In this study, we investigate whether training of the posterior thigh muscles with visual feedback on muscle activity is more effective than the same training without feedback. To this end, healthy, physically active adults complete a training programme on a training device twice a week for five weeks. Muscle strength, muscle activity, and flexibility are measured before and after the training. Participants are randomly assigned to one of two groups: one group trains with feedback on muscle activity, the other without. Participation involves minimal risks, similar to those of a typical strength training session (e.g. muscle soreness). The aim of the study is to improve training methods for the prevention of muscle injuries.