Effect of summer intermission on skeletal muscle of adolescent soccer players

Background. To study the effect of some weeks of rest on three groups of ad olescent soccer players, who had undergone systematic training for eleven m onths. Methods. Experimental design: Retrospective and comparative investigation; duration 4-8 weeks. Setting: young amateur players from a Spanish football club were examined at the beginning and at the end of the summer rest perio d. Participants: 37 young soccer players aged 14, 15 and 16 years old. They were members of three football teams. Interventions: during the rest perio d they were free from any training program. Measures: biopsies of M. vastus lateralis mere taken immediately after training and after the summer holid ays. The type, percentage and diameter of the fibers, as well as the enzyme s of glycogen metabolism (glycogen synthase and glycogen phosphorylase), gl ycolysis (phosphofructokinase and lactate dehyrdrogenase), oxidative metabo lism (succinate dehydrogenase and citrate synthase) and creatine kinase and transaminase (aspartate and alanine aminotransferase) were studied. Results. Detraining had an adaptation effect, decreasing the cross-sectiona l area of type I and type II fibers, and decreasing the activities of creat ine kinase, citrate synthase, phosphofructokinase, lactate dehydrogenase an d aspartate aminotransferase. Conclusions. The results can help trainers to plan the length of the rest p eriod between training.