Journal of Preventive Medicine

Introduction
One of the most important human problems is skeletal abnormalities, which can reduce the performance and cause the individuals to be prone to injuries. Some of the musculoskeletal abnormalities are flat feet and impaired postural control which have a negative effect on the functioning of the motor system and make it difficult to perform daily activities. If these abnormalities are identified in time and the necessary measures are taken to correct and prevent their exacerbation, its complications can be prevented. Therefore, knowing the factors affecting flat feet and postural control can be useful in deciding to choose the most suitable treatment method for patients. Various methods have been proposed for the treatment of these conditions to improve the performance of the affected people. For example, Aminian et al suggested the correction of flat feet using invasive methods and Tsai et al. suggested non-invasive methods such as the use of medical orthotics. Riccio et al. suggested that rehabilitation therapy can help improve the plantar arch and correct flexible flatfoot, and control. It seems that one of the most important active and non-invasive methods to improve and prevent the increase in risks caused by foot deformities and impaired postural control is the use of corrective exercises. One of the important corrective methods that is currently used is the National Academy of Sports Medicine (NASM)’s corrective exercises. Studies have shown that NASM’s corrective exercises have a better effect on correcting some abnormalities than traditional corrective exercises.
Considering that there is scant research about the effect of NASM’s corrective exercises on flexible flatfoot and postural control in overweight school students in Iran, the present study aims to evaluate the effect of these exercises on the correction of flexible flatfoot and postural control in overweight male high school students.

Methods 
This is a quasi-experimental study with a pre-test/post-test design. Participants were 40 male high school students with flexible flatfoot and overweight who were selected using a purposeful sampling method and were randomly assigned into two groups of exercise (n=20) and control (n=20). The exercise group performed NASM’s corrective exercises for 8 weeks, three sessions per week, each for 45 minutes. The control group had no training during this period. Variables were measured at the baseline and after 8 weeks of the correction program. 
The inclusion criteria were: consent to participation, having overweight and flexible flatfoot, and not participating in other exercises or treatment programs during the study. The exclusion criteria were: History of injury, fracture or surgery in lower limbs, physical disability, medical contraindication or orthopedic problem, abnormal range of motion in lower limb joints, and absence from more than two exercise sessions. Data were analyzed using analysis of covariance (ANCOVA) in SPSS v. 24 software. The significance level was set at 0.05.

Results
The mean and standard deviation of the scores related to flatfoot and postural control in the exercise group were 1.04±0.16 mm and 0.74±0.46 degrees (angle of deviation from the vertical plane) in the pre-test phase, respectively. These values in the post-test phase were 0.90±0.12 mm and 0.54±0.32 degrees, respectively. The mean and standard deviation of the scores related to flatfoot and postural control in the control group were 1.07±0.28 mm and 0.79±0.15 degrees in the pre-test phase, respectively. These values in the post-test phase were 1.01±0.19 mm and 0.71±0.41 degrees, respectively.
The results showed that the exercise and control groups were significantly different in at least one of the study variables (flexible flatfoot or postural control) in the post-test phase (P≤0.05). ANCOVA was used to find out in which variables the two groups were different. The results showed that NASM’s corrective exercises had a significant effect on the improvement of both flexible flatfoot and postural control in overweight students (P≤ 0.05). Based on the effect size, it was found that 32% and 28% of the changes in flexible flatfoot and postural control were due to participating in the exercise program. 

Discussion
The results of this research showed that the corrective exercise based on NASM protocol had a significant effect on correcting the flexible flatfoot and postural control in overweight male high school students. These results are in agreement with the findings of Golchini et al., Ghasemi et al., Allam al., Fakor Rashid et al., Jabbar et al., Uki et al., and Atik et al. These studies used different exercise methods to improve flatfoot and postural control and each reported effective results. The results are not consistent with the findings of Arab Jafari et al., and Achachlouei et al. For example, Achachlouei et al showed that corrective exercises had no significant effect on the improvement of flatfoot. This discrepancy can be due to the use of different protocols, duration, the type of corrective movements, and subjects.
One of the important factors in flexible flatfoot and impaired postural control is weakness in the leg muscles and a decrease in dynamic stability. These abnormalities are also associated with the degree of ligament laxity and may cause changes in the soft tissues around the joint such as ligaments, muscles, and tendons. Corrective exercises, especially the NASM’s proposed corrective exercises, can strengthen muscles, correct poor posture, and reduce musculoskeletal pain.
In conclusion, NASM’s corrective exercises can improve the flexible flatfoot and postural control in overweight male high school students. Therefore, it is recommended that education officials, rehabilitation experts, trainers, and sports teachers use this corrective protocol to improve the flexible flatfoot and postural control in students.
One of the limitations of this study was the short duration (8 weeks) of the exercise program. The use of longer periods may be more effective. In addition, the current study was conducted only on male high school students (first grade).

