In Situ Power-Cadence Relationship for 2-, 5-, and 20-Minute Duration: A Proof of Concept in Under-19 Cyclists.

BACKGROUND: The force-velocity relationship suggests that maximal power (Pmax) can only be produced in optimal torque (Topt) and cadence (Copt). However, the cadence at which mean maximal power (MMP) is produced has never been studied. This study aimed to determine the individual MMP-cadence relationship from in situ data. METHOD: We analyzed 1 year of data from 14 under-19 cyclists and calculated the MMP for each cadence between 50 and 120 rpm for 2-, 5-, and 20-minute durations. The MMP-cadence relationship was fit with a second-order polynomial function. The goodness of fit (r2) and odd-day-even-day absolute and relative reliability were evaluated, respectively, for Pmax, Topt, and Copt. RESULTS: The goodness of fit was very high for every duration studied. Topt and Pmax, but not Copt, were significantly higher for shorter durations. Pmax was significantly correlated only with Topt for the 3 durations (r2 = .63, .71, and .64 for 2, 5, and 20 min, respectively). DISCUSSION: Evaluation of the MMP-cadence relationship from in situ data is feasible and reliable for 2-, 5-, and 20-minute durations. This profiling approach would enable better detection of the strengths and weaknesses of cyclists and make it possible to design more effective training interventions. PRACTICAL APPLICATIONS: The analysis makes it possible to identify the torque versus cadence component that individually limits power production. Knowing the Copt for a given duration of maximal effort could help athletes choose the right gear ratio and regulate cadence during a race in order to maximize performance.

Juvenile Xanthogranuloma of the Head and Neck: Imaging Findings in 11 Cases.

BACKGROUND: Juvenile Xanthogranuloma (JXG) is a non-Langerhans cell histiocytosis, occurring mainly in infancy. With an extracutaneous lesion, its diagnosis is difficult, because of a wide clinical spectrum. Here we demonstrate and characterize imaging features of 11 patients with JXG of the head and neck in various locations. MATERIAL AND METHODS: We recorded clinical data and reviewed all imaging studies of 11 patients with JXG of the head and neck. Ultrasonography (US) alone was performed in 1 patient; MRI alone in 6 patients; US and MRI in 1 patient; and US, CT, and MRI in 3 patients. We evaluated the following characteristics in all studies: location and number of lesions, echogenicity and vascularization on US, density on CT, signal intensity on T1- and T2-weighted images, ADC and enhancement on MRI, and tumor boundaries and bone involvement. RESULTS: Lesions were well-defined in 9 cases, and bone erosion was present in 2. On US, lesions were hypoechoic or hyperechoic and with or without vascularization. On CT, lesions were hyper-dense, with no calcification. On MRI, lesions were mildly hyper-intense or iso-intense on T1-weighted images in 8 of 9 patients, hypo-intense on T2-weighted images in 7 of 10, low ADC in 7 of 9, and enhancement in 7 of 7. CONCLUSIONS: The diagnosis of extra cutaneous JXG may be proposed, with the following suggestive criteria: age < 1 year, well-defined lesion, mild hyper-intensity on T1-weighted images, hypo-intensity on T2-weighted images, low ADC, enhancement, and possible adjacent bone involvement.

Imaging characterization of paediatric tumours with the neurotrophic tyrosine receptor kinase fusion transcript.

OBJECTIVES: The neurotrophic tyrosine receptor kinase (NTRK) fusion transcript (FT) is a major genetic landmark of infantile fibrosarcoma (IFS) and cellular congenital mesoblastic nephroma (cCMN) but is also described in other tumours. The recent availability of NTRK-targeted drugs enhances the need for better identification. We aimed to describe the anatomic locations and imaging features of tumours with NTRK-FT in children. CASE SERIES: Imaging characteristics of NTRK-FT tumours of 41 children (median age: 4 months; 63% <1 year old; range: 0-188) managed between 2001 and 2019 were retrospectively analysed. The tumours were located in the soft tissues (n = 24, including 19 IFS), kidneys (n = 9, including 8 cCMN), central nervous system (CNS) (n = 5), lung (n = 2), and bone (n = 1). The tumours were frequently deep-located (93%) and heterogeneous (71%) with necrotic (53%) or haemorrhagic components (29%). Although inconstant, enlarged intratumoural vessels were a recurrent finding (70%) with an irregular distribution (63%) in the most frequent anatomical locations. CONCLUSION: Paediatric NTRK-FT tumours mainly occur in infants with very variable histotypes and locations. Rich and irregular intra-tumoural vascularization are recurrent findings. ADVANCES IN KNOWLEDGE: Apart from IFS of soft tissues and cCMN of the kidneys, others NTRK-FT tumours locations have to be known, as CNS tumours. Better knowledge of the imaging characteristics may help guide the pathological and biological identification.

