ANNALES KINESIOLOGIAE • 14 • 2023 • 2 95 ENHANCING BALANCE IN PARKINSON’S DISEASE PATIENTS: A COMPREHENSIVE LITERATURE REVIEW ON THE EFFICACY OF EXERCISE IN AN ENRICHED ENVIRONMENT Ana PONEBŠEK1, Friderika KRESAL1, Luka ŠLOSAR2,3 1 Visokošolski zavod Fizioterapevtika, Ljubljana, Slovenia 2 Science and Research Centre Koper, Institute for Kinesiology Research, Koper, Slovenia 3 Alma Mater Europaea – ECM, Department of Health Sciences, Maribor, Slovenia Corresponding author: Ana PONEBŠEK Visokošolski zavod Fizioterapevtika Slovenska c. 58, 1000 Ljubljana, Slovenia E-mail: ponebsekana99@gmail.com ABSTRACT Various physiotherapeutic methods and approaches play a significant role in the treatment of patients with Parkinson’s disease, including the use of enriched environ- ments. Virtual reality (VR) as a type of enriched environment has the potential to create multiple sensory experiences and feedback, influencing various aspects of the patient’s information processing and response. The suitability for home use and the consider- able impact on motivation highlight its advantages over alternative approaches. The objective of this review is to investigate the impact of VR-based exercise on balance outcomes among individuals with Parkinson’s disease. The inclusion criteria consisted of randomized controlled trials (RCTs) that examined the effects of exercise in a VR environment on individuals’ static and dynamic balance outcomes. In order to gather relevant studies, we conducted a comprehensive search across three databases. From a dataset of 625 records, we conducted a comprehensive full-text screening based on spe- cific inclusion and exclusion criteria. This process resulted in the inclusion of 14 RCTs in our review. The emerging evidence regarding exercising in a VR environment does not definitively prove its superiority over standard exercise routines. However, studies have demonstrated that both the experimental and control groups showed compara- ble improvements in enhancing static and dynamic balance among individuals with Review article DOI: https://doi.org/10.35469/ak.2023.394 received: 2023-07-03 UDC: 796.413:616.858 mailto:ponebsekana99@gmail.com 96 Ana PONEBŠEK, Friderika KRESAL, Luka ŠLOSAR: ENHANCING BALANCE IN PARKINSON'S DISEASE PATIENTS ..., 95–112 ANNALES KINESIOLOGIAE • 14 • 2023 • 2 Parkinson’s disease. The comparable improvements in balance observed between the experimental and control groups signify the potential effectiveness of VR-based exer- cises. This underscores the encouragement for further development in this technology, particularly focusing on fully immersive VR environments, which may yield superior effects in enhancing balance among individuals with Parkinson’s disease. Keywords: virtual reality, Parkinson’s disease, balance, rehabilitation. UČINKOVITOST VADBE V OBOGATENEM OKOLJU ZA IZBOLJŠANJE RAVNOTEŽJA PRI PACIENTIH S PARKINSONOVO BOLEZNIJO: PREGLED LITERATURE IZVLEČEK Pri zdravljenju Parkinsonove bolezni imajo pomembno vlogo različne fizioterape- vtske metode in pristopi, med katere spada tudi uporaba obogatenega okolja. Navi- dezna resničnost kot vrsta obogatenega okolja ima potencial za ustvarjanje večkratnih senzoričnih izkušenj in povratnih informacij, ki vplivajo na različne vidike obdelave informacij in odzivov pacientov. Poleg tega je prednost vadbe v obogatenem okolju tudi v tem, da je primerna za domačo uporabo in deluje spodbudno. Namen tega dela je s pregledom literature ugotoviti, kakšni so učinki vadbe z navidezno resničnostjo na ravnotežje pri pacientih s Parkinsonovo boleznijo. Vključitvena merila vsebujejo randomizirane kontrolirane raziskave, ki proučujejo učinke vadbe v okolju navidezne resničnosti na statične in dinamične rezultate ravnotežja posameznikov. Za zbiranje rel- evantnih raziskav smo obsežno preiskali tri baze podatkov. Med 625 zapisi smo temelji- to preverili celotna besedila, upoštevajoč določena merila za vključitev in izključitev. S pomočjo tega postopka smo dobili 14 raziskav, ki smo jih vključili v svoj pregled. Na podlagi vključenih raziskav smo ugotovili, da nimamo dovolj dokazov, da bi lahko trdili, da vadba v obogatenem okolju pomembno