The FAA categorizes it with four intensity levels: light, moderate, severe, and extreme.

美国联邦航空管理局将其强度分为四个等级：轻度、中度、严重和极端。

Depending on the intensity levels that we could go, whether it's super hard, moderate, or easy, it can serve from anything technically as a recovery workout to more something as higher intensity.

根据强度的不同，无论是超级难，中等，简单，从技术上讲，它可以作为恢复性锻炼，也可以作为更高强度的锻炼。

A 2016 study found that elderly people who exercised for just 15 minutes a day, at an intensity level of a brisk walk, had a 22% lower risk of early death compared to people who did no exercise.

2016年的一项研究发现，每天只锻炼15分钟，强度相当于快走的老年人，比起那些完全不锻炼的早死的风险要低22%。