ArticlePDF Available

Abstract and Figures

The aim of this study was to evaluate and compare the effect of two training protocols on the women’s arms strength by using the patented equipment of PowerBall® and Shake Weight®. 39 females, aged 21.6±1.1yrs with body mass 60.3±7.4kg and stature 164±0.6cm were randomly divided into three groups: the PowerBall® (PGr), the Shake Weight® (SGr) and the Control (CGr). The participants of the PGr & SGr trained for 18 days by using specific arms exercises while the women of the CGr did not perform any training program. In all studied women the hand-grip test as well as the forearm and arm girths of the dominant hand was evaluated before and after the completion of the testing protocol. The interaction among the variables in each group was assessed with the use of the factorial Analysis of Variance (ANOVA). The results showed that the women in PGr had a marginal improvement in the final hand- grip measurement (18.78±3.1kg) in relation to the participants of the SGr (18.65±3.1kg). In addition, the forearm and arm girths of the women of the PGr were slightly larger than those reported in the participants of the SGr. In conclusion, the present study justifies the effectiveness of the training with the use of the innovative PowerBall® and Shake Weight® which are the proper equipment for the upper limbs muscular strength in moderate trained women.
Content may be subject to copyright.

®

D.O.I: http: doi.org/10.4127/jbe.2016.0103
THEOPHILOS PILIANIDIS
1
, NIKOLAOS MANTZOURANIS
1
,
FANI BERBERIDOU
1
, ATHANASIA SMIRNIOTOU
3
,
MILTIADIS PROIOS
2
& KONSTANTINOS MICHALOGLOU
1
1
Democritus University of Thrace Greece,
Department of Physical Education and Sports Science
2
Aristotle University of Thessaloniki, Greece,
Department of Physical Education and Sports Science
3
Kapodistrian University of Athens, Greece,
Department of Physical Education and Sports Science

The aim of this study was to evaluate and compare the effect
of two training protocols on the women’s arms strength by using
the patented equipment of PowerBall® and Shake Weight®. 39
females, aged 21.6±1.1yrs with body mass 60.3±7.4kg and
stature 164±0.6cm were randomly divided into three groups:
the PowerBall® (PGr), the Shake Weight® (SGr) and the Control
(CGr). The participants of the PGr & SGr trained for 18 days
by using specific arms exercises while the women of the CGr
did not perform any training program. In all studied women
the hand-grip test as well as the forearm and arm girths of the
dominant hand was evaluated before and after the completion
of the testing protocol. The interaction among the variables
in each group was assessed with the use of the factorial
Analysis of Variance (ANOVA). The results showed that the
women in PGr had a marginal improvement in the final hand-
grip measurement (18.78±3.1kg) in relation to the participants
of the SGr (18.65±3.1kg). In addition, the forearm and arm
girths of the women of the PGr were slightly larger than those
 Inertia, Hand grip, Adaptations, Arm strength
VOLUME 12.1, 2016
112 JBE – VOL. 12.1, 2016
reported in the participants of the SGr. In conclusion, the present study justifies the
effectiveness of the training with the use of the innovative PowerBall® and Shake
Weight® which are the proper equipment for the upper limbs muscular strength in
moderate trained women.

