Exercise induces morphological and metabolic adaptations that are highly specific to the mode of exercise training. These specific phenotypical changes are due to an equally specific molecular response that may depend on the activation and coordination intramuscular signaling pathways. Just as metabolic and morphological changes are influenced by the mode of exercise training, the signaling pathways that mediate exercise adaptation may also be directly related to the training status of skeletal muscle. For example, pre-conditioned skeletal muscle may exhibit a specific intracellular signaling response to an acute bout of exercise that is dependent on past training history. Both Akt (protein kinase B) and extra-cellular signal-related kinase (ERK 1 /2) have been shown to be phosphorylated in response to an acute bout of resistance exercise in human skeletal muscle and have been suggested to mediate the adaptive response to exercise. The purpose of this investigation was to examine the response of Akt and ERKI/2 to an acute bout of resistance exercise in three groups with distinctly different exercise training backgrounds. Twenty one subjects performed 3 sets of 10 repetitions of knee extension exercise at 70% 1-RM. The subjects consisted of a resistance-trained group (RE) (n=7), endurance trained group (END) (n=7) and a sedentary group (SED) (n=7). Muscle biopsies were taken from the vastus lateralis muscle before, immediately after, and 10 min post-exercise and were analyzed for phosphorylation of Akt and ERK1/2. ERK1/2 phosphorylation increased 47%, and 54% from pre-exercise to immediately post-exercise in the SED and RE groups respectively (p < 0.05). ERK1/2 phosphorylation increased 95%, 196%, and 47% from pre-exercise to 10 min post-exercise in the SED, RE, and END groups, respectively. (p < 0.05). The magnitude of ERK1/2 phosphorylation 10 min post-exercise was different between each group and may be linked to the group's training status. (p < 0.05) Akt phosphorylation decreased 42% and 37% from pre-exercise to immediately post-exercise in the SED and END group, respectively (p < 0.05). There was a 40 % increase in Akt phosphorylation from immediate post-exercise to 10 min post-exercise in the END group. In conclusion, training status appears to influence the magnitude and time course of activation of both Akt and ERK1/2 in response to an acute bout of resistance exercise. The immediate response of both ERK1/2 and Akt may play a key role in the adaptive response of skeletal muscle ultimately resulting in metabolic and morphological changes that are dependent on the past training history of the individual. / School of Physical Education, Sport, and Exercise Science
| Identifer | oai:union.ndltd.org:BSU/oai:cardinalscholar.bsu.edu:handle/187949 |
| Date | January 2005 |
| Creators | Conley, Travis B. |
| Contributors | Trappe, Scott William |
| Source Sets | Ball State University |
| Detected Language | English |
| Format | ix, 89 leaves : ill. ; 28 cm. |
| Source | Virtual Press |
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