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Acute effects of a cluster-set protocol on hormonal, metabolic and performance measures in resistance-trained males

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Abstract Limited research exists on rest-pause or cluster-set (CS) protocols. Acute effects of a traditional set (TS) and CS protocols of resistance exercise on serum growth hormone (GH), cortisol (C), blood lactate (BL), countermovement vertical jump (CMVJ) and standing long jump (SLJ) were compared. Eleven resistance-trained males (22.9±2.6 year; 176.9±10.6 cm; 78.5±1.6 kg; 12.9±3.1% BF) completed one repetition maximum tests for clean pull (CP), back squat (BS) and bench press (BP). Subjects were then randomly assigned to TS or CS protocols for sessions 2 and 3, and performed CP and BS lifts followed by two circuits of three sets of three exercises. GH, C, BL, CMVJ and SLJ were measured pre-exercise (Pre), mid-exercise following completion of CS or TS protocol (Mid), immediately (IP), 15 (15P) and 30 (30P) minutes post-exercise. Repeated measures ANOVAs examined differences in GH, C, BL, CMVJ and SLJ. No differences (p>0.05) existed between protocols for GH and C. GH levels 15P were elevated (p<0.05) above 30P (15.78 + 4.66 vs. 12.10 + 4.66 µg(.)L(-1)). C levels 30P were elevated (p<0.05) above Pre (716.85 + 102.56 vs. 524.79 + 75.79 nmol(.)L(-1)). Interaction (p <0.05) existed between protocol and time for BL; mid-BL was lower for CS than TS (7.69±3.73 vs. 12.78±1.90 mmol(.)L(-1)). Pooled data for CMVJ and SLJ were greater (p <0.05) across the CS protocol. The less metabolically taxing CS protocol resulted in better sustainability of jump measures.
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Acute effects of a cluster-set protocol on hormonal,
metabolic and performance measures in resistance-
trained males
Julia C. Girmana, Margaret T. Jonesb, Tracey D. Matthewsa & Richard J. Wooda
a Department of Exercise Science and Sports Studies, Springfield College, Springfield, MA,
USA
b Kinesiology, George Mason University, Manassas, VA, USA
Published online: 08 Mar 2013.
To cite this article: Julia C. Girman, Margaret T. Jones, Tracey D. Matthews & Richard J. Wood (2014) Acute effects of a
cluster-set protocol on hormonal, metabolic and performance measures in resistance-trained males, European Journal of
Sport Science, 14:2, 151-159, DOI: 10.1080/17461391.2013.775351
To link to this article: http://dx.doi.org/10.1080/17461391.2013.775351
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ORIGINAL ARTICLE
Acute effects of a cluster-set protocol on hormonal, metabolic and
performance measures in resistance-trained males
JULIA C. GIRMAN
1
, MARGARET T. JONES
2
, TRACEY D. MATTHEWS
1
,
& RICHARD J. WOOD
1
1
Department of Exercise Science and Sports Studies, Springfield College, Springfield, MA, USA,
2
Kinesiology, George Mason
University, Manassas, VA, USA
Abstract
Limited research exists on rest-pause or cluster-set (CS) protocols. Acute effects of a traditional set (TS) and CS protocols
of resistance exercise on serum growth hormone (GH), cortisol (C), blood lactate (BL), countermovement vertical jump
(CMVJ) and standing long jump (SLJ) were compared. Eleven resistance-trained males (22.992.6 year; 176.9910.6 cm;
78.591.6 kg; 12.993.1% BF) completed one repetition maximum tests for clean pull (CP), back squat (BS) and bench
press (BP). Subjects were then randomly assigned to TS or CS protocols for sessions 2 and 3, and performed CP and BS
lifts followed by two circuits of three sets of three exercises. GH, C, BL, CMVJ and SLJ were measured pre-exercise (Pre),
mid-exercise following completion of CS or TS protocol (Mid), immediately (IP), 15 (15P) and 30 (30P) minutes post-
exercise. Repeated measures ANOVAs examined differences in GH, C, BL, CMVJ and SLJ. No differences (p0.05)
existed between protocols for GH and C. GH levels 15P were elevated (pB0.05) above 30P (15.784.66 vs. 12.10
4.66 mg
.
L
1
). C levels 30P were elevated (pB0.05) above Pre (716.85102.56 vs. 524.79 75.79 nmol
.
L
1
). Interaction
(pB0.05) existed between protocol and time for BL; mid-BL was lower for CS than TS (7.6993.73 vs. 12.7891.90
mmol
.
L
1
). Pooled data for CMVJ and SLJ were greater (pB0.05) across the CS protocol. The less metabolically taxing
CS protocol resulted in better sustainability of jump measures.
Keywords: Rest-pause, growth hormone, cortisol, blood lactate, countermovement vertical jump, standing long jump
Introduction
Strength and power are vital attributes to sports
performance (Hansen, Cronin, Pickering, & Newton,
2011; Iglesias, Boullosa, Dopico, & Carballeira, 2010;
Turner, 2011). As the athlete’s resistance training age
advances, greater variability is introduced into the
training programme in order to prevent performance
plateaus (Turner, 2011). It has been suggested that
the introduction of novel stimuli promotes quicker
gains in performance over repeatedly training using
familiar tasks (Hodges, Hayes, Horn, & Williams,
2005). Rest-pause or cluster set (CS) training has
been proposed as a method of introducing variation to
any phase of periodised training in order to maximise
gains in muscle strength and power (Haff, Burgess, &
Stone, 2008; Haff et al., 2008).
