Milton here's got it all wrong. Look at him there; sitting slouched at his desk, probably in terrible men's dress shoes.
The first thing Milton needs to do is get himself a standing desk at work. http://www.marksdailyapple.com/standing-at-work/
A standing desk allows us to engage our core, keep good posture, prevent hip flexor tightening and muscular imbalance down the kinetic chain. Milton will be in a much better position to defend his swingline stapler too.
Now, we can strenghen those legs and feet. The first suggestion is always copious calf stretching. Eccentric calf stretching off the edge of a stair (forefoot on the stair, slowly lower the heel as far as you can go), or just do the classic and prop the forefoot against the wall and lean forward.
Our ability to strengthen the muscles of our core has benefits for every lower extremity exercise. For running, balancing on one leg like a flamingo is one of the easiest and best exercises you can get in at your desk. Focus on maintaining pelvic stability and neutrality when you do this; don't just let the hip bear the weight and allow drop on the opposite side. From this position, you can do one-legged squats as well.
Do sets of calf raises from a standing position (or as part of the eccentric calf stretches I mentioned before, if you have a step) Then do sets of 30 seconds standing on your heels (raise the forefoot up and bear all weight on your two heels). This strengthens the anterior leg muscles and challenges your heels to bear weight on their own.
If you can take your shoe off at work, also stretch the top of your foot by curling the toes downward, plantaflexing the ankle (downward) and stretching the top of your foot and anterior leg using the floor. While you've got your shoe off, toss a golf ball on the floor and do deep tissue massage to the bottom of the foot to the plantar fascia and deep layers of muscles in the foot. Go extreme and do the "Laird Hamilton Foot Torture" and put as much weight on the golf ball as you can tolerate. Work up slowly, but challenge the foot.
With your shoes on or off, get some toe exercises in. First, crunch your toes up in sets of 10-20, as if you're grabbing the ground or bottom of your shoe. Next, push your big toe down into the shoe or ground with force for approx 20 seconds. Repeat and try to lift your lesser toes UP at the same time you're driving your great toe DOWN.
"Might as well do somethin' while you're doing nothin'!"
FIRST, get a standing station at work!
1. Eccentric calf stretches (and calf raises)
2. Top of foot/anterior leg stretch
3. Wall calf stretch
4. Whatever other lower extremity stretching you can think of! I suggest hip flexors, but you're already pushing it! Save those for after work!
1. One legged balance, focusing on maintaining pelvic stability and not letting the hip drop
2. One legged balance with squat
3. Heel standing for 30 sec at a time
4. Foot massage with a golf ball/ Laird Hamilton Foot Torture
5. Toe crunches
6. Big toe "pushes" and big toe pushes with lesser toe raise
Keep strengthening those feet for natural foot function and health!!!!