STRENGTH DEFICIT OF KNEE EXTENSOR MUSCLES OF INDIVIDUALS WITH DOWN-SYNDROME FROM CHILDHOOD TO ADOLESCENCE

The isokinetic strength of the knee extensor muscles of both limbs, at the speed of 30-degrees/second, was evaluated in 25 children and adol escents with Down syndrome. Comparison with two control groups of 40 i ntellectually average individuals and 30 individuals with mental retar dation of unknown origin showed that both children and adolescents wit h Down syndrome were weaker than were the control subjects. Moreover, by the age of 14 years, adolescents with Down syndrome failed to show the muscle strength increase that physiologically occurs by this age. Interlimb comparison of knee extensor muscles showed a strength domina nce in the 44% of individuals with Down syndrome, with a prevalence fo r the left leg. In conclusion, our data suggest the presence of a dysf unction of the neuromuscular system both at the level of the pyramidal system and/or of the neuromuscular junction, possibly as an expressio n of premature ageing.