In the modern multi-tasking societies both athletes and exercising individuals
are continuously looking for faster and more efficient methods to improve their
physical fitness. Every year a variety of innovative sport equipment is presented in
order to make the exercise more attractive to a wide range of population. In the USA,
it was recorded that the sports industry had made a profit of more than 5.8 billion
dollars because it had offered low budget equipment which improved the human
body in a safe and effective way (4). Recently, the research in technology has led to
many radical changes in the sports science offering more efficient products which
not only maintain but also increase physical fitness. Concerning the professional
equipment, the technology in sports has released low-cost innovative products
for the physical improvement of exercising individuals. Examples of these highly
reliable products include the Bodyblade® (14), Ab Circle Pro® (19) and Perfect
Pushup® (20).
Nowadays, the muscular strength is an important component in physical fitness.
The development of strength is a main priority for both men and women who
use the sport technology in order to imitate the professional training of top-level
athletes by using similar training equipment. More specifically, a kind of training
products based on the racket (tennis, badminton, etc.) and combative sports
(judo, wrestling, etc.) has been presented in the fitness trade, which focuses on
the women’s upper body stamina development (8). In addition, relevant studies
have proved the interaction between the forearm and arm strength with the ideal
performance in individual sports such as boxing and tennis (17,13). Similarly,
another study reported that the specific arm training prevents the female athletes
from muscular injuries in baseball and softball (6).
Recently, in sports and rehabilitation market the revolutionary equipment of
PowerBall® (a spherical hand-held gyroscopic exerciser) and Shake Weight®
(dumbbell shaped fitness device) are presented. According to our knowledge,
limited research analyzing the effectiveness of the above innovative products
on the women’s physical fitness has been conducted. Therefore, the objective
of this study was to evaluate and compare the potential beneficial effect of the
two training protocols with the use of the patented equipment of PowerBall® and
Shake Weight® on the arms muscular strength in moderately trained women.
THE USE OF THE POWERBALL® AND SHAKEWEIGHT® IN MODERATE TRAINED WOMEN 113

Instruments
PowerBall® is a hand-held gyroscopic exerciser which literally explodes with
mind numbing inertial forces once you activate its internal rotor. First patented
as a therapeutic device or an exerciser in 1973 in USA as Dynabee (15) it was
later implemented under different names such as Roller ball or Gyrotwister (10).
PowerBall® does not demand batteries while it generates resistance between 1 and
75kg depending on the rotor speed. The NSD PowerBall® (Nano Second, Taiwan),
which was used in the present study, was the Regular type with digital counter
(Picture I). The above female plastic version weights 280gr with a diameter of 7cm
and it generates resistance of approximate 18kg in a maximum of 15.000reps.min-1
(http://www.PowerBallnsd.com).
 The patented equipment of PowerBall®.
Shake Weight® is a dumbbell-shaped fitness device that oscillates, purportedly
increasing the effects of exercise. The above modified dumbbell firstly designed
specifically for women and it is a non-motorized mechanical device based on
“vibration plate technology” (Fitness IQ, LLC, USA). While gripping the Shake
Weight® with one or both hands, users vigorously shake the weight back and
forth. Springs on both ends allow the weight to move back and forth, creating
a resistance. Per official company press releases, “based on a groundbreaking
workout technology called Dynamic Inertia, which engages the muscles in the
arms, shoulders and chest in an entirely new fashion, the Shake Weight® increases
upper body muscle activity by more than 300% compared to traditional free
weights” (https://www.theshakeweight.com). The women version (Classic) which
was used in this study weights 1.130gr (Picture II).
114 JBE – VOL. 12.1, 2016
 The patented equipment of ShakeWeight®.
Research Design
For the nature of this study the subjects were randomly divided in three (3)
groups of thirteen (13): the PowerBall® group (PGr), the Shake Weight® group
(SGr) and the Control group (CGr) in which the women did not perform any
training program. The testing protocol was fully explained to each subject but
they were not informed of the specific purpose of the study. A week before the
beginning of the testing, the subjects were familiarized with the training equipment
by the researchers. The participants of the groups PGr and SGr exercised in 18
consequently training sessions (7d.wk-1) with the specific program depending on
the equipment. The training protocols of the PGr and SGr were applied according
to each product manufacturers’’ recommendations for exercise commonly aiming
at the development of the subjects’ forearm and arm muscular strength.
Training procedures
Upon firstly reported at the University lab, body mass and stature of the studied
subjects were measured. Body mass was measured at the nearest 100g on a
calibrated floor scale (Seca 770). The subject was standing in the center with relaxed
arms, without shoes and wearing only light sportswear. Stature was measured
with a stadiometer (Seca 240) at the nearest 0.1cm in bare feet with the head
in Frankfort horizontal plane. In the total amount of the women who participated
in the present study, the hand-grip test (Takei 5101) and the forearm and arm
girths of the dominant hand were measured before and after the completion of the
testing protocol. From a standing position, the women who participated in the PGr
trained with dynamic, continuous and maximal exercise (Picture III).
THE USE OF THE POWERBALL® AND SHAKEWEIGHT® IN MODERATE TRAINED WOMEN 115
 Pictorial presentation of the dominant hand exercise by using the PowerBall®.
In addition, the training of the women of the SGr was based on 2 double-handed
on the even plane front exercises aiming at the improvement of the local muscle
(forearm & arm) endurance (Pictures IV,V).
 The exercises which were applied by using the ShakeWeight®.
All the testing sessions were carried out at the same time of the day in identical
training conditions with the ambient temperatures ranging from 18°C to 22°C.
During the training sessions verbal motivation and a kind of feedback about their
performance was provided. The programs of the training groups are presented in
Table 1.
116 JBE – VOL. 12.1, 2016

