**4.1. Muscle activity in lower limb and trunk**

Deep-Water Running (DWR) is one of the unique exercise forms in water environment. Using a floatation device around the waist (Figure 8), people move their feet as if running without touching the bottom of the swimming pool.

**Figure 8.** Aqua Jogger (Excel Sports Science Inc., Japan) used for DWR exercise. [Picture was taken by the authors]

This exercise form has been widely used for aerobic training and cross training for performance enhancement in athletes [30], and rehabilitation training [31]. Previous studies have investi‐ gated muscle activity during DWR by the authors and compared this with water-walking and land-walking [11, 20, 25]. The results of %MVC level in lower limb muscles and hip and trunk muscles during those exercises are presented in Figure 9, 10 and 11. The measurement procedure, environment settings and the analysis methods were the same as the previous investigation comparing water-walking and land-walking by the authors [11, 20, 25]. In the DWR, the data was collected for one cycle from a maximal knee flexion to a maximal knee extension during the backward swing phase, and from the maximal knee extension to the next maximal knee flexion during the forward swing phase. These phases represent the stance and

nhancement in

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swing phase in walking exercise, respectively. One-way repeated measures analysis of variance (ANOVA) with Tukey's post-hoc test was applied for the statistic comparison. the d from data was colle m maximal kne swing phase i ected for one c ee extension to in walking ex cycle from ma o the next max ercise, respect aximal knee fle ximal knee fle tively. One‐w exion to maxim exion during t ay repeated m mal knee exte the forward sw measures analy ension during wing phase. Th ysis of varianc the backward hese phases re ce (ANOVA) d swing phase epresent the s with Tukey's e, and stance post‐

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Figur A: sl re 9. The mean ow, B: modera ± SD of %MVC ate, C: fast. C value in each l ower limb musc cle at each spee d during backw A: slow, B: moderate, C: fast. 1] LW: land-walking, WW: water-walking, DWR: Deep-Water Running \*: significant difference (P < 0.05).

Figur This rehab wate those were

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Trunk muscles show different muscle activity between water and land based walking, as well as lower limb. However, when humans walk on a treadmill apparatus, most muscle activity decreased during water compared with land in both lower limb and trunk area [29]. In this case, the walking speed was set as one-half to one-third of the land walking in reference to the oxygen consumption [17]. Furthermore, muscle activity during treadmill water-walking without water flow further decreased muscle activity than with flow set to the same speed to the walking speed [29]. The differences between with or without treadmill may be due to the treadmill function moving the leg backward automatically without force generation during stance phase. Further, it would be possible that the displacement of the lower limb moves through less distance on treadmill walking than without treadmill in swing phase since human would be at the same position during treadmill walking. Although no previous research has clarified the biomechanical difference between walking with and without treadmill in water, researchers, exercise instructors and participants should pay attention to the differences of the muscle activity modality to determine more appropriate exercise and specific prescription

**4. The characteristics of muscle activity during deep-water running**

Deep-Water Running (DWR) is one of the unique exercise forms in water environment. Using a floatation device around the waist (Figure 8), people move their feet as if running without

**Figure 8.** Aqua Jogger (Excel Sports Science Inc., Japan) used for DWR exercise. [Picture was taken by the authors]

This exercise form has been widely used for aerobic training and cross training for performance enhancement in athletes [30], and rehabilitation training [31]. Previous studies have investi‐ gated muscle activity during DWR by the authors and compared this with water-walking and land-walking [11, 20, 25]. The results of %MVC level in lower limb muscles and hip and trunk muscles during those exercises are presented in Figure 9, 10 and 11. The measurement procedure, environment settings and the analysis methods were the same as the previous investigation comparing water-walking and land-walking by the authors [11, 20, 25]. In the DWR, the data was collected for one cycle from a maximal knee flexion to a maximal knee extension during the backward swing phase, and from the maximal knee extension to the next maximal knee flexion during the forward swing phase. These phases represent the stance and

according to water-walking style selected.

222 Electrodiagnosis in New Frontiers of Clinical Research

**4.1. Muscle activity in lower limb and trunk**

touching the bottom of the swimming pool.

