Pierre Portero

Neck Strength and EMG Activity in Fighter Pilots with Episodic Neck Pain

INTRODUCTION Neck pain is common in fighter pilots due to repeated exposure to high +Gz loads, but studies comparing neck function in symptomatic and healthy fighter pilots are lacking. This study compared neck strength and EMG activity during maximal isometric contractions in a sitting position in the sagittal and coronal planes in neck pain (SP), asymptomatic fighter pilots (AP), and healthy, male, non-pilot subjects (NPS). METHODS There were 9 SP, 10 AP, and 8 NPS, all males, who performed maximal isometric neck contractions on a specific dynamometer. Surface EMG activity was recorded bilaterally over the sternocleidomastoid and paraspinal muscles. EMG amplitude during side bending was normalized to that measured in the sagittal plane. RESULTS SP exhibited lower side-bending strength than AP (17-19%, P < 0.05). In addition, SP and NPS exhibited lower left side-bending-to-extension torque ratios (20% and 14%, respectively, P < 0.05) than AP. Similar activation level of neck flexors and extensors during side bending was found in SP and AP, whereas EMG activity of the extensors was higher than the flexors in NPS (+48%, P < 0.05). In addition, antagonistic EMG activity was higher in AP compared to NPS (26% vs. 41%, respectively, P < 0.05). CONCLUSION Our results suggest altered muscle function in SP compared with AP in the coronal but not in the sagittal plane. Further, AP appeared to be more efficient in the coronal plane with reference to neck extension than NPS, suggesting that some adaptations occurred due to flight exposure. These findings may have clinical implications for the management and the follow-up of neck pain in fighter pilots.

Musculo-tendinous stiffness of head-neck segment in the sagittal plane: An optimization approach for modeling the cervical spine as a single-joint system

Despite the multi-linked architecture of the cervical spine, all previous studies that have made estimations of mechanical properties of the neck have considered the head-neck segment as a rigid link, with a fixed center of rotation at C7. The aim of this study was to consider the head-neck segment as a changeable geometry system for locating the resultant center of rotation and for calculating the musculo-tendinous stiffness by the quick-release method. Head kinematics during quick-releases was analyzed by recording the trajectory of surface markers. With an optimization procedure, the position of the resultant center of rotation of the head-neck segment was estimated. Thereafter, the angular displacement and acceleration of the head, together with the isometric torque developed by the cervical muscles were used to calculate the segments stiffness. The results showed a consistent center of rotation and a significant increase of the musculo-tendinous stiffness with increasing torque.

Translation, cross-cultural adaptation, and validation of the french version of the 15-item Myasthenia Gravis Quality Of life scale: French Version of MG-QOL15

Introduction: Evaluation of quality of life (QOL) has become essential in healthcare. Currently no MG‐specific QOL measure exists in French. The aim of this study was to translate, culturally adapt, and evaluate the psychometric properties of the French version of the 15‐Item Myasthenia Gravis Quality of Life Scale (MG‐QOL15) scale for French myasthenia patients. Methods: Translation and cross‐cultural adaption of the MG‐QOL15 was performed, followed by reliability and validity evaluations. Results: One hundred and twenty‐five patients were included. Internal consistency was excellent (Cronbach α = 0.92) as was test–retest reliability (ICC = 0.92, 95% CI 0.86–0.96). Concurrent validity was good for both clinical scores (myasthenic muscle score: ρ = –0.52, P < 0.001; Myasthenia Gravis–Activities of Daily Living scale score: ρ = 0.62, P < 0.001). Correlations were strongest for overall QOL (ρ = 0.62, P < 0.001) and physical health (ρ = 0.67, P < 0.001) on the World Health Organization Quality of Life short score (WHO‐QOL BREF). Conclusion: The French version of the MG‐QOL15 is valid and reliable and is now available for use with French‐speaking patients. Muscle Nerve, 2016 Muscle Nerve 55: 639–645, 2017

Musculo-tendinous stiffness of the in vivo head-neck segment in response to quick-releases: A reproducibility study

This study was designed to assess the reproducibility of head-neck musculo-tendinous stiffness (HMS) findings of the head-neck segment in response to quick-release in flexion and extension. The HMS was expressed as the slope of the isometric torque-angular displacement curve of the head-neck segment derived from the first 15 ms from the peak acceleration following release at different exertion levels (10% to 80% MVC). A test—retest methodology (7 days interval) was performed to assess the measurement reproducibility. The results showed a linear relationship between the flexion and extension torque and angular displacement (0.94 < R 2 < 0.99). Moreover, HMS findings evidenced good to excellent reproducibility using relative (ICC) as well as absolute (SEM) parameters. It was concluded that that simple kinematic assessment was appropriate for investigating HMS. Nevertheless, multiple-segmentation of the head-neck segment could lead, according to exertion level, to geometrical changes after the release.

Translation, cross-cultural adaptation, and validation of the French version of the Myasthenia Gravis Quality of Life Scale (MG-QOL 15).