The training programs which were applied in the women who participated
in the PowerBall® and ShakeWeight® groups.

®®
 4set per arm 2 exercises x 4set each
 20s per arm
(5s preparatory-15s normal) 15s in each exercise
 Maximal-Constant-Continuous
(250Hz) Maximal-Continuous
 20s (1:1) per arm 2min between the set in each exercise
4min between the 2 exercises
Participants
A total of 39 moderate trained female volunteered to take part in this study in
response to a request for participants. The subjects’ mean age was 21.6±1.1yrs,
the body mass 60.3±7.4kg, the stature 164±0.6cm and they had a similar fitness
level (4-5yrs). All were on good health, physically active with varied sporting
backgrounds but none had a high degree of specialist training. Prior to the
beginning of the testing procedures, all subjects completed a questionnaire on
their medical history and it was confirmed that they had no previous history of
upper limb injuries. The study was performed according to the rules of the Ethics
Committee of the Democritus University of Thrace.
Statistical analysis
Descriptive statistics with exploration was firstly generated for all categorical
variables while the scatterplots were used in order to determine whether a linear
model is reasonable for the studied variables. The statistical design for the evaluated
variables of this study was based on the factorial analysis of variance (ANOVA).
The interaction of the 18 training sessions on the measured variables in each group
(3 x 2) was assessed in the analysis of the depended factor “measurement” (hand
grip-forearm/arm girths) and with independent factor “time” (pre-post training).
The Tukey’s HSD test(post-hoc multiple comparisons) was applied in order to
identify the inter groups (PGr-SGr-CGr) statistically significant differences in the
measured variables of this study. The acceptable level of significance was set
at 0.05 and all results were reported as mean ± standard deviation. IBM-SPSS
THE USE OF THE POWERBALL® AND SHAKEWEIGHT® IN MODERATE TRAINED WOMEN 117
statistical software version 19.0 for Windows (SPSS Inc., Chicago, IL, USA) was
used for data management and statistical calculations.

The mean values of the hand-grip test in the final measurements were better
(17.86kg) than the initial ones (15.95kg) for both training groups (PGr & SGr)
although they did not present any statistically significant differences (F=2.32,
p=0.11). In addition, the mean values in the final hand-grip measurement of the PGr
were higher than those of the SGr without any recorded significant differences as
well. The Bonferroni multiple comparisons showed that the mean values in the final
hand-grip testing measurement of the females who performed in the PGr (18.78kg)
and SGr (18.65kg) were better than those of the participants of the CGr (16.17kg).
Similarly, the mean values of the dominant hand girths of the studied women in
both PGr and SGr did not significantly differentiate (F=0.13, p=0.88) from the first
to the last measurement as far as the forearm (22.15cm vs 22.20cm) and the arm
is concerned (26.35cm vs 26.82cm). Furthermore, the evaluation of the differences
among the training groups (PGr & SGr) and the control group (CGr) during the
final measurements showed that, the women in PGr and SGr increased the mean
values in forearm and arm girths while the participants of the CGr did not present
any improvement from the first to the last measurement in the above girths of the
dominant hand. More specifically, the training program in the women of the PGr
offered a higher increase in their forearm and arm girths in comparison to the
program which was applied to the participants of SGr but without any statistically
significant differences. The results of the measurements in all testing groups (pre-
post) are presented in Table 2.