izboljša ravnotežje pri pacientih s Parkinsonovo boleznijo v primerjavi s tradicionalno vadbo. Raziskave so pokazale, da sta eksperimentalna in kontrolna skupina pokazali primerljive izboljšave v statičnem in dinamičnem ravnotežju pri posameznikih. Primerljive izboljšave v ravnotežju, opažene med eksperimentalno in kontrolno skupino, kažejo potencialno učinkovitost vadb v okolju navidezne resničnosti. To potrjuje potrebo po nadaljnjem razvoju te tehnologije, še posebej osredinjenost na imerzivno obliko navidezne resničnosti, ki ima potencial za izboljšanje ravnotežja pri posameznikih s Parkinsonovo boleznijo. Ključne besede: navidezna resničnost, Parkinsonova bolezen, ravnotežje, rehabili- tacija 97 ANNALES KINESIOLOGIAE • 14 • 2023 • 2 Ana PONEBŠEK, Friderika KRESAL, Luka ŠLOSAR: ENHANCING BALANCE IN PARKINSON'S DISEASE PATIENTS ..., 95–112 INTRODUCTION Parkinson’s disease (PD) is a neurodegenerative disorder characterized by the degeneration of dopaminergic neurons in the substantia nigra of the basal ganglia (Hague, Klaffke, & Bandmann, 2005). This results in a dopamine de- ficiency that manifests itself in primary motor signs and symptoms such as the slowing of movements, tremor, and increased muscle tone that worsen over time and negatively affect patients’ balance, gait, functional mobility, and con- sequently quality of life (Goldman & Tanner, 1998; Müller et al., 2019). The main motor features are bradykinesia, rigidity, tremor, and postural instability (Ball, Teo, Chandra, & Chapman, 2019; Roytman et al., 2023). Parkinson’s disease is not only a motor disorder, but also presents a variety of non-motor symptoms (e.g., disturbances in mood, cognition, and sleep) that often affect quality of life more than motor symptoms (Postuma, 2017). Physiotherapy plays an important role in the treatment of Parkinson’s dis- ease. The use of various physiotherapy methods can improve balance and help patients become more independent. In addition to traditional rehabilita- tion methods, virtual reality (VR) is becoming an increasingly popular method for Parkinson’s patients (Schultheis & Rizzo, 2001). Traditional rehabilitation methods include various exercise programs involving balance exercises, such as standing on one leg with eyes closed/open, stepping exercises, dual-task ex- ercises, seated and standing exercises, and exercises on a balance beam or other challenging surfaces. Later, balance exercises are supplemented with perturba- tion (Lewis & Rosie, 2012). VR as a form of enriched environment holds the potential of a breakthrough technology for non-physical rehabilitation by providing multisensory informa- tion and more realistic simulations to improve patient rehabilitation outcomes (Šlosar, Peskar, Pišot, & Marusic, 2023; Meulenberg, de Bruin, & Marusic, 2022). This computer-generated environment is not static, but responds to the user’s movements, gestures, and verbal commands, giving the user the feeling of really being in this virtual world (Lewis & Rosie, 2012). With devices that allow visual or audio interaction between a person and VR, the person can im- agine being part of the virtual environment. It can appear in it in the form of an imaginary object. In response to the user’s task (in the case of physical therapy, movement), the computer program generates changes in the virtual environ- ment through its sensors that provide feedback on performance. VR can stimulate the user’s movement and cognitive processes, increasing the patient’s chances of regaining lost motor skills. It can also be used for bal- 98 Ana PONEBŠEK, Friderika KRESAL, Luka ŠLOSAR: ENHANCING BALANCE IN PARKINSON'S DISEASE PATIENTS ..., 95–112 ANNALES KINESIOLOGIAE • 14 • 2023 • 2 ance training and visual feedback (Mirelman, Maidan, & Deutsch, 2013). The use of VR has a long-term effect on patients, as it can prevent or slow the pro- gression of movement disorders (Allen, Sherrington, Paul, & Canning, 2011). Originally designed for recreation and entertainment, the systems are now also used for therapeutic purposes due to their low cost, high availability, and port- ability (Kong et al., 2016). These devices include the Sony