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Concurrent Endurance and Strength Training
Not to Failure Optimizes Performance Gains
MIKEL IZQUIERDO-GABARREN
1
, RAFAEL GONZA
´LEZ DE TXABARRI EXPO
´SITO
1
,
JESU
´S GARCI
´A-PALLARE
´S
2
, LUIS SA
´NCHEZ-MEDINA
3
, EDUARDO SA
´EZ SA
´EZ DE VILLARREAL
3
,
and MIKEL IZQUIERDO
4
1
Research Center of Rowing Club Orio, Orio, SPAIN;
2
Faculty of Sport Sciences, University of Murcia, Murcia, SPAIN;
3
Faculty of Sport, Pablo de Olavide University, Seville, SPAIN; and
4
Research, Studies and Sport Medicine Center,
Government of Navarra, Pamplona, SPAIN
ABSTRACT
IZQUIERDO-GABARREN, M., R. GONZA
´LEZ DE TXABARRI EXPO
´SITO, J. GARCI
´A-PALLARE
´S, L. SA
´NCHEZ-MEDINA,
E. S. S. DE VILLARREAL, M. IZQUIERDO. Concurrent Endurance and Strength Training Not to Failure Optimizes Performance
Gains. Med. Sci. Sports Exerc., Vol. 42, No. 6, pp. 1191–1199, 2010. Purpose: The purpose of this study was to examine the efficacy
of 8 wk of resistance training to failure versus not to failure training regimens at both moderate and low volumes for increasing upper-
body strength and power as well as cardiovascular parameters into a combined resistance and endurance periodized training scheme.
Methods: Forty-three trained male rowers were matched and then randomly assigned to four groups that performed the same endurance
training but differed on their resistance training regimen: four exercises leading to repetition failure (4RF; n= 14), four exercises not
leading to failure (4NRF; n= 15), two exercises not to failure (2NRF; n= 6), and control group (C; n= 8). One-repetition maximum
strength and maximal muscle power output during prone bench pull (BP), average power during a 20-min all-out row test (W
20min
),
average row power output eliciting a blood lactate concentration of 4 mmolIL
j1
(W
4mmolIL
j1
), and power output in 10 maximal strokes
(W
10strokes
) were assessed before and after 8 wk of periodized training. Results: 4NRF group experienced larger gains in one-repetition
maximum strength and muscle power output (4.6% and 6.4%, respectively) in BP compared with both 4RF (2.1% and j1.2%) and
2NRF (0.6% and j0.6%). 4NRF and 2NRF groups experienced larger gains in W
10strokes
(3.6% and 5%) and in W
20min
(7.6% and 9%)
compared with those found after 4RF (j0.1% and 4.6%), whereas no significant differences between groups were observed in the
magnitude of changes in W
4mmolIL
j1
(4NRF = 6.2%, 4RF = 5.3%, 2NRF = 6.8%, and C = 4.5%). Conclusions: An 8-wk linear
periodized concurrent strength and endurance training program using a moderate number of repetitions not to failure (4NRF group)
provides a favorable environment for achieving greater enhancements in strength, muscle power, and rowing performance when
compared with higher training volumes of repetitions to failure in experienced highly trained rowers. Key Words: TRAINING
INTENSITY, OPTIMAL TRAINING VOLUME, DOSE–RESPONSE VOLUME, TRAINING TO REPETITION FAILURE
Coaches and researchers with an interest in sports
requiring both strength and aerobic endurance (e.g.,
rowing) have attempted to design and to implement
periodization schemes aimed to minimize the potential in-
terference effects traditionally associated with concurrent
training (2,5). Several studies have shown that short-term
repeated high-intensity concurrent resistance and endurance
training may compromise the magnitude of strength and
power development (7,15,24). It is also believed that for
optimal strength and endurance enhancement, special atten-
tion should be paid to the order and timing of the training
sessions. Thus, residual fatigue from a previous endurance
session may cause a reduction in the quality of subsequent
strength training by compromising the ability of the neu-
romuscular system to rapidly develop force (26) and/or
reducing the absolute volume of strength training that could
be performed in such a condition (35). The manipulation of
resistance training volume (i.e., number of exercises per ses-
sion, repetitions per set, or sets per exercise) is another issue
that has received considerable research attention. Indeed, it
has been suggested that the main effect (i.e., neural, hyper-
trophic, metabolic, and hormonal responses) and subsequent
adaptations to resistance training partially depend on the
total number of repetitions performed by an individual
(1,11,12,22). Moderate increase in training volume has been
shown to lead to further improvement in strength (1,11,12,33).
