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EFFECTS OF WHOLE-BODY ELECTROMYOSTIMULATION ON STRENGTH AND BATTING VELOCITY AMONG FEMALE COLLEGIATE SOFTBALL PLAYERS

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This study examined the effects of 8 weeks additional dynamic Whole-body Electromyostimulation (WB-EMS) on muscular strength and batting velocity performance in female collegiate softball players. Forty softball players were randomly assigned into 2 groups which are DS (n = 20); DS-EMS (n = 20). Both groups performed 100 normal swing training using a standard bat. However, DS-EMS group performed additional of whole body electromyostimulation after the dry swing training. The training programs were conducted three times a week and all players were tested before (baseline) and at the end of week 8 (wk-8) training. Both groups showed statistically significant increase in predicted 1RM torso rotational strength (p ≤ 0.01) and batting velocity strength (p ≤ 0.01) after 8 weeks of training. In addition, WB-EMS group showed significant increase in predicted 1RM bench press, and predicted 1RM squat (p ≤ 0.01). When comparing between groups, WB-EMS showed statistically greater increases (p ≤ 0.01) in BV compared to control group. These data indicate that an 8-week of additional dynamic WBEMS training can significantly increase strength (upper-body, lower-body, torso rotational) and batting velocity among female collegiate softball players.
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Whole-Body Electromyostimulation on Strength and Batting Velocity
EFFECTS OF WHOLE-BODY ELECTROMYOSTIMULATION ON STRENGTH AND
BATTING VELOCITY AMONG FEMALE COLLEGIATE SOFTBALL PLAYERS
Raja N. J. R. H.*, Kee K. M, Maisarah S. and Norizzati M. I.
Faculty of Sports Science and Recreation
Universiti Teknologi MARA
*Email: rajanuruljannat@gmail.com
Abstract
This study examined the effects of 8 weeks additional dynamic Whole-body
Electromyostimulation (WB-EMS) on muscular strength and batting velocity performance in
female collegiate softball players. Forty softball players were randomly assigned into 2 groups
which are DS (n = 20); DS-EMS (n = 20). Both groups performed 100 normal swing training using
a standard bat. However, DS-EMS group performed additional of whole body
electromyostimulation after the dry swing training. The training programs were conducted three
times a week and all players were tested before (baseline) and at the end of week 8 (wk-8) training.
Both groups showed statistically significant increase in predicted 1RM torso rotational strength (p
≤ 0.01) and batting velocity strength (p ≤ 0.01) after 8 weeks of training. In addition, WB-EMS
group showed significant increase in predicted 1RM bench press, and predicted 1RM squat (p
0.01). When comparing between groups, WB-EMS showed statistically greater increases (p ≤
0.01) in BV compared to control group. These data indicate that an 8-week of additional dynamic
WBEMS training can significantly increase strength (upper-body, lower-body, torso rotational)
and batting velocity among female collegiate softball players.
Keywords: Dry swing, electromyostimulation, batting, velocity
Introduction
Batting velocity in softball and baseball sports is an important component of a successful hitting technique
(DeRenne, 2007; Szymanski, DeRenne, & Spaniol, 2009; Szymanski, McIntyre, et al., 2007; Wilson et al.,
2012). Previous studies mentioned that there were positive correlation between strength and batting velocity
(Szymanski, 2007; D. J. Szymanski, J. Albert, et al., 2008). More specifically, past studies indicates that upper
and lower body strength (Szymanski, Szymanski, Schade, & Bradford, 2008; J. Szymanski et al., 2008) and
torso rotational strength (Szymanski, McIntyre, et al., 2007; J. Szymanski et al., 2008) have a significant
relationship with batting velocity. Therefore, it is important to apply training that is able to increase upper and
lower body and torso rotational strength.
Over the past 30 years, traditional resistance training had been implemented to increase batting velocity
among high school, collegiate, amateur, and professional softball and baseball players (Szymanski, 2007; D. J.