Lack of Proprioceptive Strategy Modulation Leads to At-Risk Biomechanics for Anterior Cruciate Ligament in Healthy Athletes.

INTRODUCTION: Anterior cruciate ligament (ACL) injuries are frequent in handball, and altered sensory integration may contribute to increased injury risk. Recent evidence showed that proprioceptive postural control strategies differ among athletes. The aim of this study was to evaluate the relationship between proprioceptive strategy and biomechanics during side-cutting maneuvers. METHODS: A total of 47 handball players performed anticipated and unanticipated cutting tasks. Their postural proprioceptive strategy was then characterized according to the perturbation of the center of pressure displacement generated by the muscle vibration on a firm and foam surface. Individuals able to reweight proprioception from ankle to lumbar signals according to the stability of the support were defined as flexible. Conversely, athletes maintaining an ankle-steered strategy on foam surface were characterized as rigid. Statistical parametric mapping analysis was used to compare pelvic and lower limb side-cutting kinematics, kinetics, and EMG activity from seven muscles 200 ms before and after initial contact (IC) using a two-way ANOVA (group-condition). RESULTS: Twenty athletes (11 females and 9 males, 18.5 yr) were characterized as flexible and 20 athletes (12 females and 8 males, 18.9 yr) as rigid. No interaction between condition and proprioceptive profile was observed. More ipsilateral pelvic tilt before IC and lower vastus lateralis (VL) activity immediately after IC was observed during CUT ant . When comparing proprioceptive strategy, rigid individuals exhibited less preactivity of the semitendinosus ( P < 0.001) and higher VL activity ( P = 0.032). Conversely, rigid showed higher gluteus medius preactivity ( P < 0.05) and higher VL activity 100 ms after IC ( P < 0.001). Ankle was also more internally rotated before and during the stance phase ( P < 0.05) among rigid athletes. CONCLUSIONS: Rigid handball players exhibited at-risk determinants for anterior cruciate ligament injuries during side-cutting maneuvers.

The "velocity barrier" in giant slalom skiing: An experimental proof of concept.

BACKGROUND: Alpine skiing involves the conversion of potential energy into kinetic energy, with the "velocity barrier" (VB) at each moment corresponding to the maximal velocity at which the athlete can ski while staying within the boundaries of the gates and maintaining control. Nevertheless, this concept has never been proven by evidence. The aim of this study was to experimentally test the existence of the VB and clarify its relationship with skier's force production/application capacities. METHODS: Fourteen skiers were equipped with ski-mounted force plates and a positional device and ran a 2-turn Giant Slalom section starting from eight different heights on the slope. Three conditions were selected for further analysis: minimal entrance velocity (vmin ); entrance velocity allowing the better section time (VB); maximal entrance velocity (vmax ). Entrance velocity, section time, mean force output, ratio of force application effectiveness, velocity normalized energy dissipation, and path length were compared between the three conditions. Moreover, skier's mechanical energy and velocity curves were compared all along the section between the three conditions using SPM analysis. RESULTS: The section time was reduced in VB compared to vmin (p < 0.001) and vmax (p = 0.002). Skiers presented an incapacity to increase force output beyond the VB (p = 0.441) associated with a lower force application effectiveness (p = 0.005). Maximal entrance velocity was associated to higher energy dissipation (p < 0.001) and path length (p = 0.005). CONCLUSION: The present study experimentally supports the existence of the VB. The force production/application capacities seem to limit the skiing effectiveness beyond the VB, associated to increased energy dissipations and path length.

Corpus callosum in children with neurodevelopmental delay: MRI standard qualitative assessment versus automatic quantitative analysis.