Playstation, Nin- tendo Wii, and Microsoft Xbox 360 Kinect, also known as exergames. VR en- courages patients to make lifestyle changes and incorporate exercise into their daily lives. In addition, patients can use these devices at home. Due to their low cost, these devices are also suitable as rehabilitation aids for patients from lower socioeconomic backgrounds (Yong Joo et al., 2010). VR ranges from non-immersive to fully immersive, according to the degree of immersiveness provided (Piron et al., 2010). Non-immersive VR refers to a virtual experience through a computer, but also allows the user to remain aware of and in control of their physical environment (Henderson et al., 2013). Common technologies in this category include gaming consoles like PlayStation, Xbox 360, and Nin- tendo Wii, which integrate exercise actions with gaming mechanics. To simpli- fy the study of the effects of these interventions, Šlosar et al. (2022) categorized them as PC-exergames. Research suggests that these systems hold promise in ameliorating symptoms in neurological disorders and fostering cognitive and motor improvements, including in Parkinson’s disease (Maggio et al., 2019). On the other hand, fully immersive VR enables natural interaction with the environment by using the entire body of the user, who thus becomes an active part of the 3D environment (Tieri, Morone, Paolucci, & Iosa, 2018). The most common types of VR technologies are the HMD (Head-Mounted Display) and CAVE (Cave Automatic Virtual Environment) systems. When physical activity is incorporated into interventions within a fully immersive VR environment, Šlosar et al. (2022) suggested the term VR-exergames to name and further in- vestigate these interventions. For a more precise analysis of intervention effects, we applied the taxonomy introduced by Šlosar et al. (2022) to classify the studies we gathered. In recent years, significant progress has been made in the field of technology and rehabil- itation methods. Therefore, a literature review is needed to update the results of the previous literature review, (Chen, Gao, He, & Bian, 2020; Lei et al., 2019) in the field of VR training to improve balance in patients with Parkinson’s dis- ease. The aim of this review is to and analyze the existing studies to determine whether exercises in enriched environments improve balance ability in patients with Parkinson’s disease. 99 ANNALES KINESIOLOGIAE • 14 • 2023 • 2 Ana PONEBŠEK, Friderika KRESAL, Luka ŠLOSAR: ENHANCING BALANCE IN PARKINSON'S DISEASE PATIENTS ..., 95–112 METHODS A literature search was performed across PubMed, PEDro, and Google Scholar (first 100 results) utilizing various keywords including “virtual real- ity,” “VR,” “Parkinson’s disease,” “balance,” “rehabilitation,” and their syn- onymous terms to locate relevant articles. Supplement A includes the distinct search strings employed for each database. The inclusion criteria to detect all the relevant articles were (i) The subjects of the study were Parkinson’s disease patients who had been formally diag- nosed by a hospital or by internationally recognized diagnostic criteria. There were no restrictions on gender, course of disease, or severity of the disease; (ii) randomized controlled trials (RCTs); (iii) studies in which the experimental group underwent PC- or VR-based exercise interventions; (iv) studies in which outcomes were related to balance, i.e., RCTs that observed whether balance im- proved in the experimental group at the end of treatment. The exclusion criteria comprised publications prior to 2010, RCTs not available under open access, irrelevant findings, non-English language studies, and those lacking a control group. In line with the Schoneburg et al. (2013) study, balance function is as- sociated to four posture systems: static balance, dynamic balance, reactive pos- ture adjustment, and expected posture adjustment. Considering their substantial impact on balance among Parkinson’s patients, our primary emphasis was on assessing static and dynamic balance as the primary outcomes. The screening process commenced by evaluating the titles and abstracts of the studies, identifying those most relevant to our topic. The second phase in- volved examining the full texts to ascertain if they met the aforementioned inclusion criteria. The retrieved studies were then classified based on the tax- onomy proposed by Šlosar et al. (2022): PC-exergame – studies conducted in non-immersive environments involving movement; PC-no-exergame – studies conducted in non-immersive environments without movement; VR-exergame – interventions fully immersing participants in a virtual environment while in- volving movement; VR-no-exergame – studies wherein participants were fully immersed in a virtual environment without movement. 