Neuromuscular characteristics in trained vs. sedentary male adults with intellectual disability.

BACKGROUND: This study aimed to explore muscle strength production and its underlying neuromuscular characteristics in sedentary and trained individuals with intellectual disability (ID) compared with healthy sedentary individuals. METHODS: Three adult groups (age: 25.07 ± 0.70) consisting of sedentary individuals with ID (IDSG), trained individuals with ID (IDTG) and a control group (CONT) participated in the present study. Peak torque (PT) during maximal voluntary isometric contraction, voluntary activation level (VAL), surface electromyography (sEMG) recordings, electrophysiological (Mmax ) and potentiated twitch torque (PTT responses) of the knee extensor muscles and thigh muscle volume were assessed. RESULTS: Compared with CONT and IDTG, respectively, IDSG presented significantly lower PT (-48% and -42%), VAL (-24% and -9%), sEMG (-49% and -29%), Mmax (-41% and -39%) and PTT (-32% and -28%) values. These deficits were reduced between IDTG compared with CONT (i.e. PT: -10%; VAL: -16%; and sEMG: -28%) or did not differ anymore (PTT and Mmax ). Normalising PT to thigh muscle volume and/or computing theoretical PT value overwhelm strength production differences between IDTG and CONT. Training background influences the outcomes with IDTG exhibiting greater PT, VAL, sEMG, Mmax and PTT than IDSG. CONCLUSIONS: Strength production deficit in IDSG was related to both muscular and neural characteristics compared with healthy controls whereas this deficit mainly arises from neural characteristics for IDTG.

Electrostimulation Training Effects on diurnal Fluctuations of Neuromuscular Performance.

This study examined the effects of electrostimulation (ES) strength training at the same time-of-day on the diurnal fluctuations of maximal voluntary isometric contractions (MVIC) and surface electromyography (EMG). 20 male performed 3 MVICs of knee extension coupled with surface EMG before and after 5 weeks of 3 ES training sessions per week. Each ES training session consisted in 45 isometric contractions. The participants were randomly assigned to either a morning (MTG, 07:00-08:00 h) or an evening (ETG, 17:00-18:00 h) training group. Both groups performed the evaluation tests at 07:00 and 17:00 h. Before ES training, MVIC was significantly higher in the evening compared to the morning for all groups, but there was no significant difference between groups for all EMG parameters. After the ES training, the diurnal variations in MVIC were blunted in the MTG and persisted in the ETG. Significant time-of-day effect was noticed for all EMG parameters but there was no group effect. The elimination of the diurnal fluctuations of MVIC and the appearance of EMG variations by training in the morning hours suggest that neural adaptations are the main source of temporal specificity of neuromuscular performance after ES strength training.

Improved tolerance of peripheral fatigue by the central nervous system after endurance training.

PURPOSE: The purposes of this study were to evaluate the effect of endurance training on central fatigue development and recovery. METHODS: A control group was compared to a training group, which followed an 8-week endurance-training program, consisting in low-force concentric and isometric contractions. Before (PRE) and after (POST) the training period, neuromuscular function of the knee extensor (KE) muscles was evaluated before, immediately after and during 33 min after an exhausting submaximal isometric task at 15 % of the maximal voluntary contraction (MVC) force. After training, the trained group performed another test at iso-time, i.e., with the task maintained until the duration completed before training was matched (POST2). The evaluation of neuromuscular function consisted in the determination of the voluntary activation level during MVCs, from peripheral nerve electrical (VAPNS) and transcranial magnetic stimulations (VATMS). The amplitude of the potentiated twitch (Pt), the evoked [motor evoked potentials, cortical silent period (CSP)] and voluntary EMG activities were also recorded on the KE muscles. RESULTS: Before training, the isometric task induced significant reductions of VAPNS, VATMS and Pt, and an increased CSP. The training period induced a threefold increase of exercise duration, delayed central fatigue appearance, as illustrated by the absence of modification of VAPNS, VATMS and CSP after POST2. At POST, central fatigue magnitude and recovery were not modified but Pt reduction was greater. CONCLUSION: These results suggest that central fatigue partially adapts to endurance training. This adaptation principally translates into improved tolerance of peripheral fatigue by the central nervous system.

Effects of endurance training on the maximal voluntary activation level of the knee extensor muscles.

