International Journal of Aquatic Research and Education, 2010, 4, 61-69
© 2010 Human Kinetics, Inc.
Muscular Activity of the Posterior
Deltoid During Swimming vs. Resistance
Exercises on Water and Dry Land
Xavier García Massó and Juan Carlos Colado
The purpose of this study was to compare muscular activity of the posterior deltoid
muscle during three typical aquatic physical conditioning activities. This interpreta-
tive case study involved a 23-year-old elite swimmer and athlete. Muscular activity
was measured with surface electromyography during swimming crawl at maximum
speed, and also while performing horizontal shoulder abduction using elastic band
and Hydro-Tone Bells resistance. During the maximum voluntary contraction, we
observed what appeared to be meaningful differences between the percentage of
muscular activation during the swimming activity and that observed during the
elastic band and aquatic resistance exercises (18.72% vs. 74.84% and 65.46%,
respectively). No meaningful differences were observed between the percentage of
muscular activation for the elastic band and aquatic resistance exercises. Resistance
exercises, both in and out of the water, produce more muscle activation and may
be more efcient for improving muscular strength than sprint crawl swimming.
Prescribing physical exercise for health reasons is the process by which a
medical professional recommends that an individual undertake a personal exercise
regimen in a systematic and individualized manner. The main objective of exercise
prescription is to encourage people to increase their level of physical activity in an
individually appropriate manner maximizing the health benets (e.g., increasing
cardiorespiratory capacity, improving strength) and minimizing adverse effects
(e.g., soreness, injuries). For an exercise prescription, the purposes, interests,
needs, environment and health status of the individual are all taken into account to
create a set of personal objectives (Jiménez, 2003). Many professional elds and
organizations have highlighted the alarming rate of chronic degenerative cardio-
vascular disease in the more technologically advanced societies (Cabri, Annemans,
& Clarys, 1988; Dishman, Washburn, & Heath, 2004). This is particularly true in
Spain, where cardiovascular disease accounts for 60% of total deaths and is, in
fact, the leading cause of death and disease in the country (NIS, 2002). Conse-
quently, since the 1960s, prescriptive physical conditioning programs for healthy
individuals almost exclusively have involved aerobic exercise while at the same
time underestimating the importance of other essential physical factors, such as
muscle strength (Zimmermann, 2004). Among others, this is one of the reasons
The authors are with the University of Valencia, Department of Physical Education and Sports in
62 García Massó and Colado
why the 7th leading cause of disease in Spain (NIS, 2002) is related to changes in
the osteomuscular system and in the connective tissue that manifests as functional
disabilities preventing carrying out essential everyday tasks with the consequent
reduction in the quality of life. On the other hand, it is known that having a well-
functioning musculoskeletal system is linked to a reduction in one or more heart
disease risk factors and that a suitable percentage of lean muscle mass enhances
overall maintenance of appropriate body composition (Graves & Franklin, 2001).
One of the most important criteria for exercise training is that certain “demands”
must exist to create the ideal conditions for the adaptation process to be carried out
effectively. It is necessary to combine sufcient frequency, intensity, duration, and
specic type of exercise modality to produce a suitable overload that results in an
optimal adaptation or “training effect.” Creating an optimal overload depends on
the amount (i.e., frequency, intensity, and duration) of the stimulus, which in turn
should depend on the needs of the person exercising (ACSM, 1998).
The pressing need for this study emerges when advanced societies such as
Spain’s begin taking up healthy physical activities in their leisure time (Sánchez,
1996). We know from works by Martínez (1999) that swimming is among the most
widely practiced sports in Spain as a leisure activity especially when persons desire
to improve their levels of physical tness. Since Greek and Roman times, the water
environment has been considered an ideal surrounding in which to improve one’s
level of physical tness. As a result, different swimming styles are usually recom-
mended as a means of improving the general physical conditioning of the population.
It is assumed that they are not only effective in improving aerobic capacity but also
muscle strength. According to the basic guidelines for prescribing health-related
physical exercise mentioned previously, it is worth asking if swimming activities
are a suitable means for improving physical conditioning oriented toward muscular
tness. Alternatively, should we recommend that people follow new aquatic exercise
criteria established for improving muscle performance and endurance such as those
outlined by Koury (1998); Sova (2000); Sanders (2001); Colado and Moreno (2001);
Colado, Moreno, and Baixauli (2002); and Colado (2002, 2003, 2004).
