Muscle activation in young men during a lower limb aquatic resistance exercise with different devices.

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Muscle Activation in Young Men During a Lower Limb Aquatic Resistance Exercise With Different Devices

DOI: 10.3810/psm.2014.05.2060

Sebastien Borreani, PhD 1 Juan Carlos Colado, PhD 1 Josep Furio, MSc 1,2 Fernando Martin, PhD 1 Víctor Tella, PhD 1 Research Group in Sport and Health, Department of Physical Education and Sports, University of Valencia, Valencia, Spain; 2University Institute of Science in Physical Activity and Sports, Catholic University of Valencia, Valencia, Spain 1

Abstract: Little research has been reported on the effects of using different devices with resistance exercises in a water environment. This study compared muscular activation of lower extremity and core muscles during leg adduction performed at maximum velocity with drag and floating devices of different sizes. A total of 24 young men (mean age 23.20 ± 1.18 years) performed 3 repetitions of leg adduction at maximum velocity using 4 different devices (ie, large/small and drag/floating). The maximum amplitude of the electromyographic root mean square of the adductor longus, rectus abdominis, external oblique on the dominant side, external oblique on the nondominant side, and erector lumbar spinae were recorded. Electromyographic signals were normalized to the maximum voluntary isometric contraction (MVIC). Unexpectedly, no significant (P . 0.05) differences were found in the neuromuscular responses among the different devices used; the average activation of agonist muscle adequate for neuromuscular conditioning was 40.95% of MVIC. In addition, external oblique activation is greater on the contralateral side to stabilize the body (average, 151.74%; P , 0.05). Therefore, if maximum muscle activation is required, the kind of device is not relevant. Thus, the choice should be based on economic factors. Keywords: resistance training; water environment; EMG; core

Introduction

Correspondence: Juan Carlos Colado, PhD, Department of Physical Education and Sports, Universidad de Valencia (FCAFE), Aulario Multiusos, C/ Gascó Oliag 3, 46010 Valencia, Spain. Tel: +34 667507636 Fax: +34 963864353 E-mail: [email protected]

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The benefits of resistance training to reduce incidence of metabolic disease and improve functional capacity and health have been well established in recent decades.1 The water environment has advantageous physical properties for exercise and is an alternative tool to use in resistance training. Swimming is the most popular form of exercise in the water environment; however, in the sedentary population, great technical skill is required to maintain exercise intensity at steady-state.2 Walking-running in deep water, walking-running in shallow water, and aquatic bicycle and resistance training exercises performed in a vertical position in water are increasing in popularity for the sedentary population or individuals without swimming abilities.3 Head-out aquatic exercises performed in the vertical position have also become a major element of rehabilitation programs for several diseases and to enhance sport performance and physical condition in athletes.2,4 Exercising in a water environment could be an effective method to improve strength and may increase fat-free mass of the extremities in elderly and young physically active people.5–12 Resistance training in water environment is performed using

© The Physician and Sportsmedicine, Volume 42, Issue 2, May 2014, ISSN – 0091-3847 ResearchSHARE®: www.research-share.com • Permissions: [email protected] • Reprints: [email protected] Warning: No duplication rights exist for this journal. Only JTE Multimedia, LLC holds rights to this publication. Please contact the publisher directly with any queries.


