运动肌的发育婴儿到了七个月,已能自由地滚动身体。也就是说,他能从仰卧翻滚到俯卧姿势,并能从俯卧再翻回到仰卧姿势。婴儿到了八个月,则能不依赖任何支撑,独立地坐在床上,并摆弄着放在他周围的玩具。婴儿在三个月时已经开始逐步形成起来的爬行动作到这阶段更加趋于协调。如果让一个九个月的婴儿面孔朝下俯卧在地毯上,并在他的双手够不到的视线范围内放上一个逗人的玩具,婴儿就会以一种强劲有力的爬行姿势力图取得玩具。尽管他还不能抓到玩具,但他的双膝已能移动,双臂往往能径直地伸向目标。 Exercise Muscle Development Infants have been able to roll freely for seven months. In other words, he can roll from supine position to prone position, and from prone position back to supine position. After eight months, the baby can sit alone on the bed and play with the toys around him without relying on any support. The baby’s crawling, which has begun to take shape at three months, tends to be more coordinated at this stage. If a nine-month-old baby faces down on a rug and puts an amusing toy in the sight of his hands, the baby tries to obtain the toy in a powerful crawling pose . Although he could not catch the toy yet, his knees had been able to move and his arms tended to reach the target straight.