There are relatively few electromyographic studies in water that have attempted
to prove that swimming activities may be effective in creating sufcient stimuli for
improving upper extremity strength and to discover if such strength actually applies
broadly to all shoulder girdle muscle groups. Even scarcer are those studies that have
evaluated the muscle response to exercises as common as those performed during
aquatic resistance exercises. The lack of research is of great relevance since it is
necessary to monitor that muscle conditioning practices being carried out within
the normal population during their leisure activity to establish whether they are as
safe as they are effective.
In view of the lack of research focused on swimming and muscular strength,
this pilot study evaluated differences in shoulder muscle activity produced when
swimming front crawl stroke compared with the change in strength of muscle
groups producing horizontal shoulder abduction using Hydro-tone Bells in the
water. In addition, we evaluated a similar dry-land exercise using an elastic band
as a control group reference for interpreting muscle activity results. Finally, it must
be pointed out that although case studies such as the current study do not normally
lead to representative results, they are often appropriate for establishing hypotheses,
corroborating methodological procedures, and, in short, they serve as a basis for
Posterior Deltoid Muscular Activity 63
initial debate and the development of subsequent larger scale studies (Heinemann,
2003; Thomas & Nelson, 2001).
An elite level 23 year old athlete (1.79 m in height, 65kg in weight and with a body
mass index of 20.29 kg/m2) volunteered to take part in this case study. A regular
swimmer since the age of 6 years, he typically combines competitive swimming
training with water polo, triathlons, and long distance open water swimming. His
competitive level is high, having won several national prizes over the past two years.
He typically trains six weekly swimming sessions at an average to high level of
intensity over a period of 1 hr and 30 min, plus seven more sessions in which he
combines cycling, running, water polo, and resistance exercises. The participant
had neither general cardiovascular nor osteomuscular contraindications nor general
or local problems in scapulo-humeral and scapulo-thoracic joints at the time of the
study. We should also point out that the participant was familiar with the proposed
resistance exercise on dry land and with the front crawl stroke but not with the
aquatic resistance exercise using Hydro-tone Bells employed in this study.
First, it should be pointed out that it was not considered appropriate for the partici-
pant to take part in several sessions to become familiarized with the movements to
be evaluated for these reasons: (a) Dry land exercises were callisthenic single joint
movements with minimum psycho-motor demand and with which the subject was
already familiar; (b) the swimming exercise consisted of performing front crawl, a
stroke with which he has competed and won prizes; (c) although he had never used
the “aqua gym,” the aim was for him to experience them just as many other new
exercisers do during their rst sessions. The idea of this was to check what type of
stimulus such a novel movement creates despite the lack of familiarity, balance,
and isolation that occurs in experienced performers, considering that when expe-
rienced on the “aqua gym” mechanism, the stimulus generated by the participant
during exercise may be even higher. Intervals of approximately 10 min rest occurred
between the three different exercise sessions performed. The temperature of the pool
air environment was 31°C, 65% humidity level, and water temperature was 29°C.
We measured muscular activity using surface electromyography, model ME6000
of the Mega brand (Mega Electronics, Kupio, Finland). Self-adhesive electrodes
were applied (Ag-AgC1) with conductor gel (Medicotest, M-00-S, Olstikke, Den-
mark). For the aquatic measurements, we employed a kit for aquatic use consisting
of a waterproof cover with integrated electromyography (EMG) electrodes and a
“Compact Flash” 256 MB capacity memory card. All data collected were analyzed
with the software provided by the manufacturer (Mega Win v.2.3). To evaluate
muscle activity, we recorded the gross signal using a sampling frequency of 1000
64 García Massó and Colado
Hz and applied a quadratic mean (RMS) smoothing procedure at 0.05 s intervals.
The signal was preamplied with a preamplier placed 6cm from the electrodes (1μ
V sensitivity, 305 gain, 8–500 Hz band). The data analyzed t the peak amplitude
obtained in a brief period during which the muscle reached its maximum contraction
intensity during the concentric phase of the movement. We followed techniques
employed by other authors both for the placing and securing of electrodes as well
as for the treatment and analysis of the data (e.g., Hintermeister, Lange, Schultheis,
Bey, & Hawkins, 1998; Kelly, Backus, Warren, & Williams, 2002; Kelly, Roskin,
Kirkendall, & Speer, 2000; Pöyhönen, 2002; Soderberg & Knutson, 2000).
