A cognitive prerequisite for education and (re)entry into the labor market is the ability to concentrate for a long period. Conducted with 39 participants, the present study examines the effect of a six-week dance-like martial arts program on prisoners' concentration ability in an open prison in Germany (n=15), and compares their concentration ability with a control group of prisoners (n=5), as well as a treatment (n=11) and control group (n=8) of university students. Concentration ability is assessed using the d2-R concentration and attention test before, after, and six weeks following the program. The program's participants showed significant improvements compared to the prisoners' control group, with levels eventually matching those of university students. The findings suggest that practicing voluntary sports with qualified coaches in an environment protected from observers enhance concentration ability and should, therefore, be implemented as an integral part of rehabilitation processes in prisons.