Rihab Borji

Individuals with intellectual disability have lower voluntary muscle activation level

The aim of this study was to explore the voluntary activation level during maximal voluntary contraction (MVC) in individuals with intellectual disability (ID) versus individuals without ID using the twitch interpolation technique. Ten individuals with mild ID (ID group) and 10 sedentary men without ID (control group) participated in this study. The evaluation of neuromuscular function consisted in three brief MVCs (3s) of the knee extension superimposed with electrical nerve stimulation (NES) to measure voluntary activation. Muscle activity levels were also measured with surface EMG. The root mean square (RMS) was extracted from the EMG signal. The RMS/Mmax ratio and the neuromuscular efficiency (NME) were calculated. Our results reported that individuals with ID present lower muscle strength (p < 0.001), lower voluntary activation level (p < 0.001), lower RMS values of vastus lateralis (p < 0.05), vastus medialis (p < 0.05), and rectus femoris (p < 0.001) muscles. In addition, our results showed lower RMS/Mmax values in the ID group than in the control group for the VM (0.05 ± 0.01 mV vs. 0.04 ± 0.01 mV; p < 0.05) and the RF (0.06 ± 0.02 mV vs. 0.05 ± 0.02 mV; p < 0.05) muscles. However, no significant difference was reported for the VL muscle (0.05 ± 0.02 mV vs. 0.05 ± 0.02 mV; p=0.463). Moreover, Individuals with ID present smaller potentiated twitch (p < 0.001). However, no significant difference was reported in the NME ratio. These results suggest that the lower muscle strength known in individuals with ID is related to a central nervous system failure to activate motor units and to some abnormal intrinsic muscle properties. It seems that the inactive lifestyle adopted by individuals with ID is one of the most important factors of their lower voluntary activation levels. Therefore, physical activities should be introduced in life style of individuals with ID to improve their neuromuscular function.

Neuromuscular fatigue during high-intensity intermittent exercise in individuals with intellectual disability

This study examined neuromuscular fatigue after high-intensity intermittent exercise in 10 men with mild intellectual disability (ID) in comparison with 10 controls. Both groups performed three maximal voluntary contractions (MVC) of knee extension with 5 min in-between. The highest level achieved was selected as reference MVC. The fatiguing exercise consists of five sets with a maximal number of flexion-extension cycles at 80% of the one maximal repetition (1RM) for the right leg at 90° with 90 s rest interval between sets. The MVC was tested again after the last set. Peak force and electromyography (EMG) signals were measured during the MVC tests. Root Mean Square (RMS) and Median Frequency (MF) were calculated. Neuromuscular efficiency (NME) was calculated as the ratio of peak force to the RMS. Before exercise, individuals with ID had a lower MVC (p<0.05) and a lower RMS (p<0.05). No significant difference between groups in MF and NME. After exercise, MVC decreases significantly in both groups (p<0.001). Individuals with ID have greater force decline (p<0.001 vs. p<0.01). RMS decreased significantly (p<0.001) whereas the NME increased significantly (p<0.05) in individuals with ID, but both remained unchanged in controls. The MF decreased significantly in both groups (p<0.001). In conclusion, individuals with ID presented a lower peak force than individuals without ID. After a high-intensity intermittent exercise, individuals with ID demonstrated a greater force decline caused by neural activation failure. When rehabilitation and sport train ID individuals, they should consider this nervous system weakness.

The effect of a combined strength and proprioceptive training on muscle strength and postural balance in boys with intellectual disability: An exploratory study.

The aim of our study was to investigate the effect of a combined strength and proprioception training (CSPT) program on muscle strength and postural balance in children with intellectual disability (ID). The maximum voluntary contraction (MVC) and postural parameters (CoPVm, CoPLX, CoPLY) of 20 children with ID were recorded before and after 8 weeks of a CSPT program. The participants were divided into two groups: an experimental group who attended a CSPT program and a control group who continued with daily activities. In the trained group, the MVC increased significantly (p<0.001) after the training period and the postural parameters decreased significantly in Double-Leg Stance (DLS) and One-Leg Stance (OLS) during the firm surface condition as well as in the DLS during the foam surface condition; in both eyes open (EO) and eyes closed (EC) conditions. A CSPT program improves postural balance in children with ID could be due to the enhancement in muscle strength and proprioceptive input integration.