BACKGROUND: The corpus callosum (CC) is a key brain structure. In children with neurodevelopmental delay, we compared standard qualitative radiological assessments with an automatic quantitative tool. METHODS: We prospectively enrolled 73 children (46 males, 63.0%) with neurodevelopmental delay at single university hospital between September 2020 and September 2022. All of them underwent 1.5-T brain magnetic resonance imaging (MRI) including a magnetization-prepared 2 rapid acquisition gradient echoes - MP2RAGE sequence. Two radiologists blindly reviewed the images to classify qualitatively the CC into normal, hypoplasic, hyperplasic, and/or dysgenetic classes. An automatic tool (QuantiFIRE) was used to provide brain volumetry and T1 relaxometry automatically as well as deviations of those parameters compared with a healthy age-matched cohort. The MRI reference standard for CC volumetry was based on the Garel et al. study. Cohen κ statistics was used for interrater agreement. The radiologists and QuantiFIRE's diagnostic accuracy were compared with the reference standard using the Delong test. RESULTS: The CC was normal in 42 cases (57.5%), hypoplastic in 20 cases (27.4%), and hypertrophic in 11 cases (15.1%). T1 relaxometry values were abnormal in 26 children (35.6%); either abnormally high (18 cases, 24.6%) or low (8 cases, 11.0%). The interrater Cohen κ coefficient was 0.91. The diagnostic accuracy of the QuantiFIRE prototype was higher than that of the radiologists for hypoplastic and normal CC (p = 0.003 for both subgroups, Delong test). CONCLUSIONS: An automated volumetric and relaxometric assessment can assist the evaluation of brain structure such as the CC, particularly in the case of subtle abnormalities. RELEVANCE STATEMENT: Automated brain MRI segmentation combined with statistical comparison to normal volume and T1 relaxometry values can be a useful diagnostic support tool for radiologists. KEY POINTS: • Corpus callosum abnormality detection is challenging but clinically relevant. • Automated quantitative volumetric analysis had a higher diagnostic accuracy than that of visual appreciation of radiologists. • Quantitative T1 relaxometric analysis might help characterizing corpus callosum better.

Analysis of the rate of force development reveals high neuromuscular fatigability in elderly patients with chronic kidney disease.

BACKGROUND: Chronic kidney disease (CKD) induces muscle wasting and a reduction in the maximum voluntary force (MVF). Little is known about the neuromuscular fatigability in CKD patients, defined as the reduction of muscle force capacities during exercise. Neuromuscular fatigability is a crucial physical parameter of the daily living. The quantification of explosive force has been shown to be a sensitive means to assess neuromuscular fatigability. Thus, our study used explosive force estimates to assess neuromuscular fatigability in elderly CKD patients. METHODS: Inclusion criteria for CKD patients were age ≥ 60 years old and glomerular filtration rate (GFR) < 45 mL/min/1.73 m2 not on dialysis, and those for controls were GFR > 60 mL/min/1.73 m2 , age and diabetes matched. The fatigability protocol focused on a handgrip task coupled with surface electromyography (sEMG). Scalars were extracted from the rate of force development (RFD): absolute and normalized time periods (50, 75, 100, 150 and 200 ms, RFD50 , RFD75 , RFD100 , RFD150 and RFD200 , respectively), peak RFD (RFDpeak in absolute; NRFDpeak normalized), time-to-peak RFD (t-RFDpeak ) and the relative force at RFDpeak (MVF-RFDpeak ). A statistical parametric mapping approach was performed on the force, impulse and RFD-time curves. The integrated sEMG with time at 0-30, 0-50, 0-100 and 0-200 ms time intervals relative to onset of sEMG activity was extracted and groups were compared separately for each sex. RESULTS: The cohort of 159 individuals had a median age of 69 (9IQR ) years and body mass index was 27.6 (6.2IQR ) kg/m2 . Propensity-score-matched groups balanced CKD patients and controls by gender with 66 males and 34 females. In scalar analysis, CKD patients manifested a higher decrement than controls in the early phase of contraction, regarding the NRFDpeak (P = 0.009; η2 p  = 0.034) and RFD75 and RFD100 (for both P < 0.001; η2 p  = 0.068 and 0.064). The one-dimensional analysis confirmed that CKD males manifest higher and delayed neuromuscular fatigability, especially before 100 ms from onset of contraction. sEMG was lower in CKD patients than controls in the 0-100 ms (at rest: P = 0.049, Cohen's d = 0.458) and 0-200 ms (at rest: P = 0.016, Cohen's d = 0.496; during exercise: P = 0.006, Cohen's d = 0.421) time windows. Controls showed greater decrease of sEMG than CKD patients in the 0-30 ms (P = 0.020, Cohen's d = 0.533) and 0-50 ms (P = 0.010, Cohen's d = 0.640) time windows. As opposite to females, males showed almost the same differences between groups. CONCLUSIONS: Our study is the first to show that CKD patients have higher fatigability than controls, which may be associated with an impaired motor-unit recruitment, highlighting a neural drive disturbance with CKD. Further studies are needed to confirm these findings.