However, it appears that once a given ‘‘optimal’’ volume is
reached, further increases in training volume do not yield any
significant gains and can even lead to reduced performance
in experienced resistance-trained subjects (11,12). Unfortu-
nately, the question of which is the optimal training volume
for the simultaneous development of strength and endur-
ance for sports requiring great demands of both components
of physical fitness (e.g., rowing) remains unresolved.
Address for Correspondence: Mikel Izquierdo, Ph.D., Research, Studies
and Sport Medicine Center, Government of Navarra, C/Sangu
¨esa 34,
31005 Pamplona, Spain; E-mail: mikel.izquierdo@ceimd.org.
Submitted for publication August 2009.
Accepted for publication October 2009.
0195-9131/10/4206-1191/0
MEDICINE & SCIENCE IN SPORTS & EXERCISE
Ò
Copyright Ó2010 by the American College of Sports Medicine
DOI: 10.1249/MSS.0b013e3181c67eec
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by the American College of Sports Medicine. Unauthorized reproduction of this article is prohibited.Copyright @ 2010
The number of repetitions performed with a given load
may impact the extent of muscle damage and cause subse-
quent decrements in velocity and force production (20,21).
Thus, the role played by training leading to repetition
failure (inability to complete a repetition in its full range
of motion) has been of interest to coaches and sport sci-
entists to understand the physiological mechanisms un-
derlying training-induced gains in strength and power.
Short-term training (G9 wk) leading to repetition failure pro-
duces greater improvements in strength (6,34) when com-
pared with a not to failure training approach. However, other
studies have concluded that training to failure may not be
necessary for optimal strength gains because the incurred
fatigue reduces the force a muscle can generate (8,25,37).
Likewise, in previously resistance-trained men, it has been
reported that when the volume and intensity variables were
equated, training not leading to repetition failure led to simi-
lar improvements in maximal strength and muscle power
output (20) compared with training leading to failure. In light
of these observations, we hypothesized that resistance
training performed with the same intensity but not leading
to failure (i.e., half the maximum number of repetitions that
could be performed per set leading to failure) and with either
identical (i.e., same number of exercises per session) or
reduced volume (i.e., half the number of exercises per
session) would lead to similar gains in maximal strength to
training to repetition failure but to greater gains in power
output and attenuate compromised strength and cardio-
vascular development when strength and endurance training
were applied concurrently. Therefore, the purpose of this
study was to examine the effect of three different 8 wk of
resistance training interventions that manipulated training
volume (moderate volume to failure, moderate volume not
to failure, and low volume not to failure) for increasing
upper-body strength and power as well as some cardiovas-
cular variables in a group of well-trained rowers who un-
derwent a combined resistance and endurance periodized
training scheme.
METHODS
Experimental Design and Approach to the Problem
A longitudinal research design using three different resis-
tance training volumes (i.e., sets repetitions) performed
with the same intensity (progressing from 10RM to 4RM)
but with a different number of exercises (4 vs 2 exercises)
and a different number of repetitions per set (i.e., leading to
failure vs not leading to failure) was used to parcel out
differential training adaptations in strength and power gains
as well as to analyze rowing performance changes during
concurrent strength and endurance training. In an attempt to
minimize the effect of potential confounding variables, rel-
ative load (percentage of one-repetition maximum (1RM))
and average intensity and frequency of training were con-
trolled by equating their values among the treatment groups.
