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International Journal of Applied Exercise Physiology
2322-3537 www.ijaep.com
Vol.5 No.2
Received: January 2016 , Accepted: May 2016, Available online: July 2016
Resistance training with slow speed of movement is better for hypertrophy and
muscle strength gains than fast speed of movement.
Paulo Eduardo Assis Pereira1,2, Yuri Lopes Motoyama1, Gilmar Jesus Esteves1,2, William Carlos Quinelato1,
Luciano Botter1, Kelvin Hiroyuki Tanaka1, Paulo Azevedo1,3.
1Group of Studies and Research in Exercise Physiology, Federal University of São Paulo, Santos, São Paulo, Brazil
2Group of Studies in Sciences Physical Education, Praia Grande College, Praia Grande, São Paulo, Brazil
3Department of Human Movement Science, Federal University of São Paulo, Santos, São Paulo, Brazil
ABSTRACT:
Repetition speed is an important variable during resistance training. However, the effects of
different speeds on the muscular strength and hypertrophy in isotonic resistance training are not
clear. The study compared fast speed with slow speed of isotonic resistance training on muscular
strength and hypertrophy in well-trained adults. Twelve healthy adults were randomly assigned
into two groups: fast speed (FS) and low speed (SS). Muscle hypertrophy was measured by an
ultrasound examination of the cross-sectional area of the brachial biceps muscle. Muscular
strength was verified by 1 RM test. To check the possible differences in strength and
hypertrophy between pre and post training and between groups there were compared by two-way
ANOVA for repeated measurements and the effect size (ES) was calculated. Improvement in the
cross-sectional area (P=0.019) and muscular strength (P=0.021) in the SS group between pre and
post training was verified. The SS group had bigger effect sizes than FS group for hypertrophy
and strength from pre to post training. SS training was more effective to improve hypertrophy
and muscle strength in well-trained adults.
KEY WORDS: strength training, isotonic contraction,muscle strength
.
INTRODUCTION
Hypertrophy and muscular strength are two
common goals in resistance training. Optimal
hypertrophy and strength response depend on
variables manipulation, such as: load, volume,
exercise order, exercise selection, rest between
sets and amplitude of movement [1]. One
training variable that is often neglected and is
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essential to achieve the goals established is the
repetition speed [2, 3].
Repetition speed alters important factors
involved in hypertrophy and strength
development, like time under tension,
metabolic and hormonal response, and muscle
activation [4]. Thus, the adequate manipulation
of speed of each repetition may maximize
hypertrophy and strength responses to
resistance training.
Despite the importance of repetition speed,
the effects of different repetition speed on
muscular strength and hypertrophy in isotonic
resistance training are not clear, since many
studies have used the isokinetic exercise [3, 5-
7].
Studies assessing the adaptations promoted by
strength training performed at different speeds
of repetitions in isokinetic exercise found that
fast speed provides greater strength gains and
muscle hypertrophy than the slow speed [5-7].
In opposite, with slow speed the muscles stay
more time under tension, which is important for
hypertrophy and strength gains [8]. Then,
studies are needed using isotonic resistance
training, since it is the most common type of
resistance training. Furthermore, the cost is
generally more feasible when compared with
isokinetic equipment. In addition the response
of different repetition speed in trained subjects
is not clear. Knowing that this population is
highly adapted to training stimulus and
consequently have low trainability. It is
necessary to know what the best strategies to
reach their goals are.
Therefore, we aimed to compare distinct
repetition speed of isotonic resistance training
on hypertrophy and muscular strength in
subjects with experience in resistance training.
METHODS
Experimental design
This is a randomized controlled clinical study.
Twelve men were randomly assigned to groups:
the Fast Speed (FS) or Slow Speed (SS). Before
the beginning of the resistance training all
subjects performed an ultrasound assessment of
the brachial biceps to check the cross-sectional
area, underwent tests of 1 repetition maximum
(1RM) and both groups had 2 weeks of
familiarization with the speed execution of
training, under the guidance of a physical
educator. After 12 weeks of resistance training
the volunteers were again subjected to an
ultrasound of the biceps brachial and remade
the 1 RM tests. The present study is in
accordance with the standards of the Helsinki
Declaration (2008) and approved by the ethics
committee of Federal University of São Paulo.