Traditionally, all repetitions (reps) within a set are
performed continuously. In rest-pause or CS proto-
cols, the configuration of the set is manipulated into
blocks or clusters of reps with a short inter-cluster
rest of 1030 seconds (Haff et al., 2003; Lawton,
Cronin, & Lindsell, 2006). Implementing inter-
cluster rest periods may improve the force and
velocity produced during each rep by providing
time for partial regeneration of phosphocreatine
stores (PCr), thus stimulating gains in strength and
power (Iglesias-Soler et al., 2012; Sahlin & Ren,
1989; Willardson, 2008). The inclusion of a 15s rest
between maximal isometric contractions yielded
approximately 79% recovery of the initial force-
generating capacity of the quadriceps (Sahlin &
Ren, 1989). Mean propulsive velocity increased
by approximately 19% following the inclusion of
Correspondence: M. T. Jones, Kinesiology, George Mason University, 10900 University Blvd, MSN 4E5, Manassas, VA 20110-2203,
USA. E-mail: mjones15@gmu.edu
European Journal of Sport Science, 2014
Vol. 14, No. 2, 151159, http://dx.doi.org/10.1080/17461391.2013.775351
#2013 European College of Sport Science
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inter-repetition rest (Iglesias-Soler et al., 2012).
Additional rest may permit completion of a greater
work volume, which may result in larger metabolic
stress and subsequent endocrine response that fa-
vours increases in muscular endurance (Iglesias
et al., 2010) and strength (Denton & Cronin,
2006). By manipulating the rest period, intensity,
number of reps or a combination of the three within
a CS protocol, specific training-phase goals can be
targeted (Haff et al., 2008).
Research on the use of different CS protocols is
limited. Some researchers have demonstrated that
CS exercise is effective in improving power in
resistance-trained males (Haff et al., 2003; Hansen
et al., 2011; Lawton et al., 2006). Findings have
included higher peak power, larger barbell displace-
ment and higher peak barbell velocity in a CS
configuration when compared to traditional set
(TS) or undulating set configurations (Haff et al.,
2003). Repeated CS training improved jump squat
performance in highly trained rugby union players
compared to TS training (Hansen et al., 2011). In
addition to improving power-generating capacity, an
acute CS protocol has been shown to be effective in
improving high-intensity muscular endurance over
an acute TS protocol (Iglesias et al., 2010). It has
been suggested that appropriately implemented rest-
loading schemes (e.g. 15s rest intervals between CS
of 1 and 2 reps) may provide a training stimulus that
favours improved muscle size, work capacity and
muscular endurance (Denton & Cronin, 2006; Haff
et al., 2008).
Improvements in muscular hypertrophy and
strength have been demonstrated in response to
regular training with heavy resistance exercise
(HRE) protocols that involve high volumes of con-
tinuous reps, high lifting intensities and short inter-
set rest periods (Gotshalk et al, 1997; Kraemer et al.,
1990,1991). It has been suggested that a threshold
level of a sufficient volume of total work and load
may need to be met in order to induce acute
hormonal responses (Ahtiainen, Pakarinen, Alen,
Kraemer, & Ha
¨kkinen, 2005; Gotshalk et al.,
1997). While researchers have indicated that the
total degree of metabolic stress [i.e. blood lactate
(BL) accumulation] of the HRE protocol may
determine the magnitude of hormonal response to
an acute exercise bout (Ahtiainen et al., 2005;
Gotshalk et al., 1997;Ha
¨kkinen & Pakarinen,
1993), others have reported no consistent relation-
ship between BL accumulation and specific hor-
mone responses to HRE protocols of varying rest
interval length and duration (Kraemer et al., 1990;
Rahimi, Qaderi, Faraji, & Boroujerdi, 2010). In
addition, the secretion of growth hormones (GH)
has been shown to be sensitive to the stimulus of
resistance exercise (Crewther, Keogh, Cronin, &
Cook, 2006). When total work remains constant
across a series of HRE protocols, changing one
programme variable (i.e. load or rest interval length)
may alter GH response patterns (Kraemer et al.,
1990). However, the effect of CS exercise on
endocrine hormone responses [i.e. GH and cortisol
(C)] in resistance-trained males during an acute
HRE protocol is unknown.
In summary, CS protocols have been shown to
elicit increases in power and muscular endurance,
yet no clearly defined CS protocol has emerged as
optimal for promoting GH release or sustainability of
jump performance. Therefore, the primary purpose
of this study was to determine whether differences
exist in GH, C, BL and performance measures of
standing long jump and countermovement vertical
jump in resistance-trained males between acute CS
and TS protocols of HRE. A secondary purpose was
to examine the effects of TS and CS protocols on the
sustainability of jump performance measures. It was
therefore hypothesised that the CS protocol would
induce less BL accumulation and better sustainabil-
ity of jump performance while eliciting similar GH
levels compared to a TS protocol.
Methods
Experimental overview
The present study was designed to determine the
acute effects of TS and CS protocols of heavy
resistance exercise (HRE) on growth hormone
(GH), cortisol (C), blood lactate (BL) and jump
performance measures in resistance-trained males.
Clean pull (CP), back squat (BS) and bench press
(BP) one repetition maximum (1RM) were deter-
mined using standardised procedures (Baechle,
Earle, & Wathen, 2008) before random assignment
to the order of the TS and CS protocols of HRE.
Loads for CP, BS and BP were assigned as percen-
tages of the 1RM. BP and BS reps were performed at
a controlled 2-0-2 tempo during testing sessions.
Both acute protocols consisted of eight identically
ordered exercises controlled for load, volume and
total rest. The set configuration (TS or CS) was
manipulated for CP and BS exercises. The remain-
ing six exercises were completed in two circuits of
three sets of three exercises using continuous reps.
The protocol was selected because it was believed to
be representative of what an athlete might do when
performing cluster training in an off-season hyper-
trophy phase of whole-body resistance training. It
would be unlikely to exclude supplemental exercises
during this time and in fact, it is a common practice
to include them as circuits. Blood samples were
collected from an intravenous catheter pre-exercise
(Pre), mid-exercise following completion of CS or
152 J. C. Girman et al.
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TS protocol (Mid) and immediately (IP), 15 (15P),
and 30 (30P) min post-exercise and used to deter-
mine GH, C and BL concentrations. Performance
tests of countermovement vertical jump (CMVJ)
height and standing long jump (SLJ) distance,
well-established field measures of sports perfor-
mance, followed the collection of each blood sample.