100 Ana PONEBŠEK, Friderika KRESAL, Luka ŠLOSAR: ENHANCING BALANCE IN PARKINSON'S DISEASE PATIENTS ..., 95–112 ANNALES KINESIOLOGIAE • 14 • 2023 • 2 RESULTS Study selection and characteristics of included studies The initial search retrieved a total of 625 articles (480 from PubMed, 100 from Google Scholar, and 45 from PEDro). After deduplication, 35 articles were excluded. Subsequently, 27 articles were excluded based on titles and 3 based on abstracts, leaving 14 articles for thorough evaluation as potential inclusions. Figure 1 illustrates the comprehensive inclusion and exclusion pro- cess of the articles. All participants were diagnosed with Parkinson’s disease at different disease stages: 4 trials reported Hoehn and Yahr stages 1 to 3, 7 trials reported Hoehn and Yahr stages 2 to 3, 1 trial reported Hoehn and Yahr stages 2 to 4, and 2 trial did not report any stage. All retrieved studies (van den Heuvel et al., 2013; Lee et al., 2015; Shih, Wang, Cheng, & Yang, 2016; Yang, Wang, Wu, Lo, & Lin, 2016; Gandolfi et al., 2017; Ribas, Alves da Silva, Corrêa, Teive, & Valderra- mas, 2017; Santos, Machado, Santos, Ribeiro, & Melo, 2019; Tollár, Nagy, & Hortobágyi, 2019; Liao, Yang, Wu, & Wang, 2015; Liao, Yang, Cheng, et al., 2015; Pazzaglia et al., 2020; Yen et al., 2011; Shen & Mak, 2014) were catego- rized as PC-exergame studies, excluding Feng et al. (2019). Feng et al. (2019) lacked sufficient intervention details, such as specific performance methods, exercise intensity progression, and supervision information during training. As a result, we included 13 studies in the PC-exergames category, while no studies were found for the other categories. Effects of virtual reality training on static and dynamic balance In all 14 studies, outcome measures used for balance assessment included the Berg Balance Scale (BBS), Limits of Stability (LOS), One-Legged Stance Test (OLS), the Activities-Specific Balance Confidence Scale (ABC), and the Sensory Organization Test (SOT). The majority of the studies used the BBS as the primary outcome measure for functional balance. The results are shown in Table 1. Several studies (Feng et al., 2019; Lee et al., 2015; Gandolfi et al., 2017; Tollár et al., 2019; Liao, Yang, Cheng, et al., 2015; Pazzaglia et al., 2020) demonstrated significant improvements in static and dynamic balance among participants in the experimental group. Ribas et al. (2017) and Yen et al. (2011) also concluded that the experimental group exhibited statistically signif- 101 ANNALES KINESIOLOGIAE • 14 • 2023 • 2 Ana PONEBŠEK, Friderika KRESAL, Luka ŠLOSAR: ENHANCING BALANCE IN PARKINSON'S DISEASE PATIENTS ..., 95–112 Figure 1: Flow chart depicting the selection process of identified articles In cl ud ed Sc re en in g Id en tifi ca tio n Records identified through database searching PubMes: n = 480 Google Scholar: n = 100 PEDro: n = 45 Records after duplicates removed n = 590 Studies included in review n = 14 Reports excluded: Not relevant outcomes: n = 3 Article not in English: n = 2 No control group: n = 3 Title and abstract screen n = 77 Full text articles assessed for eligibility n = 22 Identification of studies via databases and registers 102 Ana PONEBŠEK, Friderika KRESAL, Luka ŠLOSAR: ENHANCING BALANCE IN PARKINSON'S DISEASE PATIENTS ..., 95–112 ANNALES KINESIOLOGIAE • 14 • 2023 • 2 icant progress in maintaining balance compared to the control group; however, the progress was not sustained over time. Liao, Yang, Wu, et al. (2015) found significant improvements in balance among both the experimental