Participants in the strength-training group increased their combined plantar flexor-knee extensor strength more than the control group at 6 weeks (F(1.19)=4.58., p=0.046) and 18 weeks (F(1.18)=6.25, p=0.041). The strength of these muscles is important for erect posture and for providing support during standing and walking (Winter, 1991; Rodda & Graham, 2001). There was not a significant change in activity using the dimensions of D & E of the Gross Motor Function Measure (Russell et al. 1993). There was a trend for the strength-training group to improve walking, running, jumping, and stair climbing more than the control group.