You can practise some simple yoga poses like a partial sun salutation while you walk. Simply walk comfortably, take a deep breath, lift your arms to your sides until both palms are touching above your head, and repeat. As you lower them to your sides, let out a breath.
Try the following to open up your shoulders and chest:
As you continue to walk, interlace your fingers behind you, palms facing your back, and softly raise both arms.
As long as it’s comfortable, hold. Repeat both motions intermittently while you walk.