COCONTRACTION IN 3 AGE-GROUPS OF CHILDREN DURING TREADMILL LOCOMOTION

This study attempted to assess and compare the amount of cocontraction present in thigh and leg muscles in three groups of children during t readmill walking and running. Thirty children, aged 7-8 (n=10), 10-12 (n=10) and 15-16 (n=10) years, performed 4-min bouts of submaximal tre admill exercise at two walking and four running speeds, assigned in a randomized order. Three seconds of EMG data were collected Juring the final minute of each bout from the vastus lateralis (VL), hamstrings ( H), tibialis anterior (TA) and soleus (S). The processed linear envelo pes of VL and H, and likewise of TA and S, were overlapped and a cocon traction index calculated (area of overlap divided by the number of da ta points) for thigh and leg segments, respectively. Cocontraction was highest for the youngest children and lowest for the oldest, for both thigh and leg, whether expressed in terms of absolute speed or as a p ercentage of each child's (V) overdot O-2 max. Larger amounts of cocon traction may help to explain the higher metabolic cost of locomotion f or younger children, when compared with adolescents and adults. (C) 19 97 Elsevier Science Ltd.