Accepted Manuscript[Type of manuscript] Regular Article[Title] Effects of acute arm-cranking exercise with electrical muscle stimulation at
different intensities on the vascular endothelial function[Authors] Mizuki Nakamura1*, Hajime Miura 2, Ayako Murakami 3, Yasuaki Tamura 4[Affiliations]1

Department of Physical Therapy, Faculty of Health Science, Osaka Yukioka College of

Health Science, 1-1-41 Sojiji, Ibaraki, Osaka 567-0801, Japan
2

Laboratory for Applied Physiology, Institutes of Socio-Arts and Sciences, Tokushima

University, 1-1 Minamijyosanjima, Tokushima, Tokushima 770-8502, Japan3

Department of Health and Nutrition, Shikoku University, 123-1 Ojinchofurukawa,

Ebisuno, Tokushima, Tokushima 771-1192, Japan
4

Department of Rehabilitation Medicine, Tokushima Prefecture Naruto Hospital, 1-1-41

Muyacho, Kurosaki, Naruto, Tokushima 772-0001, Japan[Mailing address] #305 2-21-3 Doicho, Amagasaki, Hyogo 660-0083, Japan
Tables: 1, Figures: 5
Running title: Arm-cranking exercise plus EMS effect vascular function[Correspondence]
Mizuki Nakamura*, 1-1-41 Sojiji, Ibaraki, Osaka 567-0801, Japan.

TEL: +081-72-621-0881, FAX: +081-72-621-1233
E-mail: mizuki.ishikawa6@gmail.com

Abstract
Arm-cranking exercises combined with electrical muscle stimulation (EMS) of thelower limbs at maximum intensity enhance vascular endothelial function. To bring thisprocedure into clinical application, we examined the effects of acute arm-cranking
exercise combined with lower-extremity EMS at different intensities on vascularendothelial function. The study included eight healthy adult males. After resting in the．
supine position, arm-cranking exercises were performed at an intensity of 50% VO2 max
for 20 min, and the lower limb received EMS under three trials: maximum intensity trial(A+100%EMS trial), 50% intensity trial (A+50%EMS trial), and 25% intensity trial(A+25%EMS trial). Flow-mediated dilation (FMD), which reflects vascular endothelial
function, was measured before and after the procedure, and the normalized FMD (nFMD)
was calculated. The mean nFMD before and 30 min after the exercise was 0.8±0.3 and2.3±1.8, respectively, in the A+100%EMS trial and 0.9±0.4 and 1.4±1.0, respectively, in
the A+50%EMS trial, indicating a significant increase after exercise under both trials. Nochanges were observed in the A+25%EMS trial. The combination of arm-cranking

exercise and 50% intensity EMS appears to be a clinically applicable program for
improving vascular endothelial function, even with reduced exercise intensity.
[Keywords] vasodilatation; electrical stimulation; aerobic exercise; upper extremity