The measuring parameters of all studied groups (mean±SD).
 ®®

Pre Post Pre Post Pre Post

16.41±3.7 18.78±3.1 15.77±4.5 18.65±3.1 15.68±3.7 16.17±4.1

22.25±1.4 22.63±1.6 21.56±1.3 21.89±1.4 22.63±1.6 22.64±1.6

26.03±3.2 26.30±2.8 25.24±2.5 25.39±2.9 27.80±3.9 27.79±3.9
118 JBE – VOL. 12.1, 2016

The major finding of this study was that the volume, the intensity and the duration
of both training protocols which were applied in the studied women’s by using
the PowerBall® and Shake Weight® open the “window of muscular adaptations”
(9). In accordance with the relevant literature which evaluates the above exercises
with the surface electromyography (EMG), the current study confirms that both
training programs with the use of the PowerBall® and Shake Weight® activate the
involved muscles of the upper body in a quite satisfactory way (7). In conjunction
with the bibliography which observed that the muscular endurance training
reflects adaptations in upper limbs strength in female athletes, this study showed
that the workout structure and the selected exercises of PowerBall® and Shake
Weight® improve muscular endurance in the dominant hand in moderate trained
women (1, 5).
More specifically, from the results of this study, it was shown that the women
who exercised with the PowerBall® had greater hand-grip values in the final
measurement of their dominant hand in relation to those who trained with the
use of the Shake Weight®. The above findings were interpreted by the fact that
the centrifugal power which was applied during the rotor spin-up exercise by the
use of the PowerBall® primarily affected the tone in the wrist and the forearm (2) in
comparison to the ShakeWeight® which, with the vibrated notion of training reflects
a muscular activation in both exercised forearm and arm (3).
In addition, the training protocols which were applied by using the PowerBall®
and Shake Weight® increased marginally the forearm and arm girths of the
dominant hand from the initial to final measurement in the studied women. It is
therefore interesting that the training with the PowerBall® offered a greater increase
the women’s arm girth (27mm) in the final measurements in comparison to the
lower increase which was recorded in the arm girth (15mm) of the participants in
the Shake Weight® group. The above findings are consistent with other studies
which showed that the muscular endurance derived from the PowerBall® maximizes
the training outcomes of each exercised hand (16, 18). In contrast, the exercises
which are based on the vibration technology of Shake Weight® aim at the muscular
fitness of both hands (11, 12).

In summary, this study showed that both PowerBall® and Shake Weight® are
easy to use products and completely adjusted to the physical characteristics and
demands of women, fulfilling their needs for safe and effective exercise. The above
THE USE OF THE POWERBALL® AND SHAKEWEIGHT® IN MODERATE TRAINED WOMEN 119
innovative training equipment which is not only easy to carry and use but also of
low cost is beneficial for the upper limbs muscle endurance in moderate trained
women. Future research based on the use of the PowerBall® and Shake Weight®
products in longer exercising periods and in a variety of muscle endurance or
hypertrophy training programs could possibly be the “key” difference in the upper
body muscular fitness in top-level or recreational athletes.