PURPOSE: The aim of this study was to investigate the neural adaptations to endurance training, and more specifically the adaptation of the cortical voluntary activation of the knee extensor (KE) muscles. METHODS: Sixteen sedentary men were randomly allocated into an endurance training (n = 8) or a control group (n = 8). All subjects performed a maximal aerobic speed test (MAS) before and immediately after the training period. Training lasted 8 weeks and was based on endurance running. During Pre- and Post-training testing sessions, maximal voluntary contraction (MVC) was measured and voluntary activation (VA) was calculated via peripheral nerve (PNS) and transcranial magnetic stimulations (TMS) superimposed to MVC. Electromyographic activity (EMG) of the KE muscles was also measured during MVC, PNS (M-wave) and TMS (motor evoked potentials-MEP). The cortical silent period following TMS was also assessed. RESULTS: Despite a significant improvement in endurance running performance, as suggested by the increase of MAS in the training group (Pre 15.4 ± 1.6 vs. Post 16.4 ± 1.6 km·h(-1)), endurance training did not affect MVC or VA as measured with PNS and TMS. Similarly, the EMG of KE muscles during MVC did not show any significant changes. Furthermore, the MEP amplitude and the duration of the silent period also remained unchanged after endurance training. CONCLUSIONS: The present study suggests an 8-week endurance-training program does not generate adaptations of neural factors in sedentary subjects.

[Three species of gregarines (apicomplexa: eugregarinorida) observed in the annelid polychaete Marphysa sangunea (montagu, 1815) in the lake of Tunis]. / Presence de trois espèces de grégarines (apicomplexa: eugregarinorida) chez l'Annélide polychete marphysa sanguinea (montagu, 1815) dans le lac de Tunis.

Three species of gregarines were found in specimens of the annelid polychaete Marphysa sanguinea collected in the Lake of Tunis: Bhatiella marphysae Setna, 1931, described from Marphysa sanguinea (India); Ferraria cornucephala iwamusi H. Hoshide, 1956, found in Marphysa iwamusi (Japan); and Viviera sp. a species sharing characteristics with Viviera marphysae Schrével, 1963, described in France from Marphysa sanguinea. These gregarines are reported for the first time from this host in Tunisia. Bhatiella marphysae and Viviera sp. belong to the family Lecudinidae (Aseptatorina). Our observations confirm the occurrence of a true septum in Ferraria cornucephala which must be maintained in Polyrhabdinae (Septatorina).

[Cerbussowia cerruti Wilhelmi 1901, from the Tunisian Golf (Platyhelminths, marine Tricladida)]. / Cerbussowia cerruti Wilhelmi 1909, du golfe de Tunis (Plathelminthe, Triclade marin).

Cerbussowia cerruti Wilhelmi, 1909 (Plathyhelminthe, Turbellaria, Tricladida) is described in Tunisia for the first time. A morphological, anatomical and histological accounts of this marine flatworm are presented. Some differences between the anterior ends of the tunisian animals and accounts in the literature are discussed.

[The presence of the epitokous type of Perinereis cultrifera (Polychaeta) in the Mediterranean]. / Sur la présence en Méditerranée de la race épitoque de Perinereis cultrifera (Polychètes).

The reproduction of Nereid Perinereis cultrifera in the English Channel and the Atlantic is of an epitokous type. The same Nereid in the Mediterranean (Bay of Alger) has been described as atokous (Marcel, 1962) and since that time epitoky in mediterranean specimens has been considered to be an accidental phenomenon. However, in the present study polychaetes collected at Salammbô (near Tunis) show that those P. cultrifera reproduce exclusively by epitoky.

[Morphological characteristics of the pharynx of Nereis diversicolor Müller, 1776 (Polychaetes, Nereidae)]. / Caractéristiques morphologiques du pharynx de Nereis diversicolor Müller, 1776 (Polychetes Nereidae).

Within the biometrical study of the Nereidae and in order to characterize the different populations, we looked for the most relevant biometrical characteristics. In fact, for these sea-animals, the weight and length remain just significant statements within certain limits; on the other hand the length of the maxillary, the number of paragnaths which decorate the proboscis can be precisely known.

[Turbellaria in the lagoon of Ghar-el-Melh. Research on the regenerative ability of Monocelis fusca Oersted (Turbellaria, Monocelididae)]. / Sur les turbellariés de la lagune de Ghar-el-Melh. Recherche du pouvoir de régénération chez Monocelis fusca Oersted (Turbellaria, Monocelididae).

The Turbellarian Monocelis fusca Oersted is abundant in the lagoon of Ghar-el-Melh. Traumatic regeneration in this animal is realised for the first time. Transversal sections through two levels of the body are made, and pointed out the presence or the absence of regeneration ability with the considered fragment.

[Turbellaria in the gulf of Tunis. I. Morphology]. / Sur les Turbellariés du golfe de Tunis. I. Etude morphologique.

This is a preliminary work for a regeneration study which experimental results will be published posteriorly. This first note describes three triclads Turbellaria found in the gulf of Tunis for the first time: Procerodes lobata O. Schmidt, 1862, Procerodes dohrni Wilhelmi, 1909 and Sabussowia dioica Claparède, 1863. Precisions concerning ecological preferences and geographical distribution have been given.