Devices for Water Resistance Exercises

different devices; however, no evidence supports 1 device being more appropriate than another for use in training in a water environment.13 There are 2 primary types of devices. Devices that take advantage of the buoyancy property of water are often called floating devices, and devices that take advantage of the drag property of water are often called drag devices.14 The devices also may have different sizes. The buoyancy property is the main force that is acting against the floating devices. This force has an upward direction and is proportional to the gravity, the fluid density, and the volume of the submerged body.14 Drag force is the result of the high density of the water fluid. This force is the main property acting against drag devices.15 The force generated when using drag devices in water depends on the parameters included in the general fluid equation16: Fdrag = 0.5 . CD . A . ρ . v², wherein “CD” is the drag coefficient that depends on body form and texture, A is the frontal surface of the body area, ρ is the fluid density, and v is the body velocity during movement in water. Most of the resistance training studies in water have used maximum velocity of movement in all the exercises performed.9,17–19 However, the literature on the effect of producing maximum velocity of movement using different devices is scant. Regarding the effect of velocity on muscular activation in a water environment, it is known that when using the same device, greater velocity induces more activation, especially if submaximum velocity is compared with maximum velocity.20 Pöyhönen et al17 reported that the angular velocity in multiple repetitions at maximum velocity is significantly greater when barefoot than when wearing a large drag device (hydroboot), whereas muscular activation does not vary. Two primary types of devices are available: those that take advantage of the buoyancy property of water are often called floating devices, and those that take advantage of the drag property of water are often called drag devices.14 Studies have concentrated on drag devices, because these present great advantages for resistance training.14 For example, drag devices allow activation of a greater number of muscular groups with a smaller number of movements. Although this is advantageous, the most commonly used devices in fitness centers are the floating kind.21,22 Floating devices have the disadvantage that subjects must be placed in very uncomfortable positions to take advantage of the specific properties of this device (eg, lying down for knee extension). However, few studies have compared the effect of both devices on muscular activation. Thus, when performing resistance training in a water environment, deciding which device is more appropriate is difficult because of the lack of knowledge.

Resistance training may include exercises to strengthen the muscles of the extremities and the spinal stabilizer muscles (also called core muscles).23 Core muscle training has frequently been shown to be necessary to prevent and rehabilitate low back disorders in the sedentary and physically active populations.24,25 Because flotation reduces axial load on the spine, exercises in the water environment are prescribed for people with lumbar pain.25 Moreover, hydrostatic pressure and water temperature help maintain balance and control pain, respectively.25 Few studies have reported muscular activation of the core muscles in a water environment. Bressel et al22 analyzed the performance of 4 abdominal trunk exercises in water and on land and found that the activation of most core muscles was greater in all the exercises performed on land than in those performed in water. The investigators attributed this finding to the flotation component, and recommended the performance of these exercises in water in the first phases of low back disorder rehabilitation. Furthermore, Bressel et al26 indicated that abdominal bracing, Swiss ball pushdowns, and lateral pushdowns maximize trunk muscle activity, whereas abdominal hollowing and pelvic tilt minimize electromyographic (EMG) amplitude during water immersion. Colado et al27 showed that erector lumbar spinae muscle activation was higher in water than on dry land when performing the same horizontal shoulder abduction and adduction exercises at the same intensity. Nevertheless, a lack of evidence exists on the use of different devices during the performance of water resistance exercises, especially at maximum velocity and involving the lower body. Because the benefits of resistance training include core muscle strengthening, and because performing exercises in a water environment have been shown to improve physical performance and health, it is important to clarify the effects of different devices used during water resistance exercises. Consequently, the present study compared muscular activation of the lower extremity and core muscles during leg adduction performed at maximum velocity using different devices (ie, large/small and drag/floating properties). It was hypothesized that the greatest lower extremity and core muscular activation would be obtained when using a larger device that increased the drag force.

Materials and Methods Experimental Approach to the Problem

A total of 24 volunteers participated in 2 different sessions. In the first session, the participants were familiarized with the movement and protocol, and in the second session they

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Borreani et al

performed a leg adduction in 4 conditions at the xiphoid process depth. Xiphoid process depth was selected to analyze the effects of different devices, because it is the most commonly used immersion depth for performing resistance exercises.13 Surface EMG signals were recorded for the following muscles: adductor longus (AL), rectus abdominis (RA), external oblique on the dominant side (EOD), external oblique on the nondominant side (EOND), and erector lumbar spinae (ES). Surface EMG is the most common technique to measure muscle activation (ie, electrical activity in response to a nerve’s stimulation of the muscle). The force/EMG relationship illustrates that increases in muscle EMG are associated with increases in muscle force or strength output,28 and exercises that produce higher EMG signal amplitudes are also assumed to generate larger strengthening effects.29 The data obtained were normalized by using the maximum root mean square (RMS) values obtained during the maximum voluntary isometric contraction (MVIC), and were expressed as a percentage of the maximum EMG.

