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1 Human Performance Laboratory, Ball State University, Muncie, IN, USA
* To whom correspondence should be addressed. E-mail: strappe{at}bsu.edu.
Two pathways that have been implicated for cellular growth and development in response to muscle contraction are the ERK1/2 and Akt signaling pathways. Although
these pathways are readily stimulated following exercise, little is known about how nutritional status may affect stimulation of these pathways in response to resistance
exercise in human skeletal muscle. To investigate this, experienced cyclists performed 30 repetitions of knee extension exercise at 70% 1-RM following a low (2%; LCHO) or high (77%; HCHO) carbohydrate diet, which resulted in low (~174 mmol/kg dry wt) or high (~591 mmol/kg dry wt) pre exercise muscle glycogen content. Muscle biopsies
were taken from the vastus lateralis pre, post (~20 s), and 10 min post exercise. ERK1/2 and p90rsk phosphorylation increased (P 
0.05) 10 min post exercise regardless of muscle glycogen availability. Akt phosphorylation was elevated (P < 0.05)
10 min post exercise in HCHO, but was unaffected following exercise in LCHO. mTOR phosphorylation was similar to that of Akt during each trial, however changes or lack
thereof were not significant. In conclusion, the ERK1/2 pathway appears to be unaffected by muscle glycogen content. However, muscle glycogen availability appears
to contribute to the regulation of the Akt pathway, which may influence cellular growth and adaptation in response to resistance exercise in a low glycogen state.
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