This pose is one of the most comfy ones for the lower back and hips. It will also stretch your neck, shoulders, and chest. Lie on your back and hug your knees into your chest. Breathe in deeply, and then exhale completely, lowering both legs to the floor on your left (keep your knees higher than your hips). Position your arms out to your sides, or place your left forearm on your right thigh (as pictured) to encourage a deep stretch, relaxing both shoulders to the floor. Shift your gaze over your right shoulder. Close your eyes, take 10 deep breaths, and then release. Repeat to your other side.
For example, one workout you may want to do lateral lunges with mini-band ankle walks. Another workout you may choose rotational step-ups with the 4-way cable hip exercise. The activation, mobility, and flexibility exercises can be done more frequently and not necessarily as part of a stand-alone workout. There's no one-right way to incorporate these exercises, so don't be afraid to experiment.
You can strain or tear one or more of your hip flexors when you make sudden movements such as changing directions while running or kicking. Sports and athletic activities where this is likely to occur include running, football, soccer, martial arts, dancing, and hockey. In everyday life, you can strain a hip flexor when you slip and fall, for example.