Szymanski, J. Albert, et al., 2008; Szymanski et al., 2009) and these studies have reported increment muscular
strength and batting velocity. It is well known that traditional resistance training takes up to 60 minutes per
session (Nybo et al., 2010). However, coaches nowadays have limited time to train their athletes. Therefore,
they usually neglect the conditioning practice and focus more on techniques and tactics of the game. These lead
to players having weak strength and only worsen their sports performance.
As the technology improves, short period of electrical stimulation (EMS) training which usually used for
rehabilitation purpose has become as a method to increase the physiology and physical characteristics of healthy
population. The EMS training was proven able to works as an alternative to the traditional resistance training for
developing maximal strength performance in athletes (Filipovic, Kleinöder, Dörmann, & Mester, 2012).
Several previous studies reported a significant changes in strength (Babault, Cometti, Bernardin, Pousson, &
Chatard, 2007; Billot, Martin, Paizis, Cometti, & Babault, 2010; Girold et al., 2012; Maffiuletti et al., 2000;
Maffiuletti, Dugnani, Folz, Di Pierno, & Mauro, 2002; Pichon, Chatard, Martin, & Cometti, 1995) Moreover,
EMS has also showed positive effects on sports performance such as swimming (Girold et al., 2012; Pichon et
al., 1995), kicking soccer ball (Billot et al., 2010) and rugby (Babault et al., 2007). Previous meta-analysis
review on EMS study revealed that past studies applied single electrodes of EMS at specific muscles. This is
2
because at that moment, limited electrodes can be used at one time. Nowadays, EMS technology is improving
and WB-EMS had evolved which this equipment able to train several muscle groups simultaneously through
vest and electrode belt system (e.g., Miha BodyTec, Augsburg, Germany). This specification becomes handy to
all coaches who have limited time for conditioning practice. In comparison with the single electrodes EMS
method, there is only few studies that apply WB-EMS methods on athletes (Filipovic et al., 2016). For this
reason, the aim of this study is to measure the effects of implementing a WB-EMS training in female collegiate
softball training routine on muscular strength and batting velocity.
Methods
Participants
Forty female collegiate softball players participated in this study. All players were randomly assigned into 2
groups which is the dry swing (DS, n = 20; age 23.40 (1.85) years; height 156 (1.62) cm, weight 54.11 (3.21)
kg) group and dry swing with whole-body EMS (DS-EMS, n = 20; age 23.80 (1.85) years; height 156.25 (1.71)
cm, weight 52.83 (3.47) kg) group. All players performed normal 100 swings training using standard bat weight
(24Oz) during their softball practice (3 times a week). However, DS-EMS performed additional training that
involved electrical stimulation after the swing training. All players have no experience/trained with any EMS
training before and written informed consent was obtained from them. All players were briefed about the
procedures and risks of the study. The experimental procedures performed were been approved by the Ethic
Committee of the Research Management Institute (RMI), Universiti Teknologi MARA, Malaysia (600-RMI
(5/1/6/01)).
Training Protocols
WB-EMS training was performed three times a week after swing practice for 8 weeks. The WB-EMS training
includes of various exercises that usually been used in increasing muscular strength and batting velocity
(Szymanski, McIntyre, et al., 2007). This training was programmed according to stepwise periodized (Table 1)
method which is similar to previous resistance training used (Stone et al., 2000; Szymanski, Szymanski,
Bradford, Schade, & Pascoe, 2007; Szymanski, Szymanski, Molloy, & Pascoe, 2004). The intensity between
free weight training and electrical stimulation was being equated in previous study (Hussain et al., 2016).
Therefore, this training followed the intensity recommended to increase muscular strength (Baechle, Earle, &
Baechle, 2004). A Whole-body EMS system by Miha Bodytec (Augsburg, Germany) was used by the
WB-EMS group. This system used electrode vest that stimulate upper body muscles (pectoralis major and
minor, latissimus dorsi, and external oblique), used a belt system to the lower body muscles (recus femoris and
biceps femoris). Specific ball exercises were include in training program (2 days a week) as it perform similar
sequential, ballistic, and rotational movement as batting movement. Biphasic rectangular wave pulsed currents
(50 - 90Hz) were used with an impulse width of 350μs and the maximally tolerated intensity were varied
between 60 and 100 miliAmpere (mA) depending on the differences among subjects in pain threshold. Every
impulse for a single lift in each exercise lasted for 5s followed by another 5s of a rest period.
