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Greater Gains in Strength and Power With Intraset Rest Intervals in Hypertrophic Training

Authors:
  • Gatorade Sport Science Institute
  • Mayo Clinic Health System

Abstract and Figures

We sought to determine if hypertrophic training with intra-set rest intervals (ISR) produced greater gains in power compared to traditional (TRD) hypertrophic training. Twenty-two males (25±5yrs, 179.71±5.04cm, 82.1±10.6kg, 6.5±4.5yrs training) matched according to baseline characteristics were assigned to 12 weeks training using TRD or ISR. Body composition, strength (1RM bench and squat), and power output (60% 1RM bench and squat, and vertical jump) were assessed at baseline, 4, 8, and 12 weeks. Determination of myosin heavy chain (MHC) percentage from the vastus lateralis was performed pre and post training. Body composition was analyzed by ANOVA, while performance measures and MHC were analyzed by ANCOVA with baseline values as the covariate. Data are presented as means ± SD changes pre to post. ISR produced greater power output in bench (TRD 32.8±53.4W; ISR 83.0±49.9W, p=0.020) and vertical jump (TRD 91.6±59.8W; ISR 147.7±52.0W; p=0.036) with squat power approaching significance (TRD 204.9±70.2W; ISR 282.1±104.2W; p=0.053) after post hoc analysis (p<0.10). ISR produced greater gains in bench (TRD 9.1±3.7kg; ISR 15.1±8.3kg; p=0.010) and squat (TRD 48.5±17.4kg; ISR 63.8±12.0kg; p=0.002) strength. Both protocols produced significant gains in lean mass with no significant differences between groups (1.6±2.1kg; p=0.869). MHCIIX percentage decreased (-31.0±24.5%; p = 0.001) while MHCIIA percentage increased (28.9±28.5%; p=0.001) with no significant differences between groups. Results indicate that hypertrophy training with ISR produces greater gains in strength and power, with similar gains in lean mass and MHC alterations as TRD. ISR may be best used in hypertrophic training for strength and power sports.
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GREATER GAINS IN STRENGTH AND POWER WITH
INTRASET REST INTERVALS IN HYPERTROPHIC
TRAINING
JONATHAN M. OLIVER,
1,2
ANDREW R. JAGIM,
1
ADAM C. SANCHEZ,
3
MICHELLE A. MARDOCK,
4
KATHERINE A. KELLY,
5
HOLLY J. MEREDITH,
6
GERALD L. SMITH,
3
MIKE GREENWOOD,
1
JANET L. PARKER,
5
STEVEN E. RIECHMAN,
1
JAMES D. FLUCKEY,
1
STEPHEN F. CROUSE,
1
AND
RICHARD B. KREIDER
1
1
Department of Health and Kinesiology, Texas A&M University, College Station, Texas;
2
Department of Kinesiology,
Texas Christian University, Fort Worth, Texas;
3
Texas A&M Naval ROTC Unit, Texas A&M University, College Station,
Texas;
4
Walter Reed National Military Medical Center, Bethesda, Maryland;
5
Department of Systems Biology and
Translational Medicine, Texas A&M University Health Science Center, College Station, Texas; and
6
2d Maintenance
Battalion, United States Marine Corps, Camp Lejeune, North Carolina
ABSTRACT
Oliver, JM, Jagim, AR, Sanchez, AC, Mardock, MA, Kelly, KA,
Meredith, HJ, Smith, GL, Greenwood, M, Parker, JL, Riechman,
SE, Fluckey, JD, Crouse, SF, and Kreider, RB. Greater gains in
strength and power with intraset rest intervals in hypertrophic
training. J Strength Cond Res 27(11): 3116–3131, 2013—We
sought to determine if hypertrophic training with intraset rest
intervals (ISRs) produced greater gains in power compared
with traditional rest (TRD) hypertrophic training. Twenty-two
men (age 25 65 years, height 179.71 65.04 cm, weight
82.1 610.6 kg, 6.5 64.5 years of training) matched according
to baseline characteristics were assigned to 12 weeks of train-
ing using TRD or ISR. Body composition, strength (1-repetition
maximum [1RM] bench and squat), and power output (60%
1RM bench and squat, and vertical jump) were assessed at
baseline, 4, 8, and 12 weeks. Determination of myosin heavy
chain (MHC) percentage from the vastus lateralis was per-
formed pretraining and posttraining. Body composition was ana-
lyzed by analysis of variance, whereas performance measures
and MHC were analyzed by analysis of covariance with baseline
values as the covariate. Data are presented as mean 6SD
changes pre to post. The ISR produced greater power output
in bench (TRD 32.8 653.4 W; ISR 83.0 649.9 W, p= 0.020)
and vertical jump (TRD 91.6 659.8 W; ISR 147.7 652.0 W;
p= 0.036) with squat power approaching significance (TRD
204.9 670.2 W; ISR 282.1 6104.2 W; p= 0.053) after post
hoc analysis (p,0.10). The ISR produced greater gains in
bench (TRD 9.1 63.7 kg; ISR 15.1 68.3 kg; p=0.010)
and squat (TRD 48.5 617.4 kg; ISR 63.8 612.0 kg;
p= 0.002) strength. Both protocols produced significant gains
in lean mass with no significant differences between groups
(1.6 62.1 kg; p= 0.869). The MHC
IIx
percentage decreased
(231.0 624.5%; p= 0.001), whereas the MHC
IIA
percentage
increased (28.9 628.5%; p= 0.001) with no significant differ-
ences between groups. Results indicate that hypertrophy training
with ISR produces greater gains in strength and power, with similar
gains in lean mass and MHC alterations as TRD. The ISR may be
best used in hypertrophic training for strength and power sports.
KEY WORDS intraset rest intervals, cluster training,
interrepetition rest, power, strength, performance
INTRODUCTION
The velocity of contraction decreases over the
course of performance of successive repetitions
(21). In sports where the ability to generate power
is a necessary aspect of performance, the resultant
decrease in velocity is counter to the principle of specificity.
One method for counteracting the aforementioned phenom-
enon is to reduce the number of repetitions performed at
a given percentage repetition maximum (%RM). Although
reducing the number of repetitions enables less reduction in
power output over successive sets (35), to achieve the same
volume of training this method extends the total training
time. This is a consideration to both individuals and strength
coaches as time with athletes is often regulated. Other meth-
ods for the maintenance of velocity, and thus power output,
include interrepetition rest, intraset rest (27), and cluster sets
(16,17). Interrepetition rest training involves a brief rest
between each repetition, whereas intraset rest incorporates
rest between groups of repetitions (27). Cluster sets is a more
Address correspondence to Jonathan M. Oliver, jonathan.oliver@tcu.edu.
27(11)/3116–3131
Journal of Strength and Conditioning Research
Ó2013 National Strength and Conditioning Association
3116
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specific form of interrepetition rest in which only a 10- to
30-second rest is employed between each repetition or
group of repetitions within a set (16,17).
Previous studies comparing traditional (4 set 36 repeti-
tions with 260-second rest) and intraset rest (8 sets of 3 with
113-second rest) using intensities $85% 1RM in upper body
exercises have demonstrated that intraset rest intervals
(ISRs) do not provide a benefit over training with traditional
rest (TRD) (13,27). However, lower body training with clus-
ter sets has demonstrated a tendency toward greater gains in
measures of power output (19), whereas intraset rest has
demonstrated significantly greater gains in power output
compared with TRD between sets in athletes (22). The only
study demonstrating significantly greater gains on power
output was performed over a periodized training period to
include phases of hypertrophy, strength, and power.
Izquierdo et al. (21) demonstrated that the reduction in
average velocity was similar over all intensities examined
using intensities prescribed for the development of hypertro-
phy. Although the process of hypertrophy is no doubt mul-
tifactorial, the recommended intensity for the development
of hypertrophy (4) corresponds with that for the develop-
ment of muscular power in trained subjects performing mul-
tijoint exercises (24). Furthermore, it has been demonstrated
that the total volume load and intensity at which that vol-
ume load is performed are the primary variables associated
with optimal gains in lean mass (10). Thus, if the total vol-
ume load is equated, intraset rest may allow for greater
velocity training, resulting in a greater improvement in
power over TRD while producing similar gains in lean mass.
Despite this evidence, the effect of ISRs in a periodized resis-
tance training program designed specifically to elicit hyper-
trophy has not been evaluated. Therefore, the purpose of our
investigation was to determine if intraset rest hypertrophy
training, equated for total volume load and rest, improved
power more than traditional hypertrophy training. We
hypothesized ISRs would result in greater gains in power
output compared with TRD, whereas both training interven-
tions would produce similar gains in strength and lean mass.
Although it is well established that resistance training
results in a shift in myosin heavy chain (MHC) composition,
primarily an increase in percentage of MHC
IIA
and
MHC
IIA/x
hybrids with a concomitant decrease in MHC
IIx
(10), recent evidence suggests that changes in MHC com-
position may be velocity dependent. Liu et al. (29) demon-
strated a shift in the MHC
slow
to MHC
IIA
with no change in
the MHC
IIx
when performing traditional resistance training
followed by ballistic exercise. Higher peak velocities have
been reported using ISRs (17). However, whether or not
differential effects manifest in MHC composition as a result
of training with ISRs has yet to be determined. Therefore,
a secondary purpose of our investigation was to evaluate
changes in MHC composition as a result of ISRs. We
hypothesized that ISRs would result in less reduction in
the MHC
IIx
percentage compared with TRD.
