What makes rowing popular with elite athletes and CrossFitters is exactly what many in the general fitness population dislike about it: your weaknesses cannot be hidden on the rowing machine. It is a human polygraph of physical and mental performance. Stroke for stroke, you are provided with feedback that both reveals any weak spots and very visibly demonstrates the relationship between performance and proper technique.  —Angela Hart, "Rowing Technique," CFJ

The box step-up is similar in mechanics to any lunging variation. The athlete must use the strength of one leg to elevate themselves. The higher the box, the greater the demand on both strength and flexibility. Although often used as a scaled version of the box jump, the step-up can provide a challenge to even the most advanced athletes.