group and the group that performed traditional exercises, when compared to the control group. Shen & Mak (2014) reported that participants in the experimental group showed a significantly increased level of self-confidence in maintaining bal- ance, as assessed by the self-assessment ABC test. Shih et al. (2016) found that the experimental group achieved improved postural stability compared to the control group, which followed a traditional balance training program. Both ex- ercise programs were effective in improving functional balance in patients with Parkinson’s disease. In the study by van den Heuvel et al. (2013) the results did not show a significant improvement in balance among the participants. Simi- larly, Yang et al. (2016) found that balance improved equally in both groups, with no significant differences observed between them. Santos et al. (2019) also reported that a combination of traditional exercise and Nintendo Wii training, as well as each individual intervention with an equal amount of physiotherapy, led to balance improvement. However, when analyzing all the results, no statis- tically significant differences were found between the two groups. 103 ANNALES KINESIOLOGIAE • 14 • 2023 • 2 Ana PONEBŠEK, Friderika KRESAL, Luka ŠLOSAR: ENHANCING BALANCE IN PARKINSON'S DISEASE PATIENTS ..., 95–112 Ta bl e 1: S um m ar y of th e 14 in cl ud ed st ud ie s St ud y Po pu - la tio n In te rv en tio n D ur at io n tim e O ut co m es a nd re su lts Ex pe rim en ta l g ro up C on tro l g ro up va n de n H eu - ve l e t a l. (2 01 3) n = 33 V is ua l f ee db ac k tra in in g, w hi ch w as e xp lic itl y in te gr at ed in e ac h w or ks ta tio n. W or ks ta tio ns c on si st ed of a fl at -p an el L C D m on ito r c on - ne ct ed to a P C c on ta in in g, in te ra c- tiv e dy na m ic b al an ce e xe rc is es . (n = 1 7) C on ve nt io na l b al an ce tra in in g (n = 1 6) 60 m in / 10 tre at m en t se ss io ns / 5 w ee ks Th er e w er e no st at is tic al ly si gn ifi - ca nt d iff er en ce s b et w ee n gr ou ps in c ha ng e sc or es fo r B B S an d SL S te st . N .-Y . L ee e t a l. (2 01 5) n = 20 D an ce e xe rc is e w ith N in te nd o W ii + ne ur od ev el op m en t t re at m en t + fu nc tio na l e le ct ric al st im ul at io n (n = 1 0) . N eu ro de ve lo pm en t tre at m en t + fu nc tio na l e le ct ric al st im ul at io n (n = 1 0) . 30 m in / 5 tim es p er w ee k / 6 w ee ks B al an ce h ad si gn ifi ca nt ly im - pr ov ed in th e EX P gr ou p w hi le C O N g ro up sh ow ed n o si gn ifi ca nt im pr ov em en t. B al an ce w as m ea s- ur ed b y B B S. Sh ih e t a l. (2 01 6) n = 20 B al an ce -b as ed e xe rg am in g in te r- ve nt io n us in g th e K in ec t s en so r. (n = 1 0) C on ve nt io na l b al an ce tra in in g (n = 1 0) 50 m in / 2 tim es p er w ee k/ 8 w ee ks B ot h tra in in g pr og ra m s i m pr ov ed fu nc tio na l b al an ce in p eo pl e w ith PD a cc or di ng to th e re su lts o f B B S te st s. Th er e w er e no si g- ni fic an t d iff er en ce s b et w ee n th e gr ou ps . Ya ng e t a l. (2 01 6) n = 23 H om e- ba se d ba la nc e tra in in g sy s- te m in cl ud ed to uc hs cr ee n co m pu te r a nd a w ire - le ss b al an ce b oa rd . (n = 1 1) C on ve nt io na l b al an ce tra in in g (n = 1 2) 50 m in / 2 tim es p er w ee k / 6 w ee ks A fte r t ra in in g, b ot h gr ou ps p er - fo rm ed b et te r i n th e B B S at p os t- te st a nd fo llo w -u p th an a t p re te st . N o si gn ifi ca nt d iff er en ce s w er e fo un d be tw ee n th es e tw o gr ou ps at p os t-t es t a nd fo llo w -u p. 104 Ana PONEBŠEK, Friderika KRESAL, Luka ŠLOSAR: ENHANCING BALANCE IN PARKINSON'S DISEASE PATIENTS ..., 95–112 ANNALES KINESIOLOGIAE • 14 • 2023 • 2 St ud y Po pu - la tio n In te rv en tio n D ur at io n tim e O ut co m es a nd re su lts Ex pe rim en ta l g ro up C on tro l g ro up G an do lfi e t a l. (2 01 7) n = 76 B al an ce tr ai ni ng w ith N in te nd o W ii an d ba la nc e bo ar d. (n = 3 8) Se ns or y In te gr at io n B al an ce T ra in in g (n = 3 8) 50 m in / 3 da ys p er w ee k / 7 w ee ks Si gn ifi ca nt b et w ee n- gr ou p di ffe r- en ce s w er e fo un d fo r B B S sc