METHODS
Experimental Approach to the Problem
A longitudinal research design was employed to compare
the effects of TRD and ISRs in a program designed to elicit
hypertrophy. To eliminate any possible confounding factors,
the type and order of exercises performed and the volume
load and total rest were equated between groups. This was
critical to the design of the study as others have shown
variations in these variables to impact training adaptations
(10). After baseline testing, the subjects were matched
according to baseline physical and performance character-
istics and randomly assigned to perform hypertrophic train-
ing using TRD or intraset rest (ISR) within a periodized
hypertrophic training program. Body composition, strength,
and power output of the upper and lower body musculature
were assessed at baseline, after 4, 8, and 12 weeks of training.
Dietary intake was reported, and analysis was conducted
before each testing session. Muscle biopsies for MHC con-
tent were performed at baseline and at the conclusion of
the training program.
Subjects
Twenty-two men completed this study. Selection criteria
included (a) men between the ages of 20 and 35; (b) having
at least 2 years of resistance training experience to include
upper and lower body at least once per week; and (c)
reporting not having consumed any nutritional or ergogenic
supplements excluding protein supplementation and a daily
vitamin for the previous 6-week period. Those meeting entry
criteria were asked to fill out a medical history questionnaire
to eliminate those with any possible contraindications to
exercise. The subjects meeting all criteria were informed of
the experimental procedures and asked to sign an informed
consent approved by the Institutional Review Board. Base-
line characteristics for the 22 subjects (n= 22) are presented
in Table 1.
Of the 22 subjects, 45% (n= 10) were active duty military,
41% (n= 9) were members of the Naval Reserve Officer
Training Corps Unit, whereas the remaining 14% (n=3)
were not involved in military operations. All the subjects
reported participating in resistance training of both upper
and lower body at least once a week for the previous 2 years.
Evaluation of self-report logs demonstrated that the subjects
primarily engaged in resistance training for the development
of strength and hypertrophy. Additionally the subjects re-
ported having consistently engaged in endurance (primarily
running) and high-intensity interval training as part of their
training before participation in training intervention. None of
the subjects were competitive weightlifters.
Testing Sessions
Figure 1 provides a summary of testing and training proce-
dures. Before baseline testing, the subjects underwent an
exercise familiarization session led by a National Strength
and Conditioning Association (NSCA) Certified Strength
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and Conditioning Specialist (CSCS) to demonstrate profi-
ciency in all lifts used for training and testing. During the
same week, the subjects attended a nutrition seminar detail-
ing macronutrient guidelines for athletes involved in a resis-
tance training program (5) and instruction on proper dietary
intake recording provided by a registered dietitian. Before
each testing session, the subjects completed a dietary record
to include 3 weekdays and 1 weekend day. Dietary recording
was completed 1 week before each testing session corre-
sponding to the highest vol-
ume and intensity of training
during each 4-week cycle
(Figure 1). All food logs were
reviewed by a registered dieti-
tian and analyzed using dietary
analysis software (ESHA Food
Processor Version 8.6, Salem,
OR, USA). Postworkout sup-
plementation (20 g of protein,
45 g of carbohydrates, 3.5 g of
fat) was provided on training
days (Muscle Milk Collegiate;
Cytosport, Benicia, CA, USA)
for all the subjects. In the week
of testing sessions, the subjects
reported to the laboratory after having fasted for at least 10
hours for body composition measurement. Height and body
mass were recorded to the nearest 0.01 cm and 0.02 kg,
respectively, using a self-calibrating digital scale (Healthometer,
Bridgeview, IL, USA) in socks or bare feet. Body composi-
tion was then determined using dual x-ray absorptiometry
(DEXA; Hologic Discovery W DXA software version 12.1,
Waltham, MA, USA) calibrated according to the manufac-
turer’s guidelines and performed by a trained technician.
Previous studies indicate DEXA
to be an accurate and reliable
means to assess changes in
body composition (3). The sub-
jects had their strength and
power output assessed accord-
ing to standardized procedures
outlined below. Muscle biopsies
were obtained before baseline
testing and at the conclusion
of the exercise intervention.
Strength Testing
Upper and lower body
strength was assessed using
the 1RM parallel back squat
(1RM
BS
) and bench press
(1RM
BP
) exercises. The sub-
jects reported to the laboratory
after having refrained from any
exercise outside of daily living
for at least 72 hours before
baseline testing and at least 48
hours before testing in weeks 4,
8, and 12. The initial progres-
sion strategy for 1RM determi-
nation of both exercises was
estimated from self-reporting.
Subsequent 1RM progression
strategies were based on
TABLE 1. Baseline group characteristics.*
TRD ISR Combined p
Age (y) 25 6525642565 0.790
Height (cm) 179.71 66.18 179.71 63.90 179.71 65.04 1.000
Body mass (kg) 81.7 611.6 82.5 610.0 82.1 610.6 0.878
Lean mass (kg) 61.9 68.9 63.3 67.0 62.6 67.9 0.689
Fat percentage (%) 14.3 62.7 12.9 65.5 13.6 64.3 0.466
Years trained 6.5 64.0 6.0 65.0 6.5 64.5 0.815
# Days trained 3.5 62.0 3.5 62.0 3.5 62.0 1.000
*TRD = traditional rest; ISR = intraset rest intervals; Combined = collapsed across time.
Data are mean 6SD.
Figure 1. Testing and training program design.
Intraset Rest Intervals in Hypertrophic Training
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training logs kept throughout the study. A dynamic warm-
up lasting approximately 8–10 minutes was performed
before 1RM determination. Two warm-up sets of 5 repeti-
tions at 40–60% 1RM separated by 2 minutes of rest were
followed by a 3-minute rest period and 1–2 sets of 2–3 rep-
etitions at a load corresponding to 60–80% 1RM. The sub-
jects then began performing sets of 1 repetition of increasing
weight for 1RM determination. Three to 5 minutes of rest
was provided between each successive attempt. All 1RM
determinations were made within 3–5 attempts. The subjects
were required to reach parallel in the 1RM
BS
for an attempt
to be considered successful as determined by a CSCS certi-
fied individual providing a verbal “up” command. The
1RM
BP
was considered successful if the subject remained
in contact with the bench during the entire concentric phase
of the lift. The 1RM
BS
testing was conducted before 1RM
BP
separated by a 5-minute rest period. The same 1RM testing
procedure was used for both exercises. All strength testing
took place on an Optima Smith Machine (LifeFitness, Schil-
ler Park, IL, USA) without counterbalance technology. Foot
placement was recorded during baseline 1RM
BS
testing, and
hand placement was recorded at baseline 1RM
BP
testing.
These measurements
were then used in subse-
quent testing for strength
and power. All testing ses-
sions were supervised by
2 CSCS certified individ-
uals to determine success
during each attempt.
Power Testing
Power testing com-
menced at least 48 hours
post 1RM testing. The
subjects performed the
same warm-up before initiation of power testing. Body mass
and reach height were recorded for calculation of power as
determined by vertical jump. Two countermovement vertical
jumps (CMJs) using less than maximal effort were allowed
before testing. Three maximum effort CMJs were then
recorded separated by 2 minutes of rest. If the third attempt
was greater than the first 2, another attempt was allowed
until a decrease in jump height was observed with not .5
maximum CMJs allowed. Reach height and jump height
were recorded using a commercially available Vertec system
(Sports Imports, Columbus, OH, USA). The maximum
attempt of record was later converted to power in watts
(PWR
VJ
) using previously described procedures (38).
After vertical jump testing, power output was assessed
during the concentric phase of the parallel back squat
(PWR
BS
) and bench press (PWR
BP
) exercises using a relative
load of 60% 1RM per each respective exercise. The PWR
BS
was determined preceding PWR
BP
separated by 5 minutes of
rest. All testing was performed on the same Smith machine
used for 1RM testing. The subjects were instructed to per-
form the concentric phase of each lift as explosively as pos-
sible, preceded by the eccentric phase. After warm-up sets,
TABLE 2. The ICCs and Pearson product-moment coefficient (r) between trials.*
Day 1 Day 2 ICC r
Bench press 1RM 135.4 628.6 137.0 628.0 0.99 0.001
Back squat 1RM 171.9 647.4 173.5 647.6 0.99 0.001
Bench press power (60% 1RM) 657 6147 665 6140 0.98 0.001
Back squat power (60% 1RM) 860 6295 868 6275 0.97 0.001
*ICC = Intraclass correlation coefficients; RM = repetition maximum.
Day 1 and day 2 values are mean 6SD.
TABLE 3. Exercise performed during training.*
Day 1 (upper body push)
Day 2 (lower body +
upper body pull)
Day 3 (upper
body push)
Day 4 (lower body +
upper body pull)
Bench presszSquatszIncline presszFront squatz
Incline DB pressLeg pressDB benchDB RDL
Seated DB military pressPartial DL to power shrugPush pressDB step-up
DB flat fly Pull-ups§ DB incline fly Pull-ups§
Front DB raise One arm DB row DB rear delt Close grip lat pull-down
Side DB raises Hamstring curl Side DB raises T bar row
Straight bar skull crusher EZ bar curl EZ bar skull crusher Straight bar curl
Dips§ DB curl Dips§ DB curl
*DB = dumbbell; DL = deadlift; RDL = Romanian deadlift.
Main lift exercise performed according to training protocol (TRD or ISR), concentric phase explosively as possible.
zExercise performed on the Smith Machine.
§Exercise performed with 3 sets of maximum repetitions with 1.5 minutes of rest.
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3 sets of 5 repetitions at 40–50% 1RM, the subjects began
performing single repetitions at 60% 1RM for determination
of mean power output. During the parallel back squat, rub-
ber tubing was placed at the parallel point. This position was
determined during strength testing and ensured the subjects
reached the appropriate parallel position for the attempt to
be a success. Three attempts were allowed with the best
recorded for further analysis. If the third attempt was
greater than the first 2, another attempt was recorded until
power output declined with not .5 attempts allowed.