Assessment of the Maximum Voluntary Contraction. Once we determined that
the electrodes were in full working condition, we instructed the participant on
the movement to be conducted for obtaining a maximum voluntary contraction
(MVC). This involved pulling a nonelastic rope xed to the wall in such a way that
the upper extremities are positioned according to Kelly et al.’s (2002) description:
90° glenoid humerus abduction in the scapular plane with 45°external rotation
of the humerus, 20° elbow exion with no intervention by any other part of the
body. A submaximal trial was performed followed by a 2 min rest, after which
two maximum attempts were performed with a recovery interval of 3 min, with
subsequent analysis of the highest recording.
Horizontal Shoulder Abduction With Elastic Band. Once the MVC had been
determined, we instructed the participant about how to perform the movement
for conducting the dry land trial. This consisted of a horizontal shoulder abduc-
tion movement with the glenoid humerus joint in the same position as that of the
MVC trial. The subject held a light “Thera-Band” elastic band, measuring 1 m
in length when not expanded, at a distance that enabled him to perform approxi-
mately 15 repetitions with an effort valued at between 7 and 9 according to the
OMNI-RES scale (Robertson et al., 2003) or the qualitative equivalent of “hard.”
Held at this distance, he was to perform the movement without the elastic band
losing its complete tension in the eccentric phase and completing the concentric
phase to the pectoral level. Performance speed for exercisers at this level was
that recommended by the ACSM (2002), that is, a fast speed. The performer
completed two nonconsecutive submaximal phases during which we determined
the relative percentage of MVC used, then rested for ve minutes, and carried
out a nal series according to the criteria described previously.
Horizontal Shoulder Abduction With Hydro-Tone Bells. Once the exercise had
been carried out on dry land with the elastic band, we showed the participant the
movement to make for the aquatic exercise. This movement consisted of a hori-
zontal shoulder abduction movement with the glenoid humerus and elbow posi-
tion identical to that maintained in the MVC trial. The participant was to perform
a sideways arm-raising movement described by Colado (2003, 2004) with the
Hydro-Tone Bells (Aquatic Fitness Systems, Inc., Huntington Beach CA), mate-
rial that increased the frontal and drag resistance. To guarantee greater stability
during the movement and therefore increased performance speed and resistance,
the participant positioned himself with one leg forward and the other leg resting
on the pool wall. Both knees and hips were slightly exed to guarantee better
immobility of the spine and greater stability of the movement. The separation
distance between the feet was slightly greater than that of the width of the hips.
Posterior Deltoid Muscular Activity 65
Wrists were kept straight ahead of the forearm with resistance materials under
water so that depth of immersion reached the acromion when hips and knees were
slightly exed. In the horizontal adduction movement, the hydrodynamic position
of the Hydro-Tone Bells was not altered with regard to the abduction movement.
After both verbal and visual instructions the participant got into the water and
performed some warm-up exercises for around three minutes. He then performed
several movements according to the technique described, and we provided verbal
corrections as appropriate. Immediately after he performed two nonconsecutive
series of 15 repetitions to determine the speed at which the valid series should be
performed according to his perception, he recovered for ve minutes and performed
the denitive trial. Intensity control was conducted according to the same criteria
followed in the elastic band trial.
Performance of the Crawl Swimming Exercise at Maximum Speed. Given his
competitive swimming history, as well the indications made by the trainers of
the participant studied, it was not necessary to explain the technique of the sprint
front crawl swimming stroke to him. Therefore, once he had recovered and the
equipment was secured so that it ensured comfortable movement, we proceeded
to evaluate the muscle response over a distance of 25 m at the maximum possible
speed, using the above mentioned sprint crawl swimming stroke. After a warm
up in the water, the participant performed a single 25 m trial.
In this section we compare descriptively the values obtained in each assessment.