Table 1: Training protocols
Week 1 - 4
Week 5 - 8
Sets
Reps
Sets
Reps
%RMM
Warm-up
2
10
2
10
50-60
Parallel squat
3
6-8
3
2-4
85-90
Stiff leg deadlift
3
6-8
3
2-4
85-90
Bench press
3
6-8
3
2-4
85-90
Triceps kickback
2
10-12
2
8-10
70-75
Biceps curl
2
10-12
2
8-10
70-75
Seated Row
2
10-12
2
8-10
70-75
Ball exercise
Sets
Reps
Sets
Reps
%RMM
Hitters throw
2
6
2
8
70
Standing figure 8
2
6
2
8
70
Speed rotation
2
6
2
8
70
Standing side throw
2
6
2
8
70
Squat and throw
2
6
2
8
70
Whole-Body Electromyostimulation on Strength and Batting Velocity
Experimental Design
The study was a randomized pre-test post-test study including a dry swing training group (DS) as a control
group and a dry swing with an additional of EMS (DS-EMS) as a treatment group. This design helps in measure
the effects of the WB-EMS training on strength and bating velocity. The study was conducted during off season
and the training interventions were conducted three times per week. Maximal strength and batting velocity was
assessed before (baseline) and after 8 weeks (wk8). All tests were conducted on two different days in a
standardized order. Strength test were tested on the first day and the batting velocity was tested on the following
day.
Testing procedures
Before all tests were conducted, the players’ demographic data were recorded (Table 2).
Table 2: Mean (SD) baseline descriptive data for groups
Group
Age (years)
Height (cm)
Weight (kg)
DS (n = 20)
23.40 (1.85)
156 (1.62)
54.11 (3.21)
DS-EMS (n = 20)
23.80 (1.85)
156.25 (1.71)
52.83 (3.47)
All of the participant in this study have been involved in resistance training less than 1 year. According to
Baechle et al. (2004), these participants can be classified as beginner to intermediate lifters and due to that,
3RM test (most amount of weight lifted 3 times) of bench press, squat, and torso rotational were performed to
determine the predicted 1 repetition maximum (most amount of weight lifted at 1 time 1RM). Previous study
stated that multiple RM test is valid (r = 0.84 0.92) and reliable to determine the prediction of 1RM (Ruivo,
Carita, & Pezarat-Correia, 2016). Before 3RM bench press were conducted, full body dynamic warm-up was
performed by all participants. The procedure of conducting multiple RM test for bench press and squat were
followed Baechle et al. (2004). For torso rotational strength test, procedure from previous study by Szymanski,
Szymanski, et al. (2007) were followed. The 1RM bench press, squat and torso rotational subsequently
predicted using Bryzcki equation (Ruivo et al., 2016). To ensure the appropriate intensity (%RM) was used
during training, the predicted 1RM bench press, squat, and torso rotational tests was assessed at week 0 and end
of week 4.
Batting velocity was being tested on the following day after strength tests. Before the bat swing was
measured, a 5-minute full-body warm-up exercise was performed. Players have to perform 5 dry swings using
the same bat they used for testing. An aluminium softball bat, measuring 84 cm long and weighing 680 g, was
used. The bat swing velocity was measured by a portable swing analyzer device (ZEPP., USA) with the
reliability showed r = 0.822-0.988 (Bailey, McInnis, & Batcher, 2016). The batting velocity test begins as the
participant stands on the starting position where she can swing with her maximum batting velocity. Each
participants performed 5 swings with a break time of 30-s between swings. While encouragement to focus on
the external environment was given, each player was instructed to swing as fast as possible and keep
maintaining the same stance and same swing mechanics. Encouragement was given to elicit optimal
performance (Gray, 2009). The velocity of the five swings were manually recorded for analysis.
Statistical analysis
Normality of distribution was conducted before the other analysis. Independent t-test at week 0 and week 8
was conducted to measure the differences occur between groups in predicted 1RM strength test and batting
velocity. Paired sample t-test was conducted to measure the effect of training along 8 weeks period of time.
