Introduction
Aging is associated with various morphological and physiological changes [3]. With aging, the body’s immune system must be active for a longer period of time, and this prolongation gradually leads to chronic inflammation. Tumor necrosis factor alpha (TNF-α) and transforming growth factor beta (TGF-β) are two cytokines whose role in immune function and inflammation in old age has received more attention [5]. Physical activity, as a low-cost nonpharmacological intervention, can be a method to prevent frailty and mortality in older adults [14]. Walking backward, unlike walking forward, causes more involvement of the nervous system and has a greater effect on cognitive function [18]. Since the backward walking training programs have received less attention, this research aims to investigate the effect of a forward and backward walking training course on some inflammatory markers and physical function of older women.

Methods
This is a quasi-experimental study with a pre-test/post-test design. Thirty older women were randomly selected from postmenopausal women aged 60-75 years in Bojnord, Iran. At the beginning, six women refused to continue participating in the research. The remaining 24 women were randomly assigned to three groups: forward walking (n=9), backward walking (n=8) and control (n=7). Before starting the exercises, anthropometric characteristics including age, body height, body weight and body mass index were recorded, and pre-tests of muscle strength (30 seconds of sitting and standing) and muscle endurance (walking for two minutes) were conducted and blood sampling (for biochemical analysis) was performed. To take blood samples, 5 cc of blood was drawn from the brachial vein of the women in the fasting state. The serum levels of TGF-β, TNF-α and vitamin D binding protein (VDBP) were measured by ELISA method and according to the manufacturer’s instructions. After this stage, the training groups performed their exercises for eight weeks while the control group only did their daily and normal activities. Blood sampling and all measurements were repeated at the end of eight weeks. 
In the forward and backward walking training groups, the women walked forward and backward for 300 meters in three repetitions and the Borg scale was used to evaluate their perception of pressure and pain at the beginning and end of each exercise program. The exertion rate was considered to be 14-15 according to the Borg scale. The rest interval between repetitions was 1-2 minutes. Repeated measures ANOVA was used to analyze the data. The significance level was set at 0.05. The data were analyzed in SPSS software version 23.

Results
The results of the statistical analysis showed that in the variables of body weight (F=11.62, P=0.001) and fat percentage (F=6.37, P=0.007) the interaction effect of time and group was significant. The results of Bonferroni’s post hoc test showed that body weight (F=10.75, P=0.001) and fat percentage (F=2.755, P=0.001) in the forward walking group decreased compared to the control group. For the biochemical factors (TNF-α, TGF-β, VDBP), the results of repeated measures ANOVA showed that none of the effects of time, time×group, and group were significant. Regarding physical function indicators, it was shown that there was a significant difference between the control group and two training groups in terms of muscle endurance. Also, there was a significant difference in the control group before training compared to baseline. The interaction effect of time and group was significant for muscle endurance (F=29.15, P=0.001). For the variable of muscle strength, the interaction effect of time and group was significant (F=14.3, P=0.001) and a significant difference was observed only between the control group and the backward walking group. The effect size was 0.57 for the muscle strength and 0.73 for the muscle endurance in the backward walking group, and 0.52 for the body weight variable in the forward walking group. This indicates the greater effect of backward walking training on muscle strength and endurance and the greater effect of forward walking training on the body weight.

Conclusion
The findings of the present study showed that eight weeks of forward and backward walking training in older women aged 60-75 years resulted in a significant improvement in muscle strength and muscle endurance in the backward walking group, but there was no significant change in the levels of TNF-α, TGF-β or VDBP in any groups.

Ethical Considerations

Compliance with ethical guidelines
This study was approved by the ethics committee of Sport Sciences Research Institute (Code: IR.SSRC.REC.1398.022). Written informed consent was obtained from all participants, after explaining the study objectives to them and ensuring their confidentiality. 

Funding
This study was funded by Kosar University of Bojnord (Grant No.: 0111081950)

Authors' contributions
Conceptualization, methodology, data collection, and writing: Mitra Khademosharie and Azam Mollanovruzi; Data analysis: Marziye Azarniveh and Ayoub Saidi; Editing and supervision: Mitra Khademosharie.

Conflicts of interest
The authors declare no conflict of interest.

Acknowledgments
The authors would like to thank the participants, the personal of selected comprehensive health centers, and the Vice-Chancellor for Research of Kosar University of Bojnord.



 

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