LW: land‐walking g, WW: water‐w walking, DWR R: Deep‐Wate er Running **Figure 9.** The mean ± SD of %MVC value in each lower limb muscle at each speed during backward swing phase. [Modified from reference [11]

As seen in Figure 9 and 10, the characteristics of the DWR, %MVC of the SOL, GAS in the backward swing phase, and the VL in the forward swing phase were dramatically de‐ creased compared with water- and land-walking (P<0.05). This is likely a result of the noncontact phase during DWR compared to land walking. On the other hand, %MVC of the BF in both swing phases, and the RF in forward swing phase were much higher than land- and sometimes water-walking (P<0.05). The knee and hip joint range of motion (ROM) was increased during DWR when comparedto both land- and water-walking (Figure 12), which would cause the higher %MVC in the RF and BF. Similarly this increased ROM of the hip would also result in higher %MVC of the GMa, AL and GMe during the DWR than during water- and land-walking. Increased ROM directly indicates that thigh and knee extension and flexion muscles receive greater water resistance force. Further, it is likely that the AL and GMe activated to stabilize the pelvis against femur during an unstable floating situation as in DWR [25].

Interestingly, the %MVC of the RA, OEA and ES were higher during DWR than water- and land-walking throughout one-cycle (P<0.05, Figure 11). The authors speculated that maintain‐ ing forward inclination during DWR would increase the RA and OEA muscles activation

Figure 10.The mean ± SD of %MVC value in each lower limb muscle at each speed during forward swing phase. [Modified from reference 11] A: slow, B: moderate, C: fast. A: slow, B: moderate, C: fast. LW: land-walking, WW: water-walking, DWR: deep-water running \*: significant difference (P < 0.05).

\*: significant difference (P < 0.05).

LW: land‐walking, WW: water‐walking, DWR: Deep‐Water Running **Figure 10.** The mean ± SD of %MVC value in each lower limb muscle at each speed during forward swing phase. [Modified from reference 11]

(Figure 13). However, it is important not to lean forward excessively which would explain the ES muscle activity needed to maintain forward inclination posture. As seen in Figure 9 and 10, the characteristics of the DWR, %MVC of the SOL, GAS in the backward swing phase, and the VL in the forward swing phase were dramatically decreased compared with water‐ and land‐walking (P<0.05). This is likely a result of the

TheDWRseems tousemusclesofthehipandtrunkmore thanwater- andland-walking.Muscle activity comparing running on land and DWR was studied by Masumoto et al. [32]. This study reported the EMG data of the DWR in comparison with running on land treadmill for TA, GAS, RF and BF muscles. Masumoto et al. [32] revealed that TA and GAS muscle activity; when calculated as the average EMG; was clearly lower in DWR than land treadmill running for the same rating of perceived exertion (RPE). Similarly, RF and BF muscles tended to be lower in DWR than land treadmill running. Further investigation comparing running and DWR is necessary for more detailed understanding of muscle activity behavior during DWR. non‐contact phase during DWR compared to land walking. On the other hand, %MVC of the BF in both swing phases, and the RF in forward swing phase were much higher than land‐ and sometimes water‐walking (P<0.05). The knee and hip joint range of motion (ROM) was increased during DWR when compared to both land‐ and water‐walking (Figure 12), which would cause the higher %MVC in the RF and BF. Similarly this increased ROM of the hip would also result in higher %MVC of the GMa, AL and GMe during the DWR than during water‐ and land‐walking. Increased ROM directly indicates that thigh and knee extension and flexion muscles receive greater water resistance force. Further, it is likely that the AL and GMe activated to stabilize the pelvis against femur during an unstable floating situation as in DWR [25].

#### **4.2. Muscle activity difference between two types of deep-water running**

There are various styles of DWR depending on the type of floatation device and its usage. Previous research has investigated muscle activity during DWR using aqua pole (Pole Running: PR, Figure 14), and compared this with the DWR using an aqua belt (Belt Running: BR, Figure 8). Subjects sat on the aqua pole with one leg either side instead of using upper body (Figure 15). The results showed the mean ± SD value of the EMG data as %MVC during one cycle in the TA, SOL, GAS, RF, VL, BF, AL, GMa, GMe, RA, OEA and ES muscles (Figure 16 and 17).

In summary, the muscle activity during both Belt Running and Pole Running reported similar values. However, the SOL tended to be higher activity during Pole Running than Belt Running, whilst the VL tented to be higher activity during Belt Running than Pole Running. The reasons for the difference in the SOL activity is difficult to determine, however, the different activity level in the VL which acts on knee extension motion, was considered to be due to the different

**Figure 12.** The mean ± SD of the knee and hip joints ROM during each exercise. [Modified from reference 25]

Interestingly, the %MVC of the RA, OEA and ES were higher during DWR than water‐ and land‐walking throughout one‐cycle (P<0.05, Figure 11). The authors speculated that maintaining forward inclination during DWR would increase the RA and OEA muscles activation (Figure 13). However, it is important not to lean forward excessively which would explain the ES muscle

