1·He threw a summersault on the bed.
他在床上翻了一个筋斗。
2·AB: I was 24 years old and at the top of my game when a freak summersault while downhill skiing paralyzed me.
阿曼达：我24岁时在生命的最巅峰，我速降滑雪时不慎摔倒，我瘫痪了。