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3D Virtual Reality Motionless Imagery Exercise through Avatar in Older People

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19 March 2024

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Abstract
Background: 3D virtual reality (VR) Motionless Imagery Exercise through Avatar (MIEA) was developed to improve elderly’s psychological (cognitive and emotional) and physical health. This study observed the impact of this program on the cognitive functions and emotional well-being and the electrophysiological changes in older adults. Methods: This study was conducted using a randomized controlled trial design. The participants included 38 adults, 65 to 84 years of age, who were physically mobile and neurologically healthy. Among them, 19 participants were assigned to the experimental group, who underwent exercises using elderly avatars in a VR virtual exercise program. The other 19 participants were assigned to the control group who underwent the VR program. Both groups engaged in the VR intervention for 20 minutes three times a week, over six weeks. Results: The cognitive functions, including attention restraint, working memory, and phonemic fluency, of the experimental group showed significant improvements compared to the control group. Regarding emotional well-being, the experimental group showed greater self-efficacy. The electrophysiological changes revealed similar patterns to exercise-induced reactions in electromyography of the experimental group after intervention. Conclusions: These findings confirm that participation in 3D VR MIEA enhances cognitive functions and physical self-efficacy among the elderly. Therefore, 3D VR MIEA can be utilized in the rehabilitation therapy of patients or elderly with limited physical activity.
Keywords: 
Subject: Public Health and Healthcare  -   Physical Therapy, Sports Therapy and Rehabilitation

1. Introduction

Cognitive functions in humans change due to factors such as aging and disease. These changes are referred to as a continuous phenomenon of cognitive decline. The decline in cognitive functions observed in the elderly increases the risk of mild cognitive impairment and dementia, and the resulting decrease in intellectual abilities limits functional activities in daily life [1,2]. Addressing these changes through psychological and social interventions is crucial [3]. In particular, psychological training through exercise has a positive impact on enhancing cognitive and emotional functions [4,5].
While exercise participation for the general population often focuses on physical changes, elderly individuals exercise to enhance cognitive functions and emotional well-being [6]. Integrating aerobic exercise with cognitive stimulation improves brain function, particularly in Alzheimer's patients and those with cognitive impairments [7,8,9]. Based on these studies, exercise participation among the elderly is crucial for dementia prevention and cognitive enhancement.
Despite the importance of exercise, physical constraints often challenge elderly individuals. Therefore, innovative approaches are necessary to involve them in exercise. Could visualizing oneself engaging in exercise through imagination, even without physical movements, have an effect? If so, this approach could hold significant clinical implications for elderly individuals with limited physical abilities.
The continuous advances of cognitive neuroscience are unveiling the interactions between the body and mind, emphasizing embodied cognition [10]. This paradigm emphasizes the embodied cognition concept, which views the external environment, body, and brain as an integrated unit. Within this framework, imagery training involves brain-based imagination without bodily movement, inducing motor sensations through visualization [11,12,13]. Essentially, cognition and action dynamically engage the functional networks of the brain, interacting with each other and influencing aspects such as aging, diseases, and overall health [14,15,16,17].
A previous study involving 3D virtual reality (VR) Motionless Imagery Exercise through Avatars (MIEA) demonstrated improved cognitive functions in normal adults [18]. Studies have shown that imagery exercise, while not equivalent to actual physical exercise, can still have meaningful effects. This concept has been proven through research and is used actively in the treatment of patients with physical disabilities or chronic pain who are unable to engage in physical movement [19,20,21].
On the other hand, applying imagery training universally to untrained individuals is challenging. It induces neuroplasticity by visualizing motor skills reacquisition or imitation [22,23,24]. Combining "body swap" and a virtual reality paradigm offers a solution [25]. Body swapping involves perceiving an avatar as one's body in a virtual environment [26,27,28] This synchronicity between movements and mental states can be maximized within a VR context.
Utilizing VR enhances imagery immersion and training efficiency, providing therapeutic exercise effects to vulnerable individuals, such as the elderly, who might able to engage in physical exercise. Research conducted on elderly and patients using VR has provided results, such as upper limb function recovery and stress reduction, through activation of the parasympathetic nervous system in stroke and hemodialysis patients [23,29]. Therefore, inducing the integration of various sensory information in the virtual environment to perceptually and cognitively engage elderly individuals might have therapeutic exercise effects within the realm of VR.
The effects of imagery exercise within a VR without actual physical movement must be verified before VR exercise programs based on imagery training can be developed. Moreover, multidimensional research exploring the cognitive and emotional effects of VR exercise programs is lacking. Thus, this study verified the effects of 3D VR MIEA on the cognitive, emotional, and physiological functions of the elderly. This study reports foundational therapeutic methods and promotes the widespread use of VR imagery exercise programs in healthcare and exercise rehabilitation.
Therefore, the purpose of this study is to develop a 3D virtual reality exercise program. And it is to verify whether some exercise effects are issued just by the thought of exercising by embodying an avatar that moves in virtual reality without the subject's actual movement. This study observes the emotional, cognitive, and physiological changes in exercise effects in the elderly who are vulnerable to exercise.