Interestingly, the %MVC of the RA, OEA and ES were higher during DWR than water‐ and land‐walking throughout one‐cycle (P<0.05, Figure 11). The authors speculated that maintaining forward inclination during DWR would increase the RA and OEA muscles activation (Figure 13). However, it is important not to lean forward excessively which would explain the ES muscle

Figure 12.The mean ± SD of the knee and hip joints ROM during each exercise. [Modified from reference 25]

Figure 12.The mean ± SD of the knee and hip joints ROM during each exercise. [Modified from reference 25]

(A) (B)

(A) (B)

Figure 11.The mean ± SD of %MVC value in each hip and trunk muscle at each speed during one cycle. [Modified from reference 25]

Figure 11.The mean ± SD of %MVC value in each hip and trunk muscle at each speed during one cycle. [Modified from reference 25]

**Figure 11.** The mean ± SD of %MVC value in each hip and trunk muscle at each speed during one cycle. [Modified

\*

\*

\*

\*

\*

(A) (B)

(A) (B)

LW WW DWR

LW WW DWR

\*

\*

\* \* \*

\* \* \*

%

%

AL GMa GMe RA OEA ES

AL GMa GMe RA OEA ES

Underwater Electromyogram for Human Health Exercise

\* \*

\* \*

http://dx.doi.org/10.5772/55115

225

\* \*

\* \*

AL GMa GMe RA OEA ES

AL GMa GMe RA OEA ES

AL GMa GMe RA OEA ES

AL GMa GMe RA OEA ES

\*

\*

\*

\*

\*

\*

A: slow, B: moderate, C: fast.

A: slow, B: moderate, C: fast.

from reference 25]

(C)

(C)

A: slow, B: moderate, C: fast.

\*: significant difference (P < 0.05).

\* \*

\* \*

\*

\*

%

%

\*

\*

\* \* \*

\* \* \*

%

%

\*: significant difference (P < 0.05).

\*: significant difference (P < 0.05).

A: knee joint, B: hip joint

A: knee joint, B: hip joint

\*: significant difference (P < 0.05)

\*: significant difference (P < 0.05)

A: knee joint, B: hip joint \*: significant difference (P < 0.05)

LW: land‐walking, WW: water‐walking, DWR: Deep‐Water Running

LW: land‐walking, WW: water‐walking, DWR: Deep‐Water Running

LW: land-walking, WW: water-walking, DWR: deep-water running

LW: land‐walking, WW: water‐walking, DWR: Deep‐Water Running

LW: land‐walking, WW: water‐walking, DWR: Deep‐Water Running

LW: land-walking, WW: water-walking, DWR: deep-water running

activity needed to maintain forward inclination posture.

activity needed to maintain forward inclination posture.

Figure 11.The mean ± SD of %MVC value in each hip and trunk muscle at each speed during one cycle. [Modified from reference 25] A: slow, B: moderate, C: fast. A: slow, B: moderate, C: fast. LW: land-walking, WW: water-walking, DWR: deep-water running \*: significant difference (P < 0.05). Figure 11.The mean ± SD of %MVC value in each hip and trunk muscle at each speed during one cycle. [Modified from reference 25] A: slow, B: moderate, C: fast.

\*: significant difference (P < 0.05).

A: knee joint, B: hip joint

\*: significant difference (P < 0.05)

(Figure 13). However, it is important not to lean forward excessively which would explain the

**Figure 10.** The mean ± SD of %MVC value in each lower limb muscle at each speed during forward swing phase.

As seen in Figure 9 and 10, the characteristics of the DWR, %MVC of the SOL, GAS in the backward swing phase, and the VL in the forward swing phase were dramatically decreased compared with water‐ and land‐walking (P<0.05). This is likely a result of the non‐contact phase during DWR compared to land walking. On the other hand, %MVC of the BF in both swing phases, and the RF in forward swing phase were much higher than land‐ and sometimes water‐walking (P<0.05). The knee and hip joint range of motion (ROM) was increased during DWR when compared to both land‐ and water‐walking (Figure 12), which would cause the higher %MVC in the RF and BF. Similarly this increased ROM of the hip would also result in higher %MVC of the GMa, AL and GMe during the DWR than during water‐ and land‐walking. Increased ROM directly indicates that thigh and knee extension and flexion muscles receive greater water resistance force. Further, it is likely that the AL and GMe activated to stabilize the pelvis

Figure 10.The mean ± SD of %MVC value in each lower limb muscle at each speed during forward swing phase. [Modified from reference 11]