Three minutes rest was used between successive maximal
power attempts. Power output was measured using a linear
position transducer (Tendo Fitrodyne; Tendo Sport
Machines, Slovak Republic) with only bar weight used for
the determination of average power. The highest average
power output was used for statistical analysis. The reliability
of the Fitrodyne (Tendo Fitrodyne; Tendo Sport Machines,
Slovakia) has been previously reported (23). During post-
training (12 weeks), power output was assessed on both
parallel back squat (APWR
BS
) and bench press (APWR
BP
)
using loads corresponding to 60% baseline 1RM followed by
60% posttraining 1RM.
Reliability of Strength and Power Testing
The reproducibility of the methods for determination of strength
andpowerwereassessedin2trialsseparatedby7daysin10
resistance trained men (age 25 65 years, height 181.48 611.21
cm, weight 91.3 614.0 kg with 8 65 years 5 61d$wk
21
resistance training experi-
ence). After signing consent
forms approved by the
Institutional Review Board,
the subjects performed
strength and power output
assessment according to the
previously described proce-
dures. After 7 days, the sub-
jects returned to perform
the same testing protocol.
The reliability statistics are
presented in Table 2.
Training
All training sessions com-
menced with a dynamic
TABLE 4. Kilocalories, protein, carbohydrate, and fat intake, percent of total kilocalories, and relative intake at
baseline, 3, 7, and 11 weeks of training.*
Baseline 3 wks 7 wks 11 wks p
Overall
kcal 2,620 6581 2,918 6601 2,923 6573 2,793 6481 T= 0.084
Protein (g) 147 639 196 650z191 634z201 640zT= 0.001
Carbohydrate (g) 261 694 270 663 231 685§ 182 669z§kT= 0.001
Fat (g) 101 633 109 632 110 632 101 626 T= 0.517
Percent total kcal
Protein (%) 22.7 64.6 26.8 63.5z27.2 68.0z29.1 65.8z§T= 0.001
Carbohydrate (%) 40.1 613.3 37.4 66.9 31.0 69.0z§ 26.0 68.5z§kT= 0.001
Fat (%) 34.4 68.0 33.5 64.7 33.8 65.6 32.7 67.2 T= 0.754
Relative to bodyweight
kcal (g$kg
21
) 32.3 67.9 35.5 68.2 35.7 69.5 33.6 66.8 T= 0.128
Protein (g$kg
21
) 1.8 60.5 2.4 60.7z2.3 60.5z2.4 60.5zT= 0.001
Carbohydrate (g$kg
21
) 3.3 61.3 3.3 60.8 2.8 61.1z§ 2.2 60.8z§kT= 0.001
Fat (g$kg
21
) 1.2 60.4 1.3 60.4 1.4 60.5 1.2 60.4 T= 0.424
*T= time effect.
Data are mean 6SD.
zSignificantly different from baseline.
§Significantly different from 3 weeks.
kSignificantly different from 7 weeks.
TABLE 5. Total training volume for TRD and ISR over 12 weeks of training.*z
TRD ISR p
Major lifts (kg)
Upper body 102,711.67 625,484.80 119,728.80 622,587.40 0.113
Lower body 220,811.80 635,827.50 235,807.10 635,002.30 0.333
Assistive lifts
Push 34,041.40 69,085.40 37,356.70 610,251.40 0.432
Pull 58,978.80 67,697.00 60,791.90 611,089.70 0.661
*TRD = traditional rest; ISR = intraset rest intervals.
Data are mean 6SD.
zMajor lifts performed according to group assignment. Assistive lifts all performed same rest to
work ratio.
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warm-up identical to that used for strength and power
testing. Four supervised workouts a week were performed in
the following sequence: 2 days on, 1 day off, 2 days on, 2
days off. Training intensity was structured into 4-week cycles
of increasing intensity as described in Figure 1 with an
unloading week during each week of testing. All the sessions
were supervised by trained staff with at least 1–2 CSCS
certified personnel leading sessions. The subjects were not
TABLE 6. Power measures at baseline, 4, 8, and 12 weeks of training.*
TRD ISR p
Bench press power (W)
Baseline 560 6122 575 6102 T= 0.568
4 wks 541 6105 586 6123 G= 0.011
8 wks 572 6122 646 6103z§kT3G= 0.020
12 wks 593 6135k658 6113z§k
Bench press power to body mass ratio
Baseline 6.84 60.96 6.99 61.10 T= 0.627
4 wks 6.46 60.91 7.09 61.28 G= 0.056
8 wks 6.77 60.92 7.77 60.92z§kT3G= 0.003
12 wks 6.96 60.96k7.90 61.24z§k
Bench press to lean mass ratio
Baseline 9.01 61.14 9.07 61.21 T= 0.793
4 wks 8.56 61.24 9.18 61.32 G= 0.066
8 wks 8.88 61.11 10.02 60.96z§kT3G= 0.006
12 wks 9.20 61.39k10.21 61.17z§k
Back squat power (W)¶
Baseline 625 6245 632 6171 T= 0.001
4 wks 704 6233§ 734 6179§ G= 0.081
8 wks 723 6227§ 783 6179§ T3G= 0.053
12 wks 830 6232§k# 914 6207§k#
Back squat to body mass ratio¶
Baseline 7.57 62.23 7.83 62.33 T= 0.001
4 wks 8.37 62.14§ 9.09 62.42§ G= 0.101
8 wks 8.53 61.94§ 9.57 62.35z§T3G= 0.015
12 wks 9.78 62.03§k# 11.11 62.64§k#
Back squat to lean mass ratio¶
Baseline 9.96 62.77 10.19 62.62 T= 0.001
4 wks 11.04 62.57§ 11.83 62.65§ G= 0.068
8 wks 11.15 62.31§ 12.41 62.63z§T3G= 0.017
12 wks 12.86 62.49§k# 14.45 62.87z§k#
Vertical jump power (W)¶
Baseline 1,378 6237 1,389 6179 T= 0.001
4 wks 1,418 6214 1,434 6152 G= 0.205
8 wks 1,452 6210§ 1,470 6149§ T3G= 0.036
12 wks 1,470 6215§k1,537 6150z§k#
Vertical jump to body mass ratio¶
Baseline 16.83 61.36 17.12 62.05 T= 0.001
4 wks 16.93 61.28 17.71 61.98§ G= 0.243
8 wks 17.27 61.22 18.01 61.76§ T3G= 0.001
12 wks 17.36 61.13k18.68 61.72z§k#
Vertical jump to lean mass ratio¶
Baseline 22.19 61.37 22.40 61.95 T= 0.001
4 wks 22.40 61.10 22.16 61.72 G= 0.141
8 wks 22.66 61.11 23.41 61.42§ T3G= 0.004
12 wks 22.89 61.11 24.40 61.38z§k#
*TRD = traditional rest; ISR = intraset rest intervals; T= time effect; G= group effect; T3G= time 3group interaction effect.
Data are mean 6SD.
zSignificantly different from TRD.
§Significantly different from baseline.
kSignificantly different from 4 weeks.
One subject was excluded because of failure to follow protocol.
#Significantly different from 8 weeks.
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engaged in any other training outside of daily living for the
duration of the study.
Throughout the training program, both groups performed
the same exercises, in the same order and intensity (Figure 1).
Table 3 provides the exercises
performed and the order in
which they were performed.
All major lifts tested for
strength and power output
were performed on the same
apparatus used for the determi-
nation of 1RM and power out-
put. The subjects were
instructed to perform the con-
centric phase of all major lifts
in an explosive manner. Verbal
encouragement was provided
throughout training. To deter-
mine differences between train-
ing programs, groups differed
on the sets, repetitions and rest
in all major lifts performed
(Figure 1). The subjects in
TRD performed a standard
hypertrophic training protocol
of 4 sets of 10 repetitions for all
major lifts with 120 seconds of
rest between sets. In accor-
dance with previous studies
evaluating ISR (12,27), each
set was divided into half, and
rest was equated so that the
ISR group performed 8 sets of
5 repetitions with 60 seconds
of rest. This manipulation of
rest to work where the set is
divided in half using an intraset
rest and equating rest between
groups has previously been
used for the determination of
differences between TRD and
ISR in strength training
(12,27). Both TRD and ISR
performed 3 sets of 10 repeti-
tions with 90 seconds of rest
for all assistive lifts. The load
was reduced if the subjects
were unable to complete the
prescribed number of repeti-
tions. Intensity was increased
if the subjects were able to
complete at least 85% of the
total volume on major lifts.
Timing of rest was performed
using stop watches on all lifts
by trained personnel. The total volume load (weight 3reps
3sets) was grouped according to lifts using the upper and
lower body for main lifts and push and pull exercises for
assistive exercises for later analysis. The training intensity
Figure 2. Percent change in mean power from baseline in bench press (A), parallel back squat (B), and vertical
jump (C). Data are mean 6standard error. TRD = traditional rest; ISR = intraset rest intervals; significantly
different from baseline; zsignificantly different from 4 weeks; § significantly different from 8 weeks; *significantly
different from TRD.
Intraset Rest Intervals in Hypertrophic Training
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(total volume load/repetitions performed) was grouped
according to upper and lower body for main lifts only.
Workout logs were maintained and verified throughout the
12-week period. Compliance throughout the entire 12-week
study was 95%.
Biopsy and Myosin Heavy Chain Analysis
Before baseline testing and within 72 hours of posttesting,
a 100- to 200-mg muscle biopsy of the vastus lateralis was
obtained from the participant’s right leg with suction using
a 5-mm biopsy needle (Pelomi Industries, Denmark) accord-
ing to a modification of Bergstrom’s technique (8) as
described by Evans et al. (14). All muscle samples were
cleansed of visible fat, connective tissue, and blood and
immediately frozen in liquid nitrogen (21908C), then trans-
ferred and stored at 2808C until analyzed. Muscle samples
were later prepared (6), and MHC was analyzed according
to previously described procedures (30). Briefly, after the
samples were loaded (15 ml), electrophoresis was performed
at a constant voltage of 200 V for 22 hours in a gel system (R.