Article title
一過性の上肢の有酸素性運動と異なる強度の骨格筋電気刺激が血管内皮機能に及ぼす影響
Author names中村

みづき 1*,

三浦

哉 2,

村上

亜弥子 3,

田村

靖明 4

Affiliations
1

大阪行岡医療大学医療学部理学療法学科，〒567-0801 大阪府茨木市総持寺１

丁目 1−412

徳島大学大学院社会産業理工学研究部，〒770-8506 徳島市南常三島町 2-1

3

四国大学生活科学部健康栄養学科，〒771-1192

徳島県徳島市応神町古川字戎子野 123-1
4徳島県鳴門病院リハビリテーション部，〒772-0001

小谷 32

徳島県鳴門市撫養町黒崎

Abstract
上肢の有酸素性運動と最大耐性強度の下肢への骨格筋電気刺激(EMS)の併用
運動は血管内皮機能を向上させる．このプログラムを臨床応用させるためには，運動プログラムの低強度化が求められるが低強度化した運動プログラムが血管内皮機能に及ぼす影響については，十分に検討されていない．本研究では，一過性の上肢の有酸素性運動と異なる強度の下肢 EMS の併用が上腕動脈の血管内皮機能に及ぼす影響について検討した．被験者は，健康な成人男性 8 名であり．
仰臥位安静後，50% VO2max 強度で 20 分間の上肢クランク運動と下肢への EMS
を最大耐性強度 (A+100%EMS) 条件，50%強度 (A+50%EMS) 条件，25%強度 (A+25%EMS) 条件の 3条件を実施させた．運動前後に血管内皮機能を反映する FMDを測定し，標準化 FMD (nFMD)を算出した． 運動前および運動終了 30 分後のnFMD は，A+100%EMS 条件で 0.8±0.3，2.3±1.8 であり，A+50%EMS 条件で0.9±0.4，1.4±1.0 であり，両条件ともに運動前と比較して運動終了 30 分後に有意な増加を示した．A+25%EMS 条件では，運動前後に変化は認められなかった．
50％強度の EMS においても，他動的な筋収縮による血流量の増加，一酸化窒素などの血管拡張物質の産生促進などにより，nFMD が増加したことが考えられる．上肢の有酸素性運動と 50%強度の下肢 EMS の併用運動は，血管内皮機能の改善を目的とした臨床応用可能な運動プログラムとなる可能性が示唆された．

1

Introduction

2

Walking and bicycle pedaling are used as exercise therapies for cardiovascular3

diseases (CVDs) and metabolic diseases. The effects of such lower-limb aerobic exercises4

on arterial function include improved arterial compliance 1), improved flow-mediated5

dilation (FMD) 2), and decreased pulse wave velocity (PWV) 3). The mechanism for this6

is that increased blood flow due to exercise increases shear stress, a mechanical stress on

7

the vessel wall that causes vasodilation due to the release of nitric oxide from vascular8

endothelial cells 4). Thus, aerobic exercise of the lower extremities has been shown to9reduce the risk of developing CVDs.

10

However, patients with spinal cord injury (SCI) and paralysis of the lower extremities

11

and orthopedic patients with joint pain and deformity have difficulty performing the12

recommended aerobic exercises, limiting daily physical activity and rehabilitation.

13

Patients with SCI have higher resting femoral artery PWV 5) and lower arterial

14compliance than healthy patients 6). Moreover, they are associated with increased15

mortality from CVD due to atherosclerosis and hypertension 7). Aerobic exercise of the16

upper extremities may be considered when aerobic exercise of the lower extremities is17difficult. Miura et al. reported no significant change in the brachial-ankle PWV before

18

and after 30 min of moderate-intensity arm crank exercise in healthy adult men 8). These19

results suggest that aerobic exercise of the upper extremities does not alter arterial

20function; however, electric muscle stimulation (EMS), which is effective in increasing

21

muscle strength 9), energy metabolism 10), and blood flow 11), has attracted attention as a22possible solution. Rappelt et al. reported that a hybrid exercise involving arm-cranking

23(35.9±8.4 W, 50% of body mass) combined with EMS (4 Hz, 350 μs) at the maximum

24

tolerated intensity increased oxygen uptake compared to arm-cranking exercise alone

25(hand cycle: approximately 13.5 ml/min/kg vs. hand cycle with EMS: approximately 19.0

26．
ml/min/kg) 12). In addition, arm-cranking exercise at 50% VO2 max combined with EMS

27of the lower extremities at maximal tolerable intensity has been reported to improve28

brachial artery (BA) endothelial function 13), suggesting the possibility of improving

29

endurance and cardiovascular performance in patients with SCI and those that are30

wheelchair-dependent. However, in both studies, the stimulation intensity of EMS was at31

the maximum tolerable intensity. In clinical physical therapy, it is difficult to actively

32

perform high-intensity exercise because many patients have a combination of various

33

diseases associated with poor physical function and various risks associated with exercise.

34

In addition, discomfort and pain caused by high-intensity electrical stimulation (ES) may

35

affect withdrawal from therapy 14). Therefore, identification of more clinically appropriate

36

stimulus intensities for ES conditions is important to implement physical therapy. A new37

program combining low-intensity aerobic exercise for the upper extremities and EMS for38

the lower extremities should be developed. If the beneficial effects of combined arm-

39

cranking exercise and low-intensity EMS on vascular endothelial function are40

demonstrated, this could be a new exercise therapy that could be applicable to more

41

patients; however, this point has not been adequately investigated and may be a factor

42

preventing the widespread use of this hybrid exercise.

43

Therefore, this study aimed to investigate the effects of acute arm-cranking exercise

44

combined with EMS of the lower extremities at different intensities on BA vascular45

endothelial function.