The three testing sessions were completed in the
morning at the same time of day, with each separated
by approximately 1 wk. The same trained research
assistants performed all measurements during data
collection.
Subjects
Eleven resistance-trained males (age 22.992.6
years; height 176.9910.6 cm; weight 78.5912.6
kg; body fat 12.993.1%; training experience 6.49
1.5 years) volunteered to participate. Subjects were
experienced lifters who were familiar with the
resistance training exercises, CS and TS protocols
of HRE and jump performance measures included in
the current study. Each subject had the risks and
benefits explained to him beforehand, signed an
institutionally approved informed consent form to
participate, and completed a medical history form.
The Institutional Review Board for Human Subjects
approved all procedures. Subjects were instructed to
keep an exercise log for 1 wk prior to each testing
session and to replicate any exercise sessions prior to
testing sessions. Subjects also recorded a nutrition-
sleep log for 3 days prior to testing and were
instructed to replicate nutritional intake and the
number of hours of rest attained prior to testing
sessions. Subjects were asked to refrain from (1) any
form of supplementation (excluding protein) during
the study, (2) strenuous exercise 72 hr prior to
testing, (3) consumption of alcohol and caffeine 24
hr prior to testing and (4) carbohydrate and protein
supplementation on the test morning. Subjects
reported for each testing session after an overnight
fast (]8 hr) and were provided with a standard
breakfast.
Procedures
1RM Strength Testing (Session 1). A standard 1RM
testing protocol was used for CP, BS and BP,
respectively, during a morning session between
0600 and 1000, 1 wk prior to performing the first
of two experimental protocols (CS or TS). Testing
was conducted in a power rack (Samson Equipment,
Las Cruces, NM, USA). A portable high-pull
indicator (Sorinex Exercise Equipment, Irmo, SC,
USA) was aligned with the greater trochanter of each
subject’s right femur and used to standardise barbell
pull height for CP reps. Safety spot bars and a safety
squat beeper (Bigger, Faster, Stronger, Salt Lake
City, UT, USA) were individually set to ensure that
each subject squatted to parallel. A metronome set at
a cadence of 60 beats per minute controlled the 2s
eccentric2s concentric tempo (2-0-2) of BS and BP
reps. Information from 1RM testing was used to
determine subsequent loads for CP, BS and BP
exercises.
Ninety minutes after eating the provided break-
fast, subjects performed a supervised, 5-min whole-
body, dynamic warm-up of 12 exercises performed
in rapid succession. Testing of CMVJ, SLJ and 1RM
followed the dynamic warm-up, respectively. For
each lift tested (CP, BS and BP), three warm-up sets
of 25 reps at 5085% 1RM with 2-min rest in
between were completed before single-rep sets were
performed. Rest between 1RM attempts was three
minutes, and no more than two failed 1RM attempts
were allowed. Rest between each lift tested was
three minutes. A 5-min whole-body, cool-down
was performed following 1RM testing (Figure 1).
Jump performance measures. CMVJ height (cm) was
estimated from flight time using a pressure-sensitive
jump mat (Just Jump System, Perform Better,
Cranston, RI, USA). Subjects were instructed to
use a countermovement of the body and arms for all
jumps.
To measure SLJ distance (cm), an SLJ testing mat
(Perform Better, Cranston, RI, USA) was used. The
measurement was taken from the heel of the trail leg
as long as it remained in contact with the floor upon
landing. The dynamic warm-up served both the pre-
exercise CMVJ and SLJ tests. During experimental
testing sessions 2 and 3, CMVJ and SLJ testing were
performed following each blood draw at Pre, Mid,
IP, 15P and 30P (Figure 1). The best trial of three
jumps at each time point was used for statistical
analysis.
CS or TS protocols of HRE (sessions 2 and 3). The
order of the experimental testing sessions was
counterbalanced and randomised. All subjects per-
formed both acute CS and TS protocols. Each data
collection session was (1) conducted in the morning
between 0600 and 1300, (2) separated by approxi-
mately 1 wk, (3) performed at the same time of day
respective to the individual and (4) lasted approxi-
mately 3.5 hr. Sixty minutes after eating the standard
breakfast, an intravenous catheter was inserted for
blood sampling throughout each session. After a 30-
min equilibrium period, the Pre blood sample was
collected. Subjects then completed the dynamic
warm-up, followed by CMVJ, SLJ testing and either
the CS or TS protocol of HRE (Figure 1) consisting
of eight identically ordered exercises controlled for
intensity, volume and total rest. CP and BS (Table I)
Acute effects of a cluster-set protocol 153
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were performed using either CS or TS for a total of
four sets of six reps at 5075% 1RM and five sets of
410 reps at 5570% 1RM, respectively. In the TS
protocol, all repetitions of CP and BS were com-
pleted in a continuous fashion and followed by a
2-min rest period. In the CS protocol of HRE, 15s of
rest was taken between every two reps of CP and BS
until the total assigned volume was completed, and
then the remainder of the 2-min total rest period was
taken prior to initiating the next set. The six
remaining exercises (Table I) were completed after
the mid-exercise blood draw in two circuits of three
sets of three exercises each using continuous repeti-
tions and separated by one minute of rest. Subjects
were provided with a minimum of 1.5 L of water to
consume as needed during the protocol. All BS and
BP repetitions were performed at the 2-0-2 tempo in
order to avoid affecting the exercise demands
through changes in speed of movement.
Growth hormone, cortisol and blood lactate (sessions 2
and 3). The same trained phlebotomist performed all
blood collections via an indwelling catheter inserted
into the superficial vein in the antecubital space of
the arm. Subjects were in the seated position for
blood collection and samples were obtained pre-
exercise after a 30-min equilibrium period (Pre),
mid-exercise (Mid), immediately (IP), 15 (15P) and
30 (30P) min post-exercise (Figure 1). The catheter
was flushed with 0.9% non-buffered saline following
each blood collection, wrapped with gauze and
secured with an adhesive bandage. All samples
were allowed to clot at room temperature for
15 min and then centrifuged for 15 min at 4
o
Cat
2000g. Serum was transferred into separate vials
and stored at 80
o
C until analysed. GH (mg
.