2. Materials and Methods

2.1. Participants

The determination of the research participants was based on the statistical program G-power 3.1, using an effect size of f=.26, α=.05, and 1-β =.95, resulting in a calculated total sample size of 40 individuals. For this study, the participants were selected from old adults aged 65 to 84 years. Those who scored 24 or higher on the K-MMSE-K (Korean-Mini Mental State Examination) and were physically and neurologically healthy, without any physical movement discomfort, were included. Thirty-eight experimental subjects were enrolled in this study. The participants were instructed not to engage in additional physical activities and to maintain their daily routines throughout the study. Table 1 shows the participants’ demographics. The objectives and research methods were explained to the participants before participating in the study. All participants provided written informed consent before participating. This study was approved by the Institutional Review Board (PNU IRB 2018-84-HR). Participants who participate in the experiment and completely complete the experiment receive a reward of about $80 in US dollars.

2.2. Procedures

The study participants were assessed for eligibility based on the selection and exclusion criteria outlined in a telephone interview and checklist. Thirty-eight participants were selected for the study. The participants were divided into two groups using a randomized controlled trial design: an experimental group (n=19) who performed a 3D VR MIEA and a control group (n=19) who performed a VR program with exercise context. The allocation was performed using single blinding and a random number generator program (Microsoft Office Excel 2017, Microsoft Corporation, Redmond, WA, USA).
The exercise program was conducted three times a week, for 20 minutes per session, totaling 18 sessions over six weeks. All exercise sessions were conducted on-site at a senior center by the researchers because of the mobility limitations of the elderly participants. The researchers conducted the experiments. Prior to the experiment, apart from the intervention, all subjects had time to freely experience virtual reality for 10-20 minutes to see if they can experience virtual reality without discomfort such as motion sickness and adapt to participate in 3D virtual reality.
All participants underwent a total of two tests before and after the experimental intervention. A licensed psychologist administrated the cognition and emotion assessments, and collect electro physiological responses, ensuring separation between the experimental procedures and the assessments.
In the experimental group, participations were learned and practiced by avatars provided in virtual reality to embody themselves. The experiment group was instructed to focus their gaze on the legs of a third-person view avatar before running began. They were instructed to synchronize their leg movements with the sound of footsteps, inducing a heightened sense of leg movement embodiment. The participants in the experimental group were able to control the speed of the avatar running in real time through the controller.
The control group was given only 3D virtual reality without avatars and was unable to control anything. The control group was instructed only to experience the VR comfortably without specific instructions. The control group was not given instructions such as exercising or thinking that they were moving on their own.
All participants were not engaged any physical movements or required motions while participating in the 3D VR MIEA (see Figure 1).

