Introduction
The aging of the population and the increase in the share of elderly people in the population are some of the most important social developments of the 21st century, and their consequences affect almost all sectors of society and intergenerational relations [1]. Sports exercises have been introduced as an effective and correct solution to improve muscle strength and volume, as well as the functional capacity of elderly people [7]. Research shows that about one billion people worldwide have vitamin D deficiency [12]. Alkaline phosphatase (ALP), the regulating agent of vitamin D can be considered an important substance in increasing the absorption of calcium and phosphorus and preventing the reduction of bone density [16]. Therefore, this study investigates the effect of eight weeks of combined exercises with and without flow restriction and Vitamin D supplementation on serum levels of ALP in elderly women.

Methods
The present research was conducted for practical purposes in the form of a clinical trial, specifically a semi-experimental study involving four groups of 40 women aged between 65 and 75 years. These groups consisted of three experimental groups and one control group. The study followed a pre-test-post-test design and was conducted in Alborz Province, Iran. The participants’ weights were measured accurately using a Seka scale made in Germany with a precision of 0.1 kg. Meanwhile, the height was measured using a Saka caliper with a precision of 0.1 cm. The exercise program for the participants in the exercise groups lasted eight weeks, with sessions three times a week, each lasting approximately 1 h. The aerobic training program included Running on a treadmill for 20 min with an intensity equal to 60%-70% of the maximum heart rate and was controlled by a Polar heart rate monitor made in Finland. The resistance training with an additional load equal to 70% of one maximum repetition and 10 repetitions in two consecutive rounds with A 30-S and 2-min rest period between each station and round was considered. Resistance exercises consisted of 10 station movements in a circle, including leg flexion, leg extension, leg press, squat, armpit stretch, chest press, cross-movement with dumbbells, front arm, back arm, and rowing movement with a rope. In the supplement group, vitamin D in the amount of 5000 international units was used every week in the amount of one capsule (Dana Pharmaceutical Company) after lunch. After 12 h of fasting, 6 mL of blood was collected from the vein of the left hand in a sitting position and on two occasions, 24 h before the first training session and 48 h after the last training session to check the changes in ALP levels.

Results
The results of the paired t-test showed a significant difference in the amount of intra-group changes of the examined variables (high-density lipoprotein, low-density lipoprotein, triglyceride, glucose, total cholesterol, and body fat percentage) in both training groups (P≥0.05). However, in the control group and vitamin D-consuming group, no significant difference was observed in any of the investigated variables between the pre-test and post-test (P<0.05). To compare the effects of combined exercises and exercises with flow restriction and the supplement group on the measured variables in women, analysis of variance was used to determine the differences between groups in the post-test. In the pre-test stage, there was no significant difference in the three groups (P<0.05). The results of the analysis of the ANCOVA test showed that after controlling for the effect of the pre-test, there was a significant difference in the indicators (ALP, high-density lipoprotein, triglyceride, glucose, total cholesterol, and fat percentage; P<0.05). In the post-test, there was a significant difference between the three groups (P<0.05).

Conclusion
The results of the present study showed that resistance training with and without restrictions caused a decrease in fat mass, a decrease in fasting sugar, and an increase in ALP. The results also indicated that exercise with flow restriction had a greater effect on stimulation than resistance exercise without flow restriction in ALP of the elderly. The use of combined exercise with flow restriction and without flow restriction, along with vitamin D supplementation, affects improving the regulation of ALP indicators. Performing combined exercise in elderly women leads to an improvement in physical performance. Therefore, it is recommended to use a combined exercise program with flow restriction instead of high-intensity combined exercise for the elderly.

Ethical Considerations
Compliance with ethical guidelines
This study has been approved by the Ethics Committee of the Sports Sciences Research Institute, Tehran, Iran (Code: IR.SSRI.REC.1401.1583). The objectives of the research were explained to the elderly, and informed consent was obtained from all participants, ensuring the confidentiality of their information.

Funding
This research did not receive any grant from funding agencies in the public, commercial, or non-profit sectors.

Authors' contributions
Conceptualization: All authors; Methodology, investigation, writing and resources: Saeid Shamlou Kazemi, and Maryam Rashvand; Supervision: Saeid Shamlou Kazemi, Maryam Rashvand, and Ali Hemmati Afif;

Conflicts of interest
The authors declared no conflict of interest.


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