46
47

Methods

48

Participants

49

The study participants were eight healthy adult men (age: 21.6±0.5 years, height:

50

169.4±5.8 cm, weight: 67.1±9.1 kg, body mass index: 23.6±3.0 kg/m2) who had never51

smoked, did not take regular medications or supplements, and exercised for 1–2

52

times/week. This study was approved by the Research Ethics Committee of the53

Department of Physical Therapy, Faculty of Health Science, Osaka Yukioka College of54

Health Science (#33-0005), Japan. Additionally, the participants were provided with an55oral explanation of the content and purpose of the study, including refusal, withdrawal,

56

and interruption of participation, and written informed consent was obtained.

57
58

Study Design

59

The protocol used in this study and the picture of the experiment are shown in Figures60

1 and 2. All participants visited the laboratory four times for measurements. On the first61

day, a maximal exercise test with arm-cranking exercise was performed, and at least 1

62week after the test, the participants were randomly assigned to a trial combining EMS

63with maximum tolerable intensity for pain and moderate-intensity arm-cranking exercise

64(A+100% EMS trial), a trial combining moderate-intensity EMS (A+50%EMS trial), or65

a trial combining low-intensity EMS (A+25%EMS trial). For the maximal exercise

66

tolerance test and arm-cranking exercise for each trial, the participants sat in a chair and67

grasped the pedals of a bicycle ergometer (AEROBIKE 75XL Ⅲ; Combi Co., Tokyo,

68

Japan) fixed on a platform with both hands. The bicycle ergometer was grounded such

69

that the crankshaft and the participants’ acromion were level, and the participants sat with70

their knee joints flexed at 90˚. The rotation rate of the arm-cranking exercise in the71

maximal exercise tolerance test and each condition was defined as 60 rotations per minute.

72

All the participants were instructed to limit their alcohol consumption, caffeine intake,

73

and strenuous exercise from the day before to the end of the experiment. Measurements

74

were taken simultaneously in a room with controlled room temperature (23–25°C) and75

humidity (50–70%) at least 4 hours after eating.

76

Figure 1

77

Figure 2

78
79

Maximal Exercise Tolerance Test

80

To determine the intensity of the arm-cranking exercise, a multistage exercise tolerance

81．
test was performed on a bicycle ergometer to measure the maximal oxygen uptake (VO282max). After resting in a chair for 3 min, a maximal exercise tolerance test was performed,

83

starting at 6W and increasing the load in 6 W/min steps.

84
85

Flow-Mediated Vasodilation86

In this study, the endothelial function of the BA was assessed. The endothelial function

87of the BA is an indicator of systemic endothelial function. Moreover, the FMD of the BA88

is highly significant because it is a predictor of CVDs 15, 16). The participants were asked89

to rest in the supine position for at least 15 min to obtain the resting arm systolic blood

90

pressure (SBP) and diastolic blood pressure (DBP) using a standard sphygmomanometer91

on their left arm. An occlusion cuff was placed around the right forearm, and two

92

electrocardiogram leads were attached to the wrists to measure the heart rate (HR). The

93

FMD was quantified using high-resolution ultrasonography (UNEXEF 38G; UNEX Co.,

94

Nagoya, Japan) to measure endothelial function. The BA was scanned longitudinally 5–

95

10 cm proximal to the elbow joint. To occlude the blood flow, the cuff was inflated to 50

96mmHg above the SBP for 5 min. Upon cuff deflation, the blood flow velocity and arterial

97

diameter were measured for an additional 3 min, and the change in the BA diameter was

98

immediately expressed as a percentage change relative to the vessel diameter before cuff

99

inflation. The FMD was calculated as the baseline value (Di base) before the cuff was100

released to the peak value after cuff release (Di peak). The FMD was calculated using the101

following equation: FMD (%) = {(Di peak–Di base)/Di base} × 100. A detailed

102

description of the measurements was provided in a previous study 17).

103

In this study, peak shear rate (PSR) was calculated from the vessel diameter and blood

104

flow velocity to compare the FMD in different trials. The blood flow velocity was105

calculated from the color Doppler data and displayed as a waveform in real-time. The

106

PSR was calculated using the formula: PSR = [difference in flow velocity between the107

hyperemic response (peak after cuff deflation; FV peak) – baseline (FV base)] / baseline

108

BA diameter. Subsequently, the normalized FMD (nFMD) was calculated as follows 18):

109

nFMD (a. u.) =FMD/PSR

110

All measurements were performed after 15 min of supine rest and 30 min after each111

trial. FMD was measured by all participants with the right hand. The HR was measured

112

every 5 min during each trial using thoracic bipolar induction (POLAR H-10; Polar Co.,

113

Ltd., Tokyo, Japan).

