Stretching periodically is one of the best things that you can do to prevent muscle stiffness. Every hour or so, stand up from your chair and stretch different parts of your body. Do this slowly to avoid pulling a muscle.
Chair squats do not require any equipment yet it can strengthen your legs, glutes, and core. Your bodyweight provides more than adequate resistance. Stand straight with feet shoulder-width apart. Lower yourself with hands forward until you are an inch above the chair. Stand up slowly and do it all over again.
Sitting on an exercise ball one of the best low impact desk exercises since you don’t even need to move around or expend much energy. However, you can develop better balance and core strength just maintaining this position.
Walking on a desk treadmill is another option to consider if you have the budget and space for it.