L
1
,
i.e. 22 kDa) and C (nmol
.
L
1
) were analysed in
duplicate using enzyme-linked immunosorbent as-
saying techniques (ELISA; MP Biomedicals, Diag-
nostics Division, Orangeburg, NY, USA). The
coefficient of variance and sensitivity of the GH
ELISA testing kits were 11.8% and 0.5 ng/mL,
respectively. The coefficient of variance and sensi-
tivity of the C ELISA testing kits were 8.6% and 0.25
mg/dL, respectively. A Lactate Plus Meter (Nova
Biomedical, Waltham, MA, USA) was used to
analyse whole BL (mmol
.
L
1
) in duplicate using
enzymatic determination and reflectance photome-
try (wavelength 660 nm).
Statistical analyses
Descriptive statistics were computed for the five
dependent variables (GH, C, BL, CMJ and SLJ).
Figure 1. Procedural order for the three data collection sessions.
154 J. C. Girman et al.
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To evaluate changes between resistance exercise
protocols (CS and TS) and the five time points
(Pre, Mid, IP, 15P and 30P) in each dependent
variable, a total of five 25 [(CS and TS)(Pre,
Mid, IP, 15P and 30P)] repeated measures ANOVAs
were calculated. If significant interaction existed,
Bonferroni pairwise post hoc analyses examined
differences between CS and TS, and across test
times. The alpha level was set at pB0.05. All
statistical analyses were computed using the Statis-
tical Package for the Social Sciences (SPSS 18.0 for
Windows, SPSS, Inc., Chicago, IL, USA). Statistical
power was calculated using G*Power version 3.1 for
repeated measures factorial ANOVA. Using an effect
size set at 0.40, a correlation between measures set at
0.50, and power set at 0.80, a total of 10 subjects
were required to find a treatment effect.
Results
Growth hormone and cortisol
For GH (mg
.
L
1
), no interaction (p0.05) was
found between protocol and time. Also, no main
effect (p0.05) was observed for protocol. How-
ever, a significant main effect (p50.05) for time was
observed (Table II). GH levels 15P (15.7894.66
mg
.
L
1
) were significantly elevated (p50.05) above
GH levels 30P (12.1094.39 mg
.
L
1
). For C
(nmol
.
L
1
), there was no interaction (p0.05)
between protocol and time. Also, no main effect
(p0.05) was observed for protocol. However, a
significant main effect (p50.05) for time was
observed (Table II). C levels 30P (716.859102.56
nmol
.
L
1
) were significantly elevated (p50.05)
above Pre C levels (524.79975.79 nmol
.
L
1
).
Blood lactate
For BL (mmol
.
L
1
), a significant interaction (p5
0.05) was found between protocol and time (Table
II). Mid-exercise BL was significantly lower (p5
0.05) for CS (7.6993.73 mmol
.
L
1
) than TS
(12.7891.90 mmol.L
1
). No differences (p0.05)
in BL were observed between protocols for Pre, IP,
15P or 30P.
Jump performance measures
For CMVJ, there was no interaction (p0.05)
between protocol and time and no main effect (p
0.05) for time. However, a significant main effect
(p50.05) for protocol was observed (Table II).
Mean CMVJ height was greater (p50.05) for CS
(61.2692.11 cm) than for TS (58.2992.08 cm).
For SLJ, there was no interaction (p0.05) between
protocol and time and no significant main effect (p
0.05) for time. However, a significant main effect
(p50.05) for protocol was observed (Table II).
Mean SLJ distance was greater (p50.05) for CS
(223.4996.71 cm) than for TS (215.7597.11 cm).
Table I. HRE training protocols
TS protocol CS protocol
Tempo Load Volume Intra-set rest Inter-set rest Volume Intra-set rest Inter-set rest
Exercise
Clean pull (CP) X 50% 16 0 2 min 32 15 s 1:30 s
75% 16 0 2 min 32 15 s 1:30 s
75% 16 0 2 min 32 15 s 1:30 s
75% 16 0 2 min 32 15 s 1:30 s
Back squat (BS) 2-0-2 55% 14 0 2 min 22 15 s 1:45 s
65% 14 0 2 min 22 15 s 1:45 s
70% 110 0 2 min 5 2 15 s 1:00 s
70% 110 0 2 min 5 2 15 s 1:00 s
6267% 1 10 0 Blood draw 52 15 s Blood draw
Inter-set
Circuit 1
Bench press (BP) 2-0-2 65% 10 0 30 s 10 0 30 s
40% 1RM
Barbell RDL n/a BS 10 0 30 s 10 0 30 s
Quadruped opposites n/a Body weight 10 ea 0 30 s 10 ea 0 30 s
Circuit 2 1-min rest between circuit 1 and 2 1-min rest between circuit 1 and 2
Chin-ups n/a Body weight 10 0 30 s 10 0 30 s
Three-way plank
a
n/a Body weight 30 s ea 0 30 s 30 s ea 0 30 s
20% 1RM
Tricep extensions
b
n/a BP 20/AMRP 0 30 s 20/AMRP 0 30 s
a
Three-way plank full front plank, full-side plank (right), full-side plank (left) performed consecutively before 30-s rest taken.
b
Triceps extension was the only exercise performed for two instead of three sets. Final set was for as many reps as possible (AMRP).
Acute effects of a cluster-set protocol 155
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The percent change in CMVJ and SLJ values at Mid,
IP, 15P and 30P from Pre are shown in Figure 2.
Discussion
The primary purpose of the current study was to
determine whether differences exist in GH, C, BL
and jump performance measures in resistance-
trained males between an acute CS or TS protocol
of HRE. Although previous researchers have demon-
strated CS to be effective for improving power (Haff
et al., 2003; Hansen et al., 2011; Lawton, Cronin,
Drinkwater, Lindsell, & Pyne, 2004; Lawton et al.,
2006) and muscular endurance (Iglesias et al.,
2010), this was the first study to examine the acute
effects of a CS protocol of HRE on hormonal and
metabolic responses in resistance-trained males.
