[2] In 1982, Yessis traveled to the Soviet Union to work with Yuri Verkhoshansky, a biomechanist and sports trainer.

[citation needed] Yessis' teaching career focused on a performance-based version of sports conditioning and training.

Yessis was the editor-in-chief for The Fitness and Sports Review International, a quarterly publication from 1966 to 1994.

In addition, Yessis provided translation and original writing contributions to Soviet Sports Review.

Yessis served as a training and technique consultant to the Los Angeles Rams and Los Angeles Raiders of the NFL and trained former All-American and Oakland Raider Marv Marinovich and his son, Todd[6] Marinovich,[7] helping Todd to become a first-round draft[8] choice.