Shadel, San Franscisco, CA, USA). For stacking gel penetra-
tion, the first hour, the voltage was kept at 160 V. During
electrophoresis, the gel system was kept in a temperature-
controlled ventilated hood. The gels were subsequently
stained with a silver staining kit (Bio-Rad, Hercules, CA,
USA) according to the manufacturer’s instructions. The pro-
tein bands of each MHC isoform on the silver-stained acryl-
amide gel were densitometrically digitalized using a digital
camera (Fugi LAS 4000; Fujifilm Life Sciences, Wayne, NJ,
USA). The densitometric values were derived as an integral
of the band density and band area (MultiGauge 3.0; Fujifilm
Life Sciences). The amount of each isoform was expressed as
a percentage calculated as (IntegProtein/IntegAll) 3100%,
where IntegProtein is the densitometric integral of the cor-
responding protein band, and
the IntegAll is the densitomet-
ric integral of all isoforms in
the sample.
Statistical Analyses
All statistical analyses were per-
formed using SPSS Version 19.0
(Chicago, IL, USA). One-way
analysis of variance (ANOVA)
was used to determine baseline
differences in physical and per-
formance characteristics. A 2 3
4 (group 3time) ANOVA was
used to determine differences in
body mass, lean mass, and per-
cent body fat. Macronutrient
content was analyzed in a 2 3
4(group3time) ANOVA.
Overall total volume load and
training intensity were analyzed
by independent t-test. A 2 34
(group 3time) analysis of covariance (ANCOVA) covaried
for baseline values as the covariate was used to determine
changes over the training period in 1RM
BP
,1RM
BS
,PWR
BP
,
PWR
BS
, and PWR
VJ
. Independent t-tests were used to deter-
mine the difference between pre- and post-APWR
BP
and
APWR
BS
.A232 (group 3time) repeated measure ANCO-
VA using baseline values as the covariate was used to deter-
mine changes in percentage MHC
slow
,MHC
IIA
,andMHC
IIx.
Statistical power for all tests was .0.82. Where necessary,
post hoc analysis was performed using the Bonferroni correc-
tion. Statistical significance was defined as p#0.05.
The use of null-hypothesis testing in sports science
to assess practical significance may be inadequate (7).
As such, the effect size was used in accordance with the
scale proposed by Rhea (32) for highly trained individuals
to determine the treatment effect of both training programs.
Additionally, Batterham and Hopkins’ (7) method for the
determination of magnitude-based inference was used at
5% for both TRD and ISR to provide a qualitative inference.
The difference in the absolute change from pre to post
between ISR and TRD was also calculated, and a qualitative
inference was determined on the effect of ISR (7).
RESULTS
Baseline Characteristics
No significant differences were observed at baseline in age,
height, body mass, or lean mass. Additionally, no significant
differences were observed in training status between subjects
(Table 1).
Macronutrient Intake
Absolute macronutrient intake and percent total calories and
intake relative to body mass are presented in Table 4. No
significant between-group differences were observed in any
Figure 3. Percent change in the absolute mean power from baseline in bench press and parallel back squat. Data
are mean 6standard error. TRD = traditional rest; ISR = intraset rest intervals; *significantly different from TRD.
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of the macronutrients measured. Caloric intake did not
change over the course of the study. Protein intake increased
significantly from baseline to 3 weeks with no further
increase observed. Carbohydrate intake decreased over the
course of the experimental period. No significant changes
were observed in absolute fat intake, as a percentage of total
calories or relative to body mass.
Training Volume Load and Intensity
Total volume load of main lifts (upper and lower body) and
assistive exercises (push and pull) is provided in Table 5.
There were no significant differences between groups for
total volume load of main lifts or assistive exercises. Addi-
tionally, there were no significant differences in upper (p=
0.113) or lower body (p= 0.333) training intensity between
TRD and ISR.
Power Output
Data from power output assessments are presented in Table 6.
There were no significant differences between groups in
any power measurements at baseline. The subjects in ISR
experienced greater gains in PWR
BP
. A graphical represen-
tation of percentage increase in PWR
BP
is presented in Fig-
ure 2A. Similar increases were observed in PWR
BS
in both
groups. A significant interaction was observed with post hoc
analysis revealing no significant between-group differences
at any training time point. However, the difference between
groups at both 8 (ISR, 151.0 674.0 W; TRD, 97.5 660.9 W;
p= 0.084) and 12 (ISR, 282.1 6104.1 W; TRD, 204.9 670.2
W; p= 0.063) weeks approached significance with the sub-
jects in ISR showing a greater increase. The magnitude of
the effect was also greater in ISR and the qualitative infer-
ence on the effect of ISR demonstrated a likely positive effect
TABLE 7. Strength measures (1RM) at baseline, 4, 8, and 12 weeks.*
TRD ISR p
Bench press 1RM (kg)
Baseline 104.1 627.6 110.9 620.1 T= 0.018
4 wks 102.7 629.0 117.5 623.7z§G= 0.013
8 wks 107.0 625.3k120.8 622.6z§T3G= 0.010
12 wks 113.2 627.3§k 126.0 622.8z§k
Bench press to body mass ratio
Baseline 1.27 60.22 1.35 60.23 T= 0.016
4 wks 1.22 60.24 1.42 60.24zG= 0.035
8 wks 1.26 60.18 1.45 60.23z§T3G= 0.002
12 wks 1.33 60.19k 1.51 60.22z§k
Bench press to lean mass ratio
Baseline 1.67 60.27 1.75 60.26 T= 0.101
4 wks 1.61 60.29 1.84 60.30zG= 0.066
8 wks 1.66 60.22 1.88 60.29z§T3G= 0.007
12 wks 1.75 60.25k 1.95 60.29z§k
Back squat 1RM (kg)
Baseline 123.3 639.3 130.1 625.1 T= 0.001
4 wks 139.6 638.7§ 152.6 624.8§ T= 0.016
8 wks 160.2 636.1§k179.8 624.5z§kT3G= 0.010
12 wks 171.8 634.5§k 193.9 624.2z§k
Back squat to body mass ratio
Baseline 1.50 60.34 1.59 60.30 T= 0.001
4 wks 1.66 60.34§ 1.85 60.27§ G= 0.038
8 wks 1.90 60.30§k2.17 60.25z§kT3G= 0.001
12 wks 2.03 60.30§k 2.33 60.27z§k
Back squat to lean mass ratio
Baseline 1.97 60.42 2.05 60.30 T= 0.001
4 wks 2.19 60.41§ 2.40 60.27§ G= 0.045
8 wks 2.49 60.36§k2.79 60.26z§kT3G= 0.001
12 wks 2.67 60.36§k 3.02 60.26z§k
*TRD = traditional rest; ISR = intraset rest intervals; T= time effect; G= group effect; T3G= time 3group interaction effect.
Data are mean 6SD.
zSignificantly different from TRD.
§Significantly different from baseline.
kSignificantly different from 4 weeks.
Significantly different from 8 weeks.
Intraset Rest Intervals in Hypertrophic Training
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(Table 10). Evaluating PWR
BS
relative to lean mass, the subjects
in ISR showed a greater increase at both 8 (p= 0.016) and 12 (p
= 0.038) weeks. Although the pattern of increase appeared
greater when evaluating percentage change from baseline in
PWR
BS
(Figure 2B), only a time effect was noted with no group
or interaction effects observed. The subjects in ISR experienced
a greater increase in PWR
VJ
. This corresponded to a significant
difference at 12 weeks compared with TRD in absolute (Table
6) and percentage change from baseline (Figure 2C).
Percentage change from baseline in APWR
BP
and
APWR
BS
is presented in Figure 3. The subjects in ISR dem-
onstrated a significantly greater improvement in the percent-
age increase from baseline in APWR
BP
(p= 0.012),
corresponding to an absolute increase of 71.0 W compared
with 13.5 W for TRD (p= 0.010). Both ISR and TRD
increased in APWR
BS
from baseline, no significant differen-
ces were observed (p= 0.496). However, the magnitude of
effect size was greater for the ISR group (Table 10).
Muscular Strength
The results of strength testing
are presented in Table 7. There
were no significant differences
between groups observed at
baseline in either 1RM
BP
or
1RM
BS
. Only the subjects in
ISR experienced an increase at
4, 8, and 12 weeks. This corre-
sponded to greater increases at 4
(ISR, 6.6 66.6 kg; TRD, 21.4
66.2 kg; p=0.012),8(ISR,9.9
66.8 kg; TRD, 2.9 65.8 kg, p=
0.016), and 12 (ISR, 15.1 68.3
kg; TRD, 9.1 63.7 kg; p=
0.051) weeks. Percent change in
the 1RM
BP
from baseline in pre-
sented in Figure 4A. Again, only
ISR increased at 4, 8, and 12
weeks. Greater percent increase
from baseline was observed in
ISR at 4 and 8 weeks (p=
0.017 and 0.034, respectively),
with 12 weeks approaching sig-
nificance (p=0.082).
The subjects in the ISR
experienced greater increases
in the 1RM
BS
at both 8 weeks
(ISR, 49.7 613.8 kg; TRD,
36.9 613.5 kg; p= 0.024)
and 12 weeks (ISR, 63.8 6
12.0 kg; TRD, 48.5 617.4 kg;
p= 0.011). Percent change in
the 1RM
BS
from baseline is
presented in Figure 4B. Percent
change from baseline demon-
strated a significant interaction
(p= 0.048) in which post hoc analysis revealed an almost
significant greater gain in week 8 (p= 0.066) and a significant
greater gain in week 12 (p= 0.041) for the subjects in ISR.