Introduction: Evaluation of quality of life (QOL) has become essential in healthcare. Currently no MG‐specific QOL measure exists in French. The aim of this study was to translate, culturally adapt, and evaluate the psychometric properties of the French version of the 15‐Item Myasthenia Gravis Quality of Life Scale (MG‐QOL15) scale for French myasthenia patients. Methods: Translation and cross‐cultural adaption of the MG‐QOL15 was performed, followed by reliability and validity evaluations. Results: One hundred and twenty‐five patients were included. Internal consistency was excellent (Cronbach α = 0.92) as was test–retest reliability (ICC = 0.92, 95% CI 0.86–0.96). Concurrent validity was good for both clinical scores (myasthenic muscle score: ρ = –0.52, P < 0.001; Myasthenia Gravis–Activities of Daily Living scale score: ρ = 0.62, P < 0.001). Correlations were strongest for overall QOL (ρ = 0.62, P < 0.001) and physical health (ρ = 0.67, P < 0.001) on the World Health Organization Quality of Life short score (WHO‐QOL BREF). Conclusion: The French version of the MG‐QOL15 is valid and reliable and is now available for use with French‐speaking patients. Muscle Nerve, 2016 Muscle Nerve 55: 639–645, 2017

Marathons and myasthenia gravis: a case report

BackgroundThe cardinal symptoms of auto-immune myasthenia gravis are fatigue and weakness. Endurance events such as marathon running would seem incompatible with this chronic disease. Many patients stop sport altogether. There is limited literature of patients with auto-immune myasthenia gravis undergoing regular endurance exercise.Case presentationWe report the case of a 36-year-old female who began long-distance running whilst experiencing initial symptoms of myasthenia gravis. She was diagnosed with auto-immune myasthenia gravis and whilst advised to stop all sport, her way of fighting and living with this chronic and unpredictable disease was to continue running to maintain a healthy body and mind. Despite suffering from ocular, bulbar and localized limb fatigability, she managed to complete multiple marathons and achieve disease stability with cholinesterase inhibitors.ConclusionsMarathon and half-marathon running lead to distinct changes in mediators of inflammation in an exercise-dose-dependent manner. Despite symptoms of weakness and fatigue in certain muscles in myasthenia gravis, physical exertion remains possible and may not worsen symptoms as demonstrated in this case and recent studies. The immunomodulatory role of exercise could be considered in this case however this hypothesis remains to be confirmed in future studies with quantitative data.

Influence of Cervical Muscle Fatigue on Musculo-Tendinous Stiffness of the Head-Neck Segment during Cervical Flexion.

Aim The aim of this study is to determine if the fatigue of cervical muscles has a significant influence on the head-neck segment musculo-tendinous stiffness. Methods Ten men (aged 21.2 ± 1.9 years) performed four quick-release trials of flexion at 30 and 50% MVC before and after the induction of muscular fatigue on cervical flexors. Electromyographic activity was recorded on the sternocleidomastoids (SCM) and spinal erectors (SE), bilaterally. Musculo-tendinous stiffness was calculated through the quick-release method adapted to the head-neck segment. Results We noticed a significant linear increase of the head-neck segment musculo-tendinous stiffness with the increase of exertion level both before (P < 0.0001) and after the fatigue procedure (P < 0.0001). However, this linear relationship was not different before and after the fatigue procedure. EMG analysis revealed a significant increase of the root mean square for the right SCM (P = 0.0002), the left SCM (P < 0.0001), the right SE (P < 0.0001), and the left SE (P < 0.0001) and a significant decrease of the median power frequency only for the right (P = 0.0006) and the left (P = 0.0003) SCM with muscular fatigue. Discussion We did not find significant changes in the head-neck segment musculo-tendinous stiffness with fatigue of cervical muscles. We found a significant increase in EMG activity in the SCM and the SE after the induction of fatigue of the SCM. Our findings suggest that with fatigue of cervical flexors, neck muscle activity is modulated in order to maintain the musculo-tendinous stiffness at a steady state.

Caractérisation des propriétés mécaniques passives du système musculo-articulaire

Using isokinetic dynamometers for the characterisation of the passive mechanical properties of the musculoarticular system. Traditionally, isokinetic dynamometers have been used to measure variables associated with strength, power and endurance characteristics of muscle. Much less attention has been given to their potential for measuring the passive mechanical properties of the musculoarticular system (MAS). These dynamometers are configured in order to i) mobilise passively the joint at low speeds and over all the range of motion, ii) maintain a steady level of stretching or stress, iii) realise a loading–unloading protocol, iv) apply cyclic stretching on the MAS. The mechanical behaviour of the MAS can be characterised by stiffness and viscoelasticity properties. Other methods allowed, either to control the passive conditions of the method as the surface electromyography, or to reach the mechanical properties of the muscle-tendon complex.

In vivo Neck Musculo-Tendinous Stiffness in Response to Quick-Releases

This study was designed to assess musculo-tendinous stiffness of the head-neck segment in response to quick-release in flexion and extension. Musculo-tendinous stiffness of the neck was calculated using analysis of head kinematics with optimization procedure during the first 30 ms after the acceleration peak following the release at different exertion levels (20 % to 70 % MVC). Results showed a linear relationship between torque and musculo-tendinsous stiffness for flexion (R = 0.82, P < 0.5) and extension (R = 0.69, P < 0.05). Resultas shows also an increase of moment of inertia with torque. Correlation between stiffness and torque indicates that quick-release perturbations applied to the head associated with optimization procedure to assess head kinematics provide an attractive approach to investigate head-neck musculo-tendinous stiffness. In addition, changes noticed on head-neck moment of inertia shows that mechanical properties evaluated in this study could be altered by modifications of geometry of the corporal segment induced by exertion level.