An open‐label randomized control trial of hopping and jumping training versus sensorimotor rehabilitation programme on postural capacities in individuals with intellectual disabilities

BACKGROUND This study aimed to compare the effectiveness of a hopping and jumping training programme (HJP) versus a sensorimotor rehabilitation programme (SRP) on postural performances in children with intellectual disability. METHODS Three groups of children with intellectual disability participated in the study: the HJP group, the SRP group and a control group. Postural capacities were tested with the Berg Balance Scale (BBS) and the Tinetti tests. The HJP and the SRP groups participated in the training programmes for eight weeks. Then, all participants were retested. RESULTS Results showed that before the training period, there are no significant differences between the three groups. After the training period, the BBS and the Tinetti scores increased significantly in the HJP group and the SRP group with greater extent in the HJP group than in the STP group. CONCLUSION We suggest that HJP training is more recommended to improve postural capacities in children with intellectual disability.

Combined physical-cognitive training enhances postural performances during daily life tasks in older adults

ABSTRACT Physical‐cognitive interventions seem promising to improve balance and gait performances and prevent falls in the elderly. Although these beneficial effects, it is still not clear whether these physical‐cognitive training modalities leads to more general non‐specific adaptations that can be transferred to some measures reflecting every day abilities. This randomized controlled trial examined postural (center of pressure oscillations), physical (lower body strength, gait speed, functional mobility, dynamic balance) and cognitive performances (reaction time) and postural performance during daily life tasks (walking while conversing on a phone and maintaining an upright standing posture while buttoning a shirt) in older adults (66.29 ± 3.61 years) pre‐ and post‐ 6‐months physical and physical‐cognitive interventions. Results showed that both training modalities improve balance (p < 0.001), physical functions (p < 0.01) and attention (p < 0.001) in older adults. Only simultaneous physical‐cognitive training enhances performance in daily life tasks. Three months after the intervention, these improvements were generally maintained for physical functions and attention and were not maintained for the postural performances in daily life task. In conclusion, physical training improves postural balance, mobility, attention and physical functions in older adults. Only simultaneous physical‐cognitive training modality enhances performance in some tasks relative to every day abilities. Nonetheless, these gains were lost after 3 months of detraining period suggesting a need for older people to participate regularly in such training for their daily life independence. HIGHLIGHTSPhysical‐cognitive training enhances postural control in daily life functions.These enhancements are not maintained 3 months after the end of the training.Physical and physical‐cognitive training improve physical and postural performances.

Effect of a 16 week combined strength and plyometric training program followed by a detraining period on athletic performance in pubertal volleyball players

The purpose of this study was to determine the effects of 16 weeks of combined strength and plyometric training or plyometric training alone, and how a detraining program can modify adaptations in response to the training stimulus. Sixty male volleyball players (circa PHV:-1 to +1 years from PHV) were assigned to a Combined Training group (CTG) (n=20), a Plyometric Training group (PTG) (n=20) or a control group (CG) (n=20). The experimental groups (CTG and PTG) participated in training twice weekly for 16 weeks. Thigh muscle volume, body fat, flexibility, sprint, jump height and medicine ball throw were measured at pre-training, post-training and detraining. Respectively, the CTG and PTG showed increases in thigh muscle volume (Effect size: 0.71 and 0.42), and decreases in body fat (-0.42 and -0.34) as well as improvements in 5 m sprint (-0.69 and -0.46) 10 m sprint (-0.31 and -0.3), lower body muscle power (0.44 and 0.36) and upper body muscle power (1.32 and 0.7). After the detraining period, all groups maintained previously attained muscle power (6.79% to 9.87%; p<0.001). In conclusion, combined strength and plyometric training provided better improvements than plyometric training only. The combination of strength and plyometric training is a time-effective training modality that confers improvements in physical performance measures, muscle size and body fat. A temporary period of detraining may not undermine performance gains in pubertal volleyball players.