Generating High-Resolution Synthetic CT from Lung MRI with Ultrashort Echo Times: Initial Evaluation in Cystic Fibrosis.

Background Lung MRI with ultrashort echo times (UTEs) enables high-resolution and radiation-free morphologic imaging; however, its image quality is still lower than that of CT. Purpose To assess the image quality and clinical applicability of synthetic CT images generated from UTE MRI by a generative adversarial network (GAN). Materials and Methods This retrospective study included patients with cystic fibrosis (CF) who underwent both UTE MRI and CT on the same day at one of six institutions between January 2018 and December 2022. The two-dimensional GAN algorithm was trained using paired MRI and CT sections and tested, along with an external data set. Image quality was assessed quantitatively by measuring apparent contrast-to-noise ratio, apparent signal-to-noise ratio, and overall noise and qualitatively by using visual scores for features including artifacts. Two readers evaluated CF-related structural abnormalities and used them to determine clinical Bhalla scores. Results The training, test, and external data sets comprised 82 patients with CF (mean age, 21 years ± 11 [SD]; 42 male), 28 patients (mean age, 18 years ± 11; 16 male), and 46 patients (mean age, 20 years ± 11; 24 male), respectively. In the test data set, the contrast-to-noise ratio of synthetic CT images (median, 303 [IQR, 221-382]) was higher than that of UTE MRI scans (median, 9.3 [IQR, 6.6-35]; P < .001). The median signal-to-noise ratio was similar between synthetic and real CT (88 [IQR, 84-92] vs 88 [IQR, 86-91]; P = .96). Synthetic CT had a lower noise level than real CT (median score, 26 [IQR, 22-30] vs 42 [IQR, 32-50]; P < .001) and the lowest level of artifacts (median score, 0 [IQR, 0-0]; P < .001). The concordance between Bhalla scores for synthetic and real CT images was almost perfect (intraclass correlation coefficient, ≥0.92). Conclusion Synthetic CT images showed almost perfect concordance with real CT images for the depiction of CF-related pulmonary alterations and had better image quality than UTE MRI. Clinical trial registration no. NCT03357562 © RSNA, 2023 Supplemental material is available for this article. See also the editorial by Schiebler and Glide-Hurst in this issue.

French survey of sedation practices for pediatric magnetic resonance and computed tomography imaging.

BACKGROUND: Pediatric magnetic resonance imaging (MRI) and computed tompgraphy (CT) require patient immobility and therefore often require sedation or general anesthesia of patients. Consensus on these procedures is lacking in France. OBJECTIVE: Thus, the aim of this study was to describe the current sedation practices for pediatric MRI and CT in France. MATERIAL AND METHODS: From January 2019 to December 2019, an online questionnaire was delivered by electronic mail to a representative radiologist in 60 pediatric radiology centers registered by the French-speaking pediatric and prenatal imaging society. Questions included protocols, drugs used, monitoring and side effects. RESULTS: Representatives of 40 of the 60 (67%) radiology centers responded to the survey. Among them, 31 performed sedation including 17 (55%) centers where radiologists performed sedation without anesthesiologists present during the procedure. The premedication drugs were hydroxyzine (n = 8, 80%) and melatonin (n = 2, 20%), Sedation drugs used for children ages 0 to 6 years old were pentobarbital (n = 9, 60%), midazolam (n = 2, 13%), chloral hydrate (n = 2, 13%), diazepam (n = 1, 6.5%) and chlorpromazine (n = 1, 6.5%). A written sedation protocol was available in 10/17 (59%) centers. In 6/17 (35%) centers, no monitoring was used during the procedures. Blood pressure monitoring and capnography were rarely used (< 10%) and post-sedation monitoring was heterogeneous. No life-threatening adverse effect was reported, but 6 centers reported at least one incident per year. CONCLUSION: For half of the responding radiology centers, radiologists performed sedation alone in agreement with the local anesthesiology team. Sedation procedures and monitoring were heterogenous among centers. Adjustment and harmonization of the practices according to the capacity of each center may be useful.