Participants

A total of 24 young men volunteered to participate in this study (age, 23.20 ± 1.18 years; height, 178.10 ± 7.26 cm; body mass, 77.7 ± 7.6 kg; body fat percentage: 11.40% ± 3.24%). The number of subjects chosen was calculated using G*Power (University of Kiel, Kiel, Germany) and was based on effect size 0.25 standard deviation (SD) with an α level of 0.05 and power at 0.80. Participants included in the research had $ 1 year experience in resistance training on land, performing $ 2 sessions per week at moderate to vigorous intensity, and were familiar with the performance of exercises in a water environment. No subject included in this study presented with musculoskeletal pain, neuromuscular disorders, or any form of joint or bone disease. This study was performed during the spring and was conducted according to the ethical standards of the International Journal of Sports Medicine described by Harriss and Atkinson.30 All participants signed an institutional informed consent form before starting the protocol, and the study was approved by the Institutional Review Board of the University of Valencia.

Procedures

Each subject participated in 2 sessions, consisting of familiarization and the experimental sessions. The first session occurred 48 to 72 hours before data collection during the experimental session, and both sessions were held at the same time in the morning. Several restrictions were imposed on the 82

volunteers: no food, drinks, or stimulants (eg, caffeine) could be consumed 3 to 4 hours before the sessions and no physical activity more intense than daily living activities could be performed 12 hours before. Subjects were encouraged to sleep . 8 hours the night before data collection.

Familiarization Session

In the first session, participants were familiarized with the leg abduction and adduction exercise, movement amplitude, intensities, and devices that would later be used during data collection. Moreover, height (IP0955, Invicta Plastics Limited, Leicester, England), body mass, and body fat percentages (BF-350 Body Composition Analyzer, Tanita Corporation of America, Arlington Heights, IL) were recorded according to the protocols used in previous studies.31

Experimental Session

The aquatic protocol started with the preparation of participants’ skin, followed by MVIC collection and exercise performance. All hair was removed from the skin covering the muscles, which was then cleaned with cotton wool dipped in alcohol for the subsequent placement of electrodes (positioned according to the recommendations of Cram et al32) on the dominant side of the body for the AL, RA, EOD, and ES, and on the nondominant side of the body for the EOND. Pre-gelled bipolar silver/silver chloride surface electrodes (Blue Sensor M-00-S, Medicotest, Ølstykke, DNK) were placed with an interelectrode distance of 25 mm on the following muscle groups: AL (on the medial aspect of the thigh in an oblique direction 4 cm from the pubis); RA (2 cm lateral and across from the umbilicus); EOD; EOND (2 cm apart, lateral to the rectus abdominis and directly above the anterior superior iliac spine, halfway between the crest and the ribs at a slightly oblique angle so that they ran parallel to the muscle fibers); and ES (2 cm from L3, placed parallel to the spine). The reference electrode was placed between the active electrodes, approximately 10 cm away from each, according to the manufacturer’s specifications. All signals were acquired at a sampling frequency of 1 kHz, amplified and converted from analog to digital. All records of myoelectrical activity (in microvolts) were stored on a hard drive for later analysis. The insulation procedures described by Pinto et al18 were used to avoid interference caused by the contact of electrodes with water, which can produce noise in the EMG signal. Previous studies have shown high EMG reliability for aquatic exercises.18,33,34 To acquire the surface EMG signals produced during exercise,




an ME6000P8 (Mega Electronics, Ltd., Kuopio, Finland) biosignal conditioner was used. The MVIC for all muscle groups analyzed was performed on land. The MVIC executed on land can be used for normalization of the EMG activity of dynamic exercises in water.18 A 5-second MVIC was performed for each muscle involved (ie, AL, RA, EOD, EOND, and ES) to estimate the maximum EMG amplitude.35,36 The participants started the exercise in the standing position with their hands on the iliac crest. Each subject performed 3 repetitions with the dominant leg in all conditions. The first phase of the movement consisted of a leg abduction from 0º to 45º at a very slow velocity; a 5.33-second rate was maintained by a 80-Hz metronome during 4 beats (Ableton Live 6, Ableton AG, Berlin, Germany) to avoid generating a turbulent flow.19 The second phase consisted of a leg adduction at maximum velocity. Visual feedback was given to the participants to maintain the range of movement during data collection. The exercise was performed under the following 4 conditions at xiphoid process depth: drag hydroboot (DH; Hydro-Tone Fitness System, Orange, CA, USA), drag aquafins (DA; TheraBand, Hadamar, Germany), floating boot (FB; Leisis, S.L., Valencia, Spain), and floating support (FS; Leisis, S.L., Valencia, Spain). These devices integrated large and small sizes and floating and drag properties (Figure 1). The participants performed all exercises on an aquatic step (Leisis, S.L., Valencia, Spain) and wearing nonskid socks (Akkua, Roncadelle, Italy) to minimize displacement of the feet. Each condition was performed randomly with a 2-minute interval between them (between each device). The different devices were located in the distal part of the leg and were fixed with their own Velcro straps around the ankle joint; each has a typical size according at the manufacturer standards. Verbal encouragement was provided to motivate all participants to achieve maximum velocity in the leg adduction phase. The encouragement was identical for all participants in every condition. Throughout the experiment, both air and water were maintained at thermoneutral temperatures at 24ºC and 30°C, respectively.37