Previous researchers have demonstrated greater
glycolytic involvement (Iglesias-Soler et al., 2012)
and increases in endocrine hormone levels in re-
sponse to TS protocols involving high training
volumes, high lifting intensities and short inter-set
rest periods (e.g. 35 sets of 10 repetitions at 70 75%
1RM with 60120s inter-set rest) (Ahtiainen et al.,
2005; Goto, Ishii, Kizuka, & Takamatsu, 2005;
Gotshalk et al., 1997; Kraemer et al., 1990,1991;
Linnamo, Pakarinen, Komi, Kraemer, & Ha
¨kkinen,
2005). Since GH plays a crucial role in the growth
and development of muscle tissues and cortisol
plays a major role in protein degradation, program-
ming the appropriate training stimuli and training
variations are essential to stimulate recovery and
adaptation (Haff et al., 2008).
Growth hormone secretion has been shown to be
sensitive to the stimulus of resistance exercise with
changes in as few as one programme variable
resulting in alterations in GH response (Crewther
et al., 2006; Goto et al., 2005; Kraemer et al., 1990).
However, during the present study, changing only
the configuration of the resistance training set did
not alter the GH response patterns between the CS
and the TS protocols of HRE. We observed acute
increases of similar magnitude in GH and C
responses following the CS and TS conditions;
therefore, the threshold level for stimulating the
release of these two hormones may have been
achieved during both protocols. Little to no change
in GH values was observed from pre- to mid-exercise
yet the observed range for post-exercise GH re-
sponses in our subjects (1020 mg/L) was within the
normal ranges reported by other researchers (Ahtiai-
nen et al., 2005; Kraemer et al., 1990,1991;
Linnamo et al., 2005; Rahimi et al., 2010). A
possible explanation for this observed GH response
may be that the threshold level for GH had not been
achieved by mid-exercise. The non-responsiveness of
GH during the first half of the exercise protocols may
be attributed to large inter-individual variation in
Table II. Hormonal, metabolic, and jump performance measures for cluster and traditional set protocols
Pre Mid IP 15P 30P
Hormonal and metabolic measures
Blood lactate (BL) (mmol
L
1
;N11)
Cluster 1.41 90.12 7.6991.12
a
14.2590.43 10.25 90.82 5.7190.93
Traditional 1.37 90.57 12.78 90.57 14.57 90.39 11.25 90.61 6.53 90.81
Growth hormone (GH) (mg
L
1
;A/10)
Pooled 2.7092.09 3.78 92.10 18.64 95.85 15.78 94.66
b
12.10 94.39
Cluster 2.90 92.34 5.02 92.59 16.73 96.22 13.64 95.08 10.2294.49
Traditional 2.5191.85 2.53 91.67 20.55 95.96 17.92 94.92 13.97 94.72
Cortisol (C) (nmol L
1
;
N11)
Pooled 524.79975.79 469.95977.6 632.92994.39 655.36 991.47 716.859102.56
c
Cluster 518.33 993.09 393.58 943.5 560.009114.93 566.639102.89 616.03 9110.4
Traditional 531.309104.94 546.209119.04 705.73 9120.64 744.10 9115.51 817.799125.94
Jump performance measures
Countermovement vertical
jump (CMVJ) height
(cm; N11)
Cluster
d
63.80 92.15 63.73 92.33 60.3392.21 59.31 92.35 59.16 92.26
Traditional 62.13 92.35 57.71 92.78 54.99 92.69 57.58 91.99 59.03 92.06
Standing long jump distance
(SLJ) (cm; N11)
Cluster
d
231.01 96.30 228.73 96.18 214.76 96.17 219.84 98.18 223.16 98.12
Traditional 228.14 95.87 215.2196.26 207.82 99.45 210.34 98.95 217.17 98.15
Notes: All values are mean9SE. Significant interaction (pB0.05) existed between protocol and time for BL. Pre, pre-exercise; Mid, mid-
exercise; IP, immediately post-exercise; 15P, 15-min post-exercise; 30P, 30-min post-exercise; CS, cluster-set protocol; TS, traditional set
protocol.
a
Mid-BL was lower for CS than TS.
b
GH main effect. Significant (p50.05) difference from corresponding 30P.
c
C main effect. Significant (p50.05) difference from corresponding Pre.
d
CS vs. TS main effect. CMVJ height and SLJ distance were greater (p50.05) for CS than for TS.
156 J. C. Girman et al.
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GH response, which has been demonstrated to exist
within homogenous populations (Raastad, Bjøro, &
Halle´n, 2000). In addition, while previous research-
ers have demonstrated increases in GH during
protocols using 2-min rest between resistance train-
ing sets (Ahtiainen et al., 2005; Linnamo et al.,
2005), other researchers have demonstrated that rest
interval lengths of 1 min or less induce the largest
GH response to exercise (Kraemer et al., 1990,
1991; Rahimi et al., 2010).
Researchers have indicated that the total degree of
metabolic stress of the exercise may determine the
magnitude of hormonal response to an acute exercise
bout (Ahtiainen et al., 2005; Gotshalk et al., 1997;
Ha
¨kkinen & Pakarinen, 1993). We observed higher
BL levels directly following the TS protocol of the
CP and BS exercises as compared to the CS
protocol, a finding supported by previous research
(Denton & Cronin, 2006; Goto et al., 2005; Iglesias-
Soler et al., 2012). Perhaps the total glycolytic stress
placed upon the body may have been affected by the
implementation of the controlled 2-0-2 tempo for
each BS repetition. Because no rest was taken
between repetitions in the TS protocol, greater
than 30s of continuous, high-intensity mechanical
work was performed per training set. Since a short
15s intra-rest was taken after every second repetition
during the CS protocol, only approximately 8s of
continuous, high-intensity mechanical work was
performed per cluster set, despite completing more
than 30s of total high-intensity work during the
overall training set. The short intra-set rest intervals
may have allowed for partial regeneration of PCr
stores (Lawton et al., 2006; Willardson, 2008),
resulting in low demand on anaerobic glycolysis
and ultimately less BL accumulation. Based on the
results of the present study, it appears that BL
accumulation is not the sole determinant of hormo-
nal response to exercise. Additionally, Kraemer et al.