or es . EX P gr ou p – pr og re ss , a cc or di ng to th e B B S R ib as e t a l. (2 01 7) n =2 0 Th e ex er ga m in g in te rv en tio n co n- si st ed o f W ii Fi t g am es . T he d ev ic e us ed w as a N in te nd o vi de o ga m e co ns ol e w ith a W ii B al an ce B oa rd (n = 1 0) C on ve nt io na l e xe rc is e pr og ra m (W ar m in g, st re tc hi ng ac tiv e an d re si st an ce ex er ci se s) (n = 1 0) 30 m in / 2 tim es p er w ee k / 12 w ee ks Si gn ifi ca nt im pr ov em en t i n ba l- an ce re la tiv e to B B S in th e EX P gr ou p; th is b en efi t w as n ot su s- ta in ed a fte r t he 6 0- da y fo llo w -u p. Sa nt os e t a l. (2 01 9) n = 45 EX P1 g ro up Tr ai ni ng w ith N in te nd o W ii (n =1 5) C O N g ro up : a ct iv e as si st ed a nd re si st ed m ov em en ts , b as ed on th e PN F an d ga it tra in in g. (n = 1 5) 50 m in / 2 a w ee k / 8 w ee ks Th er e w as n o st at is tic al ly si gn ifi - ca nt d iff er en ce b et w ee n EX P1 , EX P2 g ro up a nd C O N g ro up ac co rd in g to th e B B S. EX P2 g ro up : T ra in in g w ith N in - te nd o W ii + ac tiv e as si st ed a nd re si st ed a ct iv e m ov em en ts , b as ed o n th e PN F. (n = 1 5) Fe ng e t a l. (2 01 9) n = 28 B al an ce tr ai ni ng w ith M ic ro so ft X bo x 36 0 K in ec t (n = 1 4) Tr ad iti on al re ha bi lit a- tio n tra in in g (w ar m up e xe rc is es , b al an ce ex er ci se s, ex er ci se s f or ph ys ic al c on di tio n an d co or di na tio n) (n = 1 4) 45 m in / 5 tim es p er w ee k / 12 w ee ks Si gn ifi ca nt im pr ov em en t i n B B S sc or es in b ot h gr ou ps ; B B S w er e be tte r i n EX P gr ou p th an in C O N g ro up . 105 ANNALES KINESIOLOGIAE • 14 • 2023 • 2 Ana PONEBŠEK, Friderika KRESAL, Luka ŠLOSAR: ENHANCING BALANCE IN PARKINSON'S DISEASE PATIENTS ..., 95–112 St ud y Po pu - la tio n In te rv en tio n D ur at io n tim e O ut co m es a nd re su lts Ex pe rim en ta l g ro up C on tro l g ro up To llá r e t a l. (2 01 9) n = 74 EX P1 g ro up : E xe rg am es u se d th e vi su al fe ed ba ck m od ul es o f t he X bo x 36 0 co re sy st em . (n = 2 5) C O N g ro up : W ai t-l is te d C O N g ro up co nt in ue d w ith th ei r ha bi tu al a ct iv ity . (n = 2 4) 60 m in / 5 tim es p er w ee k / 5 w ee ks EX P1 g ro up : p at ie nt s h ad b et te r re su lts in B B S sc or e co m pa re d to th e EX P2 g ro up . EX P2 g ro up : s ta tio na ry c yc lin g (C Y C ) p at ie nt s p ar tic ip at ed in a sp in ni ng c la ss . (n = 2 5) Li ao , Y an g, W u, e t a l. (2 01 5) n = 36 EX P1 g ro up : T ra in in g w ith N in - te nd o W ii (s tre ng th a nd b al an ce ex er ci se s) (n = 1 2) C O N g ro up : d id n ot un de rg o th e st ru ct ur ed ex er ci se p ro gr am b ut re ce iv ed fa ll- pr ev en - tio n ed uc at io n in st ea d. (n = 1 2) 60 m in / 2 tim es p er w ee k / 6 w ee ks B ot h th e EX P1 a nd E X P2 gr ou ps sh ow ed si gn ifi ca nt im - pr ov em en ts in S O T te st . EX P2 g ro up : T ra di tio na l e xe rc is es su ch a s s tre tc hi ng , s tre ng th en in g, ba la nc e ex er ci se , a nd tr ea dm ill tra in in g (n = 1 2) Li ao , Y an g, C he ng , e t a l. (2 01 5) n = 36 EX P1 g ro up : T ra in in g w ith N in - te nd o W ii (s tre ng th a nd b al an ce ex er ci se s) (n = 1 2) C O N g ro up : fa ll- pr ev en tio n ed uc a- tio n (n = 1 2) 60 m in / 2 tim es p er w ee k / 6 w ee ks Pa tie nt s i n th e EX P1 g ro up h ad be tte r r es ul ts in th e LO S an d SO T te st th an p ar tic ip an ts in c on tro l gr ou p. EX P2 g ro up : t ra di tio na l e xe rc is e (s tre tc hi ng , s tre ng th en in g an d ba l- an ce e xe rc is es ) (n = 1 2) 106 Ana PONEBŠEK, Friderika KRESAL, Luka ŠLOSAR: ENHANCING BALANCE IN PARKINSON'S DISEASE PATIENTS ..., 95–112 ANNALES KINESIOLOGIAE • 14 • 2023 • 2 St ud y Po pu - la tio n In te rv en tio n D ur at io n tim e O ut co m es a nd re su lts Ex pe rim en ta l g ro up C on tro l g ro up Pa zz ag lia e t a l. (2 02 0) n= 5 1 Ex er ci se to im pr ov e ba la nc e w ith th e N IR VA N A sy st em . (n = 2 5) C on ve nt io na l r eh a- bi lit at io n pr og ra m (e xe rc is es o f m ot or co or di na tio n, b al an ce tra in in g, st ar t a nd st op ex er ci se s, an d w