Data Analysis

All surface EMG signal analyses were performed using Matlab 7.0. Surface EMG signals related to isometric exercises were analyzed using the middle 3-second period of the 5-second isometric contraction. Surface EMG signals of dynamic exercises were analyzed using the entire

second-phase period to evaluate muscle activity during the concentric contraction due to the differences between the devices (drag vs floating). All signals were bandpass filtered at a 20- to 400-Hz cutoff frequency with a fourth-order Butterworth filter. Surface EMG amplitude in the time domain was quantified using RMS and processed every 100 milliseconds. Maximum RMS values were selected for each trial. The data obtained were normalized using the maximum RMS values during the MVIC and expressed as a percentage of the maximum EMG (%EMG). The global mean of all muscles (ie, AL, RA, EOD, EOND, and ES) was also calculated and analyzed.

Statistical Analyses

Statistical analysis was performed using SPSS version 17. Normality of the data distribution was tested using the Shapiro-Wilk test. Results are reported as mean ± standard error. Statistical comparisons of the conditions (DH, DA, FB, and FS) were performed using ANOVA with repeated measures. Greenhouse-Geisser correction was used when the assumption of sphericity (Mauchly’s test) was violated. Paired-sample t tests were performed to determine significant differences between EOD and EOND in each condition. Significance was accepted when P # 0.05.

Results

For all muscles analyzed in the present study, no significant differences were found (AL: F[1.73, 27.70] = 1.322, P = 0.280; RA: F[3, 30] = 1.138, P = 0.124; EOD: F[3, 39] = 0.680, P = 0.570; EOND: F[3, 30] = 1.089, P = 0.369; ES: F[3, 30] = 1.138, P = 0.350; Global: F[3, 54] = 0.187, P = 0.905) between performance of the aquatic exercise under the 4 conditions (DH, DA, FB, and FS). Subjects’ EOND showed significantly higher activation than EOD during the performance of the exercise under each condition (DH: t[10] = –4.457, P = 0.001; DA: t[13] = –3.768, P = 0.002; FB: t[9] = –2.621, P = 0.028; FS: t[12] = –4.964, P , 0.001). Results are reported in Table 1 and Figure 2.

Discussion

The present data contradict the hypothesis because they demonstrate that similar muscle activation is achieved during the performance of resistance exercises using different devices (ie, large/small and drag/floating) for lower extremity and core muscles. The agonist of movement in the leg adduction is AL and its activation was the same, independent of the use of any


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Figure 1. A) Drag hydroboot, B) drag aquafins, C) floating boot, and D) floating support.

device (Table 1). However, the results show that muscular activation was the same whether the velocity of movement was high, as occurred with small devices, or low, as occurred with large devices. In the first place, the general fluid equation should be emphasized,16 because it is known that the force generated when using devices in water depends on the following parameters: Fdrag = 0.5 . CD . A . ρ . v², wherein CD is the drag coefficient that depends on body form and texture, A is the frontal surface of the body area, ρ is the fluid density, and v is the body velocity during movement in water. Focusing on the size of the device in particular, it is known that as the maximum velocity movement is performed, if the size

of the area is small, the velocity is high, and if the size of the area is larger, the velocity is lower.17,38 It is logical to assume that if the size of A is diminished and at the same time the velocity v is increased, which is exponential in the equation, the resultant force is maintained practically constant. The studies by Pöyhönen et al17 and Black et al,38 in which knee and hip flexion and extension movements were performed respectively, should be emphasized, because they compared muscle activation with and without devices. In these studies, muscular activation while performing the movement at maximum velocity was compared in a very similar way with the methods used in the present study,