Muscular activity of the posterior deltoid was higher in the horizontal shoulder
abduction (dry-land—3001.73 μV ± 450.11- and aquatic medium –2643.18 μV ±
317.89) than in swimming crawl at maximum speed (750.82 μV ± 141.58). These
values correspond to 74.84%, 65.46%, and 18.72% of the MVC, respectively; how-
ever, there was not a large difference between the percentage of muscular activation
for the elastic band exercise and the aquatic resistance exercise.
We also observed that in the last repetitions of the set performance in the aquatic
medium, a major variability appeared in the level of muscular activation in a dif-
ferent manner than the values of the dry land exercise. This variation corresponded
with the moment at which it was possible to observe a minor stabilization of the
body during the performance of the aquatic movement. Apparently what happened
was that while the participant was adjusting his body position while also trying to
generate a rapid horizontal shoulder abduction movement may have increased the
resistance associated with aquatic drag forces, which caused the high variability
between repetitions (i.e.,: #12 rept (3401 μV), #13 rept (2801 μV), #14 rept (3200
μV), #15 rept (2208 μV).
According to Zimmermann (2004), the minimum intensity of strength training
that produces a training effect, at least in untrained or scarcely trained muscles,
should be around 40% of MVC. Therefore, those exercises prescribed for such a
purpose must at least exceed this threshold. Clarys (1988) studied muscle activ-
66 García Massó and Colado
ity in crawl swimmers performing at maximum speed. To do so, he recorded 25
muscle groups over the whole body, nding that only two of these muscle groups
managed to clearly exceed 40% MVC activity. Paradoxically, the 40% threshold
appeared in stabilizing rather than dynamic muscles, such as the toe and wrist
exors (43.10% of the MVC) and the lower abdominal muscles (48.33% of the
MVC), which registered the highest activity. Cabri et al. (1988) specically
analyzed the activity of the driving agonist muscles during the crawl motion and
found that, except at maximum speed, in which the percentage regarding MVC
was close to 40% ± 3, at the other speeds (85 and 75% of maximum speed) activ-
ity uctuated mainly between 30 and 35% of MVC. These results coincide with
those obtained by Bollens, Annemans, Vaes, and Clarys (1988). Considering that
these records are for maximum speeds in experienced and skilled swimmers, it
would be expected that people with less aquatic experience who wish to improve
their strength by means of continued movements in the water environment crawl
stroke swimming would be unlikely to achieve the desired strength gain benets
especially in dynamically contracting muscle groups such as the horizontal
From the data obtained in the current case study, we examined the mean activ-
ity of the posterior deltoid muscle produced by motion at maximum speed in crawl
stroke swimming. Descriptively, the EMG values observed were not enough to
generate a local training effect to improve muscular strength, since the recording
obtained indicated that mean muscular activation activity achieved was quite low,
representing only 18.72% of MVC. Similar results were obtained in other studies
such as the Clarys study (1988) that used participants with similar characteristics to
our case study, where neither competitive swimmers nor novice swimmers reached
a minimum threshold for improving strength.
Therefore, we conclude from our case study that prescribing exercises for
improving muscle strength based solely on crawl swimming strokes is a mistake,
since, in healthy people, activity levels sufcient for bringing about the desired
training changes for strength in agonist or synergist muscles are not achieved. On
the other hand, not all muscle groups are exercised when practicing a swimming
stroke (Miyashita, 1997). This limitation could therefore oblige those who prac-
tice swimming to practice and master several swimming strokes to activate, albeit
insufciently, a greater number of muscle groups so that in doing so, the minimum
stimulus created by training is shared across the majority of joints. This is the reason
why we must identify other types of water activities that fulll the dual mission of
reaching an optimum training threshold for improving strength, regardless of the
level of physical aptitude of the exerciser, as well as be able to create changes in
the most important muscle groups for good osteomuscular health with a few easy
movements (Colado, 2004; Sanders, 2001).