Body Composition
The results of body composition testing are presented in
Table 8. Although the subjects in TRD experienced an
increase in body mass at 4 weeks, no further increase was
observed, and post hoc analysis revealed no significant dif-
ference between groups at any time point. Lean mass
increased in both groups from baseline to 4 weeks and
showed a continued increase at 8 weeks. No further in-
creases were noted. No between-group differences were
identified. When evaluating percentage change from base-
line, a significant time effect was noted (p= 0.001) with no
significant group (p= 0.124) or interaction effects (p= 0.219)
observed. There were no significant changes in percent body
fat as measured by DEXA during the 12-week training.
Figure 4. Percent change in strength from baseline in bench press (A) and parallel back squat (B). Data are
mean 6standard error. TRD = traditional rest; ISR = intraset rest intervals; significantly different from baseline;
zsignificantly different from 4 weeks; § significantly different from 8 weeks; *significantly different from TRD.
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Myosin Heavy Chain Composition
Studentized t-tests of baseline MHC demonstrated a signifi-
cantly higher percentage of the MHC
IIx
in the ISR group
(p= 0.023) compared with TRD. No significant differences
were observed at baseline in
the percentage MHC
IIA
or
MHC
slow
.ResultsfromMHC
analysis are presented in Table 9.
Both training protocols expe-
rienced a significant reduction in
MHC
IIx
after 12 weeks of train-
ing, with a concomitant increase
in the MHC
IIA.
No interaction
or group effects were observed
in either MHC
IIx
or MHC
IIA
.
Evaluating the percentage
change from baseline, a signifi-
cant time effect (p= 0.001) was
noted with both ISR and TRD
experiencing a decrease in the
MHC
IIx
,237.9 624.1% and
223.4 623.8%, respectively,
with no differences noted
between groups. A time effect
was also noted in the percentage
change from baseline in MHC
IIA
for both ISR and TRD, with both
showing an increase, 32.0 628.8
and 25.4 629.1%, respectively (p
= 0.001). Again, no interaction or
group effect was noted. A small but significant decrease in the
percentage MHC
slow
wasobservedinbothgroups.However,
when evaluating percent change from baseline, this did not reach
significance (p=0.164).
Effect Size and Magnitude
Effect size, magnitude of effect
size, and qualitative inferences
are reported in Table 10. The
ISR magnitude of effect sizes
were all moderate or large in
performance measures, whereas
TRD was found to have a small
magnitude of effect as defined
by Rhea (32) for highly trained
individuals in 1RM
BP
,PWR
BP
,
and PWR
VJ
.TheTRDhad
a greater effect size magnitude
for lean mass gain; however,
the effect size for both TRD
and ISR were small and trivial,
respectively. The ISR demon-
strated a greater effect size mag-
nitude in both MHC
IIx
and
MHC
IIA
(large) compared with
TRD, whereas TRD demon-
strated a greater effect size for
MHC
slow
. Qualitative inferences
were greater for IRS at the
TABLE 8. Body composition at baseline, 4, 8, and 12 weeks of training.*
TRD ISR Combined p
Weight (kg)
Baseline 81.7 611.6 82.5 610.0 82.1 610.6 T= 0.001
4 wks 83.6 610.0z82.7 69.7 83.1 69.6 G= 0.898
8 wks 84.1 610.7z83.1 69.2 83.6 69.7 T3G= 0.018
12 wks 84.7 610.9z83.6 69.2 84.1 69.9
Lean mass (kg)
Baseline 61.9 68.9 63.3 67.0 62.6 67.9 T= 0.002
4 wks 63.2 68.2 63.5 67.3 63.4 67.6zG= 0.869
8 wks 64.0 68.3 64.3 66.9 64.2 67.4z§T3G= 0.227
12 wks 64.2 68.5 64.3 66.8 64.2 67.5z§
Percent fat (%)
Baseline 14.3 62.7 12.9 65.5 13.6 64.3 T= 0.133
4 wks 15.0 63.3 13.3 65.9 14.1 64.7 G= 0.445
8 wks 14.7 63.5 13.2 65.5 14.0 64.6 T3G= 0.869
12 wks 15.1 63.5 13.5 65.6 14.3 64.6
*TRD = traditional rest; ISR = intraset rest intervals; T= time effect; G= group effect; T3
G= time 3group interaction effect.
Data are mean 6SD.
zSignificantly different from baseline.
§Significantly different from 4 weeks.
TABLE 9. Myosin heavy chain isoform in percentage total at baseline and 12
weeks of training.*
TRD ISR Combined p
MHC
IIx
Baseline 11.1 64.2 16.5 65.7 13.9 65.7 T= 0.020
12 wks 7.9 62.5 9.8 64.5 8.9 63.7zG= 0.649
T3G= 0.649
MHC
IIA
Baseline 35.6 67.7 34.5 67.6 35.0 67.5 T= 0.001
12 wks 43.2 67.5 43.9 66.2 43.6 66.7zG= 0.002
T3G= 0.756
MHC
slow
Baseline 53.3 67.9 49.0 67.6 51.1 67.9 T= 0.002
12 wks 48.9 65.9 46.2 67.1 47.5 66.5zG= 0.568
T3G= 0.568
*TRD = traditional rest; ISR = intraset rest intervals; T= time effect; G= group effect;
T3G= time 3group interaction effect.
Data are mean 6SD.
zSignificantly different from baseline.
§One subject was excluded because of lack of sufficient sample.
Intraset Rest Intervals in Hypertrophic Training
3126
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smallest worthwhile change 5%, which is much larger than
expected in highly trained athletes, ISR demonstrated greater
qualitative inferences in 1RM
BS,
PWR
BP
,APWR
BP
, APWR
BS
,
PWR
VJ
,MHC
IIx,
and MHC
IIA
, with TRD demonstrating
a greater qualitative inference in lean mass only. Additionally,
a likely or very likely positive effect of ISR was demonstrated
in all measured variables except lean mass, MHC
IIA
,and
MHC
slow.
DISCUSSION
In this study, we sought to determine if ISR hypertrophic
training resulted in greater power gains than TRD hyper-
trophic training did. We further sought to determine changes
in MHC composition as a result of ISR. The major findings
of this study were that after 12 weeks (a) ISR resulted in
greater power output in the bench press exercise and vertical
jump, (b) power output as measured during parallel back
squat approached significance compared to TRD, and (c)
when normalized to bodyweight and lean mass, ISR were
superior, (d) absolute power difference in the bench press
was greater in the bench press exercise with the use of ISR,
(e) ISR resulted in greater increases in strength in the bench
press and parallel back squat exercises, (f ) ISR resulted in
similar gains in lean mass, and finally (g) changes in
percentage MHC
IIx
and MHC
IIA
are similar to those expe-
rienced during TRD hypertrophic training.
To effectively compare, it was necessary to control for
total volume load and training intensity. This was accom-
plished as no significant between-group differences were
observed in major lifts or assistance exercises in total volume
load or training intensity in major lifts. Additionally,
although dietary intake was not controlled, no significant
between-group differences were observed in any macro-
nutrients. Data suggest that the loss of calories from
carbohydrate intake was made up by the high intake of
protein, which met current guidelines (5), as evidenced by
increased protein intake with a concomitant decrease in car-
bohydrate intake with no change in total calories or fat over
the 12-week period.
Our original hypothesis regarding power output was
supported only in part because power difference in the
parallel back squat exercise only approached significance.
However, the effect size was greater, and the magnitude-
based qualitative inference demonstrated a likely positive
effect of ISR. When power output was evaluated using the
initial load from baseline, ISRs resulted in greater increases
in bench press but not in parallel back squat, though the
effect size and qualitative inference at 5% were greater for
ISRs and a likely positive magnitude-based inference from
ISR. In contrast to trends observed in bench press and
parallel back squat exercises, the difference in power output
of the vertical jump took the full 12 weeks to manifest. Once
demonstrated, the difference in the change from the
baseline, magnitude of effect size, and qualitative inference
at 5% were greater in ISR.
The role of inorganic phosphate (P
i
) in the velocity of
shortening has recently received considerable attention.
Increases in P
i
occur during muscle contractions, mainly from
the breakdown of phosphocreatine (PCr). Models of cross-
bridge cycling propose that P
i
is released in the transition
TABLE 10. Effect size, magnitude of effect (32), and qualitative inferences (7).*
Magnitude of effect sizeQualitative inferencezQualitative
inference on
difference§TRD ISR TRD ISR
Bench press 1RM 0.33 (Small) 0.75 (Moderate) Likely Likely Likely
Back squat 1RM 1.23 (Large) 2.54 (Large) Likely Very likely Very likely
Bench press power 0.27 (Small) 0.81 (Moderate) Very unlikely Possibly Very likely
ABS bench press
power
0.11 (Trivial) 0.69 (Moderate) Most unlikely Unlikely Very likely
Back squat power 0.84 (Moderate) 1.65 (Large) Likely Likely Likely
ABS back squat
power
0.41 (Small) 0.76 (Moderate) Possibly Likely Likely
Vertical jump power 0.39 (Small) 0.83 (Moderate) Possibly Likely Very likely
Lean mass 0.25 (Small) 0.14 (Trivial) Unlikely Most unlikely Very unlikely
MHC
IIx
0.72 (Moderate) 1.18 (Large) Very unlikely Possibly Likely
MHC
IIA
0.99 (Moderate) 1.25 (Large) Very unlikely Unlikely Unclear
MHC
slow
0.57 (Moderate) 0.36 (Small) Most unlikely Most unlikely Unclear
*TRD = traditional rest; ISR = intraset rest intervals.