\* \* \*

LW WW DWR

\*

%

TA SOL GAS RF VL BF

\* \*

\* \*

\*

TheDWRseems tousemusclesofthehipandtrunkmore thanwater- andland-walking.Muscle activity comparing running on land and DWR was studied by Masumoto et al. [32]. This study reported the EMG data of the DWR in comparison with running on land treadmill for TA, GAS, RF and BF muscles. Masumoto et al. [32] revealed that TA and GAS muscle activity; when calculated as the average EMG; was clearly lower in DWR than land treadmill running for the same rating of perceived exertion (RPE). Similarly, RF and BF muscles tended to be lower in DWR than land treadmill running. Further investigation comparing running and DWR is

There are various styles of DWR depending on the type of floatation device and its usage. Previous research has investigated muscle activity during DWR using aqua pole (Pole Running: PR, Figure 14), and compared this with the DWR using an aqua belt (Belt Running: BR, Figure 8). Subjects sat on the aqua pole with one leg either side instead of using upper body (Figure 15). The results showed the mean ± SD value of the EMG data as %MVC during one cycle in the TA, SOL, GAS, RF, VL, BF, AL, GMa, GMe, RA, OEA and ES muscles (Figure

necessary for more detailed understanding of muscle activity behavior during DWR.

**4.2. Muscle activity difference between two types of deep-water running**

16 and 17).

A: slow, B: moderate, C: fast.

(C)

\*: significant difference (P < 0.05).

A: slow, B: moderate, C: fast.

%

%

224 Electrodiagnosis in New Frontiers of Clinical Research

\*: significant difference (P < 0.05).

[Modified from reference 11]

ES muscle activity needed to maintain forward inclination posture.

(A) (B)

TA SOL GAS RF VL BF

TA SOL GAS RF VL BF

\*

\*

LW: land‐walking, WW: water‐walking, DWR: Deep‐Water Running

LW: land-walking, WW: water-walking, DWR: deep-water running

against femur during an unstable floating situation as in DWR [25].

LW: land‐walking, WW: water‐walking, DWR: Deep‐Water Running **Figure 11.** The mean ± SD of %MVC value in each hip and trunk muscle at each speed during one cycle. [Modified from reference 25] LW: land‐walking, WW: water‐walking, DWR: Deep‐Water Running \*: significant difference (P < 0.05).

Figure 12.The mean ± SD of the knee and hip joints ROM during each exercise. [Modified from reference 25] Figure 12.The mean ± SD of the knee and hip joints ROM during each exercise. [Modified from reference 25] LW: land‐walking, WW: water‐walking, DWR: Deep‐Water Running LW: land-walking, WW: water-walking, DWR: deep-water running A: knee joint, B: hip joint \*: significant difference (P < 0.05)

LW: land‐walking, WW: water‐walking, DWR: Deep‐Water Running

A: knee joint, B: hip joint **Figure 12.** The mean ± SD of the knee and hip joints ROM during each exercise. [Modified from reference 25]

In summary, the muscle activity during both Belt Running and Pole Running reported similar values. However, the SOL tended to be higher activity during Pole Running than Belt Running, whilst the VL tented to be higher activity during Belt Running than Pole Running. The reasons for the difference in the SOL activity is difficult to determine, however, the different activity level in the VL which acts on knee extension motion, was considered to be due to the different \*: significant difference (P < 0.05) Interestingly, the %MVC of the RA, OEA and ES were higher during DWR than water‐ and land‐walking throughout one‐cycle (P<0.05, Figure 11). The authors speculated that maintaining forward inclination during DWR would increase the RA and OEA muscles activation (Figure 13). However, it is important not to lean forward excessively which would explain the ES muscle activity needed to maintain forward inclination posture. Interestingly, the %MVC of the RA, OEA and ES were higher during DWR than water‐ and land‐walking throughout one‐cycle (P<0.05, Figure 11). The authors speculated that maintaining forward inclination during DWR would increase the RA and OEA muscles activation (Figure 13). However, it is important not to lean forward excessively which would explain the ES muscle activity needed to maintain forward inclination posture.

rence (P < 0.05

5)

rd inclination to use muscle as studied by M TA, GAS, RF MG; was clea BF muscles t ssary for more

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erence 25]

alking. Muscle ta of the DWR TA and GAS m the same ratin ing. Further in uring DWR.

e activity com R in compariso muscle activit ng of perceiv nvestigation c

mparing runnin on with runnin ty; when calcu ved exertion (R comparing run

ng on ng on ulated RPE). nning

gated a belt ). The GMe,

There is still a limited amount of research published on muscle activity during DWR as well as running in water. When determining the most suitable style or type of activity in DWR for rehabilitation and cross training, further insight into muscle activity during the running would

