Boris Jidovtseff

Is the Sørensen test valid to assess muscle fatigue of the trunk extensor muscles

BACKGROUNDnVery few studies have quantified the degree of fatigue characterized by the decline in the maximal voluntary contraction (MVC) force of the trunk extensors induced by the widely used Sørensen test.nnnOBJECTIVEnMeasure the degree of fatigue of the trunk extensor muscles induced by the Sørensen test.nnnMETHODSnEighty young healthy subjects were randomly divided into a control group (CG) and an experimental group (EG), each including 50% of the two genders. The EG performed an isometric MVC of the trunk extensors (pre-fatigue test) followed by the Sørensen test, the latter being immediately followed by another MVC (post-fatigue test). The CG performed only the pre- and post-fatigue tests without any exertion in between.nnnRESULTSnThe comparison of the pre- and post-fatigue tests revealed a significant (P< 0.05) decrease in MVC force normalized by body mass (-13%) in the EG, whereas a small increase occurred in the CG (+2.7%, P= 0.001).nnnCONCLUSIONSnThis study shows that the Sørensen test performed until failure in a young healthy population results in a reduced ability of the trunk extensor muscles to generate maximal force, and indicates that this test is valid for the assessment of fatigue in trunk extensor muscles.

Influence of Isoinertial-Pneumatic Mixed Resistances on Force-Velocity Relationship.

PURPOSEnMuscle strengthening is commonly based on the use of isoinertial loading, whereas variable resistances such as pneumatic loading may be implemented to optimize training stimulus. The purpose of the current study was to determine the effect of the ratio between pneumatic and isoinertial resistance on the force-velocity relationship during ballistic movements.nnnMETHODSnA total of 15 participants performed 2 concentric repetitions of ballistic bench-press movements with intention to throw the bar at 30%, 45%, 60%, 75%, and 90% of the maximal concentric repetition with 5 resistance ratios including 100%, 75%, 50%, 25%, or 0% of pneumatic resistance, the additional load being isoinertial. Force-, velocity-, and power-time patterns were assessed and averaged over the concentric phase to determine the force-velocity and power-velocity relationships for each resistance ratio.nnnRESULTSnEach 25% increase in the pneumatic part in the resistance ratio elicited higher movement velocity (+0.11 ± 0.03 m/s from 0% to 80% of the concentric phase) associated with lower force levels (-43.6 ± 15.2 N). Increased isoinertial part in the resistance ratio resulted in higher velocity toward the end of the movement (+0.23 ± 0.01 m/s from 90% to 100%).nnnCONCLUSIONSnThe findings show that the resistance ratio could be modulated to develop the acceleration phase and force toward the end of the concentric phase (pneumatic-oriented resistance). Inversely, isoinertial-oriented resistance should be used to develop maximal force and maximal power. Resistance modality could, therefore, be considered an innovative variable to modulate the training stimulus according to athletic purposes.

Wat zijn de risico’s van vroege sportspecialisatie op de gezondheid van kinderen?

SamenvattingEnkele wetenschappelijke studies uit de jaren 90xa0toonden aan dat wie in bepaalde domeinen zoals sport een zeer hoog niveau wil bereiken, al heel vroeg en intens moet beginnen te trainen. Wie te lang wacht, maakt maar weinig kans om ooit de top te bereiken. De media-aandacht voor jonge sporters, de organisatie van belangrijke jeugdcompetities en de prestatiedrang op erg jonge leeftijd, hebben bijgedragen tot vroege specialisaties. Echter toonden de onderzoekers aan dat die aanpak niet bijzonder efficiënt is en bovendien de ontwikkeling en de gezondheid van het kind in het gedrang kan brengen. De laatste jaren worden alternatieve en kindgerichte oplossingen voorgesteld als ontwikkelingsmodellen op lange termijn.

Effects of twelve weeks of aerobic or strength training in addition to standard care in Parkinson’s disease: a controlled study

BACKGROUNDnPhysical exercise in addition to standard care (SC) in patients with Parkinsons disease (PD) is now a common practice in many care units. However, exercises can cover a wide range of interventions, and the specific effects of different interventions still deserve to be further investigated.nnnAIMnThe aim of this study was to compare the effects of 12 weeks of two different types of physical exercises with SC in patients suffering from PD.nnnDESIGNnPseudo-randomized controlled trial.nnnSETTINGnUniversity laboratory for outcomes, University Hospital Centre for interventions.nnnPOPULATIONnFifty-two outpatients suffering from mild to moderate PD at baseline.nnnMETHODSnParticipants were allocated to three groups: the strength training (ST) group performed individualized upper and lower limbs strength training, the aerobic training (AE) group performed tailored gradual aerobic cycling, and the third group received SC. The effects of the interventions on body function were assessed by measuring isokinetic concentric peak torque for knee extension and flexion, peak oxygen consumption (VO2peak) and peak work load (PWL) during an incremental maximal cycling test. Changes in mobility were evaluated from spatial-temporal gait features measured by mean of an accelerometer system and the Six-Minute Walk Distance (6MWD) Test. We used questionnaires to estimate health-related quality of life and habitual physical activity.nnnRESULTSnNo significant changes in any outcome measures occurred in the SC group. More than 80% of the participants adequately completed the AE and the ST interventions. The ST group significantly improved all peak torque measures (P≤0.01), except knee extension in the least affected side (P=0.13). This group also improved the PWL (P=0.009) and 6mwd (P=0.03). The AE group improved the VO2peak (P=0.02) and PWL (P<0.001).nnnCONCLUSIONSnPhysical fitness in patients with PD rapidly improved in compliance with training specificities, but better fitness hardly translated into better mobility and health-related quality of life.nnnCLINICAL REHABILITATION IMPACTnPhysiotherapists can efficiently propose physical conditioning to patients with mild to moderate PD, but these interventions are insufficient to improve gait and participation. Notwithstanding, ST is an efficient intervention for improving walking capacity.