2.3. Content Development

For this study, a 20-minute running program designed for the elderly was developed using the Unity platform, a VR development program. In the experimental group, avatars were provided to match the participants' sex, and the participants could adjust the running speed within the running track. Footstep sounds were synchronized with the running speed. In addition, to minimize motion sickness and exclude emotional elements that the environment could evoke, the virtual environment was designed with basic elements, such as mountains and trees, offering a monotonous yet suitable environment to verify the exercise effects. The purpose of these designs was to focus on evaluating the exercise effects, while minimizing the potential emotional factors that could influence the outcomes of the VR contents.
In the control group, a track was designed where participants could move at a constant speed and view the scenery, without providing avatars. This was done to ensure that both groups experienced similar aspects of the virtual environment, except for the presence of avatars and the ability to control running speed (see Figure 2).

2.4. Apparatus

The HTC Vive VR equipment (HTC Corporation, New Taipei City, Taiwan) was utilized. The equipment consisted of a head-mounted display (HMD) and two hand controllers. The VR implementation software was developed using the Steam VR Unity plugin. The Procomp Infiniti equipment (Think Technology Ltd., Montreal, Canada) was used to measure the electrophysiological responses.

3. Measurement

3.1. Cognition

The Stroop Test was performed to evaluate the cognitive processing speed and inhibition by assessing the interference in naming the color of a word when the word itself spells out a different color [30]. The Controlled Oral Word Association Test (COWAT) measured the executive functions through verbal fluency tasks [31]. The Rey–Kim Memory Test assessed the memory [32]. The Digit Span Task using the K-WAIS-IV assessed short-term memory and attention [33]. The Stop Signal Task (Millisecond Software, 2008) evaluated inhibitory control and attention restrain. K-MMSE was assessed too [34].

3.2. Emotional Well-Being

The State-Trait Anxiety Inventory (STAI) first assesses the participants' anxiety tendencies [35]. The reliability of the STAI in this study was Coronbach's α=.905. The Physical Self-Efficacy Questionnaire developed by Ryckman, Robbins, Thomton, and Cantrell and adapted into a Korean version was used to assess the participants' perception of their physical self-efficacy [36]. The reliability of the Physical Self-Efficiency Scale in this study was Coronbach's α=.913. The Stress Response Inventory (SRI) was used to evaluate participants' stress responses [37]. The reliability of the Stress scale in this study was Coronbach's α=.880. The Positive and Negative Affect Schedule (PANAS) measured the participants' affective states [38]. The reliability of the positive and negative scale in this study was Coronbach's α=.771.

3.3. Physiological Response

The electrophysiological changes during the virtual environment experience were measured. The electrocardiogram (ECG) recorded the electrical activity of the heart. A photoplethysmogram (PPG) monitors the heart rate through changes in blood volume in the skin. The Galvanic Skin Response (GSR) measures the changes in skin conductance caused by emotional arousal. Respiration (RESP) was measured to assess the changes in breathing patterns. Electromyogram (EMG): Recording muscle activity. The skin resistance for surface electrodes was reduced by disinfecting the attachment sites with alcohol and using disposable electrodes (Electrode2237, 3M, USA) made of silver (Ag)/silver chloride (AgCl).

3.4. Data Analysis

The social science statistical package program, IBM SPSS 22.0 for Windows (SPSS Inc., Chicago, IL, USA), was used for statistical analysis. The descriptive statistics (mean and standard error) were calculated for all measurements and demographic information. Paired-sample t-tests and repeated measures analysis of variance (RM-ANOVA) were performed to compare the effects of the 3D VR MIEA between the two groups. The factors were the assessment (pre-test and post-test) and group (experimental and control). The program's effectiveness on the outcome measures was determined based on the interaction between the group and time, with a significance level set to p < 0.05.

4. Results

4.1. Cognition

Various tools were used to assess changes in cognitive function, including the MMSE-K, Stroop test and Stop signal task for evaluating the attention restrain, K-AVLT for memory testing (immediate recall, delayed recall, delayed recognition), Digit-span task for assessing working memory, and COWAT (semantic fluency, phonemic fluency) for evaluating the frontal lobe function. These measurements were analyzed using RM-ANOVA (Table 2). The results indicated significant time effects for all measures except the Stop signal task, with significant time-by-group interactions observed in the Stroop test (F=17.48), Immediate recall (F=8.34, p< .01), Delayed recall (F=4.17, p< .05), Digit-span task (F=14.27, p< .001), and semantic fluency (F=7.47, p< .001).