1. Adair RK. Play ball! Science 268 (5218): 1681-1682, 1995.
2. Bosco C, Cardinale M and Tsarpela O. Influence of vibration on mechanical
power and electromyogram activity in human arm flexor muscles. Eur J Appl
Physiol 79: 306-311, 1999.
3. Brehm ΒΑ. Too good to be true? Protect yourself from health fraud. Fitness
Manag www.fitnessmanagement.com, 2002.
4. Chan FMA. A ton to prevention: The fitness industry. www. forbes.com, 2002.
5. Chow JW, Carlton LG, Lim YT, Shim JH et al. Muscle activation during the
tennis volley. Med Sci Sports Exerc 31(6): 846-854, 1999.
6. Coleman EA. 52-Week baseball training. Champaign IL: Human Kinetics, 2000.
7. Glenn MJ, Cook I, Di Brezzo R, Gray M, et al. Comparison of the shake
weight® modality exercises when compared to traditional dumbbells. J
Sports Sci Med 11: 703-708, 2012.
8. Guidetti L, Musulin A and Baldani C. Physiological factors in middleweight
boxing performance. J Sports Med Phys Fitn 42: 309-314, 2002.
9. Hakkinen K. Factors influencing trainability of muscular strength during short
term and prolonged training. NSCA J. 7: 32–34, 1985.
10. Heyda PG. Roller ball dynamics revisited. Am J Physiol 70(10): 1049-1051,
2002.
11. Houston EM. Gaining weight: The Scientific basis of increasing skeletal muscle
mass. Can J Appl Physiol 24(4): 305-316, 1999.
12. Kraemer WJ, Adams K, Cafarelli E, Dudley A et al. Progression models in resistance
training for healthy adults. Med Sci Sports Exerc 34(2): 364-380, 2002.
13. Kraemer WJ, Hakkinen K, Triplett-McBride NT, Fry CA et al. Physiological
changes with periodized resistance training in women tennis players. Med Sci
Sports Exerc 35(1): 157-168, 2003.
14. Lister JL, Del Rossi G, Ma F, Stoutenberg M et al. Scapular stabilizer activity
during body blade, cuff weights, and thera-band use. J Sport Rehabilon 16(1):
50-67, 2007.
15. Mishler AL. Gyroscopic device. U.S. Patent 3726146, 1973.
120 JBE – VOL. 12.1, 2016
16. Mueller KJ and Buehrle K. Comparison of static and dynamic strength of the
arm extensor muscles. IN: Biomechanics X-A. Johnson B. (Ed.), Champaign,
IL Human Kinetics, 1987, pp 501-505.
17. Murphy P. and Forney J. Complete conditioning for Baseball. Complete
conditioning series. Champaign, IL: Human Kinetics, 1997, pp 89-125.
18. Puch SF, Kovaleski JE, Heitman RJ and Gilley WF. Upper and lower body
strength in relation to ball speed during a serve by male collegiate tennis
players. Percept Motor Skills 3(1): 867-872, 2003.
19. Willardson J, Behm D, Huang S, Rehg M et al. A comparison of trunk muscle
activation: Ab circle vs traditional modalities. J Strength Cond Res 24(12):
3415-3421, 2010.
20. Youdas JW, Budach BD, Ellerbusch JV, Stucky C et al. Comparison of muscle-
ctivation patterns during the conventional push-up and perfect pushup
exercises. J Strength Cond Res 24(12): 3352-3362, 2010.
Address for correspondence:
Theophilos Pilianidis, Associate Professor
Democritus University of Thrace,
Department of Physical Education & Sports Science,
University Campus, 69130, Komotini, Greece,
E-mail: thpilian@phyed.duth.gr
ResearchGate has not been able to resolve any citations for this publication.
Full-text available
Article
In order to stimulate further adaptation toward a specific training goal(s), progression in the type of resistance training protocol used is necessary. The optimal characteristics of strength-specific programs include the use of both concentric and eccentric muscle actions and the performance of both single- and multiple-joint exercises. It is also recommended that the strength program sequence exercises to optimize the quality of the exercise intensity (large before small muscle group exercises, multiple-joint exercises before single-joint exercises, and higher intensity before lower intensity exercises). For initial resistances, it is recommended that loads corresponding to 8-12 repetition maximum (RM) be used in novice training. For intermediate to advanced training, it is recommended that individuals use a wider loading range, from 1-12 RM in a periodized fashion, with eventual emphasis on heavy loading (1-6 RM) using at least 3-min rest periods between sets performed at a moderate contraction velocity (1-2 s concentric, 1-2 s eccentric). When training at a specific RM load, it is recommended that 2-10% increase in load be applied when the individual can perform the current workload for one to two repetitions over the desired number. The recommendation for training frequency is 2-3 d·wk-1 for novice and intermediate training and 4-5 d·wk-1 for advanced training. Similar program designs are recommended for hypertrophy training with respect to exercise selection and frequency. For loading, it is recommended that loads corresponding to 1-12 RM be used in