These are large, full-range movements of one or more joints at once, often performed standing and sometimes while walking or jogging. They resemble old-school movements you might have done in calisthenics or gym class: arm swings, leg swings, high-knee walks. You usually count off reps, rather than time, on dynamic stretches, which work best as a warm-up activity before a workout, or any time you need a pick-me-up boost throughout the day.
A sedentary lifestyle can lead to having weak and tight hip flexors as they are always in the shortened position. Tight hip flexors can lead to a limited range of motion, poor posture, lower back and hip pain, and even injuries. These muscles need to get a workout when you are standing and doing movements such as raising your leg to climb stairs, run, or ride a bicycle.