4.2. Emotional Well-Being

An analysis of repeated measurements was conducted on the data related to physical self-efficacy. The results revealed a significant effect of time (F=5.87, p< .05), indicating a meaningful change over time. Although the effect of the group was not significant, the interaction between the group and time had a statistically significant effect (F=11.27, p< .01). In terms of the group effect, significant effects were observed for stress (F=13.52, p< .01), positive emotions (F=5.74, p< .05), and negative emotions (F=6.13, p< .05) (Table 3).

4.3. Electrophysiological Response

Repeated measures analysis of variance (ANOVA) was used to verify the physiological responses. Table 4 lists the results of the repeated measures ANOVA. The repeated measures ANOVA revealed a significant time effect (F=8.88, p< .05) in the left lateral gastrocnemius muscle (EMG C), indicating a meaningful change over time. Although the group effect (F=3.69) was not statistically significant, there was an observed medium effect size. Furthermore, there was a significant interaction between the group and time (F=5.52, p< .05).

5. Discussion

This study examined the physiological, cognitive, and emotional changes in the elderly after experienced 12 times 3D VR MIEA for 6 weeks. The main findings are as follows.
Regarding the changes over time in cognitive function, significant effects were observed in MMSE-K, Stroop test, Rey–Kim task (immediate recall, delayed recall, delayed recognition), Digit–span task, and COWAT (semantic fluency and phonemic fluency). The group-related changes significantly affected MMSE-K, Stroop test, Rey–Kim task (immediate recall), and COWAT (semantic fluency). Moreover, in the interaction between time and group, significant effects were found in the Stroop test, Rey–Kim task (immediate recall, delayed recall), Digit-span task, and COWAT (phonemic fluency). In emotional well-being, significant effects were observed the interactions between time and group in physical self-efficacy. (3) Regarding electrophysiological responses, significant effects were the interaction between time and group on EMG C. Overall, the 3D VR MIEA significantly affected cognitive, emotional, and electrophysiological aspects among the elderly participants.

5.1. Cognitive Functions

The study revealed significant improvements in specific cognitive function, including response inhibition (Stroop test), working memory, and executive function. This cognitive improvement aligned with previous research suggesting that exercise positively influences memory and executive function among older adults [39,40,41,42]. Steinberg et al. reported that exercise participation among older adults positively influences memory and executive function, which is consistent with the study findings [43].
In addition, VR-based training programs provide a safe environment for the elderly and can adjust the difficulty levels based on individual abilities, enhancing motivation and enjoyment during training. Such programs benefit memory, executive function, and various cognitive domains [44,45]. In the context of this study, the 3D VR MIEA provided cognitive benefits through simulated exercises, which could positively influence cognitive enhancement among elderly individuals with motionless exercise like imagery training.

5.2. Emotional Well-Being

Although most emotional well-being results did not show significant findings, the experimental group showed emotional improvement compared to the control group regarding the changes in physical self-efficacy from pre-experiment to post-experiment. Although many emotional factors tended to decline in older age, including activity levels and willingness to exercise, this result is significant. The result aligns with studies suggesting that increased physical self-efficacy after exercise is associated with enhanced positive beliefs [46]. Therefore, an experience of achievement in physical activity can help form strong positive beliefs in individuals. These results may show that older adults who are fearful and unmotivated for exercise can have the efficacy of actually exercising, thereby increasing the actual exercise participation rate.
On the other hand, considering the limitations of not observing other emotional effects, the experiment, conducted without physical movement, may have lacked the physiological responses required to induce various emotional changes. Furthermore, the monotony of graphics and composition of the VR content could have been insufficient to trigger various emotional effects.

