GSK3B and myotonic dystrophy type 1: To determine if the increase in active GSK3β in the blood samples of patients with adult-onset DM1 correlates with muscle weakness, we examined the skeletal muscle performance in the group of DM1 patients, in which GSK3β levels were evaluated (Figure 1B,C), by measuring the grip strength, ankle dorsiflexion strength, manual strength and walking distance during the 6 min test.