translation.en: The head is held in line with the spine, so that you use strategic water pressure to raise your legs up -- very important, especially for people with lower body fat.
translation.zh: 头部和脊柱保持直线， 令你能够利用水压抬起你的双腿。 这点非常重要，尤其是对于身体脂肪含量少的人来说。