**Figure 16.** The mean ± SD of %MVC value in each lower limb muscle at each speed during Belt Running and Pole

In summary, the muscle activity during both Belt Running and Pole Running reported similar values. However, the SOL tended to be higher activity during Pole Running than Belt Running, whilst the VL tented to be higher activity during Belt Running than Pole Running. The reasons for the difference in the SOL activity is difficult to determine, however, the different activity level in the VL which acts on knee extension motion, was considered to be due to the different knee joint ROM during exercise, where the ROM of

Figure 16. The mean ± SD of %MVC value in each lower limb muscle at each speed during Belt Running and Pole Running. [Unpublished data]

(A) (B)

BR PR

%

TA SOL GAS RF VL BF

Underwater Electromyogram for Human Health Exercise

http://dx.doi.org/10.5772/55115

227

TA SOL GAS RF VL BF

TA SOL GAS RF VL BF

**\***

**\***

There are many types of exercise in the water environment and walking and running in water are representative of the common forms. The authors reported the effect of buoyancy and water resistance during exercise in water and categorized exercises by its movement direction [33]. The exercise category was reported as follows: forward walking and backward walking as a horizontal movement, squat and calf raise as a vertical movement, and leg range and leg pendulum motion as a both horizontal and vertical included movement. Nine male subjects were involved in this study, where muscle activity of TA, SOL, GAS, RF and BF was measured. Each exercise was conducted both in water and on land conditions at the same pace. The data was collected at 1000Hz, and calculated integrated EMG (IEMG). Time constant was 0.03sec that is equal to 5.3Hz high pass filter. Results showed IEMG values during each exercise were dramatically decreased in the water condition compared with the land condition. Predomi‐ nantly the agonist muscles were active in the vertical movement and both horizontal and

There is still a limited amount of research published on muscle activity during DWR as well as running in water. When determining the most suitable style or type of activity in DWR for rehabilitation and cross training, further insight into muscle

In hip and trunk muscles, the AL, RA and OEA muscles tended to have higher activation during Belt Running than Pole Running. The reason for this result is that the exercise style where subjects place aqua pole between their legs in Pole Running may require AL muscle to be less involved in the movement as the subject legs are wider apart during Pole Running than Belt Running. The higher muscle activity of RA and OEA muscles during Belt Running may be due to the trunk inclination angle being larger than that used in Pole Running (Figure 19). Thus, Pole Running is comparably a more upright position compared to Belt Running, which may explain the slight differences of muscle activity during the two forms of exercise. Researchers, instructors and

**5. Insight into muscle activity during various exercises in water**

participants can design a variety of exercise styles by simply varying the type of floatation device used in the activity.

be a very useful regardless of running style.

activity during the running would be a very useful regardless of running style.

Belt Running was greater than that of Pole Running (Figure 18).

A: slow, B: moderate, C: fast.

BR: Belt Running, WW: Pole Running.

Running. [Unpublished data]

A: slow, B: moderate, C: fast. BR: Belt Running, PR: Pole Running. \*: significant difference (P < 0.05).

(C)

%

%

\*: significant difference (P < 0.05).

ch has investig using an aqu dy (Figure 15) BF, AL, GMa, G

± SD of the trun g, WW: water‐w nk inclination an walking, DWR ngle during eac R: Deep‐Wate ch exercise. [Mo er Running odified from refe LW: land-walking, WW: water-walking, DWR: deep-water running \*: significant difference (P < 0.05) Positive: forward inclination Negative: backward inclination

> s of the hip an Masumoto et F and BF musc rly lower in D ended to be lo e detailed unde

**Figure 13.** The mean ± SD of the trunk inclination angle during each exercise. [Modified from reference 25]

**ctivity diff ference be etween two o types of deep‐wate er running gFigure 14.** Aqua Pole (Footmark Corp., Japan) used for DWR exercise. [Picture was taken by the authors]

knee joint ROM during exercise, where the ROM of Belt Running was greater than that of Pole Running (Figure 18).

In hip and trunk muscles, the AL, RA and OEA muscles tended to have higher activation during Belt Running than Pole Running. The reason for this result is that the exercise style where subjects place aqua pole between their legs in Pole Running may require AL muscle to be less involved in the movement as the subject legs are wider apart during Pole Running than Belt Running. The higher muscle activity of RA and OEA muscles during Belt Running may be due to the trunk inclination angle being larger than that used in Pole Running (Figure 19). Thus, Pole Running is comparably a more upright position compared to Belt Running, which may explain the slight differences of muscle activity during the two forms of exercise. Researchers, instructors and participants can design a variety of exercise styles by simply varying the type of floatation device used in the activity. e (Footmark Cor ing (BR) and Po rp., Japan) used ole Running (PR d for DWR exerc R). [Pictures wer cise. [Picture wa re created by the as taken by the a e authors] authors]

A: slow, B: moderate, C: fast. A: slow, B: moderate, C: fast. BR: Belt Running, PR: Pole Running. \*: significant difference (P < 0.05).