Ethical Considerations

Compliance with ethical guidelines
All ethical principles in research have been observed in this article.

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

Authors' contributions
All authors equally contributed to preparing this article.

Conflicts of interest
The authors declared no conflict of interest.

 

1. Li Y, Levine WS, Loeb GE. A two-joint human posture control model with realistic neural delays. IEEE Trans Neural Syst Rehabil Eng. 2012; 20(5):738-48. [DOI:10.1109/TNSRE.2012.2199333] [PMID]
2. Kamali M, Ghasemi B, Bagherian Dehkordi S. [Effect of 8-week NASM›s corrective exercise continuum on correction of lumbar lordosis and some biomotor skills in female students with hyperlordosis (Persian)]. J Res Sport Rehabil. 2015; 3(5):31-41. [Link]
3. Fyfer JJ, Broatch JR, Trewin AJ, Hanson ED, Argus CK, Garnham AP, et al. Cold water immersion attenuates anabolic signaling and skeletal muscle fiber hypertrophy, but not strength gain, following whole-body resistance training. J Appl Physiol. 2019; 127(5):1403-18. [DOI:10.1152/japplphysiol.00127.2019] [PMID]
4. Otsuka R, Yatsuya H, Miura Y, Murata C, Tamakoshi K, Oshiro K, et al. [Association of flatfoot with pain, fatigue and obesity in Japanese over sixties (Japanese)]. Nihon Koshu Eisei Zasshi. 2003; 50(10):988-98. [PMID]
5. Toullec E. Adult flatfoot. Orthop Traumatol Surg Res. 2015; 101:11-7. [DOI:10.1016/j.otsr.2014.07.030] [PMID]
6. Ueki Y, Sakuma E, Wada I. Pathology and management of flexible flat foot in children. J Orthop Sci. 2019; 24(1):9-13. [DOI:10.1016/j.jos.2018.09.018] [PMID]
7. Yalcin E, Kurtaran A, Selcuk B, Onder B, Yildirim MO, Akyuz M. Isokinetic measurements of ankle strength and proprioception in patients with flatfoot. Isokinet Exerc Sci. 2012; 20(3):167-71. [DOI:10.3233/IES-2012-0453]
8. Sedaghati P, Zolghadr H, Daneshmandi H. [Postural control status in relation to anthropometric and postural indices of active people (Persian)]. J Sport Biomech. 2019; 5(1):50-61. [DOI:10.32598/biomechanics.5.1.5]
9. Teasdale N, Hue O, Marcotte J, Berrigan F, Simoneau M, Doré J, et al. Reducing weight increases postural stability in obese and morbid obese men. Int J Obes. 2007; 31(1):153-60. [DOI:10.1038/sj.ijo.0803360] [PMID]
10. Tsai LC, Yu B, Mercer VS, Gross MT. Comparison of different structural foot types for measures of standing postural control. J Orthop Sports Phys Ther. 2006; 36(12):942-53. [DOI:10.2519/jospt.2006.2336] [PMID]
11. Atik A, Ozyurek S. Flexible flatfoot. North Clin Istanb. 2014; 1(1):57-64. [DOI:10.14744/nci.2014.29292] [PMID] [PMCID]
12. Kothari A, Dixon PC, Stebbins J, Zavatsky AB, Theologis T. Are flexible flat feet associated with proximal joint problems in children? Gait Posture. 2016; 45:204-10. [DOI:10.1016/j.gaitpost.2016.02.008] [PMID]
13. Cote KP, Brunet ME, Gansneder BM, Shultz SJ. Effects of pronated and supinated foot postures on static and dynamic postural stability. J Ath Train. 2005; 40(1):41-6. [PMID] [PMCID]
14. Aminian G, Farhoodi M, Safaeepour Z, Farjad Pezeshk A. [The assessment of the effect of longitudinal arch support insole on plantar pressure distribution in subjects with flexible flatfoot (Persian)]. Iran J War Public Health. 2012; 4(4):43-8. [Link]
15. Riccio I, Gimigliano F, Gimigliano R, Porpora G, Iolascon G. Rehabilitative treatment in flexible flatfoot: A perspective cohort study. Chir Organi Mov. 2009; 93(3):101-7. [DOI:10.1007/s12306-009-0037-z] [PMID]
16. Vassão PG, Toma RL, Antunes HK. Renno AC. Photobiomodulation and physical exercise on strength, balance and functionality of elderly women. Fisioter Mov Curitiba. 2018; 31:e003109. [DOI:10.1590/1980-5918.031.AO09]