(1990) reported no consistent relationship between
blood lactate and specific hormone responses to
exercise of varying rest interval length and duration
of exercise.
As a secondary purpose, we examined the effects
of TS and CS protocols of HRE on the sustaina-
bility of jump performance. While HRE protocols
Figure 2. (A) Percent change in countermovement vertical jump performance measures over time for cluster and traditional HRE
protocols. (B) Percent change in standing long jump performance measures over time for cluster and traditional HRE protocols.
Acute effects of a cluster-set protocol 157
Downloaded by [European College of Sport Science ] at 09:02 20 September 2014
designed to produce high levels of fatigue are
effective in stimulating muscular endurance and
hypertrophy, such set and repetition schemes may
be detrimental for power development (Lawton
et al., 2006). Power performance is primarily depen-
dent upon the phosphagen system. When sufficient
rest is not taken between resistance training sets,
energy production shifts to emphasise anaerobic
glycolysis, resulting in a lowered intracellular pH
and substantially depressed power-producing cap-
abilities (de Salles et al., 2009; Iglesias-Soler et al.,
2012). The TS protocol of HRE was observed to
induce larger elevations in BL and larger decreases in
jump performance than the CS protocol, suggesting
that two minutes of rest may be insufficient for
replenishment of PCr stores. Using a CS configura-
tion of one to three repetitions with short intra-set
rest periods may best utilise the fast recovery
component of PCr and potentially enhance power
development (Haff et al., 2003; Lawton et al., 2006).
In the current study, when total rest remained
constant and clusters of two reps were separated by
15s rest, jump performance was observed to be
better sustained throughout the HRE protocol.
Previous researchers who observed higher peak
power outputs during CS than TS exercise (Haff
et al., 2003; Hansen et al., 2011; Lawton et al, 2006)
directly assessed the power output produced during
each repetition of the actual lifting movement. In the
current study, power was not measured. Instead,
jump performance was measured with the CMVJ
and SLJ, two field tests that have been demonstrated
to be reliable and valid methods for estimating lower
body power in physically active men (Markovic,
Dizdar, Jukic, & Cardinale, 2004).
The results of the current study may have been
limited by the total rest period length between sets of
CP and BS. Further research is warranted to
investigate the acute effects of CS protocols of
HRE on total rest periods and anabolic hormone
responses as well as the effects of CS on long-term
hormonal and neuromuscular adaptations. Finally,
because the mean resistance training age (6.491.5
years) of the male participants was high, the results
of the current study may be limited to programming
training variations for highly trained individuals.
In summary, during a CS protocol of HRE,
elevations in GH and C were similar to those of a
TS protocol of HRE. However, the CS protocol
resulted in lower BL accumulation and better
sustainability of jump performance. While the overall
training volume and intensity of the two protocols
may have been sufficient to induce similar elevations
in GH and C which may favour increases in muscle
size and strength, the greater accumulation of BL
during the TS protocol may depress power-produ-
cing capabilities. The inclusion of intra-set rest
during a CS protocol may place less demand on
anaerobic glycolysis, thereby making the CS protocol
less metabolically taxing.
Conclusion
The results from this acute study suggest that a CS
protocol of HRE may elicit an improvement in
performance measures of jump performance in
resistance-trained men.
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Acute effects of a cluster-set protocol 159
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... In the companion article (3), we discussed the studies that elucidated mechanical responses between rest redistribution (RR) and traditional sets (TS) and how these responses can be affected by additional loads during the RR with heavier loads (RR 1 L) protocol. Apart from the mechanical responses, multiple researchers have focused on examining metabolic (10,14,27,30,31,33,39) and perceptual (1,7,16,18,19,26,27,33,39) responses to RR. Jukic et al. (15) demonstrated that the use of RR reduces mechanical fatigue, metabolic stress, and perceived exertion in a systematic review and meta-analysis. Nonetheless, various other physiological [endocrine (10,27,30), inflammatory (24,29), and cardiovascular (1,13)] responses have been elucidated less widely. ...
... Apart from the mechanical responses, multiple researchers have focused on examining metabolic (10,14,27,30,31,33,39) and perceptual (1,7,16,18,19,26,27,33,39) responses to RR. Jukic et al. (15) demonstrated that the use of RR reduces mechanical fatigue, metabolic stress, and perceived exertion in a systematic review and meta-analysis. Nonetheless, various other physiological [endocrine (10,27,30), inflammatory (24,29), and cardiovascular (1,13)] responses have been elucidated less widely. While mechanical responses per se provide information about performance and fatigue (15,22,38), an understanding of other physiological responses can provide more insight into various fatigue indices and training considerations from a longitudinal adaptation perspective (4)(5)(6)35). ...
... To date, studies have examined endocrine responses between RR and TS using the same % back squat (BS) 1 repetition maximum (1RM) (10,27,30). Oliver et al. (30) observed greater growth hormone (GH) (a main effect of protocol) and cortisol (C) (at 30 minutes postexercise) responses for TS compared with RR, but total testosterone (TT) responses were not found to be different. ...
