Muscle glycogen supercompensation is enhanced by prior creatine supplementation

Purpose: Recently, it was shown that glycogen supercompensation tended (P = 0.06) to be greater if creatine and glycogen were loaded simultaneously. B ecause the authors suggested that creatine loading increased cell volumes a nd, therefore. enhanced glycogen supercompensation, we decided to determine whether an enhanced glycogen supercompensation could be realized if the gl ycogen loading protocol was preceded by a 5-d creatine load. Methods: Twelv e men (19-28 yr) performed two standard glycogen loading protocols interspe rsed with a standard creatine load of 20 g .d(-1) for 5 d. The vastus later alis muscle was biopsied before and after each loading protocol. Results: T he initial glycogen loading protocol showed a significant 4% increase (P < 0.05) in muscle glycogen (<Delta> up arrow 161 +/- 87 mmol . kg(-1) d.m.), and no change (P > 0.05) in total muscle creatine. Biopsies pre- and post-c reatine loading showed significant increases in total muscle creatine level s in both the left leg (Delta up arrow 41.1 +/- 31.1 mmol . kg(-1) d.m.) an d the right leg (Delta up arrow 36.6 +/- 19.8 mmol . kg(-1) d.m.), with no change in either leg's muscle glycogen content. After the final glycogen lo ading, a significant 53% increase in muscle glycogen (Delta up arrow 241 +/ - 150 mmol . kg(-1) d.m.) was detected. Finally, the postcreatine load tota l glycogen content (694 +/- 156 mmol . kg(-1) d.m.) was significantly (P < 0.05) greater than the precreatine load total glycogen content (597 +/- 142 mmol . kg(-1) d.m.). Conclusion: It is suggested that a muscle's glycogen loading capacity is influenced by its initial levels of creatine and the ac companying alterations in cell volume.