"Bent arms" refers to the position where your arms are not fully straightened but are slightly curved or flexed at the elbows.
Sentences with «bent arms»
Keeping the body straight, lower body to the ground by bending arms at the elbows. (hundredpushups.com)
However, wrapping them with bent arms is often a disaster! (shrewdmommy.com)
Place your hands on the edge of the platform, then lower your body by bending arms until a slight stretch is felt in chest or shoulder, or your rear end touches floor. (mindbodygreen.com)