Such adjustments were critical to the study design because
it has been suggested that differences in overall training in-
tensity and volume influence performance adaptations (12,20).
After baseline testing, subjects were matched according to
physical characteristics, muscle strength and power indexes,
and rowing performance and then randomly assigned to one
of four groups: four exercises leading to repetition failure
(4RF; n= 14), four exercises not leading to failure (4NRF;
n= 15), two exercises not to failure (2NRF; n= 6), or a
control group (C; n= 8). The control group did not undergo
any resistance training but continued their usual traditional
rowing training, similar to that performed by the three
resistance training groups. All groups were assessed on two
occassions: before (PRE) and after (POST) the 8-wk train-
ing intervention.
Subjects
This study involved a group of 43 trained male rowers
with 12.1 T5 yr of regular training and competition ex-
perience in traditional rowing (Table 1). Traditional rowing
competition is a fixed-seat rowing performed on the sea, the
boat manned by 13 rowers, and a cox (23). All subjects
participated in a Spanish traditional rowing league. Before
inclusion in the study, all subjects were medically screened
and appeared to be free from any orthopedic, cardiac, endo-
crinal, or medical problems that would rule out their par-
ticipation or influence the results of the research. Each
participant gave written informed consent to participate
after the purpose and potential risks of the study were care-
fully explained. The study was conducted in accordance
with the stipulations of the Declaration of Helsinki and was
approved by the by the institutional review committee of
the Instituto Navarro de Deporte.
TABLE 1. Characteristics of the periodized resistance training program performed by each group.
Group Week 1 2 3 4 5 6 7 8 Total reps
Sessions 2 2 2 2 2 2 2 2
Sets 3 4 3 4 3 4 3 4
Intensity (%1RM) 75 75 80 80 86 86 92 92
4RF (n= 14) Scheduled reps 10 10 8 8 6 6 4 4
Reps/session 120 160 96 128 72 96 48 64 784 2 = 1568
4NRF (n= 15) Scheduled reps 5 5 4 4 3 3 2 2
Reps/session 60 80 48 64 36 48 24 32 392 2 = 784
2NRF (n= 6) Scheduled reps 5 5 4 4 3 3 2 2
Reps/session 30 40 24 32 18 24 12 16 196 2 = 392
4RF, four exercises (prone BP, seated cable row, lat pulldown, and power clean) training to repetition failure group; 4NRF, four exercises (prone BP, seated cable row, lat pulldown, and
power clean) training not to failure group; 2NRF, two exercises (prone BP and seated cable row) training not to failure group; reps, number of repetitions.
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The study took place from March to April, at the end of
the specific preparatory period. During the preceding
months, the subjects had been training six times a week
on average, with a typical training session duration of
120 min. The distribution of training was similar to that of
Olympic rowing, with 60% of the specific training done
in water, 20% of strength training in the gym, and 20%
athletic training (i.e., running training at light and moderate
intensities for cardiovascular conditioning). Furthermore, in
the 5 months preceding the beginning of the study, the
subjects took part in a resistance training program consist-
ing mainly of typical free-weight exercises (i.e., including
bench press, prone bench pull (BP), and back squat exer-
cises) with three to five sets of 8–15 repetitions and a rela-
tive intensity of 50%–80% 1RM.
Brief Overview of Testing Procedures
All rowers were familiar with the testing protocol
because they had been previously tested on several oc-
casions in previous seasons for training prescription pur-
poses. Furthermore, several warm-up muscle actions were
recorded before the actual maximal, explosive, and endur-
ance test actions.
Subjects were required to report to the laboratory on five
separate occasions over a 2-wk period. Testing sessions
were always carried out at the same time of day and under
similar environmental conditions. During the first week,
subjects visited the laboratory on three occassions, every
other day, as a part of their regular testing program. Each
rower was tested for one-repetition maximum (1RM) dy-
namic strength (day 1) and muscle power output (day 2) in
the prone bench pull (BP) exercise. On the third day, anthro-
pometric variables and power output in 10 maximal strokes
(W
10strokes
) were measured. In addition, during this first
week, two endurance rowing sessions at low intensity (blood
lactate concentration G2mmolIL
j1
) were performed 24 h
before the testing session. During the second week, par-
ticipants performed a progressive exercise test on a rowing
ergometer (day 1) and a 20-min all-out test (W
20min
; day 2).