Article
Chae, S, Hill, DW, Bailey, CA, Moses, SA, McMullen, SM, and Vingren, JL. Acute physiological and perceptual responses to rest redistribution with heavier loads in resistance-trained men. J Strength Cond Res XX(X): 000-000, 2022-The purpose of this study was to explore the effect of rest redistribution with heavier loads (RR + L) on physiological and perceptual responses in resistance-trained men. Eight men who had back squat (BS) 1 repetition maximum (1RM) to body mass ratio; 1.8 ± 0.2 completed 2 BS exercise sessions in a counterbalanced and a randomized order; RR + L: 4 sets of (2 × 5) repetitions with 90-second interset rest and 30-second intraset rest using 75% BS 1RM and traditional sets (TS): 4 sets of 10 repetitions with 120-second interset rest using 70% BS 1RM. Blood samples were collected before exercise, immediately post exercise, and 5, 15, and 30 minutes post exercise for the analysis of growth hormone (GH), total testosterone (TT), cortisol (C), and blood lactate (BL), whereas rating of perceived exertion (RPE) and heart rate (HR) were measured immediately after each set of the BS exercise. While neither main effect of condition nor interaction existed, there was a significant (p < 0.05) main effect of time point (and set) for GH, TT, C, BL, RPE, and HR. Volume load was greater for RR + L compared with TS (4,074.9 ± 786.7 kg vs. 3,796.3 ± 714.8 kg). In conclusion, RR + L increases volume load by approximately 7% but does not seem to influence GH (g = -0.15), TT (g = -0.09), BL (g = -0.22), RPE (g = 0.14), and HR (g = -0.08) responses. Practitioners may consider using RR + L to increase volume load without increasing acute fatigue responses.
... One study [72] was at unclear risk of attrition bias, not reporting how the outcome of interest was collected when participants could not complete the protocols. Two studies were at a high risk of effort bias since the participants were not encouraged to perform the concentric phase of the lift with the maximal intent or they used a metronome instead [72,75], whereas this information was unclear in one study [76]. Three studies were of a high risk of equipment bias since they used non-officially validated equipment to measure jump height or movement velocity [19,63,75]. ...
... Two studies were at a high risk of effort bias since the participants were not encouraged to perform the concentric phase of the lift with the maximal intent or they used a metronome instead [72,75], whereas this information was unclear in one study [76]. Three studies were of a high risk of equipment bias since they used non-officially validated equipment to measure jump height or movement velocity [19,63,75]. In addition, one study [72] used a rating of perceived exertion scale not validated for resistance training purposes and therefore, was also classified to be at a high risk of equipment bias. ...
Article
Full-text available
Background: The alteration of individual sets during resistance training (RT) is often used to allow for greater velocity and power outputs, reduce metabolite accumulation such as lactate and also reduce perceived exertion which can ultimately affect the resultant training adaptations. However, there are inconsistencies in the current body of evidence regarding the magnitude of the effects of alternative set structures (i.e., cluster sets and rest redistribution) on these acute mechanical, metabolic, and perceptual responses during and after RT. Objective: This study aimed to systematically review and meta-analyse current evidence on the differences between traditional and alternative (cluster and rest redistribution) set structures on acute mechanical, metabolic, and perceptual responses during and after RT, and to discuss potential reasons for the disparities noted in the literature. Methods The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were followed, and five databases were searched until June 2019. Studies were included when they were written in English and compared at least one acute mechanical, metabolic, or perceptual response between traditional, cluster or traditional and rest redistribution set structures in healthy adults. Random-effects meta-analyses and meta-regressions were performed where possible. Results: Thirty-two studies were included. Pooled results revealed that alternative set structures allowed for greater absolute mean [standardized mean difference (SMD) = 0.60] and peak velocity (SMD = 0.41), and mean (SMD = 0.33) and peak power (SMD = 0.38) during RT. In addition, alternative set structures were also highly effective at mitigating a decline in velocity and power variables during (SMD = 0.83-1.97) and after RT (SMD = 0.58) as well as reducing lactate accumulation (SMD = 1.61) and perceived exertion (SMD = 0.81). These effects of alternative set structures on velocity and power decline and maintenance during RT were considerably larger than for absolute velocity and power variables. Subgroup analyses controlling for each alternative set structure independently showed that cluster sets were generally more effective than rest redistribution in alleviating mechanical, metabolic, and perceptual markers of fatigue. Conclusion: Alternative set structures can reduce mechanical fatigue, perceptual exertion, and metabolic stress during and after RT. However, fundamental differences in the amount of total rest time results in cluster sets generally being more effective than rest redistribution in alleviating fatigue-induced changes during RT, which highlights the importance of classifying them independently in research and in practice. Additionally, absolute values (i.e., mean session velocity or power), as well as decline and maintenance of the mechanical outcomes during RT, and residual mechanical fatigue after RT, are all affected differently by alternative set structures, suggesting that these variables may provide distinct information that can inform future training decisions. Protocol Registration The original protocol was prospectively registered (CRD42019138954) with the PROSPERO (Inter-national Prospective Register of Systematic Reviews).
... This has been verified in the literature studies that adopted ISI between 2.85 s 14 and 130 s 13 . However, intermediate ISI values (10 s to 40 s) seem to be more frequently used [16][17][18][19] . Most studies did not adopt clear criteria for choosing the magnitude of the ISI and only Ho et al. (2021) 18 investigated the effects of two or more protocols with different ISI. ...
Article
Objective: To compare the acute effect of two training protocols until concentric failure (CF) with different intra-set interval (ISI) configurations (20 s and 40 s) on total weight, the total number of repetitions, and time under tension in trained subjects. Methods: Ten men participated in the study (age = 25.1 ± 4.4 years; body mass = 76.5 ± 10.4 kg; height = 175.8 ± 9.3 cm). Two protocols were performed with 4 sets of bench press exercises and differentiated by the ISI: i) Protocol ISI-40 (40 s) - each set consisted of 6 repetitions followed by an ISI of 40 s and completed with repetitions up to CF; ii) Protocol ISI-20 (20 s) - each set consisted of 6 repetitions with ISI of 20 s every 3 repetitions followed by repetitions to CF. The intensity was 10 repetitions maximum, and the rest interval between sets of 80 s. A minimum interval of 48 h was adopted between protocols. Results: There was no significant difference in the number of repetitions (p = 0.074), in the time under tension (p = 0.353) and in the total volume (p = 0.083) between the protocols. Conclusion: The results indicate that the different ISI configurations did not distinctly influence the number of repetitions, time under tension, and total volume.
