mechanical characteristics of the rat epitrochlearis muscle as a result of a period of hyperactivity. A tail suspension model was used to impose postural activity in the forelimb musculature with the intention of inducing a relative slowness in the fast epitrochlearis muscle. A method of dual-controlled releases was used to obtain force-velocity and tension-extension relationships characterizing muscle mechanics. Results showed that: (1) mechanical characteristics are that of a fast-twitch muscle and (2) suspension induces a decrease in the maximal shortening velocity and a decrease in the compliance of series elastic elements. Changes in fibre type proportions are consistent with these mechanical adaptations. This demonstrates that an usual model of muscle hypoactivity can also be used for imposing hyperactivity of a postural nature, inducing muscle transformations towards a slower twitch muscle.

Animals↗
PubMed1999

Viscous properties of human muscle during contraction.

The purpose of this study was to determine viscous properties of human muscle during plantarflexion efforts. Experiments were performed on 17 subjects with an ankle ergometer allowing sinusoidal oscillations during isometric contractions and isokinetic movements. Sinusoidal oscillations led to the expression of (i) Bode diagrams of the musculo-articular system allowing the determination of a damping coefficient (Bbode); and (ii) a viscous coefficient (Bsin) using an adaptation of Hill's equation to sinusoidal oscillations. Isokinetic movements led to torque-velocity relationships. They showed a fall in torque associated to an increase in angular velocity what was quantified by calculating a damping coefficient (Biso). Both experiments gave consistent results indicating that Bbode was the lowest viscous parameter. This difference is discussed in terms of (i) "analog" viscosity originating from muscle cross-bridges; and (ii) real mechanical damping of passive structures.

Adult↗
PubMed1998

Stiffness of knee extensors in Duchenne muscular dystrophy.

The series elastic component (SEC) of Hill's muscle model is sensitive to a modification in muscle functional demand. In this study, SEC stiffness was quantified from quick-released movements in knee extensors of Duchenne muscular dystrophy (DMD) boys to look for possible modifications with the stage of disease. A SEC stiffness index (SI) was defined and was found significantly lower for controls than for DMD. Moreover, a linear relationship was established between mean SI and knee extensors involvement. This suggests a role for this parameter, together with other functional tests, for following patients with DMD.

Adolescent↗
PubMed1998

Effects of chronic low frequency stimulation on contractile and elastic properties of hindlimb suspended rat soleus muscle.

Chronic low frequency stimulation (10 Hz, 8 h x day[-1]) was used in this study to prevent the changes in the contractile and elastic properties of rat soleus muscles induced by 3 weeks of hindlimb suspension (HS). Results showed that electrostimulation was able to counteract in part the decrease in soleus muscle mass and tension output induced by unweighting. On the other hand, the increases in maximal shortening velocity and twitch speed following HS were not prevented by stimulation. Unweighting was responsible for an increase in series elastic compliance of soleus muscle. Chronic stimulation successfully counteracted this increase in series compliance probably by changing the properties of the tendon. The partial recovery of muscle mass and tension output as a result of stimulation enhanced the role of contractile activity in preventing muscle atrophy. Moreover, the inefficiency of the tonic activity imposed by stimulation in preventing the increase in twitch speed of soleus muscle during HS demonstrated the primacy of neuronal activity. Discrepant results concerning changes in contraction kinetics deduced from the twitch could have been due to the fact that such myograms also depend on the series compliance.

Animals↗
PubMed1997

Influence of plyometric training on the mechanical impedance of the human ankle joint.

The objective of this work was to study the effects of plyometric training on the mechanical properties of the ankle joint in humans. Changes in the mechanical parameters of this musculo-articular structure were quantified with the aid of a sinusoidal perturbation technique. This technique allowed the expression of the mechanical impedance of the musculo-articular system in terms of stiffness, viscosity and inertia. Measurements were performed under passive conditions and when the subject performed plantar flexion. A 7-week period of training induced a decrease in the slope of the relationship between stiffness and plantar flexion torque, whereas passive stiffness was increased. A slight decrease in viscosity and an invariability in inertia were also found. These results are interpreted in terms of the possible adaptations of the musculo-articular structure and ultrastructure involved in the performance of plantar flexion.

