Cording one week later

Happily, there is a marked improvement! I don't feel the tight bands anymore.

Mondor's syndrom of superficial thrombophlebitis can be a side effect of breast surgery or can also be caused by vigorous exercise, see https//www..breastcancercare.org.uk/.
Some cases in men have occurred due to push-ups or  yoga postures.

In my case it is likely the combination of mastectomy and circuit training that included 3 rounds of 10 fast reps GHD sit-ups.

The occurrence is likely underreported, not well-studied, and treatments are unclear. Physical therapy is described here: physical therapy for axillary cord formation

I am using stretches (lunges with arms back), and manual self-massage whereby taking areas of the chest and pulling them apart (at first it makes popping noises, then less so), and a herbal supplement that is anti-inflammatory. A few light days of exercises, but still including Pilates and weightlifting, and bicycling. No sit-ups!

Update from the future: It took about 3-4 weeks to resolve.

Here is a comparison:

2 days after GHD sit ups

one week later