114
115

Electrical Muscle Stimulation

116

In the EMS trial, belt electrode-skeletal muscle electrical stimulation (G-TES; Homer

117

Ion Co., Ltd., Tokyo, Japan) was performed at a frequency of 4 Hz, pulse width of 250 µs

118

19)

119

including the quadriceps femoris, hamstrings, gastrocnemius, and hip adductor muscles,120

using a stimulator. A value of 4 Hz was selected because this study aimed to promote

121

peripheral circulation through aerobic exercises 20). One silicon-rubber electrode band

122

(5.3×93.3 cm) was wrapped around the lumbar region, two bands (5.3×69.6 cm) were123

wrapped around both distal parts of the thighs, and two bands (5.3×54.6 cm) were124

wrapped around both ankles. As the stimulation cycles of the bilateral thighs and lower

125

legs were synchronized, the bilateral lower-extremity muscle groups were simultaneously

126

stimulated. The average stimulus intensity was approximately 3.0±0.6 mA in the thighs, and exponentially increasing waves. EMS was applied to the calf and thigh muscles,

127

and 0.8±0.2mA in the ankle in the A+100%EMS trial, 1.6±0.3 mA in the thighs and

128

0.4±0.1 mA in the ankle in A+50%EMS trial, and 0.8±0.1 mA in the thighs and 0.3±0.1

129mA in the ankle in the A+25%EMS trial.

130
131

Statistical Analysis

132

The results of this study were analyzed for normality using the Shapiro–Wilk test to133

confirm distribution of the data. The measurements for each trial were compared using a

134

two-way repeated-measures analysis of variance to test for the presence or absence of an

135

interaction. Moreover, the Bonferroni test was performed for posterior analysis. All

136

measurements are expressed as means and standard deviations and were considered137

statistically significant at a significance level of <5%.

138
139

Results

140．
HR and VO2 during each trial

141．
The changes in HR and VO2 during the three trials are shown in Figures 3 and 4. There142

was a significant difference in the HR at 5 and 20 min during exercise in the A+100%EMS

143

trial. Moreover, the HR in the A+100%EMS trial was significantly higher than that in the

144

A+25%EMS trial at 5 and 10 min during exercise. From the 5 to 20 min timepoints, the145．
VO2 during exercise was significantly higher in the A+100%EMS trial than in the

146．
A+25%EMS trial. VO2 during exercise was also higher in the A+100%EMS trial than in

147

the A+50%EMS trial at 5 and 20 min. Moreover, in the A+100%EMS trial, there was a148．
significant increase in VO2 at 20 min of exercise compared with that at 5 min. The average

149

．
．
VO2 from 5 to 15 min of exercise was as follows: 19.1±1.02 ml/kg/min (85％VO2 max)

150．
in the A+100%EMS trial, 15.75±0.65 ml/kg/min (70％VO2 max) in the A+50%EMS trial,151．
and 13.7±0.20 ml/kg/min (60％VO2 max) in the A+25%EMS trial.

152
153

Brachial artery function before and after each trial

154

The changes in SBP, DBP, HR, Di base, Di peak, FV base, FV peak, PSR, and FMD

155

before and after each trial are shown in Table 1. No interactions were observed for all

156

measurements. In the A+50%EMS and A+25%EMS trials, a significant decrease was157

observed in the DBP 30 min after exercise compared to before (p<0.05). In addition, a158

significant increase was observed in the HR 30 min after exercise compared to before in

159

the A+100%EMS trial (p<0.05). In all trials, there was a significant increase in the Di

160

base and Di peak 30 min after exercise compared to before exercise (p<0.05 and p<0.001,

161

respectively). There was no significant main effect or interaction among the SBP, FV base,

162

FV peak, FMD, and PSR before and 30 min after exercise completion in each trial. The

163changes in nFMD before and 30 min after exercise completion are shown in Figure 5

164(0.8±0.3 and 2.3±1.8 in the A+100%EMS trial, 0.9±0.4 and 1.4±1.0 in the A+50%EMS

165

trial, and 0.8±0.2 and 1.1±0.5 in the A+25%EMS trial, respectively). In the A+100%EMS

166

and A+50%EMS trials, a significant increase in the nFMD was observed 30 min after

167

exercise completion compared with that before (p<0.05).

