ABSTRACT
Strength, power, and coactivation levels were measured during knee extension and flexion tasks in 20 children (13 males, 7 females) with developmental coordination disorder (DCD) and 20 age-matched control children (12 males, 8 females). Participants were classified according to results obtained on the McCarron Assessment of Neuromuscular Development, with each group including two age levels: 6 to 7 and 9 to 10 years. Tasks were performed on a Biodex dynamometer under isometric and isokinetic conditions with surface EMG recorded from the vastus lateralis and biceps femoris muscles. Significant effects of group and age were observed for the measures of peak torque (isometric and isokinetic) and power, with the decreased power in the group with DCD being more apparent at higher velocities. A lower flexor-extensor percentage was recorded for the group with DCD but only under isokinetic conditions. From a neuromuscular perspective, the group with DCD had increased levels of coactivation (RMS agonist:RMS antagonist) during the isometric flexion and isokinetic extension actions. Possible causes of the strength and power deficits observed in children with DCD are discussed.
Subject(s)
Knee/physiopathology , Motor Skills Disorders/physiopathology , Muscle Contraction/physiology , Anthropometry , Child , Electromyography , Female , Functional Laterality/physiology , Humans , Male , Motor Skills/physiology , Muscle, Skeletal/physiopathology , Physical Exertion/physiology , Postural Balance/physiology , TorqueABSTRACT
The patellar tendon reflex (PTR) and simple visual reaction time (RT) were fractionated and compared in 40 subjects with developmental coordination disorder (DCD) and normal coordination (NC) in two age groups. Four equal groups of subjects, 6 years DCD (6DCD), 6 years NC (6NC), 9 years DCD (9DCD), and 9 years NC (9NC) were compared using ANOVA for the main effects of coordination and age. PTR and its components of reflex latency and motor time were not significantly affected by the level of coordination; however, a significant coordination by age interaction (p < .05) revealed an increased motor time in the 6DCD group. RT, premotor time, and motor time were all significantly (p < .05) increased in children with DCD; the increased RT and premotor time support earlier findings, whereas the increased motor time has not previously been found. These findings suggest that the processing of reflexive and volitional responses by children with DCD differs from that of their NC peers.