Opposition Skill Efficiency During Professional Rugby Union Official Games Is Related to Horizontal Force-Production Capacities in Sprinting.

PURPOSE: This study aimed to determine relationships between parameters of force-production capacity in sprinting and opposition skill efficiency in rugby union games according to position. METHODS: The sprint force-velocity profile of 33 professional rugby union players divided into 2 subgroups (forwards and backs) was measured on a 30-m sprint. Skill efficiencies (in percentage) of offensive duels, tackles, and rucks were assessed using objective criteria during 12 consecutive competitive games. Pearson correlation was used to determine the relationships between parameters of horizontal force-production capacity in sprinting (maximum propulsive power, theoretical maximum force [F0], theoretical maximum velocity, maximum ratio of horizontal force [RFmax], and rate of decrease of this ratio of forces with increasing velocity) and skill efficiencies. Two multiple linear regression models were used to observe whether skill efficiencies could depend on determinants of horizontal force application in low- or high-velocity conditions. A first model including F0 and theoretical maximum velocity was used as a macroscopic analysis, while a second model including RFmax and rate of decrease of this ratio of forces with increasing velocity was used as microscopic analysis to determine the most significant determinants of skill efficiency. RESULTS: All skill efficiencies were strongly correlated with maximum propulsive power in forwards and backs. In forwards, F0 and RFmax were the key predictors of dueling, rucking, and tackling efficiency. In backs, F0 was the main predictor of dueling and rucking efficiency, whereas RFmax was the key predictor of dueling and tackling efficiency. F0 and theoretical maximum velocity equivalently contributed to tackling performance. CONCLUSIONS: In rugby union forward and back players, skill efficiency is correlated with maximum propulsive power and may be more explained by horizontal force-production capacity and mechanical effectiveness at lower velocities than at higher velocities.

The monthly incidence of abusive head trauma, inflicted skeletal trauma, and unexplained skin lesion in children in six French university hospitals during the COVID-19 pandemic.

INTRODUCTION: The COVID-19 pandemic was a stressful period. Lockdowns may have added to parental difficulty leading to an increase in violence. This study aimed to compare the monthly incidence of high suspicion of child physical abuse before and during the COVID-19 pandemic. MATERIAL: We have retrospectively reviewed imaging examinations of children having a skeletal X-ray examination in six university hospitals with high suspicion of abusive head traumatism (AHT), inflicted skeletal trauma (IST) and unexplained skin lesions (USL) between March 2020 and June 2021 and compared with the similar period from 2018 to 2019. The monthly incidence of the different physical maltreatment was analyzed using a QuasiPoisson regression model. RESULTS: We included 178 children (n = 127 boys, 71.3 %), 110 during the pandemic period, median age 5 months. AHT was diagnosed in 91 children, 55 had inflicted skeletal trauma (IST) and 46 had unexplained skin lesions (USL). Among the 91 patients with AHT, 86 had a subdural hematoma (95.6 %) and 40 had bridging veins thrombosis (44 %). The ophthalmological examination performed on 89 children (97.9 %) revealed retinal hemorrhages in 57 children (89.8 %). The incidence of AHT doubled during the months of COVID-19 lockdowns (rate ratio = 2; 95 % CI [1.1; 3.6], p = 0.03). No difference in monthly incidence was observed for IST and USL groups. CONCLUSION: A significant increase in AHT was observed during the months with lockdowns and curfews during the COVID-19 pandemic. This highlights the need for developing a national strategy to prevent physical abuse in children in this context.

Neural Drive Impairment in Chronic Kidney Disease Patients Is Associated with Neuromuscular Fatigability and Fatigue.