Further analysis using Pearson product-moment correlation was conducted to detect correlation among strength
variables and batting velocity.significance value was set as the p-value less than 0.05 and all statistical analyses
were conducted using IBM statistic Version 20 (Armonk, NY).
4
Results
Group comparison
After 8 weeks, the DS-EMS showed a significant (p ≤ .01) higher in predicted 1RM bench press, squat, and
torso rotational strength as well as batting velocity compared to DS group (Table 3). DS group showed no
significant improvement in predicted 1RM bench press and squat (p > .05).
Table 3: Mean (SD) DS and DS-EMS for pre-test, post-test and percent (%) change
Variable
Pre-test
Post-test
% change
Bench Press
DS
DS-EMS
25.10 (3.02)
24.08 (3.50)
25.33 (2.88)
26.46 (3.07)
0.92
9.88†‡
Squat
DS
DS-EMS
42.71 (2.15)
42.04 (2.53)
42.83 (1.93)
46.01 (2.36)
0.28
9.44†‡
Torso Rotational
DS
DS-EMS
28.29 (5.16)
27.70 (5.57)
30.95 (5.03)
33.31 (4.06)
9.40†
20.25†‡
Batting Velocity
DS
DS-EMS
54.20 (3.65)
54.30 (3.64)
55.00 (3.48)
56.25 (3.21)
1.48
3.59†‡
* DS = Dry Swing, DS-EMS = Dry Swing and EMS
† Significant difference within groups at p≤0.05.
‡ Significant difference between groups at p≤0.05
Correlation
At baseline, this study documented a significant correlation between predicted 1RM bench press (r = 0.876, p
≤ .001), squat (r =.897, p .001) and torso rotation (r = .847, p ≤ .001) with batting velocity. After 8 weeks of
training, the analysis showed significant correlations between improvement in predicted 1RM torso rotational
and batting velocity for DS (r = .832, p ≤ .001) and DS-EMS (r = .873, p ≤ .001). While DS group showed no
significant (p > .05) correlation between gain in predicted 1RM bench press and squat and batting velocity,
DS-EMS group demonstrated significant (p ≤ .05) correlation between gain in predicted 1RM bench press (r =
545, p = .013) and predicted 1RM squat (r = 450, p = .047) and batting velocity.
Discussion
The primary finding of this study was additional of WB-EMS (three times a week) after swing training over
8 weeks demonstrated increase in muscular strength (bench press, squat, and torso rotational) and sports skill
performance (batting velocity) in collegiate female softball players.
In regards to predicted maximal strength (predicted 1RM) the DS-EMS group showed significant increases in
mean predicted 1RM bench press, squat, and torso rotational after 8 weeks of training. Gain in predicted 1RM
bench press and torso rotational have not been discovered by any study using WB-EMS yet. Nonetheless, gain
in predicted 1RM for lower body strength have been shown by one study using WB-EMS (Filipovic et al.,
2016). In Filipovic’s study, he demonstrated a significant increase in 1RM leg strength of +13.06% after 7
weeks of dynamic WB-EMS. Considering predicted 1RM strength test of squat results are in line with the
findings of studies using 12-28 sessions local EMS training (Babault et al., 2007; Filipovic et al., 2012;
Maffiuletti et al., 2000; Maffiuletti et al., 2002; Willoughby & Simpson, 1998) and findings using resistance
training (Szymanski et al., 2009; Szymanski, McIntyre, et al., 2007; Szymanski, Szymanski, et al., 2007; D. J.
Szymanski, J. M. Szymanski, et al., 2008) on the upper body, lower body, and torso rotational muscles in
trained athletes.
The studies using isometric and dynamic EMS on quadriceps femoris muscles showed significant increase in
Fmax isometric knee extensor up to +14.5% (Maffiuletti et al., 2002). Further EMS study also showed
significant gain of isokinetic torque in eccentric condition (+29% at -120 º·s-1; +17.9% at -60 º·s-1; p ≤ .01), and
concentric condition (+37.6% at 60 º·s-1 and +48.9% at 300 º·s-1; p .05) (Brocherie, Babault, Cometti,
Maffiuletti, & Chatard, 2005).