Adult↗
PubMed1997

A mechanical device for studying mechanical properties of human muscles in vivo.

A mechanical device, primarily devoted to biomechanical studies of human calf muscles during microgravity experiments is presented. It allows investigation of both contractile and visco-elastic properties of musculo-articular systems using, respectively, isokinetic movements, quick-release tests and sinusoidal perturbations. This device is a specifically designed ergometer associated to an experimental protocol designed for pre- and post-flight tests. The protocol was evaluated on 22 healthy subjects and typical results are briefly presented. Preliminary results are discussed in terms of agreement with currently available data and a detailed evaluation of test-retest measurements is provided for quick-release experiments. Complementary investigations are suggested and potential fields of research are indicated.

Ankle Joint↗
PubMed1997

Citrulline malate limits increase in muscle fatigue induced by bacterial endotoxins.

Citrulline malate is known to improve performance in weakened muscles. The present experiment was designed to test the hypothesis that citrulline malate can limit the effect of endotoxins on muscle fatigability. Endotoxemia was induced in rats by injection of lipopolysaccharides from Klebsiella pneumoniae. Resistance to fatigue was quantified by measuring tension production during repetitive electrical stimulation of the isolated epitrochlearis muscle. Oral treatment by citrulline malate was found to increase resistance to fatigue in infected rats, whereas twitch tension was not modified. This demonstrates the efficacy of citrulline malate for limiting an increase in muscle fatigue elicited with bacterial endotoxins.

Animals↗
PubMed1996

Neuromuscular adaptations in rats trained by muscle stretch-shortening.

The aim of this study was the analysis of neurophysiological, mechanical and histochemical parameters to demonstrate muscle adaptation with training. If the parameters studied were to show correlated changes, it would be possible to propose that the neural and the muscle components of motor units are both affected by the training programme used. The training consisted of repeated stretch-shortening cycles known to use extensively fast fibres. After the training period electromyographical reflex activities of the ankle plantar-flexors were recorded in awake rats and then mechanical and histochemical measurements were made on isolated soleus muscles of the control and trained rats. The reflexes studied were the H-response to electrical stimulation of the sciatic nerve and the T-response to an Achilles tendon tap. The H-response analysis indicated a decrease in reflex excitability of the trained muscles. The trained soleus muscle also presented a higher contractility as demonstrated by significantly smaller twitch contraction times and higher maximal velocities of shortening measured during tetanic contractions. The reflex and contractile muscle changes were accompanied by relative increases in the number of type II fibres. The T-response was not significantly modified by training despite the decrease in motoneuron excitability demonstrated by the decrease in H-response. This would suggest that the peripheral components of the reflex pathway such as tendon stiffness and/or spindle sensitivity might be modified by training. This would imply that both the motor and the sensory parts of a muscle are affected by training.

Adaptation, Physiological↗
PubMed1996

Reproducibility of kinetics of electromyogram spectrum parameters during dynamic exercise.

During incremental exercise on a cycle ergometer a study was made of the reproducibility of changes in electromyographic activity (EMG) of human quadriceps muscles. Seven subjects performed three periods of incremental exercise either every 2 weeks (G1: four subjects) or 6 weeks (G2: three subjects). Each test was normalized with respect to the maximal aerobic power (MAP) of the subject. It consisted of a quasilinear increase in mechanical power (from 20% to 100% MAP) during 8 min. For rectus femoris muscle activity, changes in total power spectrum (PEMG) and in mean power frequency (MPF) were fitted by a 3rd order polynomial function (named profile) and normalized with respect to the maximal value for PEMG and to the mean value for MPF. A curvilinear increase was found for PEMG. The MPF kinetics varied from one subject to another. These changes were either a continuous increase, or a continuous decrease, or an increase followed by a decrease. Only for G2, was MAP determined before each test in order to update the limits of the test. A good reproducibility of PEMG was shown by its mean magnitude [95.88%, (SD 3.92)] and by computing a mean correlation coefficient between profiles two by two [r2 = 0.948 (SD 0.028) n = 21]. Intraclass coefficient correlation (ICC) calculated for each subject indicated a high level of reproducibility for five of the seven subjects (ICC > 0.80). No clear effect of MAP updating on PEMG and MPF profile reproducibility was observed. Thus it is suggested that MPF kinetics may characterize a subject at a given moment while PEMG kinetics may illustrate a normal profile, and they may both characterize EMG changes for a population during incremental exercise.

