1Davie A, 2Yao M, 2Wang Y, 2Huang L, 1Zhou S. Comparison of cumulative effects of four days of alternate or continuous training on expression of selected mitochondrial genes in rat skeletal muscle. 1Davie A, 2Yao M, 2Wang Y, 2Huang L, 1Zhou S. 1. School of Health and Human Sciences, Southern Cross University, Australia 2.Department of Health and Exercise Science, Tianjin University of Sport, China.

Introduction Adaptation to training represents the cumulative effect of repeated bouts which is highly specific to the exercise mode, intensity, duration, and frequency of the stimuli. At the molecular level, adaptations are thought to be due to the cumulative effects of transient changes in gene expression that follow each acute training session. The recovery intervals between the repeated exercise bouts or sessions can influence such cumulative effects and subsequently the adaptation to training.

WHY STUDY PGC-1α: The peroxisome proliferator-activated receptor-γ coactivator 1-α (PGC-1α) has been thought to be a master regulator of mitochondrial biogenesis, as well as many other pathways including mitochondrial dynamics and protein metabolism, and has been hypothesised to be a critical mediator of the muscle adaptive response to training.

Objectives: Therefore the present study investigated the responses of PGC-1α mRNA to the two training conditions, together with its upper stream factors CaMKIV and AMPK, and downstream factors NRF-1 (regulating nuclear gene transcription). The expression of cytochrome c oxidase IV (COXIV) mRNA was also examined. COXIV is the last enzyme on the mitochondrial respiratory chain involved in synthesis of ATP This image shows dramatically enhanced muscle tissue in a high performing mouse, which has greater numbers of mitochondria (brown), the energy factories of cells

Methods: Fifty-four male Sprague-Dawley rats were randomly divided into 9 experimental groups, within two experimental conditions (Continuous; Alternate) with six rats in each group. The groups were: control (CAO); no training one day of training (CA1); Training for 1 day continuous training groups who trained for a further two to four days (C2,C3,C4) followed by three days recovery (C7); alternate-day training consisting of a further two to four sessions (A2,A3,A4) finishing on the 7th day. On each training day, the animals ran on a motor driven treadmill at the slope of 10° and speed of 19.3m/min (~76%VO2max) for 90 minutes.

Methods: Gastrocnemius muscle specimens were obtained from the respective groups 1 hour after training ceased. Real-time PCR was performed to determine the changes (in fold) in mRNA of PGC1α, COXIV, CaMKIV, NRF1, AMPKα1 and α2. One-way ANOVA was used in comparisons of the mean values between groups.

Results c1,c2,c3,c4 represents 4 continuous days training, c7 following 3 days recovery a1,a2,a3,a4 represents 4 alternate days of training The results showed that mRNA expression was significantly different between the training conditions for the 4th training session

Results c1,c2,c3,c4 represents 4 continuous days training c7 following 3 days recovery a1,a2,a3,a4 represents 4 alternate days of training For NRF1, one day training induced an increase of mRNA (p=0.056) compared to baseline, and at the end of week C7 showed significantly higher values than the control, C3, C4 and A2 and A4 groups.

Results c1,c2,c3,c4 represents 4 continuous days training, c7 following 3 days recovery a1,a2,a3,a4 represents 4 alternate days of training The results showed that mRNA expression was significantly different between the training conditions for CaMKIV only following three days of recovery.

Results c1,c2,c3,c4 represents 4 continuous days training, c7 following 3 days recovery a1,a2,a3,a4 represents 4 alternate days of training The results showed that mRNA expression was significantly different between the training groups for AMPkα1 after the 3rd training session, COXIV and mtTFA were not significantly different at any point.

Conclusion Training design has differing effects on expression of the selected genes. Overall, the data suggests and supports the paradigm that there is an initial signal following exercise, however, even though the response may be different with repeated stimuli, similar changes in protein content occurs. This data has provided insight into the importance of training design and recovery intervals which warrants a need for further research.