INTRODUCTION: Chronic kidney disease (CKD) patients have a high degree of fatigue relating to neuromuscular symptoms. There is a lack of evidence regarding the etiology of neuromuscular fatigability in elderly CKD patients. METHODS: Inclusion criteria are as follows: age ≥60 yr, glomerular filtration rate (GFR) <45 mL·min -1 per 1.73 m 2 in CKD patients, and GFR >60 mL·min -1 ·1.73 m -2 in controls. The fatigability protocol consisted in a submaximal handgrip task at 40% peak force. Fatigue was assessed using the Multidimensional Fatigue Inventory-20 items (MFI-20) and the Functional Assessment of Chronic Illness Therapy-Fatigue questionnaires. Peak rate of force development (RFD peak , normalized: NRFD peak ) and rate of EMG rise (RER) were measured during explosive contractions; peak force and mean surface EMG were measured during maximum voluntary contractions. Multilevel models tested neuromuscular parameters adjusted for clinical and Multidimensional Fatigue Inventory-20 items subscales. Neuromuscular fatigability contribution to fatigue description was tested using model comparison. RESULTS: The study included 102 participants; 45 CKD patients and 57 controls. CKD mainly affected the mental and the reduced motivation subscales of fatigue. CKD was associated with greater neuromuscular fatigability assessed using NRFD peak (group-time interaction, -16.7 % MVF·s -1 , P = 0.024), which increased with fatigue severity ( P = 0.018) and with a higher rate of decrement in RER compared with controls (RER at 50 ms: ß = -121.2 µV·s -1 , P = 0.016, and ß = -48.5 µV·s -1 , P = 0.196, respectively). Furthermore, these patients show an association between the reduced motivation subscale and the RER (e.g., 30 ms: ß = -59.8% EMG peak ·s -1 , P < 0.001). Only peak force fatigability contributed to fatigue variance, whereas RFD peak did not. CONCLUSIONS: In CKD patients, the neuromuscular fatigability assessed using RFD peak is related to an impairment in motor-unit recruitment or discharge rates, whereas only peak force fatigability was related to fatigue. This suggests that targeting exercise interventions might lessen fatigue and improve quality of life in CKD patients.

Reliability of 3-D Virtual Abdominal Tele-ultrasonography in Pediatric Emergency: Comparison with Standard-of-Care Ultrasound Examination.

Ultrasound is currently recommended as the first-line examination for abdominal symptoms in children. However, a pediatric radiologist is not always available on site, especially during on-call duty. This study was aimed at evaluating the reliability of an innovative 3-D virtual abdominal tele-ultrasonography in this context. A prospective study was conducted between December 2020 and May 2021 that recruited 103 children undergoing ultrasound for abdominal pain. Trauma cases were excluded. Four tridimensional acquisitions were performed with a Smart Sensor 3D device (Canon Medical Systems, Otawara, Japan). Each tele-ultrasonography was secondarily blindly reviewed by two radiologists (one senior and one resident) with Fusion software (Canon Medical Systems). Acceptance and quality of the acquisitions were evaluated on a Likert scale. Inter-rater reliability was quantified using Cohen's κ coefficient and intraclass correlation coefficient. The ultrasound examination was normal in 66 cases (64%), abnormal in 36 cases (35%) and inconclusive in 1 case (1%). The acquisitions were obtained without objections from the children, their parents or the operators in more than 95% of cases. The quality of the acquisitions was considered good to excellent in 84% and 70% of cases. The sensitivity of the senior radiologist and the resident was 86% and 84%, respectively; specificity was 95% and 92%, positive predictive value 92% and 86% and negative predictive value 92 and 91% when comparing the conclusions of the standard and the tele-ultrasound examinations. Cohen's κ coefficients of the diagnosis obtained with the standard and the tele-ultrasound examinations were 0.82 and 0.71, respectively. The inter-rater Cohen's κ coefficient was 0.84. The intraclass correlation coefficient between the standard abdominal examination and the 3-D tele-ultrasound reformatted images for the following quantitative variables on pathological cases was 0.99 (confidence interval: 0.98-0.99). Virtual abdominal tele-ultrasonography is a promising method in pediatric emergencies.

Repeated practice runs during on-snow training do not generate any measurable neuromuscular alterations in elite alpine skiers.

Background: Alpine skiers typically train using repeated practice runs requiring high bursts of muscle activity but there is little field-based evidence characterizing neuromuscular function across successive runs. Purpose: To examine the impact of repeated ski runs on electromyographic activity (EMG) of the knee extensors and flexors in elite alpine skiers. Methods: Nineteen national team alpine skiers were tested during regular ski training [Slalom (SL), Giant Slalom (GS), Super Giant Slalom and Downhill (Speed)] for a total of 39 training sessions. The surface EMG of the vastus lateralis (VL), rectus femoris (RF), vastus medialis (VM), biceps femoris (BF) and semimembranosus/semitendinosus (SMST) muscles was continuously recorded along with right knee and hip angles. The EMG root mean square signal was normalized to a maximal voluntary contraction (%MVC). The first and fourth runs of the training session were compared. Results: There was no meaningful main effect of run on EMG relative activation time or mean power frequency beyond the skier's intrinsic variability. However, EMG activity of the vastii increased from the first to the fourth run in SL [VM, ~+3%MVC for IL and outside leg (OL), p = 0.035)], speed (VL, IL:+6%/OL:+11%, p = 0.015), and GS (VM, IL:0/OL:+7%, p < 0.001); the later with an interaction with leg (p < 0.001) due to a localized increase on the OL. The run time and turn time did not change from the first to the fourth run. There were no meaningful changes in angular velocities, amplitude of movement, or maximal and minimal angles. Conclusion: Neuromuscular activity remains highly stable in elite skiers with low variability across four runs.