periodized fashion, with emphasis on the 6-12 RM zone using 1- to 2-min rest periods between sets at a moderate velocity. Higher volume, multiple-set programs are recommended for maximizing hypertrophy. Progression in power training entails two general loading strategies: 1) strength training, and 2) use of light loads (30-60% of 1 RM) performed at a fast contraction velocity with 2-3 min of rest between sets for multiple sets per exercise. It is also recommended that emphasis be placed on multiple-joint exercises, especially those involving the total body. For local muscular endurance training, it is recommended that light to moderate loads (40-60% of 1 RM) be performed for high repetitions (> 15) using short rest periods (< 90 s). In the interpretation of this position stand, as with prior ones, the recommendations should be viewed in context of the individual's target goals, physical capacity, and training status.
Full-text available
Article
The aim of this study was to evaluate the influence of vibration on the mechanical properties of arm flexors. A group of 12 international level boxers, all members of the Italian national team, voluntarily participated in the experiment: all were engaged in regular boxing training. At the beginning of the study they were tested whilst performing forearm flexion with an extra load equal to 5% of the subjects' body mass. Following this. one arm was given the experimental treatment (E; mechanical vibration) and the other was the control (no treatment). The E treatment consisted of five repetitions lasting 1-min each of mechanical vibration applied during arm flexion in isometric conditions with 1 min rest between them. Further tests were performed 5 min immediately after the treatment on both limbs. The results showed statistically significant enhancement of the average power in the arm treated with vibrations. The root mean square electromyogram (EMGrms) had not changed following the treatment but, when divided by mechanical power, (P) as an index of neural efficiency, it showed statistically significant increases. It was concluded that mechanical vibrations enhanced muscle P and decreased the related EMG/P relationship in elite athletes. Moreover, the analysis of EMGrms recorded before the treatment and during the treatment itself showed an enormous increase in neural activity during vibration up to more than twice the baseline values. This would indicate that this type of treatment is able to stimulate the neuromuscular system more than other treatments used to improve neuromuscular properties.
Article
Individuals are continuously looking for faster, more efficient methods with which to develop physical fitness. This has led to the development of products and programs marketed towards increasing physical fitness in minimal time. The Shake Weight(®) (SW) has been advertised to increase muscular strength among other factors in less time than traditional weightlifting. The purpose of this study was to compare the electromyographic (EMG) muscle activity of the SW to a traditional dumbbell (DB) performing the same exercises. Twelve men (22.9 ± 1.6 years) and 13 women (23.0 ± 1.9 years) volunteered to participate in this study. Subjects performed the chest shake (CS), biceps shake (BS), and triceps shake (TS) using the SW and DW. Maximal voluntary isometric contractions (MVIC) were exhibited for all muscles. EMG activity was recorded for the pectoralis major (PM), triceps brachii (TB), biceps brachii (BB), anterior deltoid (AD), trapezius (TR), and rectus abdominus (RA) and compared to detect differences between modalities. EMG activity for each muscle group was reported as a percentage of each subject's individual MVIC. A repeated measures ANOVA revealed no significant differences between the SW and DB modalities during each exercise for all muscles except the BB (p < 0.05). During the CS exercise muscle activity was significantly greater for DB in the BB muscle when compared to the SW mode (50.8 ± 28.9%; 35.8 ± 30.8%). The SW did not have any advantage over the DB for any exercise, nor for any muscle group. Further, no muscle group during any of the SW trials exhibited an MVIC over 60%, the level necessary to increase muscular strength.
Article
The rotor in a hand held gyroscopic device can be accelerated to high revolutions by simple movements of the hand. The dynamics of the device is presented with straightforward mathematics while maintaining realistic physics.
Article