Subjects
Twelve healthy adults were randomly
assigned in the FS and SS groups (Table 1).
The inclusion criteria established for
participation of the subjects in the study were:
resistance training time equal to or greater than
twelve months; the absence of diseases that
compromise the health of the subjects; use of
any type of sports supplement or anabolic
agents; absence of aerobic training.
Body Composition
The subjects were submitted to the assessment
of total body mass (kg), fat mass (kg) and body
fat percentage by means of skinfolds. The
protocol was used according to the proposed by
Jackson and Pollock [9].
Evaluation of maximum strength
Maximum strength was evaluated through the
1RM test. Before starting the 1RM test all
subjects performed a specific muscular warm-
up composed of 20 repetitions with load of
40% to 50% of the subjective perception of
effort. After the warm up the 1RM test started.
The initial load was estimate through the
perceived exertion of the subject based on the
training loads before the study. The 1RM test
was execute for Scott curl with bar. A
maximum of five attempts were executed out
with increasing loads, and five-minute intervals
between retries. The 1RM test was remade after
12 weeks of training with the same parameters
used at the beginning of the program to
determine the strength gains.
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Transverse section area
Thickness of biceps brachial muscle was
measured before and after 12 weeks of training
by ultrasound. The thickness of biceps brachial
was measured between the external muscle
boundary and the definitive band of connective
tissue that runs longitudinally down the middle
of the muscle. This measure was made 5 cm
from the right-hand edge of the image (i.e., 6–7
cm proximal to the crease of the elbow). The
ultrasound system used was the Toshiba Xario
(Toshiba, Tokyo, Japan), with an electronic
linear array probe of 12 MHz frequency, to
determine the cross-sectional area. With the
transducer coated with water-soluble gel,
ultrasound probe was oriented transverse mode
with regard to location, and the images were
recorded with the subjects sitting with the right
arm slightly flexed and totally relaxed, with the
forearm fully supported on the right thigh.
All evaluations were conducted in the same
time of day and the participants were instructed
to hydrate themselves normally 24hrs before
the tests. At all times, the same researcher, a
physician with experience in ultrasound,
performed the measurements.
Training Protocol
The training had 12 weeks, 2 times a week,
always respecting minimum 48-hour interval
between stimuli. The subjects were instructed
to perform 3 sets of 8 repetitions maximum, if
the subject made less than 8 reps or more than 8
reps, the weight load was adjusted the next
training session. The training consisted of Scott
curl exercise. Rest interval between sets was of
two minutes.
The speed of the repetition of movement was
different between the groups. The FS group
performed repeating the following cadence: 1s
in the concentric phase, 0s in the transitional
phase from the concentric for the eccentric
phase, 1s in the eccentric phase and 0s in the
transitional phase from the eccentric to the
concentric phase (1010). The SS group
performed the repetitions with 1s in the
concentric phase, 0s in the transitional phase
from the concentric for the eccentric phase, 4s
in the eccentric phase and 0s in the transitional
phase from the eccentric to the concentric phase
(1040).
Statistical analysis
For the data presentation, a descriptive
statistics (mean ± standard deviation) was used.
ANOVA for repeated measured was used to
verify possible differences in strength and
hypertrophy gains between time and groups.
The Mauchly’s sphericity test was applied and
correction, when necessary, was made by
Greenhouse-Geissenger. Significance P-level
≤0.05 was accepted. When the F test was
significant, complement analysis by
Bonferroni's multiple comparison tests was
made.
The Hedge’s g approach was used to calculate
effect size (ES) and data was shown with their
respective 95% Confidence Interval (CI) [10].
Effect size was classified according to the scale
proposed by Rhea [11].
STATISTICAL RESULTS
No significant differences (P≥0.05) were
observed in the sample characteristics before
training between FS and SS groups (Table 1).
Comparisons pre and post training and
between groups for the cross-sectional area and
maximum repetition on the Scott curl are
shown in Table 2. There was a difference
between the SS group moments of pre and post
training in cross-sectional area (P = 0.019) and
strength (P = 0.021).
The ES was greater for the SS group than FS
group for CSA and 1RM test (Table 3).
Figure 1. Demo Should be in image format.