Adult↗
PubMed1996

Surface electromyogram power spectrum changes in human leg muscles following 4 weeks of simulated microgravity.

Surface electromyogram (EMG) spectrum changes in human tibialis anterior (TA) and gastrocnemius medialis (GM) muscles were studied to investigate the effect of 4-week bed rest (BR) on muscle fatigability. An exhausting isometric test at 50% of the maximal voluntary contraction was performed by 12 clinically healthy men before and after BR. During this test, mean power frequency (MPF) calculated from surface EMG decreased linearly for TA and GM. When changes in MPF were expressed in terms of rate of decrease a significant difference appeared between TA and GM. Furthermore, as a result of BR, the shift in MPF increased significantly for GM (6.1% vs 10.4%) whereas it was not significantly changed for TA (28.6% vs 20.95%). Alterations in maximal torque were also observed with a more pronounced decrease for plantar-flexor (20.5%) compared with dorsiflexor (15.1%) muscles. These results would seen: to indicate that simulated microgravity preferentially affects muscles having an antigravity function.

Adult↗
PubMed1995

Relationship between muscle myosin isoforms and contractile features in rabbit fast-twitch denervated muscle.

The effects of 8-day-old rabbit fast-twitch gastrocnemius denervation on the type of myosin isoforms and on contractile features (maximum velocity Vmax and contraction time (CT) of the muscle were followed between 15 and 60 days postnatal. The myosin isoforms and the Vmax and CT values of the denervated gastrocnemius displayed large changes during this period. These changes, which led at 2 months postnatal to a muscle displaying the properties of a slow-twitch muscle did not occur in synchrony: complete conversion to slow-type myosin isoforms occurred only at 60 days postnatal, whereas complete conversion to slow-twitch Vmax and CT values occurred as soon as 35 days postnatal. The results address a new question concerning the relationship between muscle myosin and contractile features.

Aging↗
PubMed1995

Changes in stiffness induced by hindlimb suspension in rat soleus muscle.

Soleus muscle atrophy was induced by hind-limb suspension of rats for 3 weeks with the intention of inducing a relative increase in the percentage of fast-twitch fibres and assessing modifications in muscle stiffness. A method of dual controlled releases was used to obtain tension/extension curves and force/velocity relationships characterizing the mechanical behaviour of the soleus. Fibre typing was achieved by myofibrillar adenosine 5'-triphosphatase staining. Results showed that hindlimb suspension decreased the percentage of slow-twitch fibres (-31%) to the profit of fast-twitch fibres (+370%) and intermediate fibres (+255%). This led to an increase in maximal shortening velocity. Tension/extension curves indicated a decrease in soleus stiffness after 3 weeks of unloading. Changes in elastic properties are interpreted in terms of modifications occurring in the active part and the passive part of the so-called series elastic component. These changes also suggest that the parameters derived from a twitch are inappropriate to account for modifications in speed-related properties of muscle.

Adaptation, Physiological↗
PubMed1995

Endotoxins modify muscle fatigue characteristics.

To test the hypothesis that endotoxins can directly modify muscle fatigue characteristics, in vitro experiments were performed on rat muscles 48 hours after injection of lipopolysaccharides (LPS) from Klebsiella pneumoniae. Resistance to fatigue was quantified by measuring tension production during repetitive electrical stimulation of the isolated epitrochlearis muscle. LPS treatment did not significantly modify initial force production whereas fatigability of the muscle was increased. This in vitro preparation should be used for testing antifatigue drugs.

