The effect of decreased physical activity on the expression of muscle atrophy-related genes after resistance, endurance and combined exercise training

Decreased physical activity due to sciatic nerve ligation (SNL) cause muscle atrophy. The purpose of the present study was to investigate the effect of decreased physical activity in the form of spinal nerve ligation (SNL) on the expression of muscle atrophy-related genes (TWEAK and Fn14) after resistance, endurance and combined exercises.

Thirty rats were randomly divided into four groups: 1- Control group-SNL (Sham+SNL) (N=7),2- Mixed training group-SNL (Mix+SNL) (N=7), 3- Endurance training group-SNL (TE+SNL) (N=8), and 4- Resistance training group-SNL (LA+SNL) (N=8). Mix+SNL, TE+SNL and LA+SNL groups participated in training program for six weeks. Decreased physical activity was implemented for four weeks. Real time-PCR technique was used to measure gene expression. To determine the difference between research variables, analysis of variance, Tukey's post hoc test were used at a significance level of 0.05.

The results showed that the gene expression of TWEAK and Fn14 increased by decreased activity. The expression of TWEAK in SNL+La and SNL+Mix groups was significantly lower than Sham+SNL group (P=0.001), and the expression of Fn14 was significantly lower only in the SNL+Mix group compared to the Sham+SNL group (P=0.003). However, there was no significant change in the expression of TWEAK and Fn14 genes in SNL+TE group compared to Sham+SNL group.

These findings show that performing six weeks of resistance or combined training compared to endurance training before reduced activity (SNL), prevents the increase in the gene expression of TWEAK and Fn14. Therefore, the animals that included resistance training in their training program are more resistant to muscle atrophy caused by reduced physical activity than the group that only did endurance training.