168

Table 1

169

Figures 3, 4, and 5

170
171

Discussion

172

In this study, we investigated the effects of moderate-intensity arm-cranking exercises

173

with different EMS intensities on vascular endothelial function in healthy adult men. The

174

results showed that the BA nFMD increased 30 min after exercise completion compared

175

to that before in the maximum tolerable intensity EMS trial (A+100%EMS trial) and176

moderate-intensity EMS trial (A+50%EMS trial). It even showed a higher trend in the177

A+100%EMS trial than in the A+50%EMS trial. These results suggest that moderate-178

intensity arm-cranking exercise with 100%EMS enhances vascular endothelial function,

179

similar to the results of previous studies 13). However, a lower intensity of 50%EMS also180

enhances vascular function.

181

Acute responses after EMS include increases in oxygen uptake and HR 21), which have182

been reported to rise with increasing intensity of ES 22) and combined upper- and lower-

183

extremity exercise rather than with upper- and lower-extremity exercise alone. Rappelt et184

al. found that exercise with EMS to the lower-extremity (4 Hz, 250 μs, maximal tolerance)

185．
combined with a hand cycling resulted in higher VO2 and vasodilatory blood lactate levels

186

than using the hand cycling alone or EMS to the lower-extremity alone 12). Moreover,187

increases in stimulus intensity and pulse width have also been reported to increase blood

188

flow 23). This finding indicates that the combination of active exercise and ES has

189

beneficial effects on cardiac dynamics and metabolism. In the A+50%EMS and190

A+25%EMS trials, DBP decreased significantly 30 min after exercise compared to before.

191

This may be due to an increase in circulating blood flow caused by the muscle pumping

192

action of EMS to the lower limbs at low to moderate intensities. However, no change in193

blood pressure was observed before and after exercise in the A+100%EMS trial, possibly194

due to the effects of high-intensity ES and high-intensity aerobic exercise on the195

autonomic nervous system. Painful ES, such as in the A+100%EMS trial, may be

196

perceived as a nociceptive stimulus, which increases sympathetic nerve activity, resulting197

in the inhibition of peripheral vasodilation, and high-intensity aerobic exercise may

198

increase the level of protein carbonyl, an oxidative stress marker, and contribute to199

inactivation of nitric oxide 24). Thus, A+100%EMS trial had no effect on blood pressure

200

before or after exercise, suggesting that the A+50%EMS and A+25%EMS trials are not201

overloading exercises for blood pressure.

202

Most importantly, the nFMD increased significantly in the A+100%EMS and203

A+50%EMS trials after exercise completion compared to that before exercise, with the204

degree of increase being greater in the A+100%EMS trial but not significantly different

205

between trials. Regarding the stimulation intensity of EMS, Karavidas et al. found that206

after 6 weeks of functional ES training (25 Hz; stimulus intensity was a visible, painless207

muscle contraction) in 16 patients with chronic heart failure, the BA FMD improved

208

compared to before the training (5.77±2.58％, before; 7.56±2.63%, after) 25). It has also

209

been reported that acute low-intensity EMS (10.7±4.7% of HR reserve, approximately 2

210

metabolic equivalent during EMS exercise) improves brachial-ankle PWV and cardio-

211

ankle vascular index, which reflect arterial function 26). This was attributed to increased

212

local blood flow due to EMS-induced muscle pumping in the lower-extremity muscles.

213

However, no effect on arterial function in the upper extremity was observed. In the present

214

study, it was suggested that blood flow in the lower extremities, the site of stimulation,215

may have increased; however, the increase in nFMD in the BA may have been due to a

216

greater effect of EMS-induced metabolites. Muscle contraction induced by ES partially217

reverses the order of motor units to be mobilized 27). Moreover, when more type II fibers

218

are mobilized (type II fiber preferential recruitment) during ES, the release of vasodilators,

219

such as hydrogen ions and phosphate, increases, which may affect vasodilation 28). Since

220

these vasodilators increase depending on the ES intensity, a similar vasodilatory response221

to stimulation intensity may have been observed in the present study 29). In addition, EMS

222

stimulation releases vasodilator P and calcitonin gene-related peptides from nociceptive

223

C fibers, which causes dilation of the skin vessels. The dilation of cutaneous vessels

224

requires an increase in cardiac output, which may be involved in the increase in blood

225

flow in the conduit arteries. These factors suggest that EMS can promote peripheral

226

circulation and vasodilation even without the maximum intensity that can be tolerated,

227

and the nFMD may have been improved by medium-intensity EMS in this study.