Table 1. Mean ± SEM of the Percentage of Maximal Muscle Activation During Exercise Performance With Different Devices (N = 24) AL RA EOD EOND ES Global

DH

DA

FB

FS

P

43.61 ± 8.27 13.61 ± 3.04 13.05 ± 3.37 53.13 ± 10.40a 20.42 ± 3.96 28.39 ± 3.14

36.10 ± 6.81 13.22 ± 2.20 16.12 ± 4.04 39.27 ± 9.89a 18.38 ± 3.26 28.29 ± 2.63

35.87 ± 7.24 11.84 ± 3.25 11.98 ± 2.53 45.78 ± 11.42a 14.57 ± 2.03 28.71 ± 2.83

48.21 ± 9.39 20.95 ± 5.75 14.64 ± 3.11 41.11 ± 7.06a 18.78 ± 4.26 30.22 ± 2.65

0.280 0.124 0.570 0.369 0.350 0.905

Significant differences (P # 0.05) between muscle activation (%EMG) of EOD and EOND. Abbreviations: %EMG, percentage of maximum electromyography regarding the maximum voluntary isometric contraction; AL, adductor longus; DA, drag aquafins; DH, drag hydroboot; EOD, external oblique dominant side; EOND, external oblique nondominant side; ES, erector spinae; FB, floating boot; FS, floating support; Global, mean of all the muscles (ie, AL, RA, EOD, EOND, and ES); RA, rectus abdominis; SEM, standard error of the mean. a

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Figure 2. Muscle activation (%EMG) of EOD and EOND during the performance of the exercise in the 4 conditions.

*Significant differences (P # 0.05). Abbreviations: %EMG, percentage of maximum electromyography regarding the maximum voluntary isometric contraction; EOD, external oblique on the dominant side; EOND, external oblique on the nondominant side; DA, drag aquafins; DH, drag hydroboot; FB, floating boot; FS, floating support.

and neither study found significant differences between performing the movement with and without the devices. Moreover, in the study conducted by Kruel et al,9 an intervention of 11 weeks’ training with women in a water environment was applied. In this study,3 groups were compared: a control group and 2 experimental ones (one group that trained without devices and another with devices; both performed the exercises at maximum velocity). The experimental groups showed improvement compared with the control group, and no significant difference was found between the groups with or without devices in a one maximum repetition test. In the same vein, the property of the floating devices does not seem to be an influential factor. Floating equipment is characterized by a density considerably lower than that of the water, thus the main property of this material is to increase the buoyancy or flotation force. In addition to the buoyancy force, floating devices have a frontal surface area, and consequently, the resistance is the sum of buoyant and drag forces.15 Buoyancy force combined with the size of the floating device means that a lower velocity is reached and therefore the resulting end force is maintained. Pinto et al33 analyzed 15 women performing stationary jogging combined with elbow flexion and extension without devices, with a drag device and a floating device at maximum cadence. The results showed no significant differences between performance of the exercise with or without devices

for most muscles evaluated. However, taking into account the results of the present study, it would be interesting for future studies to evaluate whether the devices had a significant effect on the velocity of the hip adduction, because this could influence not only the muscular activation but also the type of muscular fiber that could be activated. Regarding the comparison of core muscles, it was found that different devices did not modify the activation. Studies have also shown that the forces generated by the extremities directly affect the activation of core muscles.31,39 Therefore, the greater the force generated by the extremity, the greater the activation of the core muscles.31,39 This finding would explain why core muscle activation did not vary significantly, because AL activation with different devices did not vary either. Chulvi-Medrano et al39 compared the maximum isometric force when performing a deadlift exercise in a stable position and in different unstable conditions (unidirectional and multidirectional), and noted a 34.19% reduction when performing a deadlift on a Bosu (imbalance in all directions) and a 8.80% reduction when performing deadlift on a T-Bow (imbalance only in the frontal plane). At the same time, muscular activation of the erectors and multifidus was significantly greater in the stable conditions than in other unstable conditions. To activate the core muscles, the force that can be applied by the extremities is more decisive than the imbalance generated