\*: significant difference (P < 0.05).

knee joint ROM during exercise, where the ROM of Belt Running was greater than that of Pole

In hip and trunk muscles, the AL, RA and OEA muscles tended to have higher activation during Belt Running than Pole Running. The reason for this result is that the exercise style where subjects place aqua pole between their legs in Pole Running may require AL muscle to be less involved in the movement as the subject legs are wider apart during Pole Running than Belt Running. The higher muscle activity of RA and OEA muscles during Belt Running may be due to the trunk inclination angle being larger than that used in Pole Running (Figure 19). Thus, Pole Running is comparably a more upright position compared to Belt Running, which may explain the slight differences of muscle activity during the two forms of exercise. Researchers, instructors and participants can design a variety of exercise styles by simply

re created by the

cise. [Picture wa

varying the type of floatation device used in the activity.

Running (Figure 18).

e (Footmark Cor

ing (BR) and Po

± SD of the trun g, WW: water‐w rence (P < 0.05

226 Electrodiagnosis in New Frontiers of Clinical Research

\*: significant difference (P < 0.05) Positive: forward inclination Negative: backward inclination

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**Figure 14.** Aqua Pole (Footmark Corp., Japan) used for DWR exercise. [Picture was taken by the authors]

e of floatation ng: PR, Figure le with one le MVC during

er Running

**Figure 13.** The mean ± SD of the trunk inclination angle during each exercise. [Modified from reference 25]

nd trunk mor al. [32]. This s cles. Masumot DWR than la ower in DWR erstanding of

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g on the type e (Pole Runnin n the aqua pol MG data as %

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**Figure 15.** Belt Running (BR) and Pole Running (PR). [Pictures were created by the authors]

R). [Pictures wer

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WR depending sing aqua pole ubjects sat on value of the EM re 16 and 17).

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BR: Belt Running, WW: Pole Running. **Figure 16.** The mean ± SD of %MVC value in each lower limb muscle at each speed during Belt Running and Pole Running. [Unpublished data]

There is still a limited amount of research published on muscle activity during DWR as well as running in water. When determining the most suitable style or type of activity in DWR for rehabilitation and cross training, further insight into muscle activity during the running would be a very useful regardless of running style. In summary, the muscle activity during both Belt Running and Pole Running reported similar values. However, the SOL tended to be higher activity during Pole Running than Belt Running, whilst the VL tented to be higher activity during Belt Running than Pole Running. The reasons for the difference in the SOL activity is difficult to determine, however, the different activity level in the VL which acts on knee extension motion, was considered to be due to the different knee joint ROM during exercise, where the ROM of Belt Running was greater than that of Pole Running (Figure 18).

In hip and trunk muscles, the AL, RA and OEA muscles tended to have higher activation during Belt Running than Pole Running.

that used in Pole Running (Figure 19). Thus, Pole Running is comparably a more upright position compared to Belt Running,

#### **5. Insight into muscle activity during various exercises in water** The reason for this result is that the exercise style where subjects place aqua pole between their legs in Pole Running may require AL muscle to be less involved in the movement as the subject legs are wider apart during Pole Running than Belt Running. The higher muscle activity of RA and OEA muscles during Belt Running may be due to the trunk inclination angle being larger than

There are many types of exercise in the water environment and walking and running in water are representative of the common forms. The authors reported the effect of buoyancy and water resistance during exercise in water and categorized exercises by its movement direction [33]. The exercise category was reported as follows: forward walking and backward walking as a horizontal movement, squat and calf raise as a vertical movement, and leg range and leg pendulum motion as a both horizontal and vertical included movement. Nine male subjects were involved in this study, where muscle activity of TA, SOL, GAS, RF and BF was measured. Each exercise was conducted both in water and on land conditions at the same pace. The data was collected at 1000Hz, and calculated integrated EMG (IEMG). Time constant was 0.03sec that is equal to 5.3Hz high pass filter. Results showed IEMG values during each exercise were dramatically decreased in the water condition compared with the land condition. Predomi‐ nantly the agonist muscles were active in the vertical movement and both horizontal and which may explain the slight differences of muscle activity during the two forms of exercise. Researchers, instructors and participants can design a variety of exercise styles by simply varying the type of floatation device used in the activity. There is still a limited amount of research published on muscle activity during DWR as well as running in water. When determining the most suitable style or type of activity in DWR for rehabilitation and cross training, further insight into muscle activity during the running would be a very useful regardless of running style.

