This study aims to compare the neural motor control performance between the flexion and extension phase of kicking using Electromyography (EMG)in 3-5 months old full-term infants.
Twelve healthy full-term infants aged 3 to 5 months were recruited. Infants were placed in supine position to record five minutes kicking data at home. Twelve EMG sensors were placed on six lower limb muscles bilaterally (rectus femoris; RF, biceps femoris; BF, vastus lateralis; VL, adductor longus; AL, tibialis anterior; TA, and medial gastrocnemius; MG). EMG data were recorded with simultaneous video recordings for coding. The percentage of co-contraction time and duration between agonist-antagonist muscle pairs (RF/BF, TA/MG, RF/TA, RF/MG, BF/MG, BF/TA, AL/VL) and integrated EMG (iEMG) during co-contraction of each muscle in both the flexion and extension phases were compared. Wilcoxon signed-rank test will be used for the statistical analyses (α=0.05).
There is no significant difference on the co-contraction duration between flexion and extension phase while the percentage of co-contraction time was significantly larger during the extension phase in all muscle pairs except TA/MG (p0.05) when compared with flexion phase. Additionally, a trend of greater activation of RF in RF/BF muscle pair (p=0.084) and MG in BF/MG muscle pair (p=0.071), as well as significantly larger VL in AL/VL muscle pair (p=0.034) were detected.
This preliminary study showed that 3-5 months old infants exhibit longer proportion of co-contraction time in different muscle pairs during the extension phase than the flexion phase. It means that infants at this age may start to demonstrate the ability of eccentric contraction or be able to adjust the direction and speed during the extension phase of a kicking cycle. However, accompanied ankle synergy may still present with the movement of other joints at this stage.
The finding of this preliminary study gives insight into the maturation level of neuromotor control ability during kicking in 3-5 months old infants. The result can serve as the basis for future longitudinal study to fully understand the course of kicking development, which can provide a valuable reference to assess aberrant development in high-risk infants.
kicking
infants