228

It has been reported that individuals with SCI (especially those with high lesions)229

have lower aerobic capacity than normal and healthy individuals due to reduced physical230

activity (due to wheelchair-dependent living) and that aerobic capacity decreases linearly231

with increasing injury levels 30). To address this issue, previous studies have examined the232

effects of hybrid exercise combining active exercise and ES on cardiorespiratory function.

233

These studies have reported that combined exercise of the upper extremities and ES of234

the lower extremities improves aerobic capacity in wheelchair-dependent individuals with235

SCI 12). In the present study, the oxygen uptake during the hybrid exercise was

236

．
．
approximately 85%VO2 max in the A+100%EMS trial and 70%VO2 max in the

237

A+50%EMS trial, suggesting the possibility of improving endurance capacity with

238

habitual continuation. These results suggest that EMS at 50% of the maximum tolerable

239

intensity may be a new exercise program that can improve vascular function and240

endurance at a lower intensity than that used in the A+100%EMS trial.

241

The clinical implications of the present study are that the combined use of arm-

242

cranking exercises with EMS at a lower intensity may be indicated for more patients with243

the goal of improving vascular endothelial function. Previous studies have reported that244

the stronger the intensity of ES, the greater the effect on circulatory dynamics; however,245

in clinical practice, the appropriate exercise intensity should be set while assessing the246

respiratory-circulatory response to exercise due to the reduced physical activity and247

exercise tolerance caused by paralysis of the lower extremities, such as in patients with

248

SCI. Furthermore, ES therapy often requires a gradual increase in exercise intensity249

because patients may discontinue treatment due to discomfort caused by stimulation.

250

Therefore, combining arm-cranking exercise with moderate-intensity lower-extremity

251

EMS may be a more clinically suitable exercise program compared to combining it with252

ES of maximum tolerable intensity.

253

This study had several limitations. In clinical applications, it is necessary to consider

254

paralysis accompanied by sensory disturbances, such as SCI. In this study, low-strength

255

conditions were set from the maximum tolerable strength; however, it is necessary that256

the examiner objectively evaluates muscle contraction because it may be difficult to257

report the maximum tolerance due to sensory impairment. In addition, it has been shown

258

that the percentage of type II fibers is higher in paralyzed muscles than in non-paralyzed

259

muscles 31); therefore, whether the results of that study will be similar to those of the260

present study remains unclear. Furthermore, since the present study was conducted in the261

acute phase, changes in vascular function and aerobic capacity due to the intervention

262

were unknown. The vasoactive substances produced by exercise, such as nitric oxide,

263

were also unknown, as no biochemical tests were performed. The FMD is usually264

normalized using the area under the curve of the shear rate. However, in the present study,265

it was normalized using PSR only. Furthermore, since the stimulation intensity of EMS

266

was determined subjectively, the possibility of individual differences in muscle

267

contraction and body composition (lean body mass, subcutaneous fat thickness, and268

circumference) cannot be ignored. Muscle contraction and body composition should be269

measured in future studies.

270

271

Conclusion

272

The beneficial effects of ES on the body have been shown in various studies, making it

273

an important therapeutic option in rehabilitation. However, patients' disability profiles274

vary widely, and rehabilitation needs to be tailored to their unique severity and symptoms.

275

In the present study, the combination of moderate-intensity arm rotation exercise and 50%

276

intensity EMS suggests that vascular endothelial function can be improved even at277

reduced exercise intensity. Therefore, this may be a new exercise program option for

278

patients who are harmed by the intensity and stimulation of ES and high exercise intensity.

279
280

Acknowledgments

281

The authors wish to thank Tatsuya Fujikawa for their skillful assistance with data282

collection for this study.

283

This work was supported by JSPS KAKENHI Grant Number JP20K23304.

284
285

Conflict of Interests

286

There is no conflict of interests for this study.

287
288

289

Contributions

290

All authors contributed to the study conception and design. MN collected the data and291

drafted the manuscript. HM, AM, and YT revised the manuscript. All authors approved292

the final version of the manuscript.

