Effects of Contraction Mode and Velocity on the Maximal Voluntary Activation Level of the Knee Extensors in Boys and Men - The 2016 Wingate Congress of Exercise and Sport Sciences

Vincent Martin ¹ Virginie Kluka ^1,2 Sebastian Garcia Vicencio ¹ Mathias Giustiniani ³ Claire Morel ³ Cédric Morio ² Emmanuel Coudeyre ^3,4,5 Sébastien Ratel ¹

¹Laboratory of Metabolic Adaptations During Exercise in Physiological and Pathological Conditions, Clermont Auvergne University, Blaise Pascal University, France
²Decathlon Research & Development, Decathlon, France
³Clermont University Hospital, France
⁴Human Nutrition Unit, INRA, France
⁵Clermont Auvergne University, Auvergne University, France

Background: The maximal voluntary activation level (VA) has been shown to be lower in children than adults in isometric condition but no data are available in dynamic condition. However, one may suggest that the effect of the tension-limiting mechanism may be lower in children, owing to their lower musculo-tendinous stiffness.

Aim: To compare the effects of contraction mode and velocity on the VA of the knee extensors (KE) between boys and men.

Methods: Seven boys (11.3 ± 0.5 y) and fifteen men (25.3 ± 2.8 y) performed maximal voluntary contractions (MVC) of the KE muscles at three contraction modes and two knee angular velocities (isometric condition: 50° of knee flexion, 0° = full extension; eccentric conditions: -20°.s^-1, -60°.s^-1; concentric conditions: +20°.s^-1, +60°.s^-1). Single magnetic stimulations were delivered to the femoral nerve during MVCs during eccentric and concentric contractions to determine VA.

Results: On average, MVC torque was significantly higher in men than in boys. MVC torque was also significantly higher during isometric contraction compared to eccentric and concentric contractions in adults, but not in children. No significant interaction of group × contraction velocity was found on VA, but a significant effect of contraction velocity was observed, VA being greater in isometric condition compared to eccentric and concentric modalities, whatever the group considered.

Discussion and Conclusion: The results of the current study suggest that a tension-limiting factor seems present in children and adults during isokinetic contractions, but that its effect on voluntary torque output is less significant in children.