Therefore, it was suggested that vertical and both horizontal and vertical included movement in water environment are useful for rehabilitation training from injury or disability due to the

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**Figure 19.** The mean ± SD of the trunk inclination angle during Belt Running and Pole Running.

Figure 17.The mean ± SD of %MVC value in each hip and trunk muscle at each speed during Belt Running and Pole Running. [Unpublished data]

A: forward walking, B: backward walking, C: squat, D: calf raise, E: leg range, F: leg pendulum motion. [Modified from

Further research by the authors has investigated lower limb and trunk muscle activity in ten kinds of water exercise [Unpublished data]. The mean EMG values of each muscle were shown in Figure 21. The data was collected at 1000Hz, and the mean EMG values were calculated from %MVC of RMS values with 100ms window of the data applied during one cycle of each exercise form. The exercises performed in this study were: forward walking, backward walking, DWR, normal running, side walking, walking with long step, walking with trunk twisting, walking with kicking, walking with knee-up, walking with elbow-knee alternative touching. These exercises are considered basic variations of walking exercise in water which

**Figure 20.** The mean ± SD of the lower limb muscle activity during water and land exercise.

are often implemented in practical exercise sessions.

lower levels of stress in water activity than on land.

Figure 19.The mean ± SD of the trunk inclination angle during Belt Running and Pole Running.

Figure 18.The mean ± SD of the lower limb joint ROM during each exercise. [Unpublished data]

(A) (B) (C)

(A) (B)

reference 33]

A: slow, B: moderate, C: fast.

BR: Belt Running, WW: Pole Running.

(C)

\*: significant difference (P < 0.05).

BR: Belt Running, PR: Pole Running

BR: Belt Running, PR: Pole Running

BR: Belt Running, PR: Pole Running \*: significant difference (P < 0.05) Positive: forward inclination

\*: significant difference (P < 0.05)

\*: significant difference between (P < 0.05)

A: slow, B: moderate, C: fast.

\*: significant difference (P < 0.05)

A: slow, B: moderate, C: fast. BR: Belt Running, PR: Pole Running. \*: significant difference (P < 0.05).

**Figure 18.** The mean ± SD of the lower limb joint ROM during each exercise. [Unpublished data]

vertical included movement, for example, RF in the squat, GAS in the calf raise, RF in the leg range, and RF and BF in the leg pendulum motion (Figure 20). In contrast, the EMG values were more increased in the water condition than the land condition in the horizontal move‐ ment especially for the thigh muscles (Figure 20). It can be said that the only horizontal movement in water environment gives higher muscle stimulus than the same exercise on land.

Figure 17.The mean ± SD of %MVC value in each hip and trunk muscle at each speed during Belt Running and Pole Running. [Unpublished data]

BR: Belt Running, PR: Pole Running BR: Belt Running, PR: Pole Running \*: significant difference (P < 0.05) Positive: forward inclination

A: slow, B: moderate, C: fast.

BR: Belt Running, WW: Pole Running.

(C)

\*: significant difference (P < 0.05).

BR: Belt Running, PR: Pole Running

\*: significant difference between (P < 0.05)

A: slow, B: moderate, C: fast.

\*: significant difference (P < 0.05) **Figure 19.** The mean ± SD of the trunk inclination angle during Belt Running and Pole Running.

Figure 18.The mean ± SD of the lower limb joint ROM during each exercise. [Unpublished data]

(A) (B) (C)

(A) (B)

Therefore, it was suggested that vertical and both horizontal and vertical included movement in water environment are useful for rehabilitation training from injury or disability due to the lower levels of stress in water activity than on land.

A: forward walking, B: backward walking, C: squat, D: calf raise, E: leg range, F: leg pendulum motion. [Modified from reference 33]

\*: significant difference (P < 0.05)

vertical included movement, for example, RF in the squat, GAS in the calf raise, RF in the leg range, and RF and BF in the leg pendulum motion (Figure 20). In contrast, the EMG values were more increased in the water condition than the land condition in the horizontal move‐ ment especially for the thigh muscles (Figure 20). It can be said that the only horizontal movement in water environment gives higher muscle stimulus than the same exercise on land.