Early Plasma Magnesium in Near-Term and Term Infants with Neonatal Encephalopathy in the Context of Perinatal Asphyxia.

Magnesium ions are implicated in brain functioning. The disruption of brain metabolism subsequent to a perinatal hypoxic-ischaemic insult may be reflected by plasma magnesium. Infants at 36 weeks after birth or later with neonatal encephalopathy and who were admitted to our neonatal unit from 2011 to 2019 were retrospectively included. The kinetics of plasma magnesium were investigated for the first 72 h of life and correlated to the Barkovich MRI score. Among the 125 infants who met the inclusion criteria, 45 patients (36%) had moderate to severe brain lesions on neonatal MRI. Plasma magnesium values were not strongly associated with the severity of clinical encephalopathy, initial EEG background and brain lesions. Intriguingly, higher plasma magnesium values during the 0−6 h period were linked to the presence of brain injuries that predominated within the white matter (p < 0.001) and to the requirement of cardiac resuscitation in the delivery room (p = 0.001). The occurrence of seizures was associated with a lower mean magnesium value around the 24th hour of life (p = 0.005). This study supports that neonatal encephalopathy is a complex and multifactorial condition. Plasma magnesium could help to better identify the subtypes of neonatal encephalopathy. Further studies are needed to confirm these results in this prospect.

Influence of Repeated-Sprint Ability on the in-Game Activity Profiles of Semiprofessional Rugby Union Players According to Position.

This study investigated the influence of repeated-sprint ability (RSA) on the activity of rugby union players in a competitive situation according to their position. Thirty-three semiprofessional rugby union players (age, 25.6 ± 4.3; height, 184.0 ± 8.0 cm; weight, 98.9 ± 13.9 kg, ~20 h training a week), divided into two position subgroups (forwards n = 20, backs n = 13) or four positional subgroups (front row and locks n = 13, back row n = 7, inside backs n = 6, outside backs n = 7), were tested. Their RSA was assessed with a 12 × 20 m sprint test over a 20 s cycle. GPS data (distance, acceleration, number of sprints, maximum velocity, and high-velocity running) and technical data were collected on 18 semiprofessional division rugby union games. In forwards, players with lower cumulated sprint time in the RSA test produced significantly more accelerations (ρ = -0.85, p < 0.001) and more combat actions per match minute (ρ = -0.69, p < 0.001). In backs, RSA was significantly correlated with high-intensity running [distance (ρ = -0.76), Vmax (ρ = -0.84), sprints frequency (ρ = -0.71), high-velocity running (ρ = -0.76), all p < 0.01]. Then, the players were divided into four subgroups (front row and locks, back row, inside backs and outside backs). RSA was significantly associated with the number of accelerations (ρ = -0.96, p <001) and combat actions in front row and locks (ρ = -0.71, p = 0.007). In the back row, RSA was correlated with distance (ρ = -0.96, p = 0.003) and the frequency of combat actions (ρ = -0.79, p = 0.04). In inside backs, RSA was significantly (all p < 0.01) correlated with distance (ρ = -0.81), number of accelerations (ρ = -0.94) and high-velocity running (ρ = -0.94), while in outside backs, RSA was associated with sprint frequency (ρ = -0.85) and the maximal in-game velocity reached (ρ = -0.89). These results demonstrate that RSA is associated with match running and combat activity performance (i) regardless of the position on the pitch and (ii) specifically for each player's position by improving the corresponding activity profile.

Is the Most Commonly Used Strategy for the First 1,500 m of a 2,000 m Rowing Ergometer Race the Most Appropriate?