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DISCUSSION
We verified the influence of repetition speed
during isotonic resistance training to induce
hypertrophy and muscular strength in well-
trained men. No differences were verified in
hypertrophy and muscle strength between FS
and SS groups. The ES was bigger to SS than to
FS for hypertrophy and muscular strength
gains. By ES it is possible to check the changes
caused by the same treatment in independent
groups or different treatments within the same
group, allowing the verification of the
effectiveness of each method to be determined
[12]. These results show us the superiority of
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SS to improve hypertrophy and muscle
strength.
The improved hypertrophy in SS group could
be explained by a longer time under tension,
especially with a slower eccentric phase [13]. It
causes higher muscular tension, with a higher
stress on a small number of active fibers,
leading to greater muscle damage (especially
fast twitch fibers, that are more hypertrophy
prone) [13]. This promotes greater activation of
satellite cells, which are related to muscle
hypertrophy [14, 15]. A longer time under
tension also increases acute mitochondrial,
sarcoplasmic and myofibrillar protein synthesis
after resistance exercise, stimulating
hypertrophy response [8]. Furthermore, a
longer time under tension promotes compressed
blood vessels for a longer period of time that
leads to vascular occlusion and metabolic
stress, contributing to the increased
hypertrophy response [14, 15]. Therefore,
controlled repetitions with slow eccentric phase
promotes greater muscular hypertrophy, in a
balance between significant metabolic stress
and muscle tension [13].
This increase in hypertrophy in SS group can
explain the greater strength response post
training from this group, since muscle
hypertrophy plays an important role in strength
development, in conjunction with neural
adaptations [16]. These neural adaptations, like
higher firing frequency and motor unit
synchronization, increases strength and can be
best developed in well trained individuals
through training with both faster (lifting as fast
as possible) [17-19] and slower accelerations
(unintentional slow) [20]. Unintentional slow
velocity is present in repetitions in which either
a heavy load or fatigue is responsible for the
repetition length [20].
The concept of “move as fast as possible
independent of the resistance” can benefit
strength development [21]. Knowing that
strength can be defined as the product of mass
times acceleration [22], an individual can
develop strength through increases in both
variables of the equation. Thus, training with
high loads and unintentional slow speed
(traditional powerlifting training) [2, 13, 20] or
training with lower loads lifting as fast as
possible can both develop strength [17-19].
Then strength can be increased through
different mechanisms. The SS group had a
slower repetition length that favored muscular
hypertrophy and as a consequence, strength
development. On the other hand, the velocity
used by FS group did not provide either the
most adequate stimulus for increased
hypertrophy or strength through neural
enhancement, as evidenced by the results. A
repetition length “as fast as possible” could
have provided better stimulus for neural
adaptations that would lead to greater strength
levels post training, even in the short term [21].
An optimal approach for enhanced resistance
training responses is periodization, with
variations in training variables, allowing
continuous training adaptations [20, 22]. Thus,
despite a greater response in muscle
hypertrophy in SS group, training could involve
faster repetition length too, with less priority.
This type of training have important
hypertrophy mechanisms too, leading to higher
muscle activation and lactate increases [4].
Higher concentration of lactate can make
regulate protein synthesis go up through
increased cell swelling and mediate anabolic
hormones and cytokines elevations [13].
Moreover, hormonal and metabolic responses
are similar within moderate velocity range [22].
Then, a variety of repetition length could be
used to develop hypertrophy and strength [20].
This range of different velocities can be
assigned to untrained individuals too [20]. A
wide range of repetition length works well for
untrained individuals [20, 23] with similar
results between fast and slow repetition length
[24]. This variety of positive responses by
different repetition length can be explained by
the high trainability of untrained subjects. Thus,
both fast and slow velocity results in strength
and hypertrophy. Strength is developed more
quickly through a rapid starting period of neural
adaptation (first weeks) and hypertrophy
increases more after this initial period [25].
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In summary, no differences were found
between groups for hypertrophy and muscular
strength. However, the effect size for SS is
greater than FS, pointing to a greater
effectiveness of slow muscular actions for
induction of muscular strength and
hypertrophy. Thus, we conclude that SS
training is more effective to improve
hypertrophy in well-trained adults.
Consequently, this causes an increase in
strength levels, which can be developed
through different mechanisms and repetition
lengths. Finally, variety of stimulus in
periodization is needed to optimize resistance-
training programs.
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