293
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Table 1. Changes in brachial artery function before and after each trial
A+100%EMS trial

A+50%EMS trial

beforeafter 30
minutestime effectwithin₋groupp₋value

SBP (mmHg)

118.9 ± 11.6

118.0 ± 6.6

DBP (mmHg)

66.3 ± 6.9

HR (bpm)

A+25%EMS trial

beforeafter 30
minutestime effectwithin₋groupp₋value

beforeafter 30
minutestime effectwithin₋groupp₋valuegroup × timeinteraction
p₋value

0.80

119.8 ± 10.5

120.3 ± 10.1

0.81

119.4 ± 15.4

121.0 ± 16.8

0.35

0.50

62.0 ± 5.1

0.18

67.0 ± 6.4

61.1 ± 6.5

0.04*

67.4 ± 5.5

62.3 ± 6.0

0.01*

0.72

63.8 ± 10.0

74.4 ± 8.4

0.03*

63.5 ± 10.0

70.5 ± 6.8

0.06

64.3 ± 10.0

72.3 ± 7.7

0.12

0.60

Di base (mm)3.8 ± 0.2

4.3 ± 0.3

0.002*

3.7 ± 0.2

4.15 ± 0.4

0.003*

3.8 ± 0.2

4.1 ± 0.5

0.03*

0.47

Di peak (mm)4.1 ± 0.3

4.6 ± 0.3

0.001**

4.0 ± 0.2

4.5 ± 0.4

0.002*

4.0 ± 0.2

4.4 ± 0.5

0.03*

0.14

FV base(cm/sec)

10.4 ± 5.2

11.4 ± 6.6

0.33

11.8 ± 8.7

10.3 ± 3.1

0.53

11.0 ± 5.5

12.6 ± 8.8

0.48

0.65

FV peak (cm/sec)

48.1 ± 12.8

40.8 ± 6.6

0.33

47.4 ± 17.8

43.8 ± 19.0

0.51

46.1 ± 5.5

44.2 ± 21.0

0.83

0.83

FMD (%)

7.3 ± 1.0

8.3 ± 2.3

0.31

7.4 ± 0.8

8.3 ± 0.9

0.13

7.3 ± 1.0

6.7 ± 0.8

0.29

0.15

PSR (s-1)

10.0 ± 3.6

7.1 ± 5.7

0.08

9.7 ± 4.4

8.2 ± 4.4

0.26

9.4 ± 3.2

7.7 ± 3.6

0.42

0.14

SBP: systolic blood pressure，DBP: diastolic blood pressure，HR: heart rate，Di base: diameter baseline，Di peak: diameter peak line，FV base: flow volume
base，FV peak: flow volume peak，FMD: flow-mediated dilation，PSR: peak shear rate. *p<0.05, **p<0.01 vs. before.

Figure 1

Figure 2

Figure 3

A+100%EMS trial
A+25%EMS trial

A+50%EMS trial

210§

HR (bpm)

175

a
a

140

105

70
5 min

10 min15 min20 minFigure.4

A+100%EMS trial
A+25%EMS trial

VO2 (ml/kg/min)

40.0

A+50%EMS trial

§

30.0

a,b
a

a,b

a

20.0

・

10.0

c

0.0
5 min

10 min15 min20 minFigure 5

A+100%EMS trial
A+25%EMS trial

A+50%EMS trial

6.0

nFMD (a.u)

4.5

*

3.0

*

1.5

0.0

beforeafter
30minutes

Figure Legends

Figure 1. Experimental protocol of test sessions. All subjects performed each test in
random order. EMS: electrical muscle stimulation, FMD: flow-mediated dilation
Figure 2. A picture of the experiment.
Figure 3. Changes in heart rate (HR) during each trial.
Values are presented as mean ± standard deviation (SD).
ap<0.05 vs. A+25%EMS trial, §p<0.05 vs. 5min.

A: arm-cranking exercise
EMS: electrical muscle stimulation．
Figure 4. Changes in oxygen uptake (VO2) during each trial.
Values are presented as mean ± standard deviation (SD).
ap<0.05 vs. A+25%EMS trial, bp<0.05 vs. A+50%EMS trial, cp<0.05 vs. A+50%EMS

trial, §p<0.05 vs. 5min.
Figure 5. Changes in normalized flow-mediated dilation (nFMD) before and after eachtrial.
*p<0.05 vs. before.