These sessions were interspersed with rest periods of a
minimum of 48 h to limit the effects of fatigue on perfor-
mance. Subjects were required to avoid any strenuous phys-
ical activity during the duration of the experiment and to
maintain their dietary habits for the entire duration of
the study.
Antropometry and Body Composition
Standing height (m), body mass (kg), percentage of body
fat (%), and fat-free mass (FFM; kg) were determined for
each subject. Height and body mass were measured using a
self-calibrated scale (An
˜o Sayol, Barcelona, Spain) and
recorded to the nearest 0.5 cm and 0.1 kg, respectively.
Whole-body fat was estimated according to the skinfold
thickness method developed by Jackson and Pollock (32).
Skinfold measurements were measured at seven sites (sub-
scapular, tricipital, midaxillary, suprailiac, pectoral, abdom-
inal, and anterior thigh) using a Harpenden skinfold caliper
accurate to 0.2 mm (Holtain Ltd., Crymych, UK). A minimum
of two measurements were taken at each skinfold site by the
same highly skilled investigator. Fat-free mass (kg) was calcu-
lated as the difference between body mass and body fat.
Maximal strength and muscle power tests. A
detailed description of the maximal strength and muscle
power testing procedure can be found elsewhere (18,20). In
brief, maximal upper-body strength was assessed using a
one-repetition maximum BP (1RM
BP
) action. The BP
exercise (elbow and shoulder flexion) was chosen because
it seems most specific to the rowing technique (27,29).
Bilateral BP tests were performed with the use of standard
free-weight equipment (Salter, Madrid, Spain). Subjects lay
facedown on the bench with both elbows in full extension,
arms completely stretched out and suspended perpendicu-
larly at 90-, and barbell grasped with hands shoulder-width
apart or slightly wider. On command, participants pulled
with maximum effort until the barbell struck the underside
of the bench, after which it was again lowered to the
starting position. A manual goniometer (Q-TEC Electronic
Co. Ltd., Gyeonggi-do, Korea) was placed at the elbow to
standardize the range of motion. Warm-up consisted of a
set of 10 repetitions with loads of 40%–60% of the per-
ceived maximum. Thereafter, five to six separate single
attempts with increasing loads were made until the subject
was unable to flex the arms to the required position. The
heaviest load that each subject could properly lift was
considered to be his 1RM. The rest period between actions
was always 2 min.
The upper-body power–load relationship was assessed
in the BP using relative loads of 15%, 30%, 45%, 60%,
75%, 85%, and 100% of the previously determined 1RM
(W
BP15%
jW
BP100%
). On command, the subjects were in-
structed to move the loads as fast as possible. Two con-
centric actions for each load were recorded, and that with
the highest absolute power output value was taken for fur-
ther analysis. The rest period between each trial was 2 min.
Each week during the intervention period, BP power
output developed with the same absolute load (that cor-
responding to the 70% 1RM pretraining value) was as-
sessed. This load was chosen because it has been proved to
be very close to the load that maximizes the average mech-
anical power output for isoinertial BP resistance exercises
(23). Four repetitions were performed as fast as possible
with this fixed load, and the mean concentric power was
retained for further analysis.
