The Influence of Training Status on ERK and Akt Phosphorylation in Human Skeletal Muscle

Abstract

PURPOSE: To examine the influence of training status on ERK and Akt phosphorylation (PHOS) at rest and following an acute bout of resistance exercise (RE). METHODS: Twenty young men comprised a sedentary (SED n=7; 21 ± 2 y, 79 ± 16 kg, 42 ± 5 ml·kg-1·min−1, 48 ± 9 kg 1-RM), a resistance trained (RT n=7; 22 ± 2 y, 90 ± 8 kg, 47 ± 5 ml·kg-1·min−1, 76 ± 6 kg 1-RM), and endurance trained group (ET n=6; 25 ± 3 y, 69 ± 5 kg, 67 ± 7 ml·kg-1·min−1, 49 ± 6 kg 1-RM) that performed three sets of 10 repetitions of unilateral knee extension at 70% of 1-RM. Vastus lateralis muscle biopsies were taken before, immediately post (PT-0) and 10 min post (PT-10) RE. Muscle tissue was analyzed for ERK and Akt PHOS using the ELISA method. RESULTS: There were no differences among the groups in ERK or Akt PHOS prior to RE. With RE, ERK PHOS increased (p<0.05) 47% and 54% at PT-0 in SED and RE, respectively, with no change in ET. At PT-10, all three groups had an increase (p<0.05) in ERK PHOS (RT>SED>ET). Akt PHOS decreased (p<0.05) 42% in SED and showed a trend to decrease (p<0.06) in ET at PT-0. At PT-10, Akt PHOS increased (p<0.05) 35% in ET. Akt PHOS was unchanged at PT-0 and PT-10 in the RT group. CONCLUSION: These data indicate that training status influences the magnitude and time course of ERK and Akt phosphorylation in response to an acute bout of RE. With chronic exercise, the observed differences in intracellular signaling may influence skeletal muscle adaptation.