5.3. Physiological Response Changes

An analysis of electrophysiological data changes between the pre-experiment and during 3D VR MIEA indicated significantly greater alterations in the left gastrocnemius muscle in the post-experiment phase compared to the pre-experiment phase. The interaction between time and group also revealed considerable changes in electrophysiological responses of the left lateral gastrocnemius muscle EMG C. These findings suggest that, despite the absence of actual movement, internal neural stimulation promoted a sense of movement through mental imagery during the exercise regimen. Similarly, Sharma et al. reported that fine muscle activity patterns resembling those during actual movement occurred during imagery exercises [47]. Hence, utilizing exercise videos or imagining movements can activate muscle responses through neural stimulation, even without physically moving the muscles, which can be explained by psychological and neuromuscular theories [48].

5.4. Limitations

This study demonstrated the feasibility of applying 3D VR MIEA to the old population. The significance lies in analyzing the cognitive and emotional effects of imagery exercises within the context of VR exercise. On the other hand, the monotony in the composition and graphics of the VR content used in this study could have limited the induction of emotional effects. Future research is needed to verify the effects of this program by incorporating various contents and VR technology that can induce emotional effects.
This study does not completely limit the environmental ecological factors of participants, and the results cannot be generalized because it is a study targeting a specific period and a specific sample. Further verification is needed as a continuous follow-up study with more samples.

6. Conclusions

In conclusion, this study aimed to verify the effects of virtual reality imagery exercise on cognitive function improvement, emotional well-being, and physiological responses in elderly individuals. Emphasis was placed on the changes in cognitive function, emotional well-being, and physiological responses through virtual reality mental imagery exercise, observing similar positive effects to those observed in actual physical exercise. Participants in this study experienced experiences similar to actual physical exercise through visual stimulation and imagery exercise in a virtual reality environment. Specifically, the results of this study revealed significant improvements in response inhibition, language memory, and working memory in cognitive function, with greater changes observed in the experimental group. Secondly, although various effects were measured in emotional well-being, positive changes were only observed in physical self-efficacy. Thirdly, in terms of physiological responses, greater changes were observed in the left lateral gastrocnemius muscle in terms of time and group interaction.
Implications
The 3D VR MIEA conducted in this study holds potential for practical use in rehabilitative clinical settings for populations, such as the elderly with mobility challenges, individuals with limb paralysis, and patients with depression who may resist physical activity. These exercises could offer rehabilitation benefits to such groups. Hence, further research is needed to explore their potential outcomes.

Author Contributions

Conceptualization, K.H.H., M.C.L., C.H.P.; Methodology, K.H.H., M.C.L., C.H.P.; Results, M.C.L.; Discussion, K.H.H. and M.C.L.; Conclusion, K.H.H. and M.C.L.; Writing—Original Draft Preparation, K.H.H. and M.C.L.; Writing—Review & Editing, K.H.H. and M.C.L. All authors have read and agreed to the published version of the manuscript.

Funding

This work was supported by a National Research Foundation of Korea (NRF) grant funded by the Korean government (MIST, 2017R1C1B5018351).

Institutional Review Board Statement

This study was approved by the Institutional Review Board (PNU IRB 2018-84-HR).

Informed Consent Statement

Informed consent was obtained from all subjects involved in the study.

Data Availability Statement

Data is unavailable to open or share due to privacy restrictions; no consent was sought by the subjects (participants) to make the data transcripts available to anyone. This is also the recommendation of the Research Ethics Committee.

Conflicts of Interest

The authors declare no conflicts of interest.