Bar displacement, mean concentric velocity, and peak
and mean concentric power during BP actions were re-
corded by attaching a rotary encoder (FitroDyne; Fitronic,
Bratislava, Slovakia) to one end of the barbell. The rotary
encoder recorded the position and direction of the bar to an
accuracy of 0.0003 m. Customized software was used to
calculate power output for each repetition of BP performed
throughout the range of motion. For comparison purposes,
TRAINING AND OPTIMIZING ROWING PERFORMANCE Medicine & Science in Sports & Exercise
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an averaged index of muscle power output with all the ab-
solute loads examined was calculated for each group sepa-
rately. The averaged index of muscle power in BP was
calculated as the sum of the power values obtained under
all experimental conditions (Windex BP ). In addition, maximal
power output was defined as the maximum power obtained
from all loads examined (Wmax BP ). The test–retest intraclass
correlation coefficients for all anthropometric, strength, and
power variables were greater than 0.93, and the coefficients
of variation ranged from 0.92% to 1.9%.
Rowing ergometer performance tests. The rowers
were fully familiar with the use of the wind-resistance
braked rowing ergometer (Concept II, model D, Morrisville,
VT). All evaluations were performed on a modified ergom-
eter with a drag factor of 145, a static seat individually
adapted to each rower, and legs in semiflexion (i.e., 160-).
Subjects warmed up by rowing progressively for 15 min,
finishing up with some strokes at maximal effort. The
highest value displayed on the monitor of the ergometer
when each subject rowed 10 strokes with maximal effort
was considered to be his maximal rowing power (W
10stroke
)
(14). Then, they undertook two 10-stroke trials, separated
by 5 min of rest. The best reading (that with the highest
power output) was taken for further analysis.
Exercise tests on the ergometer were performed using an
incremental step protocol, as defined by Ingham et al. (17).
The subjects warmed up for 10 min. Power was initially set
at 150–180 W, depending on the rowers’ body mass, and
increased thereafter by 25 W after each stage. Heart rate
was continuously recorded using a heart rate monitor (RS
800G3, Polar Electro, Kempele, Finland). Capillary whole-
blood samples were taken from the earlobe during each 30-s
rest period to measure lactate concentration ([La
j
]) using a
miniphotometer (Dr. Lange LP-20, Du
¨sseldorf, Germany).
Individual data points for blood lactate values were plotted
as a continuous function against time. The exercise lactate
curve was fitted with a second degree polynomial function
(r= 0.98–0.99, PG0.001). From the equation describing
the blood lactate response to exercise, the power output as-
sociated with a blood lactate concentration of 4 mmolIL
j1
(W
4mmol
) was interpolated. The W
4mmol
exercise intensity
has been shown to be an important determinant of en-
durance performance capacity (38). Stroke rate and ratings
of perceived exertion according to Borg’s 20-point scale
were also measured (4).
A 20-min all-out test was carried out after a 15-min
warm-up. On the basis of the results of the previous pro-
gressive test, the intensity the subjects had to maintain was
calculated as 250–350 W per stroke. Rowers were strongly
encouraged to maintain the maximum sustainable power
output for 20 min. Actual power output values were re-
corded every 4 min and at the end of the test, then the
average power during the 20 min (W
20min
) was computed.
During this time, the subjects covered distances of 5000–
6300 m, with 35–40 strokes per minute, performing a total
number of 675–725 total strokes.
Resistance and endurance rowing training
programs. All resistance training sessions started with a
general warm-up (ending with four repetitions in the BP
with 70% 1RM performed with maximal intended concen-
tric velocity) and included cooldown periods of 5–10 min
of low-intensity aerobic and stretching exercises. A trained
researcher carefully supervised each workout session and
recorded the training compliance and individual workout
data so that exercise prescriptions were properly adminis-
tered (e.g., number of sets and repetitions, rest pauses, and
movement velocity). Training compliance for this study
was 100% of the scheduled sessions.
Treatment groups were required to perform dynamic
resistance training twice per week for 8 wk. The approx-
imate training session duration for each group was 30 min
(2NRF), 45 min (4NRF), and 60 min (4RF). A minimum of
2 d elapsed between two consecutive training sessions. Four
resistance training exercises (BP, seated cable row, lat
pulldown, and power clean) were used for the 4RF and
the 4NRF groups, whereas the 2NRF group only performed
the first two (BP and seated cable row). In addition, all
intervention groups performed some supplementary exer-
cises (e.g., abdominal crunch, trunk extension) for core
conditioning.