Effect size and magnitude of effect size.
zQualitative inference with reference to smallest worthwhile change of 5%.
§Qualitative inference based on difference between groups.
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from low force weakly attached states to high force strongly
attached states (2). Westerblad et al. (39) suggested this im-
plies that the transition to the high force states is hindered by
increased levels of P
i
. Increases in adenosine diphosphate
(ADP) have also been suggested to occur during repeated
contractions, coincident with PCr depletion (33). Westerblad
et al. (40) demonstrated that in the fatigued state, the velocity
of shortening was slower after a longer tetanus compared with
a shorter contraction. The authors suggested this was because
of transient increases in ADP. Partial recovery occurred in
a matter of seconds thought to be because of rapid removal
of ADP by enzyme action or diffusion.
Although the exact cause of reduced velocity of shorten-
ing is still debated (39), this study suggests that ISR allows
for a greater power output after training for hypertrophy. It is
therefore possible that ISR in this study allowed for a partial
reduction of either P
i
or ADP by enzyme action or diffusion.
Furthermore, the ISR may have allowed for an almost com-
plete resynthesis of PCr, as after a fatiguing maximum vol-
untary contraction lasting approximately 54 seconds PCr has
been shown to be resynthesized to 67% original concentra-
tion in just 2 minutes and 87% after 4 minutes (34). The
truncated number of repetitions performed per set, 5 in this
study, would use less PCr and result in less metabolite accu-
mulation than more traditional hypertrophic training.
Although not recorded, it was observed that the time to
complete the 5 repetitions performed by ISR was approxi-
mately 10–15 seconds, whereas it took almost twice the time
for TRD to complete the desired number of repetitions (20–
25 seconds).
Support for the superiority of ISR on power output of the
upper and lower body musculature has been provided by
acute studies in which greater power output (21.6–25.1%) in
the bench press exercise compared with TRD has been
demonstrated (28), and higher peak velocity in the power
clean using cluster sets (17,20). Although these results sup-
port the use of ISR and cluster sets in chronic training, long-
term studies have demonstrated a tendency toward greater
gains in power output of the lower body musculature (19),
and significantly greater gains in power output of the lower
body musculature compared with TRD in athletes (22). The
results of ISR on upper body power output are controversial,
with some reporting no difference (22,27) and one reporting
less (13) improvement in power output of the upper body
musculature. In the current investigation, we report greater
gains in power output of both the upper and lower body
musculature after 12 weeks of training.
Differences between this study and those reporting no
difference or less improvement in power output of the bench
press exercise may at least partially explain the differing
results. It has been demonstrated peak power occurs
between 40 and 60% 1RM in the bench press using a Smith
machine (36), which was the apparatus used in this study.
Although loads in this study were greater (65–75%) than
those prescribed for bench press power, they fall closer to
the desired range than intensities used in previous investiga-
tions in which no difference (22,27) or less improvement (13)
was observed (85% 1RM or greater).
The only study to date using loads similar to the current
study using multijoint exercises was conducted by Izquierdo
et al. (22); however, the authors failed to demonstrate differ-
ences in power output in the initial phase of training with
loads corresponding to10 RM (;75% 1RM) for the bench
press. Greater improvements in power output were not com-
pletely realized in this study until 8 weeks of training. The
initial phase in which intensity of the 2 studies was similar
lasted only 6 weeks. Therefore, the differences in power out-
put may not have had an opportunity to be realized. Addi-
tionally, the assessment of power output by Izquierdo et al.
(22) involved only the concentric action beginning from
a stop position, compared with our determination, which
allowed a descent phase corresponding to an eccentric
component.
In agreement with previous studies, we demonstrated ISR
to be superior in the development of lower body power
output. Although back squat power only approached
significance, the magnitude of effect size was greater, and
the qualitative inference on the effect of ISR was likely
positive. Hansen et al. (19) recently compared TRD with
cluster sets on strength and power of the lower body mus-
culature in elite rugby union players. Cluster sets were only
used in strength and power training involving squat and
clean movements. Similar to this study, calculations of mag-
nitude-based inference demonstrated a likely positive effect
of cluster sets in peak power and peak velocity at 40 kg, and
peak velocity at bodyweight during the jump squat. The
authors concluded that TRD resulted in greater strength
improvements, whereas some evidence suggested a possible
benefit for ISR in lower body power development.
It has been demonstrated that peak power occurs between
50 and 70% in the parallel back squat exercises using a Smith
machine (36). The loads in this study fall within this range
(65–75%). Izquierdo et al. (22) have been the only group to
demonstrate significantly greater gains in lower body power
output after long-term training. Again the study by Izquierdo
et al. (22) allowed multiple comparisons in a 16-week train-
ing period corresponding to 3 microcycles. During the first 6
weeks, the subjects performed 3 sets of 10 (10RM) repeti-
tions or 6 sets of 5 (10RM) repetitions corresponding to
a hypertrophic phase. Strength training commenced in week
7 and lasted 5 weeks with the subjects performing either 3
sets of 6 (6RM) repetitions or 6 sets of 3 (6RM) repetitions.
Training concluded with both groups performing 3 sets of 2–
4 repetitions with intensities corresponding to 85–90% 1RM.
Differences in power output were not observed until the last
testing session. This is unique because there were no differ-
ences in training intervention during the last 5 weeks. Based
on the current results, adaptations may have occurred during
the initial few weeks of training and not been realized until
the end of training.
Intraset Rest Intervals in Hypertrophic Training
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Contrary to our original hypothesis, the ISR resulted in
greater increases in both bench press and parallel back squat
strength. This is the first study to report greater strength
gains with ISR. Studies comparing ISR with TRD using
multijoint exercises have demonstrated that ISR resulted in
smaller (13,19,27) or no difference (22) in strength gains
compared with TRD. Studies demonstrating smaller
strength gains with ISR used loads corresponding to
$85% 1RM. At those intensities, this may very well be the
case because increased recruitment of muscle fibers results in
greater stimulation, particularly in the fast MHC
IIx
fibers, as
measured by electromyography (EMG) techniques. The
EMG activity has been shown to increase leading up to
the sixth repetition in a 6RM (85% 1RM) bench press exer-
cise (25). On the other hand, Burd et al. (9) demonstrated
that maximal EMG activity occurred half way through (i.e.,
repetitions 5–6) the performance of a set of leg extensions
using a load corresponding to 70% 1RM. The results by Burd
et al. (9) suggest that when performing exercise with loads in
this intensity range, maximal recruitment occurs at approx-
imately 50% completion during the initial set, and perfor-
mance of repetitions past this point results in reduced
activation of fibers, which are considered quick to fatigue,
primarily MHC
IIx
. Similar to previous studies comparing
TRD with ISR (12,27), this study divided the number of
repetitions performed in TRD hypertrophic training in half
and equated rest using intensities ranging from 65 to 75%
1RM. This may have resulted in greater neuromuscular acti-
vation over consecutive sets compared with TRD, which
may have contributed to the greater strength gains demon-
strated in this study. However, further research is needed to
answer this question conclusively.
Izquierdo et al. (22) demonstrated no significant difference
in strength between TRD and ISR over a 16-week periodized
training period. Intensities during the first 6-week cycle corre-
sponded to those used in this study (10RM or ;75% 1RM). In
contrast to the results obtained by Izquierdo et al. (22), we
observed greater strength gains with ISR after only 4 weeks in
the bench press exercise. Difference in the back squat ap-
proached significance after 4 weeks and reached significance
by week 8. Although both studies used the same relative
intensities, the subjects in this study were only participating
in the training outlined, whereas the subjects in the study by
Izquierdo et al. (22) were also participating in additional train-
ing to include sport-specific and endurance training. This may
have contributed to the differing results. Furthermore,
although it is doubtful, the differences in ISR may also have
contributed to the divergent findings (1 vs. 2 minutes).
In support of our original hypothesis and in support of
Ahtiainen et al. (1), training with TRD and ISR resulted in
similar increases in lean mass over the duration of the
12-week training program. Although TRD appeared to have
greater increases, this did not reach significance when eval-
uating the absolute or percentage change from baseline. In
this study, rest intervals were short and congruent with cur-
rent recommendations for the development of hypertrophy
(4). The use of shorter rest intervals using moderate intensi-
ties has been associated with greater acute elevations in
growth hormone when compared with longer rest periods
using higher intensity loads (26). However, Ahtiainen et al.
(1) demonstrated that hormonal and hypertrophic response
did not vary when short (2 minutes) or long (5 minutes) rest
intervals were used in a chronic training program when vol-
ume was equated. There were no differences in total volume
load over the 12-week training period (p.0.05). These data
support the previous work by Ahtiainen et al. (1) demon-
strating similar hypertrophic response regardless of rest
when total volume load is equated.
Contrary to our original hypothesis, no significant differ-
ences were observed between groups in changes in MHC
percentage after 12 weeks of resistance training. Both groups
experienced a significant increase in the MHC
IIA
percentage
with a concomitant reduction in the MHC
IIx
percentage.
Furthermore, a small decrease in the MHC
slow
was also
observed, although when evaluating percentage change from
baseline this did not reach significance. It is well established
that the increase in lean mass associated with hypertrophic
training is accompanied by a shift in MHC isoforms, identified
by a decrease in the percentage of MHC
IIx
fibers with a con-
comitant increase in MH
IIA/x
and MHC
IIA
fibers (10,15,31).
However, Liu et al. (29) previously reported strength training
combined with ballistic exercise lead to a differential effect on
MHC shifts after 12 weeks of training, shifting from percent-
age MHC
slow
to MHC
IIA
. Although the training protocol in
this study did not explicitly include ballistic movements, the
use of ISR has been shown to result in greater velocity of
contraction compared with TRD training (17,18).
