Strasburg left his start Friday night at Cincinnati because of neck stiffness after 16 pitches and was put on the DL the following day.
The session Wednesday took place on the flat ground in the outfield of Nationals Park, one day after Nationals manager Matt Williams said Strasburg would not throw until he ''feels good.''
Strasburg emerged without discomfort, Williams said before Wednesday's game against Toronto.
The right-hander was examined Monday by team doctors in Washington and diagnosed with a strained left trapezius, an upper back muscle where the arm meets the neck.
Strasburg is 3-5 with a 6.55 ERA in 10 starts and failed to last four innings in four of five outings in May.