Postural control of Parkour athletes compared to recreationally active subjects under different sensory manipulations: A pilot study

Abstract In Parkour activity, the aim is to move from one place to another as quickly and efficiently as possible by running, climbing, swinging, vaulting, rolling, crawling and jumping on tiny obstacles … . Performing these actions places a great demand on the postural control system. The purpose of the present study was to investigate postural control of Parkour practitioners – called Traceurs – compared to recreationally active (RA) subjects in different postural conditions after manipulating the visual and/or proprioceptive sensory inputs. Ten Traceurs (mean experience 5.9 ± 0.9 years; >5 hours per week) and 10 RA subjects participated in this study. We measured the centre of pressure area (CoPA) of the upright standing bipedal and unipedal postures in different postural conditions: on a firm and on a foam surfaces; on an oscillating surface in the sagittal plane and in the frontal plane in eyes open and eyes closed. To evaluate vision contribution, the Romberg index (RI) was calculated. Results showed that Traceurs presented a significant (P < .001) lower CoPA values compared to RA subjects in eyes closed condition, suggesting that they were able to maintain a better balance control when vision is removed. Traceurs seems to be less dependent on visual cues (lower RI values) and proprioceptive inputs for maintaining balance than RA subjects. According to our study, Parkour training (experience for at least five years with a minimum of five hours per week) may improve postural abilities of young adult practitioners in specific postural conditions.

The effect of cell phone use on postural balance and mobility in older compared to young adults.

Cell phone use is considered as an essential part of everyday life saturating all age groups and demographics. This study aimed to explore the effect of various cell phone functions on postural control and mobility in the elderly. Twenty healthy older (mean age 72.5±2.9) and twenty young (26.3±2.8) adults participated in this study. Postural balance was assessed by measuring the center of pressure (CoP) displacement with (talking on a cell phone (CONVERSE), dialing a number (DIAL) and listening to music (MUSIC)) and without cell phone use. Mobility was assessed by the Timed Up and Go Test (TUGT). Results showed that for both groups, the CoP parameters increased significantly during the CONVERSE (p<0.001) and the DIAL (CoParea, CoPX: p<0.05; CoPY: p<0.01) conditions compared to the control condition. Moreover, the CoParea values were significantly higher during the CONVERSE condition in comparison to the DIAL (p<0.05) one. In older adults, the TUGT scores increased significantly in the DIAL (p<0.01) condition compared to the CONVERSE and the MUSIC conditions. In conclusion, cell phone use impairs similarly standing postural balance of elderly and young adults. Interestingly, in the elderly, all cell phone functions used altered mobility with the dialing function causing the largest mobility deterioration.

Neuromuscular fatigue and recovery profiles in individuals with intellectual disability

Purpose This study aimed to explore neuromuscular fatigue and recovery profiles in individuals with intellectual disability (ID) after exhausting submaximal contraction. Methods Ten men with ID were compared to 10 men without ID. The evaluation of neuromuscular function consisted in brief (3 s) isometric maximal voluntary contraction (IMVC) of the knee extension superimposed with electrical nerve stimulation before, immediately after, and during 33 min after an exhausting submaximal isometric task at 15% of the IMVC. Force, voluntary activation level (VAL), potentiated twitch (Ptw), and electromyography (EMG) signals were measured during IMVC and then analyzed. Results Individuals with ID developed lower baseline IMVC, VAL, Ptw, and RMS/Mmax ratio (root-mean-square value normalized to the maximal peak-to-peak amplitude of the M-wave) than controls (p < 0.05). Nevertheless, the time to task failure was significantly longer in ID vs. controls (p < 0.05). The 2 groups presented similar IMVC decline and recovery kinetics after the fatiguing exercise. However, individuals with ID presented higher VAL and RMS/Mmax ratio declines but lower Ptw decline compared to those without ID. Moreover, individuals with ID demonstrated a persistent central fatigue but faster recovery from peripheral fatigue. Conclusion These differences in neuromuscular fatigue profiles and recovery kinetics should be acknowledged when prescribing training programs for individuals with ID.

Unilateral Fatigue Affects the Unipedal Postural Balance in Individuals With Intellectual Disability

ABSTRACT This study aimed to explore the effect of local muscle fatigue on the unipedal stance in men with intellectual disability (ID). The Centre of pressure (CoP) excursions and the isometric maximal voluntary contraction (MVC) were measured before and after a fatiguing exercise. Higher baseline values of CoP excursions and lower MVC values were recorded in the ID group. After the fatiguing exercise, this group showed higher MVC decrease and higher percentage of increase of the mean CoP velocity. In conclusion, men with ID are more vulnerable to the disturbing effects of fatigue during the unipedal stance compared to men without ID.