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Figure 1. Study flow chart.
Figure 1. Study flow chart.
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Figure 2. Experiment setting of 3D Virtual Reality Motionless Imagery Exercise through Avatar.
Figure 2. Experiment setting of 3D Virtual Reality Motionless Imagery Exercise through Avatar.
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Table 1. Demographic information of subjects.
Table 1. Demographic information of subjects.
Variables Experimental group (n=19) Control group (n=19)
Characteristic Categorize Frequency Percentage Frequency Percentage
Age, years M(IQR) 69.20 (67.5, 73.5) 69.90 (66.5, 75)
Sex Male 9 45 10 55
Female 10 55 9 45
IQR=lower limit 25% and upper limit 75%.
Table 2. Results on cognitive functions.
Table 2. Results on cognitive functions.
Variables Group Pre -test(95% CI) Post- test(95% CI) Repeated measures ANOVA (F-value)
Time
(p-value)		 pη2 Group
(p-value)		 pη2 T×G
(p-value)		 pη2
MMSE-K Experimental 28.42(27.41, 29.10) 29.21(28.53, 29.78) 14.93***
(.000)		 .293 15.45***
(.000)		 .300 1.21
(0.30)		 .033
Control 26.68(25.95, 27.74) 27.00(26.29, 28.02)
Stroop Test Experimental 36.21(28.96, 39.55) 41.74(35.90, 44.61) 18.64***
(.000)		 .341 9.54**
(.004)		 .210 17.48***
(.000)		 .327
Control 52.16(45.31, 58.05) 52.00(45.22, 57.93)
Immediate recall
(Rey-Kim Test)		 Experimental 35.53(31.19, 39.54) 43.84(40.59, 46.67) 23.04***
(.000)		 .390 5.12*
(.030)		 .125 8.34**
(.001)		 .188
Control 34.37(30.47, 37.20) 36.05(32.90 ,38.46)
Delayed recall
(Rey-Kim Test)		 Experimental 6.37(5.38, 7.35) 8.37(7.69, 9.14) 36.80***
(.000)		 .506 0.70
(.405)		 .019 4.17*
(.019)		 .104
Control 6.63(5.87, 7.28) 7.47(6.81, 8.13)
Delayed recognition
(Rey-Kim Test)		 Experimental 10.32(9.06, 11.66) 11.89(11.27, 12.40) 15.30***
(.000)		 .298 0.34
(.564)		 .009 3.13
(.05)		 .080
Control 10.84(9.91, 11.44) 11.58(11.05, 12.10)
Stop-Signal Task Experimental 307.26(224.76 , 421.43) 309.13(285.29, 361.55) 2.51
(.088)		 .065 0.89
(.771)		 .002 2.43
(.095)		 .063
Control 370.81(274.12, 424.53) 254.78(234.17, 271.79)
Digit-Span Task Experimental 23.68(20.89, 26.47) 28.79(26.54, 31.13) 41.30***
(.000)		 .544 2.73
(.107)		 .071 14.27***
(.000)		 .284
Control 23.47(20.37, 25.51) 24.68(21.55, 26.44)
COWAT
(semantic fluency)		 Experimental 31.89(28.13, 36.39) 38.53(33.97, 43.81) 13.12***
(.000)		 .267 10.71**
(.002)		 .229 2.56
(.084)		 .067
Control 26.26(22.85, 28.72) 28.74(25.30, 30.90)
COWAT
(phonemic fluenc)		 Experimental 24.37(18.59, 30.14) 30.95(25.07, 35.55) 35.55***
(.000)		 .497 1.01
(.321)		 .027 7.47**
(.001)		 .172
Control 23.79(18.36, 28.36) 25.63(20.07, 30.87)
NOTE. Values are M±SD. *p <.05, **p <.01, ***p <.001. T×G: Time×Group Interaction, pη2: partial eta squared.
Table 3. Results on emotional well-being.
Table 3. Results on emotional well-being.
Variables Group Pre-test(95% CI) Post-test(95% CI) RM-ANOVA (F-value)