The differences in intensity and length of time of the
current protocol and that of Liu et al. (29) may at least
partially explain our divergent findings. Liu et al. (29) used
loads corresponding to a much higher intensity than the one
used in the current protocol, 93% 1RM vs. 65–75% 1RM.
Additionally, the length of training of this study was twice
that of the study by Liu et al. (11). Both protocols fall within
the time course of adaptations as have been previously re-
ported (37). Claflin et al. (11) recently suggested that an
alternative explanation must be responsible for the enhanced
fiber function as a result of high-velocity training because
they did not find any differences at the single fiber level in
size, force, or power of type II fibers after 14 weeks of train-
ing with high velocities. Although Claflin et al. (11) did not
directly assess changes in the MHC
IIA
and MHC
IIx
percent-
age, the results from this study and that of Claflin et al. (11)
suggest that the increased performance evidenced as a result
of high-velocity contractions may in fact result from neural
adaptations rather than from physiological adaptations.
PRACTICAL APPLICATIONS
The results from this study support the use of ISR during
training for muscle hypertrophy. The ISR resulted in greater
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gains in power output and strength when compared with
TRD hypertrophic training. Furthermore, ISR produced
similar gains in lean mass over the course of the training
period. The length of time prescribed in this study for ISR
intervals did not impact the total training time. This is of
importance to coaches and strength and conditioning
professionals who have rules and regulations dictating the
time allowed for training. Based on these results, it could be
suggested that the incorporation of ISR in the hypertrophic
phase of a traditional or nontraditional periodized training
program would allow for greater improvements in strength
and power. Whether these improvements would result in
greater gains in strength and power output over an entire
mesocycle is unknown, but hypothetically entering the
strength and power phases of a training mesocycle at higher
performance ability (strength and power) would allow
a continued improvement above that achieved during
traditional training models.
ACKNOWLEDGMENTS
The authors would like to thank the United States Marine
Corps for their participation in this study and the members
of the Texas A&M University Naval ROTC Unit and Corps
of Cadets. This study was funded by the National Strength
and Conditioning Association (NSCA) Doctoral Research
Grant. The results presented herein do not constitute
endorsement by the NSCA.
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... However, there is evidence to suggest that performing repetitions at or close to concentric muscular failure may not be necessary to develop these physical qualities, rather ceasing a set multiple repetitions short of concentric muscular failure may be adequate (10,16). However, the findings from these studies are highly variable (27,38), as observed in recent reviews concerning muscular strength and hypertrophy (5,48) and indicate that the current consensus is inconclusive with more research needed to build on current recommendations (42). ...
... The authors attributed the difference to the larger metabolic and hormonal response (i.e., lactate and growth hormone) that was observed in the traditional-set structure. There have been only a couple of other studies investigating this topic (27,38), but as to date, the findings are equivocal. However, it does seem that set structures that lead to greater fatigue and velocity loss during sets may be advantageous for the promotion of hypertrophy. ...
... Second, as muscular hypertrophy does not directly correlate with improvements in muscular strength (40), we hypothesized that there will be no differences in muscular strength development between groups. Because of the disparities in gross vs. local changes in muscle size after training programs where single exercises are manipulated (27,38), we hypothesized that there will be no differences in lean body mass between groups. Finally, confirmation of velocity loss magnitudes at the midpoint of the training intervention is hypothesized to be greater in the traditional-set group compared with the cluster-set group. ...
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Davies, TB, Halaki, M, Orr, R, Mitchell, L, Helms, ER, Clarke, J, and Hackett, DA. Effect of set structure on upper-body muscular hypertrophy and performance in recreationally trained men and women. J Strength Cond Res 36(8): 2176–2185, 2022—This study explored the effect of volume-equated traditional-set and cluster-set structures on muscular hypertrophy and performance after high-load resistance training manipulating the bench press exercise. Twenty-one recreationally trained subjects (12 men and 9 women) performed a 3-week familiarization phase and were then randomized into one of two 8-week upper-body and lower-body split programs occurring over 3 and then progressing to 4 sessions per week. Subjects performed 4 sets of 5 repetitions at 85% one repetition maximum (1RM) using a traditional-set structure (TRAD, n = 10), which involved 5 minutes of interset rest only, or a cluster-set structure, which included 30-second inter-repetition rest and 3 minutes of interset rest (CLUS, n = 11). A 1RM bench press, repetitions to failure at 70% 1RM, regional muscle thickness, and dual-energy x-ray absorptiometry were used to estimate changes in muscular strength, local muscular endurance, regional muscular hypertrophy, and body composition, respectively. Velocity loss was assessed using a linear position transducer at the intervention midpoint. TRAD demonstrated a significantly greater velocity loss magnitude (g = 1.50) and muscle thickness of the proximal pectoralis major (g = −0.34) compared with CLUS. There were no significant differences between groups for the remaining outcomes, although a small effect size favoring TRAD was observed for the middle region of the pectoralis major (g = −0.25). It seems that the greater velocity losses during sets observed in traditional-set compared with cluster-set structures may promote superior muscular hypertrophy within specific regions of the pectoralis major in recreationally trained subjects.
... It is known that explosive strength and strength endurance are 2 strength manifestations of paramount importance for performance in many sports (1,34). From the 10 studies examining RR set structures in the review by Jukic et al. (21), 7 evaluated explosive-strength performance as the velocity (or power) attained at submaximal loads (3,7,16,18,23,24,31) and 3 evaluated strength-endurance performance as the number of repetitions completed to failure (8), number or repetitions performed in a given time (6), or the time to task failure during an isometric submaximal contraction (18 20.72; p 5 0.038). However, despite that for actions that influence sports performance (e.g., jumps, sprints, change of direction, throws, etc.), the ability to maintain high mechanical outputs over time is generally more important than the number of repetitions completed to failure or the ability to maintain a submaximal force output; surprisingly, no study has used this variable as an indicator of strength-endurance performance when comparing the long-term adaptations between TR and RR set configurations. ...
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Janicijevic, D, González-Hernández, JM, Jiménez-Reyes, P, Márquez, G, and García-Ramos, A. Longitudinal effects of traditional and rest redistribution set configurations on explosive-strength and strength-endurance manifestations. J Strength Cond Res XX(X): 000-000, 2022-This study aimed to compare the long-term effects of resistance training programs based on traditional and rest redistribution set configurations on explosive-strength and strength-endurance performance of lower-body and upper-body muscles. Thirty physically active men were randomly assigned to a traditional group (TRG: 6 sets of 5 repetitions with 3 minutes of interset rest) or a rest redistribution group (RRG: 30 sets of 1 repetition with 31 seconds of interrepetition rest). The training program lasted 6 weeks (2 sessions·wk 21), and in each training session, the squat and bench press exercises were performed with maximal concentric effort against approximately the 75% of the 1 repetition maximum. Before and after training, explosive-strength performance (peak velocity reached at submaximal loads during the countermovement jump and bench press throw) and strength-endurance performance (mean set velocity of 10 repetitions using both traditional and cluster sets in the squat and bench press) were assessed. Significant improvements in all dependent variables were observed after training for both the TRG (p # 0.004; effect size [ES] 5 0.63-3.06) and RRG (p # 0.001; ES 5 0.58-3.23). The magnitude of the changes was comparable for both groups with the only exception of the larger improvements observed in the RRG for the bench press mean set velocity using both traditional (ES 5 0.77) and cluster (ES 5 0.82) set configurations. Traditional and rest redistribution set configurations are equally effective to improve lower-body explosive strength, lower-body strength endurance, and upper-body explosive strength, whereas rest redistribution set configurations could induce greater adaptations in upper-body strength endurance.
... In the present study no significant differences were observed in increases of quadriceps femoris CSA between the different frequencies of the RTEV condition. In fact, studies with trained individuals have not shown additional benefits to hypertrophic adaptations when the same TTV is distributed with different strategies [47,48]. In the RTUV condition, no significant differences in CSA increases were also observed between the different RT frequencies; however, the ES and CI suggest a great effect on CSA induced by the higher RT frequency, probably due to the higher TTV (i.e., ES = 0.63; CI = 0.21 to 1.10). ...
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Several studies comparing resistance training (RT) frequencies may have been affected by the large between-subject variability. This study aimed to compare the changes in lower limbs maximal dynamic strength (1RM) and quadriceps femoris cross-sectional area (CSA) after a RT with different weekly frequencies in strength-trained individuals using a within-subject design. Twenty-four men participated in a 9-week RT program, being randomly divided into two conditions: resistance training with equalized total training volume (RTEV) and with unequalized total training volume (RTUV). The RT protocol used the unilateral leg press 45° exercise and each subject's lower limb executed one of the proposed frequencies (one and three times/week). All conditions effectively increased 1RM and CSA (p<0.001); however, no significant differences were observed in the values of 1RM (p = 0.454) and CSA (p = 0.310) between the RT frequencies in the RTEV and RTUV conditions. Therefore, RT performed three times a week showed similar increases in 1RM and CSA to the program performed once a week, regardless of training volume equalization. Nevertheless, when the higher RT frequency allowed the application of a greater TTV (i.e., RTUV), higher effect size (ES) values (0.51 and 0.63, 1RM and CSA, respectively) were observed for the adaptations.
... These statistical models were selected based on previous investigations regarding musculoskeletal and cardiovascular responses to 12 weeks of physical training. 28,30,42 An independent samples t test was used to compare time to RTS and time between initial clinic visit and date of surgery between groups. For all significant pairwise comparisons between groups, ES was calculated using a Cohen d statistic, 48 and interpreted as follows: ES <0.1, negligible; 0.1 to 0.3, small; 0.3 to 0.5 moderate; 0.5 to 0.7, large; and +0.7, very large (VL). ...