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by an unstable surface.23,31,39 This evidence could explain why, even if the imbalances are modified with different devices, core muscle activation is more dependent on agonist muscle activity. Interestingly, EOND activation is much higher than EOD activation in each condition (Table 1 and Figure 2). This result is in accordance with those of previous studies,24,40 which showed that core muscle activation is asymmetrical when exercises are performed unilaterally. Greater core muscle activation was found in the contralateral side during dynamic unilateral upper limb exercises.24,40 Feldwieser et al41 found higher external oblique activation on the side that was unsupported during a prone bridge exercise compared with the supported side. External oblique activation is much greater on the contralateral side of the leg in action to stabilize the body. One limitation of the present study is that subjects are physically active men with low body fat and therefore the results could not be extrapolated to other populations. Another limitation is the lack of adjacent measurements (eg, rate of perceived exertion, blood lactate).

Conclusion

When training in a water environment, different sizes and types (drag and floating) of devices can lead to similar muscle activation when the movement is performed at maximum velocity, or at least with the maximal intentional velocity of execution. Maximum velocity of execution must always be performed using proper technique and correct body position. Therefore, if maximum muscle activation of the extremities and core muscles is required, then the kind of device is not relevant.

Acknowledgments

The authors wish to thank the participants for their contribution to this study. We also thank Leisis, S.L. for the donation of the aquatic devices used in this study and Marva Sport Center (Valencia, Spain) for the swimming pool.

Conflict of Interest Statement

Sebastien Borreani, PhD, Juan Carlos Colado, PhD, Josep Furio, MSc, Fernando Martin, PhD, and Víctor Tella, PhD, have no conflicts of interest to disclose.

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Lower limb joint angular position and muscle activity during elliptical exercise in healthy young men.

Cardiac autonomic responses during upper versus lower limb resistance exercise in healthy elderly men.

The effect of double versus single oscillating exercise devices on trunk and limb muscle activation.

Activation of back and lower limb muscles during squat exercises with different trunk flexion.

Effects of a single bout of lower-body aerobic exercise on muscle activation and performance during subsequent lower- and upper-body resistance exercise workouts.

Protein Ingestion before Sleep Increases Muscle Mass and Strength Gains during Prolonged Resistance-Type Exercise Training in Healthy Young Men.

Effect of growth hormone and resistance exercise on muscle growth in young men.

Relationship Between Lower Limb Muscle Activity and Platform Acceleration During Whole-Body Vibration Exercise.

Effects of combined exercise on changes of lower extremity muscle activation during walking in older women.

Effect of caffeine ingestion on torque and muscle activity during resistance exercise in men.

Acute post-exercise myofibrillar protein synthesis is not correlated with resistance training-induced muscle hypertrophy in young men.

Exercise-induced AMPK activation does not interfere with muscle hypertrophy in response to resistance training in men.

Effect of therapeutic aquatic exercise on symptoms and function associated with lower limb osteoarthritis: systematic review with meta-analysis.

Effect of moderate altitude on peripheral muscle oxygenation during leg resistance exercise in young males.

Lower limb antagonist muscle co-activation and its relationship with gait parameters in cerebellar ataxia.

Lower limb conduit artery endothelial responses to acute upper limb exercise in spinal cord injured and able-bodied men.

Muscle activation patterns when passively stretching spastic lower limb muscles of children with cerebral palsy.

Muscle Activation during Push-Ups with Different Suspension Training Systems.

Muscle activation during low-intensity muscle contractions with varying levels of external limb compression.

Comparison of Lower Limb Muscle Activity during Eccentric and Concentric Exercises in Runners with Achilles Tendinopathy.

Protein Supplementation Has Minimal Effects on Muscle Adaptations during Resistance Exercise Training in Young Men: A Double-Blind Randomized Clinical Trial.

A single set of exhaustive exercise before resistance training improves muscular performance in young men.

Metabolic demand and muscle activation during different forms of bodyweight supported locomotion in men with incomplete SCI.

Core Muscle Activity, Exercise Preference, and Perceived Exertion during Core Exercise with Elastic Resistance versus Machine.