Time
(p-value)		 pη2 Group
(p-value)		 pη2 T × G
(p-value)		 pη2
State anxiety Experimental 32.00(27.98, 35.38) 33.21(29.14, 37.27) .139
(.004)		 .004 3.58
(.066)		 .090 .894
(.351)		 .024
Control 36.63(34.65, 38.82) 36.10(34.88, 37.74)
Characteristic anxiety Experimental 32.84(29.64, 36.03) 33.89(30.70, 37.08) .513
(.478)		 .014 2.34
(.135)		 .061 .939
(.339)		 .025
Control 36.05(34.30, 37.58) 35.89(34.39, 37.42)
Physical self-efficacy Experimental 87.33(80.55, 92.71) 92.22(84.03, 95.22) 5.87*
(.015)		 .140 2.13
(.153)		 .058 11.27**
(.001)		 .224
Control 84.74(81.26, 91.15) 83.95(79.85, 90.77)
Stress Experimental 16.94(10.82, 23.17) 15.26(11.01, 19.71) 3.43
(.072)		 .087 13.52**
(.001)		 .273 .166
(.686)		 .005
Control 6.84(3.21, 10.67) 4.21(2.93, 5.79)
Positive affect
(PANAS)		 Experimental 31.15(27.07, 36.18) 27.68(24.31, 31.79) 1.23
(.273)		 .033 5.74*
(.022)		 .138 4.05
(.052)		 .101
Control 27.68(20.97, 25.96) 24.84(22.79, 26.78)
Negative affect
(PANAS)		 Experimental 12.73(11.84, 15.09) 11.10(11.65, 13.92) 1.55
(.221)		 .041 6.13*
(.018)		 .146 1.55
(.221)		 .041
Control 11.10(10.03, 12.07) 11.10(10.17, 11.82)
NOTE. Values are M±SD. *p <.05, **p <.01, ***p <.001. T×G: Time×Group Interaction, pη2: partial eta squared.
Table 4. Electrophysiological response changes.
Table 4. Electrophysiological response changes.
Variables Group Pre-test(95% CI) Post-test(95% CI) Repeated measures ANOVA (F-value)
Time
(p-value)		 pη2 Group
(p-value)		 pη2 T×G
(p-value)		 pη2
ECG
(beats/min)		 Experimental -0.16(-2.54, 2.24) 1.21(-2.72, 2.57) .341
(.563)		 .009 .010
(.922)		 .000 2.582
(.116)		 .064
Control 1.86(0.26, 4.85) -1.09(-3.47, 1.19)
EMG A
(㎶)		 Experimental -3.35(-8.09, 2.07) -0.88(-0.23, 0.87) .629
(.433)		 .016 2.432
(.127)		 .060 1.123
(.296)		 .029
Control 0.39(-0.73, 0.63) 0.04(-0.36, 0.35)
EMG B
(㎶)		 Experimental -0.28(-1.75, 1.21) 0.35(0.38, 1.31) .306
(.584)		 .008 .043
(.837)		 .001 .718
(.402)		 .019
Control 0.005(-0.46, 0.49) -0.13(-0.33, 0.11)
EMG C
(㎶)		 Experimental 0.21(-0.67, 1.10) 1.55(1.23, 2.03) 8.881
(.005)**		 .189 3.690
(.062)
.089		 5.5254
(.028)*		 .121
Control 0.25(-0.12, 0.56) 0.42(0.06, 0.81)
RESP
(beats/min)		 Experimental 0.77(-0.18, 1.62) 0.32(-0.37, 0.92) .351
(.557)		 .009 3.511
(.069)		 .085 .073
(.788)		 .002
Control -0.45(-2.13, 0.95) -0.62(-1.93, 0.52)
SC
(㎶)		 Experimental -1.18(-1.88, -0.61) -0.61(-0.88, -0.24) 8.973
(.018)*		 .139 2.741
(.106)		 .067 .140
(.711)		 .004
Control -0.68(-1.15, -0.26) 0.08(-0.92, 1.08)
BVP
(pulse/min)		 Experimental 0.87(-0.28, 2.16) 0.59(-0.04, 2.32) .379
(.542)		 .010 .162
(.690)		 .044 .000
(.993)		 .000
Control 1.37(-0.80, 3.12) 0.53(-3.43, 4.53)
NOTE. Values are M±SD. *p <.05, **p <.01, ***p <.001. EMG A: left biceps brachii, EMG B: left rectus femoris, EMG C: left lateral gastrocnemius. T×G: Time×Group Interaction, pη2: partial eta squared.
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