17. Wallmann HW, Player KR, Bugnet M. Acute effects of static stretching on balance in young versus elderly adults. Phys Occup Ther Geriatr. 2012; 30(4):301-15. [DOI:10.3109/02703181.2012.719076]
18. Golchini A, Rahnama N, Lotfi Foroushani M. [Effect of corrective exercises with a new approach on the isometric strength in people ‎with pronation distortion syndrome (Persian)]. J Paramed Sci Rehabil. 2021; 9(4):41-60. [DOI:10.22038/JPSR.2021.41817.1990]
19. Fakoor Rashid H, Daneshmandi H. [The effects of a 6 weeks corrective exercise program on improving flat foot and static balance in boys (Persian)]. J Pract Stud Biosci Sport. 2013; 1(2):52-66. [DOI:10.22077/jpsbs.2013.37]
20. Jabbar K, Gandomi F. The effects of national academy of sports medicine and Sahrmann training on foot pressure distribution in flexed posture students. Iran Rehabil J. 2021; 19(1):99-110. [DOI:10.32598/irj.19.1.1319.1]
21. Almasoodi M, Mahdavinejad R, Ghasmi G. The effect of 8 weeks national academy of sports medicine exercises training on posture, shoulder pain, and functional disability in male with upper cross syndrome. Sys Rev Pharm. 2020; 11(11):1826-33. [Link]
22. Niemiro GM, Rewane A, Algotar AM. Exercise and fitness effect on obesity. Treasure Island: StatPearls Publishing; 2021. [PMID]
23. Mahmoudzadeh Khalili S, Barati AH, Oliveira R, Nobari H. Effect of combined balance exercises and Kinesio taping on balance, postural stability, and severity of ankle instability in female athletes with functional ankle instability. Life. 2022; 12(2):178. [DOI:10.3390/life12020178] [PMID] [PMCID]
24. Aydog ST, Özçakar L, Tetik O, Demirel HA, Hascelik Z, Doral MN. Relation between foot arch index and ankle strength in elite gymnasts: A preliminary study. Brit J Sport Med. 2005; 39(3):e13. [DOI:10.1136/bjsm.2004.011627] [PMID] [PMCID]
25. Ghasemi V, Rajabi R, Alizadeh MH, Dashti Rostami K. [The comparison of dynamic balance in males with different foot types (Persian)]. Sport Sci Health Res. 2011; 6(1):5-20. [Link]
26. Sharifi A, Zolaktaf V. [Effect of eight weeks of NASM exercises on shoulder functional tests (Persian)]. J Res Sport Rehabil. 2019; 7(13):125-33. [DOI:10.22084/rsr.2018.16276.1374]
27. Allam HH, Muhsen A, Al-Walah MA, Alotaibi AN, Alotaibi SS, Elsayyad LK. Effects of plyometric exercises versus flatfoot corrective exercises on postural control and foot posture in obese children with a flexible flatfoot. Appl Bionics Biomech. 2021; 2021:3635660.[DOI:10.1155/2021/3635660] [PMID] [PMCID]
28. Arabjafari Z, Fatahi H, Shamsehkohan P. [The effect of 8 weeks combined exercises (core stability and theraband) on distance of knee medail condyles, Q angle and endurance of core muscles in adolescent students with genu varum (Persian)]. J Res Sport Rehabi. 2020; 8(15):101-13. [Link]
29. Kouhi Achachlouei F, Abbaszadegan M, Eghbalmoghanlou A. The effects of corrective exercise program on flat foot deformity of male and female students. Ann Biol Res. 2012; 3(2):988-94. [Link]
30. Rusu L, Marin MI, Geambesa MM, Rusu MR. Monitoring the role of physical activity in children with flat feet by assessing subtalar flexibility and plantar arch index. Children. 2022; 9(3):427. [DOI:10.3390/children9030427] [PMID] [PMCID]
31. Wernbom M, Augustsson J, Thomeé R. The influence of frequency, intensity, volume and mode of strength training on whole muscle cross-sectional area in humans. Sports Med. 2007; 37(3):225-64. [DOI:10.2165/00007256-200737030-00004] [PMID]
32. Clark M, Lucett S, National Academy of Sports Medicine. NASM essentials of corrective exercise training. Philadelphia: Lippincott Williams & Wilkins; 2010. [Link]