Previous study using resistance training demonstrated gains in bench press, squat, torso rotational and batting
velocity. Study by Szymanski, Szymanski, et al. (2007) indicate greater improvement in predicted 1RM bench
Whole-Body Electromyostimulation on Strength and Batting Velocity
press (+15.06%), predicted 1RM squat (+40.23%) and 3RM torso rotational (+17.1%) after following
resistance training and medicine ball training for 8 weeks. The results of improvement in strength and batting
velocity were correlated in this study for WB-EMS group. This was supported by previous study that also
indicated significant relationships between improvement scores of bench press, squat, and torso rotational
strength to improvement scores of batting velocity (Szymanski, Szymanski, et al., 2007).
The changes occurred in this study supports the kinetic link theory (Putnam, 1993). Putnam in his study
mentioned that if each of the muscles involved were improved in strength and velocity, it would be justifiable
that the greater momentum that generated from the large base segments (legs and hips) were then transferred
through the stronger torso muscles to the stronger, smaller adjacent segments such as shoulders and arms when
performing softball swing.
In additional, the interaction of three body segments which are hips, torso, and upper body were the segments
that a softball/baseball player depends on when they wanted to utilize their body as a kinetic link when
performing batting (rotational) movements. Shaffer, Jobe, Pink, and Perry (1993) in their study mentioned that
during the pre-swing and swing phase of hitting, the quadriceps, buttocks, and hamstring have a high level of
activity, which contributes to the legs’ stabilizing role needed to initiate power as the torso rotates during a
softball/baseball swing.
Conclusion
Three dynamic WB-EMS sessions in combination with normal 100 swings per week are sufficient for
effectively enhancing maximal strength and batting velocity in female collegiate softball players. This study
found that stimulation using WB-EMS training able to enhance softball players’ performance and also able to
complement or modify the common training structure. Further study is needed to investigate the use of
WB-EMS concurrently with swing training. This probably will be more time saving for the coaches in training
their players on the field.
Acknowledgement
We gratefully acknowledge the support of Faculty of Sports Science University Teknologi MARA
gymnasium and Miha BodyTec (United Lifestyle). None of the authors has any conflict of interest. We are also
grateful for the grant received from Research Management Institute (RMI): 600-RMI/MyRA 5/3/LESTARI
(32/2016).
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Conference Paper
Full-text available
Background: Electromyostimulation (EMS) is a training that uses electrical current to stimulate muscle contraction. The progression of EMS training is similar with principles of resistance training which are based on the parameters such as pulse frequency, electrical pulse, duration of rest, duration of contraction, the number of repetitions and the intensity (Hz) used. Rate perceived exertion (RPE) scale was used in monitoring the loading along the duration of EMS training while the percentage of repetition maximum (%RM) is globally use in monitoring loading of resistance training (RT). Since the unit of measurement for loading is different, therefore this study seek to find the relationship between multiple repetition maximum electrical pulses in EMS (miliAmpere-mA) and multiple repetition maximum lift (Kilogram-Kg) in free weight strength test. Methods: A total of 10 recreational athlete (age: 22±0.77, height: 155.6±0.92, weight: 51.6±1.02, %BF: 21.3±1.10) volunteered to participate in strength testing. Participants go through the adaptation of EMS and weight training. Multiple RM (1, 3, 5, 7, 9) was used to measure chest press and squat strength using National Strength Conditioning Association procedure. Data from the tests were analysed using Pearson Correlation. Results: There is significant positive strong relationship p<.01 between EMS and load lift for chest press (1RM; r = .96, 3RM; r = .86, 5RM; r = .91, 7RM; r = .93; 9RM; r = .94) and squat (1RM; r = .83, 3RM; r = .88, 5RM; r = .93, 7RM; r =.92, 9RM; r =.81). Discussion: The results indicate that both measurements were highly correlated between mA and Kg along the nine repetitions maximum strength test. Furthermore, it showed that both measurements can be applied in training to increase muscular strength.
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