This study investigated time-courses of physiological and psychological parameters of rowers during the first 1,500 m of a simulated race on a rowing ergometer using different pacing strategies. This provided a picture of the physiological and psychological state of the rowers at the start of the last 500 m of their race. Investigated strategies corresponded either to a degressive (degr), a progressive (prog), or a stable (stab) power output over the traveled distance. Thirteen French rowers (4 oarswomen and 9 oarsmen) of national and ex-international levels volunteered to participate. Handle force and velocity, oxygen uptake, heart rate, blood lactate concentration, and peripheral oxygen saturation were measured during the trials. Power output, generated energy [by O 2 consumption (E oxi ) and blood lactate accumulation (E non-oxi )] and efficiency were computed. Rowers also rated their perceived exertion (RPE) and protocol preference. In the explored strategies, no significant differences were found for E oxi . Final blood lactate concentration ([La] blood ) and RPE were similar for all strategies. However, the increase in [La] blood and RPE occurred sooner for degr than for stab and prog. Therefore, the time spent at higher [La] blood and RPE was longer for degr than for stab and prog. According to the questionnaire, degr was the least preferred protocol. While during 2000 m races, the first 1500 m are usually and empirically often conducted in a degr way, the present results indicate that this strategy was the least preferred by the rowers and led to a higher time spent at high [La] blood and RPE.

Advanced Brain Imaging in Preterm Infants: A Narrative Review of Microstructural and Connectomic Disruption.

Preterm birth disrupts the in utero environment, preventing the brain from fully developing, thereby causing later cognitive and behavioral disorders. Such cerebral alteration occurs beneath an anatomical scale, and is therefore undetectable by conventional imagery. Prematurity impairs the microstructure and thus the histological process responsible for the maturation, including the myelination. Cerebral MRI diffusion tensor imaging sequences, based on water's motion into the brain, allows a representation of this maturation process. Similarly, the brain's connections become disorganized. The connectome gathers structural and anatomical white matter fibers, as well as functional networks referring to remote brain regions connected one over another. Structural and functional connectivity is illustrated by tractography and functional MRI, respectively. Their organizations consist of core nodes connected by edges. This basic distribution is already established in the fetal brain. It evolves greatly over time but is compromised by prematurity. Finally, cerebral plasticity is nurtured by a lifetime experience at microstructural and macrostructural scales. A preterm birth causes a negative and early disruption, though it can be partly mitigated by positive stimuli based on developmental neonatal care.

Petit-Morel method for hip development dysplasia in toddlers: A retrospective observational study in 34 patients.

BACKGROUND: The Petit-Morel method allows the treatment of developmental hip dysplasia in toddlers by combining gradual traction to achieve reduction followed by immobilisation during which pelvic osteotomy is performed. The objective of this study was to assess the radiographic and clinical outcomes in a retrospective cohort of patients. HYPOTHESIS: The Petit-Morel method is associated with low rates of avascular necrosis and residual acetabular dysplasia at skeletal maturity, as well as with satisfactory medium-term clinical outcomes. MATERIAL AND METHODS: We conducted a single-centre retrospective study of 34 patients (35 hips) treated between 1997 and 2014. The radiological assessment criteria included an evaluation for avascular necrosis classified according to Kalamchi and MacEwan, the vertical centre edge (VCE) angle, femoral head sphericity according to Mose, and acetabular dysplasia at skeletal maturity according to Severin. Hip function was assessed by determining the Postel-Merle d'Aubigné (PMA) score. RESULTS: Mean age at treatment was 19±4 months (range, 14-29). Mean follow-up was 11 years (range, 5-20). There were two failures including one case of recurrent dislocation requiring surgical reduction. Group II avascular necrosis occurred in 1 (3%) patient. Tönnis Grade IV dysplasia was significantly associated with resolving irregularity of the ossification centre, seen in 19 (54%) cases (p=0.002). In the 18 patients followed-up to skeletal maturity, with a mean follow-up of 15 years (range, 12-20 years), 17 hips were Severin Class I. The mean VCE angle was 29° (range, 15°-38°), and the head was spherical for 34 (98%) hips. The PMA score at last follow-up was excellent (17-18). The mean VCE angle was greater in all 5 patients who experienced pain during long walks (35° [range, 32°-37°]) than in the asymptomatic patients (28° [range, 15°-38°]) (p=0.009). DISCUSSION: The Petit-Morel method is a reliable treatment that provides good clinical and radiological outcomes. Overcorrection of the VCE angle was noted in the patients who experienced walking-related pain in adulthood. LEVEL OF EVIDENCE: IV, retrospective observational cohort study.