The purpose of this study was to compare the activation of the rectus abdominis (RA), external oblique abdominis (EO), lower abdominal stabilizers (LASs), and lumbar erector spinae (LES) during performance of 3 traditional trunk exercises vs. exercise on the Ab Circle device. Surface electromyography was used to assess 12 subjects (6 men, 6 women) for 6 exercise conditions, including: abdominal crunch, side bridge, quadruped, and Ab Circle levels 1-3. For the RA, the abdominal crunch elicited significantly greater activity vs. the Ab Circle level 1, and the side bridge elicited significantly greater activity vs. the Ab Circle levels 1 and 2. For the EO, the side bridge elicited significantly greater activity vs. the quadruped. No significant differences were noted between conditions for the LASs. For the LES, the side bridge and quadruped elicited significantly greater activity vs. the abdominal crunch. The results of this study indicate that the anterior, posterior, and lateral trunk musculature can be activated to similar or even greater levels by performing the 3 traditional trunk exercises vs. the Ab Circle. This was particularly evident for the side bridge exercise, which elicited significantly greater activity of the RA vs. the Ab Circle levels 1 and 2, and elicited similar activity of the EO, LASs, and LES at all 3 Ab Circle levels.
Article
Manufacturers of Perfect·Pushup™ handgrips claim enhanced muscular recruitment when compared with the conventional hand-on-floor push-up exercise. Electromyographic (EMG) data were recorded using surface electrodes from the right-sided triceps brachii, pectoralis major, serratus anterior (SA), and posterior deltoid muscles during push-ups performed from 3 different hand positions: (a) shoulder width, (b) wide base, and (c) narrow base (NB). Push-ups were performed under 2 conditions: (a) standard push-up and (b) Perfect·Pushup™ handgrips. We recruited 20 healthy subjects, 11 men (24.9 ± 2.6 years) and 9 women (23.8 ± 1 years). Subjects completed 3 consecutive push-ups for each hand position under both conditions. Push-up speed was controlled using a metronome, and testing order was randomized. We recorded peak EMG activity for each muscle during each of the push-ups and normalized EMG values by maximum muscle contractions (% maximum voluntary isometric contraction [MVIC]). Electromyographic data were analyzed with 3 (hand position) × 2 (condition) repeated-measures analysis of variance with a post hoc Bonferroni-adjusted simple effects test to detect significant position effects for position by condition interactions (α = 0.05). A push-up required considerable muscle activation of the triceps brachii (73-109% MVIC), pectoralis major (95-105% MVIC), SA (67-87% MVIC), and posterior deltoid (11-21% MVIC) whether performed using the conventional hand-on-floor position or the Perfect·Pushup™ handgrips. The NB hand position was most effective for preferentially activating the triceps brachii and posterior deltoid muscles. Based upon EMG activation from 4 muscles, the Perfect·Pushup™ handgrips do not appear to preferentially enhance muscular recruitment when compared with the conventional push-up method.
Article
To broaden our understanding of muscle function during the tennis volley under different ball placement and speed conditions by examining the activity of selected superficial muscles of the stroking arm and shoulder (flexor carpi radialis, extensor carpi radialis, triceps brachii, deltoids, and pectoralis major) and muscles related to postural support (left and right external oblique, lumbar erector spinae, and gastrocnemius) during the volley. Seven skilled tennis players were asked to perform volley strokes under 18 experimental conditions, including variations in lateral contact location (forehand and backhand), ball contact height (high, middle, and low), and ball speed (fast, medium, and slow). A ball machine was modified so that the subjects could not predict the ball trajectory before it was released from the machine. Muscle activity was determined using surface electromyographic (EMG) techniques, and the critical instants of a volley were determined using two force platforms and two high-speed (120 Hz) video cameras. Average EMG values for different phases of the volley, defined by the critical instants, were computed. In general, muscle activity increased with increasing ball speed. The extensor carpi radialis was more active than the flexor carpi radialis during both forehand and backhand volleys, suggesting the importance of wrist extension/abduction and grip strength. The increase in EMG levels in the forearm muscles shortly before the ball impact indicated that the subjects did not tighten their grip and wrist until moments before ball impact. Both antero-middle and postero-middle deltoids were active in most stroke phases. However, the roles of the deltoid muscles during a volley cannot be determined without knowing the actions of the other shoulder joint muscles.