al ki ng tra in in g) (n = 2 6) 40 m in / 3 tim es p er w ee k / 6 w ee ks EX P gr ou p im pr ov em en t i n ba l- an ce a cc or di ng to B B S sc al e sc or es c om pa re d to th e C O N gr ou p. Ye n et a l. (2 01 1) n = 42 EX P1 g ro up : T he h ar dw ar e sy st em fo r b al an ce tr ai ni ng in cl ud es d y- na m ic b al an ce b oa rd L C D sc re en , an d a pe rs on al c om pu te r. (n = 1 4) C O N g ro up : Th ey d id n ot re ce iv e di d no t r ec ei ve a ny ph ys ic al th er ap y (n = 1 4) 30 m in / 2 tim es p er w ee k / 6 w ee ks A cc or di ng to th e SO T te st , t he EX P1 g ro up m ad e a si gn ifi ca nt im pr ov em en t c om pa re d to th e C O N g ro up , b ut th is im pr ov em en t w as n ot su st ai ne d. EX P2 g ro up : c on ve nt io na l b al an ce tra in in g, (n = 1 4) Sh en & M ak , (2 01 4) n = 51 A c om pu te riz ed d an ci ng sy st em (K SD T ec hn ol og y C o. L td ., Sh en z- he n, C hi na ) (n = 2 6) Tr ai ni ng th at em ph as iz ed im pr ov in g th e st re ng th o f t he h ip (fl ex io n, ex te ns io n, a nd a bd uc - tio n) a nd k ne e (fl ex io n an d ex te ns io n) (n = 2 5) 15 –6 0 m in / 5 ti m es pe r w ee k / 12 w ee ks Th e A B C sc al e an al ys is sh ow ed th at th er e w er e no si gn ifi ca nt d if- fe re nc es b et w ee n th e tw o gr ou ps . Th e EX P gr ou p pe rf or m ed b et te r on th e SL S te st . Le ge nd : B B S – B er g B al an ce S ca le , A B C – a ct iv iti es -s pe ci fic b al an ce c on fid en ce sc al e, S LS – S in gl e Le g St an ce , S O T – Se ns or y O rg an iz at io n Te st , L O S – Li m its o f S ta bi lit y, EX P – ex pe rim en ta l g ro up , C O N – c on tro l g ro up , P N F – pr op rio ce pt iv e ne ur om us cu la r f ac ili ta tio n, P D – P ar ki ns on d is ea se 107 ANNALES KINESIOLOGIAE • 14 • 2023 • 2 Ana PONEBŠEK, Friderika KRESAL, Luka ŠLOSAR: ENHANCING BALANCE IN PARKINSON'S DISEASE PATIENTS ..., 95–112 DISCUSSION The literature review examining the impact of VR-based exercises on the static and dynamic balance outcomes of Parkinson’s disease patients indicates that existing studies lack definitive evidence to establish the superiority of ex- ercise in a virtual environment over standard exercise. The considerable vari- ability in exercise methods makes it difficult to draw firm conclusions regarding the effect of PC-exergame training on the balance ability of Parkinson’s disease patients. Although most studies did not demonstrate the superiority of PC-exergames over standard exercise, a study by Liao, Yang, Cheng, et al. (2015) revealed that Wii Fit-based exercises were more effective than traditional exercise in improv- ing dynamic balance. One potential explanation for improved balance lies in personalized therapy protocols tailored to meet individual therapeutic needs and preferences. Wii Fit exercises provide external feedback during training in both auditory and visual forms. The participants were able to make corrections based on feedback to enhance their motor performance. Some of the Wii Fit exercises require either attention or problem-solving ability. Lee et al. (2015) observed a similar positive impact when introducing an innovative training method for elderly individuals diagnosed with Parkinson’s disease, employing Nintendo Wii dance games. Compared to the control group, balance of the experimental group was significantly enhanced. The experimental group received 30 more minutes of treatment per session comparing to control group and the difference in training time probably influenced the results. Another potential confounding factor in the study is that participants received traditional physiotherapy ac- companied with Nintendo Wii. It is challenging to determine whether changes in clinical trials should be attributed to traditional balance training or VR. Unlike the previously mentioned studies, van den Heuvel et al. (2013) did not integrate Nintendo Wii into their setup. Instead, they employed a mobile workstation setup equipped with a force plate for the intervention within the experimental group. However, this approach did not demonstrate superior ef- fectiveness compared to conventional therapy. The diversity of