Some new aquatic muscle training programs initially offer both of these
advantages. Studies conducted in young, healthy, and physically active men, such
as those by Colado and Llana (2003) and Colado (2003), have demonstrated the
efciency and safety of some of these activities using a photographic and video
study. These same studies have produced an evaluation of the changes in muscle
mass and maximum dynamic muscular strength when using a systematic strength
improvement program in water. These types of aquatic programs are based on ener-
getic and controlled performance of movements with surface devices that increase
Posterior Deltoid Muscular Activity 67
both frontal and drag resistance. These aquatic exercise programs also have the
benets of producing a minimum eccentric muscle activity that reduces the risk of
injuries, muscle overloading, and subsequent muscle soreness and inammation,
employing shorter sessions so that in a single exercise both agonist and antagonist
muscles are exercised in such a way that with only four exercises the majority of
muscle groups can be trained and requiring little prior psychomotor experience and
demand for their performance. This last requirement means that almost everyone
is able to perform them regardless of their mobility and prociency in the water.
Furthermore, because the head is above water at all times, it enhances the leisure
and social components of exercise, which can be important in maintaining compli-
ance with these types of programs.
To avoid such basic mistakes as mistaken prescription of lap swimming as a
primary means to improve muscular strength in healthy populations, one should
also evaluate the efciency and safety of aquatic exercises to guarantee evidenced-
based professional guidance. Therefore, studies such as this current case study may
be a step toward analyzing the adequacy of water-based muscle training activities.
Our case study data suggested that there were no meaningful differences between
the EMG responses created by the performance of dry land and water callisthenic
exercises for strength training, as long as they are conducted with the methodol-
ogy we have described in this paper. We also did observe that dry land and water
callisthenic activities appeared to produce a much greater percentage of MVC as
compared with maximal speed front crawl swimming.
As we mentioned earlier in this paper, several other studies involving electro-
myographic recordings that were based on callisthenic aquatic exercises aimed at
dynamically improving strength , provide similar results to our case study nd-
ings. For example, Pöyhönen, Keskinen, Hautala, Savolainen, and Mälkiä (1999)
and Pöyhönen, Heikki, Keskinen, Hautala, Savolainen, and Mälkiä (2001) found
similar results with knee exor-extensor muscles. More specically Kelly et al.
(2000) discovered the same effect using shoulder abductor muscles. Both authors
even compared their results with those obtained from equivalent dry land move-
ments, as we did in this case study. Kelly et al. (2000) conducted a study in which
the dynamic muscle activity of several abductor muscles of the scapulo-humeral
joint was evaluated both on dry land and in the water. A relevant conclusion of that
study was that as the speed of movement increased, muscle activity in the water
was similar to that achieved on dry land. At slow speeds, muscular activity was
not nearly as high as the levels stimulated on dry land. That is, no statistically sig-
nicant differences existed when employing gravity and water as stimuli creating
a training effect. Even the mean intragroup muscle activity in water was higher
than that achieved on dry land.
The level of activity achieved with shoulder abduction activation during stroke
swimming was insufcient to bring about changes in healthy populations since the
previously mentioned values of 30–40% were not reached, apparently owing to
the fact that the water resistance created was not sufcient to increase the frontal
and drag resistance produced in aquatic movements (Colado, 2004). Similarly,
Pöyhönen (2002) and Pöyhönen et al. (2002) showed that, by using large enough
equipment and a high rate of movement speed, a similar muscle activity could be
achieved in knee exors performing maximum exercise with an isokinetic machine
and another conducted with hydro-boots in the water.
68 García Massó and Colado
Data from our case study strongly supports other ndings that stroke swimming
may serve as a source for improving muscle strength is a myth. We did observe
that, unlike performing swimming strokes, aquatic resistance exercises potentially
could be effective for strength training since they exceeded muscle activation levels
of 40%. As long as aquatic resistance exercises use large surface devices, high
movement speeds, and maintain core stability, then the muscle activity produced
may reach thresholds similar to those of exercises performed on dry land. These
ndings may also be applied to physical exercise programs in prevention and
functional rehabilitation as well as sports training.
This research has been conducted thanks to the research project funding (PMAFI-PI-
01/1C/04) from the Research Funds Programme of the Catholic University San Antonio in
Murcia (Spain). We would also like to acknowledge the work of Aurelio Díaz Gea (Metron
Medica—Spain), Javier Bermell Insa (Importer for Spain of Mega Electronics products),
and Jukka Turunen (Product Manager of Mega Electronics Ltd) who made the electromyo-
graphic recordings possible. We appreciate the suggestions offered by anonymous reviewers
and the Editor of the International Journal of Aquatic Research and Education, Stephen
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