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NELSON, A. G., D. A. ARNALL, J. KOKKONEN, R. DAY, and J. EVANS. Muscle glycogen supercompensation is enhanced by prior creatine supplementation. Med. Sci. Sports Exerc., Vol. 33, No. 7, 2001, pp. 1096-1100.

Purpose: Recently, it was shown that glycogen supercompensation tended (P = 0.06) to be greater if creatine and glycogen were loaded simultaneously. Because the authors suggested that creatine loading increased cell volumes and, therefore, enhanced glycogen supercompensation, we decided to determine whether an enhanced glycogen supercompensation could be realized if the glycogen loading protocol was preceded by a 5-d creatine load.

Methods: Twelve men (19-28 yr) performed two standard glycogen loading protocols interspersed with a standard creatine load of 20 g[middle dot]d-1 for 5 d. The vastus lateralis muscle was biopsied before and after each loading protocol.

Results: The initial glycogen loading protocol showed a significant 4% increase (P < 0.05) in muscle glycogen ([DELTA][up arrow]164 /- 87 mmol[middle dot]kg-1 d.m.), and no change (P > 0.05) in total muscle creatine. Biopsies pre- and post-creatine loading showed significant increases in total muscle creatine levels in both the left leg ([DELTA][up arrow]41.1 /- 31.1 mmol[middle dot]kg-1 d.m.) and the right leg ([DELTA][up arrow]36.6 /- 19.8 mmol[middle dot]kg-1 d.m.), with no change in either leg's muscle glycogen content. After the final glycogen loading, a significant 53% increase in muscle glycogen ([DELTA][up arrow]241 /- 150 mmol[middle dot]kg-1 d.m.) was detected. Finally, the postcreatine load total glycogen content (694 /- 156 mmol[middle dot]kg-1 d.m.) was significantly (P < 0.05) greater than the precreatine load total glycogen content (597 /- 142 mmol[middle dot]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 accompanying alterations in cell volume.

(C) 2001 Lippincott Williams & Wilkins, Inc.