... CS is a set structure in which a short rest interval (15-45 seconds) is applied between repetitions to provide partial recovery and maximize movement speed and strength [10,11,12]. Recently, several studies have shown that instead of rest between sets, rest intervals between repetitions (cluster sets) result in lower speed and strength loss throughout the entire training session, improve mechanical performance [13], and allow larger training volume [11,13,14,15] and can reduce accumulated fatigue seen during the traditional set while maximizing repetition performance [10,11,12,16,17]. ...
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Full-text available
Background and Study Aim: This study aims to examine the effects of the Triphasic Training Model (TTM) applied with different set designs (15-30 sec intra-set) on reactive strength index (RSI) and vertical jump values. Material and Methods:. Sixteen male athletes over 18 with at least three years of strength training experience (2 days a week) actively engaged in sports participated in the study. The study group was divided into two groups by calculating the relative strengths. The 15-second cluster set (C15) group exercises were performed with 15 seconds of rest between repetitions, and the 30-second cluster-set (C30) group practiced the exercises with 30 seconds of rest between repetitions. The triphasic training model was applied to all study groups for six weeks. Countermovement jump (CMJ) and drop jump tests were performed on the athletes before and after the training. Optojump brand photocell system was used for CMJ and RSI tests. For the RSI test, the desk height was determined as 40cm. Kolmogorov-Smirnov values were examined to assess the homogeneity of the data. To compare the means between groups, ANOVA was used for Repeated Measures, and a t-test was used to compare the pretest-posttest mean of the groups. The statistical significance level was determined as p
... Therefore, to induce muscle hypertrophy with lighter loads (55%-70% 1RM), it may be necessary to attain higher VL thresholds than with higher intensities (70%-85% 1RM). Fatiguing bouts of resistance exercise are associated with increased metabolite accumulation, 14 endogenous hormone secretion, 15,16 and higher mechanical tension, 17 which may contribute to muscle hypertrophy. 18,19 Likewise, it has recently been shown that high VL thresholds using the squat exercise resulted in an increased basal Ca 2+ /calmodulin II-dependent protein kinase δ D phosphorylation (Thr 286 -CaMKII δ D ), which was associated with muscle hypertrophy and the number of repetitions completed during the training intervention. ...
Article
Purpose: To compare the effect of 4 velocity-loss (VL) thresholds-0% (VL0), 15% (VL15), 25% (VL25), and 50% (VL50)-on strength gains, neuromuscular adaptations, and muscle hypertrophy during the bench press (BP) exercise using intensities ranging from 55% to 70% of 1-repetition maximum (1RM). Methods: Fifty resistance-trained men were randomly assigned to 4 groups that followed an 8-week (16 sessions) BP training program at 55% to 70% 1RM but differed in the VL allowed in each set (VL0, VL15, VL25, and VL50). Assessments performed before (pre) and after (post) the training program included (1) cross-sectional area of pectoralis major muscle, (2) maximal isometric test, (3) progressive loading test, and (4) fatigue test in the BP exercise. Results: A significant group × time interaction was found for 1RM (P = .01), where all groups except VL0 showed significant gains in 1RM strength (P < .001). The VL25 group attained the greatest gains in 1RM strength and most load-velocity relationship parameters analyzed. A significant group × time interaction was observed for EMG root mean square in pectoralis major (P = .03) where only the VL25 group showed significant increases (P = .02). VL50 showed decreased EMG root mean square in triceps brachii (P = .006). Only the VL50 group showed significant increases in cross-sectional area (P < .001). Conclusions: These findings indicate that a VL threshold of about 25% with intensities from 55% to 70% 1RM in BP provides an optimal training stimulus to maximize dynamic strength performance and neuromuscular adaptations, while higher VL thresholds promote higher muscle hypertrophy.
... Therefore, to induce muscle hypertrophy with lighter loads (55%-70% 1RM), it may be necessary to attain higher VL thresholds than with higher intensities (70%-85% 1RM). Fatiguing bouts of resistance exercise are associated with increased metabolite accumulation, 14 endogenous hormone secretion, 15,16 and higher mechanical tension, 17 which may contribute to muscle hypertrophy. 18,19 Likewise, it has recently been shown that high VL thresholds using the squat exercise resulted in an increased basal Ca 2+ /calmodulin II-dependent protein kinase δ D phosphorylation (Thr 286 -CaMKII δ D ), which was associated with muscle hypertrophy and the number of repetitions completed during the training intervention. ...
Purpose: To compare the effect of 4 velocity loss (VL) thresholds—0%, 15%, 25% (VL25), and 50% (VL50)—on strength gains, neuromuscular adaptations, and muscle hypertrophy during the bench press (BP) exercise using intensities ranging from 55% to 70%, 1-repetition maximum (1RM). Methods: Fifty resistance-trained men were randomly assigned to 4 groups that followed an 8-week (16 sessions) BP training program at 55% to 70% 1RM but differed in the VL allowed in each set (VL 0%, VL 15%, VL25, and VL50). Assessments performed before (pre) and after (post) the training program included: (1) crosssectional area of pectoralis major muscle; (2) maximal isometric test; (3) progressive loading test; and (4) fatigue test, in the BP exercise. Results: A significant group × time interaction was found for 1RM (P = .01), where all groups except VL 0% showed significant gains in 1RM strength (P < .001). The VL25 group attained the greatest gains in 1RM strength and most load–velocity relationship parameters analyzed. A significant group × time interaction was observed for EMG root mean square in pectoralis major (P = .03) where only the VL25 group showed significant increases (P = .02). VL50 showed decreased EMG root mean square in triceps brachii (P = .006). Only the VL50 group showed significant increases in cross-sectional area (P < .001). Conclusions: These findings indicate that a VL threshold of about 25% with intensities from 55% to 70% 1RM in BP provides an optimal training stimulus to maximize dynamic strength performance and neuromuscular adaptations, while higher VL thresholds promote higher muscle hypertrophy.
... In relation to La accumulation, TT showed higher values in this parameter after training with respect to cluster configurations. This is in agreement with previous studies that examined the effect of different set configurations on metabolic responses [17,19,23,39]. ...
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