**Figure 18.** The mean ± SD of the lower limb joint ROM during each exercise. [Unpublished data]

**Figure 17.** The mean ± SD of %MVC value in each hip and trunk muscle at each speed during Belt Running and Pole

(A) (B)

BR PR

\*

%

AL GMa GMe RA OEA ES

\*

\*

AL GMa GMe RA OEA ES

AL GMa GMe RA OEA ES

\*

A B C

\*

228 Electrodiagnosis in New Frontiers of Clinical Research

A: slow, B: moderate, C: fast. BR: Belt Running, PR: Pole Running. \*: significant difference (P < 0.05).

Running. [Unpublished data]

BR: Belt Running, PR: Pole Running A: slow, B: moderate, C: fast. \*: significant difference (P < 0.05)

%

%

**Figure 20.** The mean ± SD of the lower limb muscle activity during water and land exercise.

Further research by the authors has investigated lower limb and trunk muscle activity in ten kinds of water exercise [Unpublished data]. The mean EMG values of each muscle were shown in Figure 21. The data was collected at 1000Hz, and the mean EMG values were calculated from %MVC of RMS values with 100ms window of the data applied during one cycle of each exercise form. The exercises performed in this study were: forward walking, backward walking, DWR, normal running, side walking, walking with long step, walking with trunk twisting, walking with kicking, walking with knee-up, walking with elbow-knee alternative touching. These exercises are considered basic variations of walking exercise in water which are often implemented in practical exercise sessions.

As seen in the figure 21, normal running in water stimulated every muscle except the RA and the OEA muscles compared to the other exercise forms. This indicates normal running provides a high intensity activity for these muscles. The DWR was apparently an effective exercise for the BF, AL, RA and OEA muscles, especially abdominal muscles as seen in the comparison with water- and land-walking in the former section. The walking with kicking exercise clearly activated the VL and RF because those muscles were the agonist muscle for the walking with kicking motion, and this exercise stimulated abdominal muscles slightly more when compared to the other exercises. The VL muscle activity was comparably higher in the normal running, side walking, walking with long step, walking with trunk twisting and walking with kicking than the other exercises which may be due to those exercises requiring the body to be immersed deeply or require stronger extension of the knee joint during this motion. The walking with knee up exercise could be said to be of a low intensity exercise as it showed lesser EMG values than the others in every muscle. The walking with elbow-knee alternative touching exercise tended to show a high muscle activity especially in the hip and trunk muscles. It was speculated that the muscle activity for this exercise happened during standing phase in measured muscles resulting from the attempt to stabilize against upper body motion moving dynamically. As just described, the figure showed the features of the muscle activity modality during several exercises in water, but further video analysis investigation would be needed for understanding the cause of the muscle activity more precisely.

**6. Rehabilitation training in water for regaining normal walking, is it truly**

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The EMG characteristics introduced in this chapter are used in the comparison of the EMG data such as mean value or quantity. However, it is important to evaluate the quality of EMG signal to identify where the stimulus happened as the mean value is nothing more than the representative mean of the data for the targeted period. The quality analysis for EMG signal of exercise in water is a comparison of the wave forms that accompany exercise movement. Normalization from 0 to 100% of one cycle was applied so as to compare the muscle activity time course pattern [26, 34]. However, there was no statistical comparison made to the time course pattern. Instead the authors compared the time course pattern of walking exercise in water and on land by applying a cross correlation function. This correlation was then used in discussing the similarity of muscle activity patterns between water- and land-walking, as well as the usability of walking in water as a form of rehabilitation training. The hypothesis being that a water environment may have the benefit of less gravity stress and greater safety in preventing falling accidents. In addition, training of the targeted movement may be more effective and movement function specific [35] in water than on land. Thus, further investigation of the similarity of muscle activity between water- and land-walking would provide increased understanding regarding the use of water activity and exercise prescription for rehabilitation.

**Figure 22.** The normalized time course pattern of %MVC during walking in water and on land. [Modified from refer‐

In the study by the authors [36], nine male subjects walked in water and on land condition at self-selected slow, comfortable, and fast speed in water as well as comfortable speed on land.

**effective?**

Values are mean ± SD of the subjects

LW: land-walking, WW: water-walking r: cross correlation coefficient

A: TA, B: GAS, C: RF, D: BF

ence [36]

A: shank muscles, B: thigh muscles, C: hip muscles, D: trunk muscles

F: forward walking, B: backward walking, D: DWR, R: normal running, S: side walking, L: walking with long-step, T: walking with trunk-twisting, K: walking with kicking, U: walking with knee-up, P: walking with elbow-knee alternative touching

**Figure 21.** The mean %MVC value of the lower limb, hip and trunk muscle during exercise in water. [Unpublished data]
