Neuromuscular, kinetic and kinematic differences in drop jumping between male adolescents with and without intellectual disability

Abstract

Background: Individuals with intellectual disability (ID) have lower performance in vertical jumps compared to individuals without ID. Training programmes including drop jump (DJ) exercises to gap this deficit are required. However, there is a lack of knowledge on biomechanical variables may influence DJ performance in young people with ID.

Research question: Are there differences in the neuromuscular, kinetic and kinematic parameters in DJ between male adolescents with and without ID (WID and NID, respectively).

Methods: Thirteen male adolescents WID (Wisk III intelligence quotient: 55.6 ± 11.2) and thirteen age-matched boys NID executed DJ from 30 cm on a force-plate. The vastus lateralis (VL) and biceps femoris (BF) electromyogram (EMG) as well as the knee kinematics and kinetics were obtained.

Results: WID had significantly (p < .05) lower DJ height, knee power, peak angular velocity and stiffness compared to NID. VL activity was higher and BF/VL co-activation was lower in WID than NID.

Significance: The deficit in DJ performance shown in WID was accompanied with lower power and stiffness, as well as lack of coordination in the lower limb muscles. Improving these variables, with specific and targeted training interventions, may diminish the performance gap with their age-matched counterparts.

Keywords: Adolescence; Biomechanics; Electromyography; Intellectual disability; Stretch-shortening cycle; Vertical jump.