Creatine feeding results in greater total muscle creatine levels . Its increase is associated with an improved performance  and higher phosphocreatine resynthesis post-workout (PWO) . Whole body and muscle creatine retention is increased when creatine is taken in conjunction with large amounts of simple carbohydrates. It was suggested that this response was attributable to glucose-mediated insulin release .
Exercise performed immediately before creatine ingestion has been suggested to enhance muscle creatine uptake (little lest than 10%) probably due to increase in blood flow . The study by Green et al.  observed that consumption of carbohydrates with creatine had greater increase in body mass than consuming creatine alone. Further investigation of creatine and carbohydrate combination revealed correlation between muscle glycogen content and creatine uptake. This correlation was not evident when creatine or carbohydrates were ingested alone.
Tristan M. Robinson and co-workers  examined the effect of exercise on muscle creatine accumulation and glycogen resynthesis during post exercise when supplemented with carbohydrates or creatine + carbohydrates. Fourteen men performed one-legged cycling exercise to exhaustion. The major finding of this study was the difference in total creatine content between exhausted and non-exhausted limb in the creatine+carbohydrate group (Pic. 1).
Pic. 1 – Muscle total creatine concentrations. A: results from exhausted (Ex) and non-exhausted (Nex) limbs of carbohydrate group after CHO supplementation B: results from Ex and Nex limbs of creatine (Cr)+CHO group after Cr + CHO supplementation.
Tristan M. Robinson and co-workers  also showed that increase in blood flow in unlikely to have been responsible for the greater creatine content in the exhausted limb. If that was the case the differences in creatine content would be the greatest 6 hours after exercise. This study found that combining creatine and carbohydrate ingestion prior exercise increased glycogen resynthesis during recovery. This increase was sufficient to produce a significant improvement in endurance exercise performance.
- Harris, R. C., K. Söderlund, and E. Hultman. “Elevation of creatine in resting and exercised muscle of normal subjects by creatine supplementation.” Clinical science (London, England: 1979) 83.3 (1992): 367.
- Greenhaff, P. L., et al. “Influence of oral creatine supplementation of muscle torque during repeated bouts of maximal voluntary exercise in man.” Clinical science (London, England: 1979) 84.5 (1993): 565.
- Greenhaff, P. L., et al. “Effect of oral creatine supplementation on skeletal muscle phosphocreatine resynthesis.” American Journal of Physiology-Endocrinology And Metabolism 266.5 (1994): E725-E730.
- Green, A. L., et al. “Carbohydrate ingestion augments skeletal muscle creatine accumulation during creatine supplementation in humans.” American Journal of Physiology-Endocrinology And Metabolism 271.5 (1996): E821-E826.
- Harris R., et al. “Elevation of creatine in resting and exercised muscle of normal subjects by creatine supplementation.“ Clin. Sci. (Colch.) 83:367–374. (1992)
Robinson, Tristan M., et al. “Role of submaximal exercise in promoting creatine and glycogen accumulation in human skeletal muscle.” Journal of Applied Physiology 87.2 (1999): 598-604.