Discussion
Findings of the present study showed that 10 weeks of RT reduced the oxidative damage indices in older adults by strengthening the antioxidant defense system. In fact, after 10 weeks of regular RT, MDA and Alikhani and colleagues in line with the present study illustrated an improvement in MDA and TAC in older and younger people after 12 weeks of RT. (Kinksly et al. examined the effect of cycling and creatine consumption on non-enzymatic indicators of antioxidant defense. The finding of the above study indicated that creatine had no effect on improving the antioxidant system (According to the results of previous research, it seems that short-term use of creatine supplementation has no effect on strengthening the antioxidant system. Available findings are limited and relatively contradictory in regards the long-term effects of this supplement which makes the final conclusion difficult. As mentioned, in the present study, 10 weeks of creatine monohydrate supplementation doubled the activity of GPX enzyme, while no synergistic effect of this supplement on TAC were observed. Therefore, further research is needed to prove the possible effects of creatine on boosting the antioxidant system. Nevertheless, it has been found that regular RT can be a logical approach for reducing exercise training-induced oxidative damage by enhancing the antioxidant capacity of older adults.The finding of the present study regarding changes in muscle strength showed that after 10 weeks of RT and creatine supplementation, the average increase in muscle strength (mean of the seven muscle groups studied) in the training-placebo group was 35.9% and in the training-creatine group was equal to 57%. These findings generally indicate the positive effect of RT on increasing muscle strength in the older adults, and in particular the synergistic effects of creatine supplementation on elevating strength in these individuals. Moreover, the results of the current study demonstrated that there was a significant decrease in body mass index only in the training-placebo group. The present research finding have been confirmed by previous research on the effect of RT on upgrading muscle strength and body composition, as well as the dual role of creatine supplementation in improving muscle strength in older adults (The present results showed an improvement of 79.9% and 89.2% of quality of life index in the training-placebo and training-creatine groups, respectively.