Biomedical subjects

Christophe Cornu

Publications and source records attributed to Christophe Cornu.

4 recordsLinked to original sources

PubMed2006

Acute effects of static stretching on passive stiffness of the hamstring muscles calculated using different mathematical models.

BACKGROUND: The aim of this study was to assess the effects of static stretching on hamstring passive stiffness calculated using different data reduction methods. METHODS: Subjects performed a maximal range of motion test, five cyclic stretching repetitions and a static stretching intervention that involved five 30-s static stretches. A computerised dynamometer allowed the measurement of torque and range of motion during passive knee extension. Stiffness was then calculated as the slope of the torque-angle relationship fitted using a second-order polynomial, a fourth-order polynomial, and an exponential model. The second-order polynomial and exponential models allowed the calculation of stiffness indices normalized to knee angle and passive torque, respectively. FINDINGS: Prior to static stretching, stiffness levels were significantly different across the models. After stretching, while knee maximal joint range of motion increased, stiffness was shown to decrease. Stiffness decreased more at the extended knee joint angle, and the magnitude of change depended upon the model used. After stretching, the stiffness indices also varied according to the model used to fit data. Thus, the stiffness index normalized to knee angle was found to decrease whereas the stiffness index normalized to passive torque increased after static stretching. INTERPRETATION: Stretching has significant effects on stiffness, but the findings highlight the need to carefully assess the effect of different models when analyzing such data.

Adaptation, Physiological↗

PubMed2004

Human muscle hardness assessment during incremental isometric contraction using transient elastography.

The aim of this study was to investigate the relationship between biceps brachii hardness using the transient elastography technique, and its activity level by quantifying the surface electromyographic signal (sEMG). Ten healthy subjects volunteered for this protocol. To assess the maximal biceps brachii myoelectric activity (sEMG-RMSm), subjects had to achieve their maximal voluntary contraction trial during an elbow flexion effort. They were then asked to perform an isometric biceps sEMG-RMS ramp trial in elbow flexion from 0% to 50% of their sEMG-RMSm in 120 s. A low-frequency pulse was sent every 5 s during all trials by an innovative shear elasticity probe previously placed over the belly of the biceps brachii allowing the calculation of a transverse shear modulus. The main results of this study were (i) the finding of a systematic linear relationship between the biceps brachii transverse shear moduli and the corresponding sEMG-RMS values. This was not the case when plotting transverse shear modulus versus the elbow flexion torque production. Therefore, the computation of a hardness index from the slope of individual transverse shear modulus-sEMG-RMS linear relationship was enabled; (ii) It was also found that the higher is the rest shear modulus, the lower is the hardness index, indicating that the transverse shear modulus change during contraction depends on its level at rest. Therefore, this non-invasive technique could be useful in the medical field to explore deep muscles which are unreachable by classical testing methods. It could also be applied for the follow-up of neuromuscular diseases inducing stiffness changes such as in Duchenne muscular dystrophy.

Adult↗

PubMed2002

Barcelona 2002: law, ethics, and human rights. Toward a more meaningful involvement of people living with HIV/AIDS.

All too often, the involvement of people living with HIV/AIDS in AIDS NGOs is tokenistic rather than meaningful. This article, which is based on a presentation by Chistophe Cornu (abstract WeOrG1292), demonstrates that, under the right conditions, the involvement of people living with HIV/AIDS can be beneficial both for the individuals and for the NGOs. The article describes the beneficial impacts of involvement observed in a study conducted in Burkina Faso, Ecuador, India, and Zambia. It also discusses the harmful effects of involvement, for individuals as well as NGOs, identified by study participants. The article concludes with a series of recommendations for NGOs to maximize the benefits of involvement.

Activities of Daily Living↗

PubMedDate not supplied

A methodologic approach for the comparison between dynamic contractions: influences on the neuromuscular system.

CONTEXT: Although isotonic and isokinetic exercises are commonly used in sports medicine and rehabilitation, studies comparing their effects on the neuromuscular system have provided conflicting results. OBJECTIVE: To compare responses of the neuromuscular system to isotonic and isokinetic contractions by controlling the total external amount of work performed and the mean angular movement velocity. DESIGN: A familiarization session was followed by isotonic and isokinetic sessions of tests performed on an isokinetic dynamometer. Each subject participated in 3 sessions. SETTING: A sport sciences research laboratory. PATIENTS OR OTHER PARTICIPANTS: Nine healthy adult males with no history of knee injury. INTERVENTION(S): The isotonic session consisted of 3 sets of 8 knee extensions at 80% of each subject's maximal voluntary isotonic contraction. The isokinetic session involved 3 sets of n knee extensions at a preset velocity equivalent to the mean velocity measured during the corresponding isotonic sets; n represented the number of repetitions subjects had to achieve to equalize the total external amount of work performed during the corresponding isotonic sets. MAIN OUTCOME MEASURE(S): We recorded mechanical parameters, n, and surface electromyographic signals from the vastus medialis, rectus femoris, and vastus lateralis muscles. Then root mean square, mean power frequency, and neuromuscular efficiency values were calculated for each repetition. RESULTS: As expected, the total external amount of work and mean angular velocity were similar between the isotonic and isokinetic sessions. The number of repetitions performed was equivalent in both sessions. In addition, although no "shift" of mean power frequency occurred, mean neuromuscular efficiency decreased linearly with repetitions for both modes in no differentiated way. CONCLUSIONS: Standardization of isotonic and isokinetic contractions based on total external amount of work and movement velocity is possible. This method can be applied by future investigators aiming to compare chronic effects of these 2 contraction modes on the neuromuscular system.

Journal Article↗