devices utilized in these studies poses a challenge in reach- ing definitive conclusions. Devices ranged from common gaming consoles like Nintendo Wii and Xbox Kinect to specialized rehabilitation systems such as the NIRVANA and the computerized dancing system (KSD Technology Co. Ltd., Shenzhen, China). Moreover, the varied frequency (ranging from 2 to 5 times per week) and duration (lasting 5 to 12 weeks) of training sessions add complexity in establishing effective protocols. This wide array of intervention 108 Ana PONEBŠEK, Friderika KRESAL, Luka ŠLOSAR: ENHANCING BALANCE IN PARKINSON'S DISEASE PATIENTS ..., 95–112 ANNALES KINESIOLOGIAE • 14 • 2023 • 2 types and frequencies significantly contributes to result heterogeneity, present- ing difficulties in establishing conclusive findings. To reduce variability in re- sults, future studies should research tailored interventions for different diseases stages. It is well known that Parkinson’s disease patients often have a preserved ability to cycle (Licen, Rakusa, Bohnen, Manganotti, & Marusic, 2022). This represents a unique aspect of their motor function that must be considered when designing research studies. If the ability to cycle is preserved in Parkinson’s disease, comparing the effectiveness of exergame / VR interventions with tradi- tional cycling could be problematic because of the potential overlap in benefits and the need for differentiated evaluation methods to distinguish the respective effects. Reviewing the literature it emerges that the PC-exergame technology for home-based training can be an effective option, particularly for individuals with limited access to rehabilitation centers and hospitals and could be used as a low-supervision home-base technology to obtain a therapeutic effect in- dependently (Yang et al., 2016). However, a notable concern with home-based exercise lies in the possibility of users adopting compensatory movements to boost game performance. This inclination might lead patients to prioritize achieving high game scores over enhancing movement quality, potentially di- minishing the genuine training effects. Before introducing computer games at home, it’s essential to prevent compensatory movements from affecting game performance. Supervised exercises by a physiotherapist can ensure safety and discourage compensatory actions. This supervision is especially vital for older adults unfamiliar with new technologies. Literature review is subject to certain limitations that should be considered. A significant limitation is the inclusion of various forms of exercise in the VR- exergaming category. In the future, as more studies become available, it would be advisable to perform sub-analyses that differentiate between different types of exercises. For instance, the Shen & Mak (2014) study incorporated dancing, while others focused on strength and balance exercises. We included studies involving participants clinically diagnosed with Parkin- son’s disease, without any limitations on gender, age, disease duration or sever- ity, and these studies exhibited variations in the types of technology employed and the duration of interventions. These factors may have introduced biases in the results and hindered direct comparisons. Future studies with improved tech- nology and research methodologies are necessary to address the limitations and provide clearer insights into the effectiveness of exercise in enriched environ- ments Additionally, these future investigations should incorporate innovative technologies that enable a holistic understanding of motor control strategies in 109 ANNALES KINESIOLOGIAE • 14 • 2023 • 2 Ana PONEBŠEK, Friderika KRESAL, Luka ŠLOSAR: ENHANCING BALANCE IN PARKINSON'S DISEASE PATIENTS ..., 95–112 Parkinson’s disease (Marusic et al., 2023), thus advancing our comprehension of the condition’s intricacies. CONCLUSIONS The literature review encompasses scientific publications that explore the use of VR as a treatment modality for individuals with Parkinson’s disease, specifically focusing on the impact of training in an enriched environment on balance improvement. 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