「パンダなりきり体操」 means a gymnastic like panda's movement and feeling. You should intend to be Panda, if you do this gymnastic.

なりきり：noun なりきる: verb＝成りきる＝pretend it perfectly. become it almost ～になる＝become~ ~きる＝perfectly do something　or 　to cut(切る　きる） ex: 走りきる＝run the all way 食べきる＝eat evrything 仕事をやりきる＝do my work pefectly パンダになりきる＝pretend Panada well.

Pretending-to-be-a-panda gymnastics.