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Background Muscle atrophy is common after an injury to the knee and anterior cruciate ligament reconstruction (ACLR). Blood flow restriction therapy (BFR) combined with low-load resistance exercise may help mitigate muscle loss and improve the overall condition of the lower extremity (LE). Purpose To determine whether BFR decreases the loss of LE lean mass (LM), bone mass, and bone mineral density (BMD) while improving function compared with standard rehabilitation after ACLR. Study Design Randomized controlled clinical trial Methods A total of 32 patients undergoing ACLR with bone-patellar tendon-bone autograft were randomized into 2 groups (CONTROL: N = 15 [male = 7, female = 8; age = 24.1 ± 7.2 years; body mass index [BMI] = 26.9 ± 5.3 kg/m2] and BFR: N = 17 [male = 12, female = 5; age = 28.1 ± 7.4 years; BMI = 25.2 ± 2.8 kg/m2]) and performed 12 weeks of postsurgery rehabilitation with an average follow-up of 2.3 ± 1.0 years. Both groups performed the same rehabilitation protocol. During select exercises, the BFR group exercised under 80% arterial occlusion of the postoperative limb (Delfi tourniquet system). BMD, bone mass, and LM were measured using DEXA (iDXA, GE) at presurgery, week 6, and week 12 of rehabilitation. Functional measures were recorded at week 8 and week 12. Return to sport (RTS) was defined as the timepoint at which ACLR-specific objective functional testing was passed at physical therapy. A group-by-time analysis of covariance followed by a Tukey’s post hoc test were used to detect within- and between-group changes. Type I error; α = 0.05. Results Compared with presurgery, only the CONTROL group experienced decreases in LE-LM at week 6 (−0.61 ± 0.19 kg, −6.64 ± 1.86%; P < 0.01) and week 12 (−0.39 ± 0.15 kg, −4.67 ± 1.58%; P = 0.01) of rehabilitation. LE bone mass was decreased only in the CONTROL group at week 6 (−12.87 ± 3.02 g, −2.11 ± 0.47%; P < 0.01) and week 12 (−16.95 ± 4.32 g,−2.58 ± 0.64%; P < 0.01). Overall, loss of site-specific BMD was greater in the CONTROL group ( P < 0.05). Only the CONTROL group experienced reductions in proximal tibia (−8.00 ± 1.10%; P < 0.01) and proximal fibula (−15.0±2.50%, P < 0.01) at week 12 compared with presurgery measures. There were no complications. Functional measures were similar between groups. RTS time was reduced in the BFR group (6.4 ± 0.3 months) compared with the CONTROL group (8.3 ± 0.5 months; P = 0.01). Conclusion After ACLR, BFR may decrease muscle and bone loss for up to 12 weeks postoperatively and may improve time to RTS with functional outcomes comparable with those of standard rehabilitation.
... The 1RM test was performed using a procedure previously published by Oliver et al. (2013). Before determining the 1RM, a dynamic warm-up lasting about 8-10 minutes was done. ...
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... Salvador et al. [30] reported that allowing subjects to take a single 30 s rest in the middle of a 10-repetition set did not significantly blunt the protein synthesis rate elicited by resistance exercise. Additionally, Oliver et al. [35] reported that individuals who performed 12 weeks of resistance training with 60 s of rest in the middle of 10 repetition sets exhibited the same changes in muscle fiber type and greater increases in power and strength compared with those who performed an equal amount of continuous resistance exercise. While these cluster set data suggest that performing an equal amount of resistance exercise with interrepetition rest might elicit the same, if not greater, adaptations as traditional continuous exercise, the impact of the increased number of repetitions associated with interrepetition rest has yet to be examined. ...
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... Various studies have used percentage-based [11,37,38] or RM zone [10,16,18,39,40] load prescription to compare different proximities to failure. However, these methods can lead to ambiguity in how far from failure a set was terminated as the number of repetitions performed at a given percentage of 1RM is highly individual and exercise specific. ...
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SUMMARY In order to stimulate further adaptation toward specific training goals, progressive resistance training (RT) protocols are necessary. The optimal characteristics of strength-specific programs include the use of concentric (CON), eccentric (ECC), and isometric muscle actions and the performance of bilateral and unilateral single- and multiple-joint exercises. In addition, it is recommended that strength programs sequence exercises to optimize the preservation of exercise intensity (large before small muscle group exercises, multiple-joint exercises before single-joint exercises, and higher-intensity before lower-intensity exercises). For novice (untrained individuals with no RT experience or who have not trained for several years) training, it is recommended that loads correspond to a repetition range of an 8-12 repetition maximum (RM). For intermediate (individuals with approximately 6 months of consistent RT experience) to advanced (individuals with years of RT experience) training, it is recommended that individuals use a wider loading range from 1 to 12 RM in a periodized fashion with eventual emphasis on heavy loading (1-6 RM) using 3- to 5-min rest periods between sets performed at a moderate contraction velocity (1-2 s CON; 1-2 s ECC). 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 dIwkj1 for novice training, 3-4 dIwkj1 for intermediate training, and 4-5 dIwkj1 for advanced training. Similar program designs are recom- mended 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 (0-60% of 1 RM for lower body exercises; 30-60% of 1 RM for upper body exercises) performed at a fast contraction velocity with 3-5 min of rest between sets for multiple sets per exercise (three to five sets). 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 (915) using short rest periods (G90 s). In the interpretation of this position stand as with prior ones, recommendations should be applied in context and should be contingent upon an individual's target goals, physical capacity, and training
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Seven alternative resistance training techniques, performed using a bench press exercise, were compared with heavy weight training (HWT) on a number of variables. These resistance training techniques included isokinetics, eccentrics, functional isometrics, super slow motion, rest pause, breakdowns, and maximal power training. The main results were that eccentrics and isokinetics had significantly (p < 0.05) greater levels of force and integrated electromyography than HWT during the eccentric phase. Likewise, functional isometrics had significantly more force and breakdowns significantly higher triceps brachii electromyography than HWT in the concentric phase. Super slow motion and maximal power training both recorded significantly lower levels of force and integrated electromyography than HWT in each phase. However, super slow motion resulted in significantly greater time under tension (61.70 +/- 2.12 vs. 21.15 +/- 0.92 seconds) than HWT. Maximal power training recorded significantly greater levels of power production than HWT in both the eccentric and concentric phases. Although no alternative resistance training techniques were found to produce significantly greater levels of blood lactate response than HWT, maximal power training and eccentrics produced significantly lower levels. (C) 1999 National Strength and Conditioning Association
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THE INTRODUCTION OF NOVEL TRAINING STIMULI PLAYS A CRUCIAL ROLE IN INDUCING SPECIFIC TRAINING ADAPTATIONS. ONE METHOD THAT CAN BE EMPLOYED TO INTRODUCE A NOVEL STIMULUS TO THE TRAINING PROGRAM WHILE MAXIMIZING THE VELOCITY AND POWER OUTPUT OF THE TRAINING EXERCISE IS THE INCLUSION OF THE CLUSTER SET CONFIGURATION. THE CURRENT REVIEW PRESENTS THE THEORETICAL AND RESEARCH FOUNDATION FOR THE USE OF THE CLUSTER SET IN PERIODIZED TRAINING PROGRAMS AND OFFERS EXAMPLES OF PRACTICAL APPLICATIONS THAT CAN BE USED IN THE PREPARATION OF ATHLETES IN A VARIETY OF SPORTS.
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Talmadge and Roy (J. Appl. Physiol. 1993, 75, 2337–2340) previously established a sodium dodecyl sulfate - polyacrylamide gel electrophoresis (SDS-PAGE) protocol for separating all four rat skeletal muscle myosin heavy chain (MHC) isoforms (MHC I, IIa, IIx, IIb); however, when applied to human muscle, the type II MHC isoforms (IIa, IIx) are not clearly distinguished. In this brief paper we describe a modification of the SDS-PAGE protocol which yields distinct and consistent separation of all three adult human MHC isoforms (MHC I, IIa, IIx) in a minigel system. MHC specificity of each band was confirmed by Western blot using three monoclonal IgG antibodies (mAbs) immuno-reactive against MHCI (mAb MHCs, Novacastra Laboratories), MHCI+IIa (mAb BF-35), and MHCIIa+IIx (mAb SC-71). Results provide a valuable SDS-PAGE minigel technique for separating MHC isoforms in human muscle without the difficult task of casting gradient gels.
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The purpose of this study was to investigate the effect of set structure, in terms of repetition work:rest ratios on force, velocity, and power during jump squat training. Twenty professional and semiprofessional rugby players performed training sessions comprising four sets of 6 repetitions of a jump squat using four different set configurations. The first involved a traditional configuration (TR) of 4 × 6 repetitions with 3 min of rest between sets, the second (C1) 4 × 6 × singles (1 repetition) with 12 s of rest between repetitions, the third (C2) 4 × 3 × doubles (2 repetitions) with 30 s of rest between pairs, and the third (C3) 4 × 2 × triples (3 repetitions) with 60 s of rest between triples. A spreadsheet for the analysis of controlled trials that calculated the P-value, and percent difference and Cohen's effect size from log-transformed data was used to investigate differences in repetition force, velocity, and power profiles among configurations. Peak power was significantly lower (P < .05) for the TR condition when compared with C1 and C3 for repetition 4, and all cluster configurations for repetitions 5 and 6. Peak velocity was significantly lower (P < .05) for the TR condition compared with C3 at repetition 4, significantly lower compared with C2 and C3 at repetition 5, and significantly lower compared with all cluster conditions for repetition 6. Providing inter-repetition rest during a traditional set of six repetitions can attenuate decreases in power and velocity of movement through the set.