Animals↗
PubMed1995

Response to denervation of rabbit soleus and gastrocnemius muscles. Time-course study of postnatal changes in myosin isoforms, fiber types, and contractile properties.

In contrast to general belief, the response of rabbit muscles to denervation is maturation to slow-like type muscles [7]. We report now an investigation by biochemical, morphological, and mechanical studies of the time course effects of muscle denervation on the slow-type soleus and fast-type gastrocnemius to help elucidate the mechanism of maturation of rabbit denervated muscles to slow-like muscles. In both muscles, denervation induced selective progressive atrophy of most fast fibers and hypertrophy of many slow fibers which displayed wide Z-lines; this was accompanied by the appearance of hybrid LC1F- and LC1E-associated slow myosins. The percentage of slow myosins increased with age similarly in the contralateral and denervated soleus. On the other hand, the percentage of slow myosins remained low in the contralateral gastrocnemius, whereas it increased to 95% in the denervated gastrocnemius; in the denervated gastrocnemius, the percentage of slow myosins reached 50% at about 35 days postnatal. At this age, the maximal shortening velocity of the denervated gastrocnemius and its twitch contraction time were already those of a slow-type muscle. This suggests that in addition to myosin, other proteins contributed to the mechanical properties of the denervated gastrocnemius. Transformation of rabbit denervated muscles to slow-like type muscles, which are associated with a lower energy requirement and higher muscle endurance than fast-type muscles, may constitute an adequate model for human neuromuscular pathology.

Aging↗
PubMed1994

The effect of denervation on myosin isoform synthesis in rabbit slow-type and fast-type muscles during terminal differentiation. Denervation induces differentiation into slow-type muscles.

The soleus and gastrocnemius medialis of eight-day-old rabbits were denervated and the effects were examined after fifty-two days by biochemical, cytochemical and mechanical methods. The contralateral soleus exhibited the properties of slow-type muscle, namely a predominance of slow-type myosin isoforms and slow-type oxidative fibers, slow twitch and low maximal velocity for shortening. The contralateral gastrocnemius exhibited the properties of fast-type muscle, namely a predominance of fast-type myosin isoforms and fast-type non-oxidative fibers, fast twitch and high maximal velocity of shortening. Denervation of muscles caused the differentiation of the two muscles towards slow-type muscles. Both denervated soleus and gastrocnemius muscles exhibited a predominance of slow-type myosins (either the normal type, made up of slow heavy and light chains, or the hybrid type, made up of slow heavy and regulatory light chains and fast essential light chains), a predominance of slow-type fibers, and slow mechanical properties. Thus, innervation in rabbit appears to be a determining factor for differentiation into fast-type muscle, but it is not necessary for differentiation into slow-type muscle. This conclusion contradicts the findings of previous studies in rat and thus raises new questions concerning the role of nerves in controlling the expression of myosin isoforms and the differentiation of muscle fibers.

Animals↗
PubMed1994

Effects of stretch-shortening cycle training on mechanical properties and fibre type transition in the rat soleus muscle.

The effects of exercise training on mechanical properties and fibre type transitions have been investigated in rat soleus muscles. The exercise was a repetition of stretch-shortening cycles. A method of dual controlled releases was applied to obtain tension/extension curves, which characterize the elastic behaviour of the series elastic component (SEC), and the force/velocity relationship characterizing the contractile elements. Other contractile measurements included: contraction time (tc), half-relaxation time (t1/2) and twitch/tetanus ratio (Pt/Po). Additionally, the muscle fibre type composition was determined by a classical histochemical method. A 12-week period of training induced a significantly higher percentage of fast-twitch fibres and a lower percentage of slow-twitch fibres (P < 0.01). This fibre adaptation led to a significant (P < 0.01) decrease in tc and an increase in maximum shortening velocity (Vmax). An increase in compliance of the SEC was also observed. This elastic adaptation is interpreted in terms of modification of the active components of the SEC. All the histochemical and mechanical data presented in this study show that rat soleus muscles trained by stretch-shortening cycles acquired faster characteristics. Thus the results confirm that a slow-twitch to a fast-twitch fibre transition is obtainable in mature rats.

Animals↗