The three treatment groups followed an 8-wk linear
periodization program of resistance training. One group
performed four exercises always leading to repetition failure
in each set (4RF), another group used the same four
exercises but only completed half the maximum number
of repetitions that could be performed per set (4NRF),
whereas the third group performed both half the number
of exercises and half the maximum number of possible
repetitions within each set (2NRF). All groups used the
same training intensity in each session. This intensity was
continuously adjusted during the 8-wk period by the
rowers’ capacity to perform sets to failure (4RF group) or
to maintain the expected movement velocity (4NRF and
2NRF, not to failure groups). Thus, for the 4RF group, in
the case that a subject was unable to perform the concentric
phase in its full range of motion, the load was slightly
reduced (and the exercise immediately resumed) for
subsequent repetitions. During a typical training session in
the 4RF group, the training load was reduced two to three
times to individually adjust the corresponding resistance to
the true repetition maximum, whereas the load remained
constant in the 4NRF and 2NRF groups.
A detailed summary of the resistance training volume and
exercise intensity performed by each treatment group for
each of the 8 wk is presented in Table 1. As already men-
tioned, all groups trained with the same relative loading
intensity (%1RM) in each session, but training volume was
distinctly manipulated for each of them. Thus, the 4NRF
group performed a final training volume (total number of
repetitions) that amounts to half that of the 4RF group.
Likewise, the 2NRF group only performed half the total
training volume completed by the 4NRF group. Subjects
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were carefully instructed to always perform the concentric
phases of all exercises at the highest possible velocity,
whereas the eccentric actions were done at a low, controlled
velocity.
Besides the resistance training program underwent by the
4RF, 4NRF, and 2NRF groups, during the 8-wk period, all
four groups performed the same endurance regimen. This
endurance program comprised two mesocycles with a 3:1-wk
training to recovery load structure. Rowers averaged a total
of 45 training sessions during which 460 minIwk
j1
of aerobic
exercise (including both ergometer and on-water rowing)
were performed. On the basis of training diary records, 87%
of the endurance sessions were performed at low intensity
([La
j
]G2mmolIL
j1
), 7% between 2 and 4 mmolIL
j1
,and
6% above 4 mmolIL
j1
.
Statistical analyses. Standard statistical methods were
used for the calculation of means and SD. One-way ANOVA
was used to determine any differences among the four
groups’ initial strength, power, and rowing ergometer en-
durance performance. The training-induced effects were as-
sessed using a two-way ANOVA with repeated-measures
(groups time). When a significant Fvalue was achieved,
Sheffe
´post hoc procedures were performed to locate the
pairwise differences between the means. Absolute changes
in selected parameters (i.e., strength, muscle power, and
endurance rowing variables) were analyzed via one-way
ANOVA. Statistical power calculations for this study
TABLE 2. Subjects’ physical characteristics before and after the training intervention.
4RF
(n= 14)
4NRF
(n= 15)
2NRF
(n=6)
Control
(n=8)
Age (yr) 25.4 T4.2 26.7 T5.7 22.1 T3.6 27.3 T7.1
Training experience (yr) 10.7 T3.1 12.6 T5.7 10.5 T4.4 15.2 T6.3
Height (cm) 181.0 T3.7 182 T4.9 184.5 T4.5 183.3 T4.1
Body mass (kg)
PRE 79.8 T5.3 83.2 T6.3 85.8 T6.6 82.7 T7.5
POST 77.6 T4.5* 81.1 T5.9* 83.1 T5.5* 81.6 T7.2*
Body fat (%)
PRE 12.1 T1.3 12.3 T1.7 13.5 T2.2 11.8 T1.5
POST 11.2 T0.7* 11.5 T1.3* 12.3 T1.4 11.3 T1.2
FFM (kg)
PRE 70.0 T4.3 72.9 T4.6 74.0 T5.2 72.9 T6.3
POST 68.8 T3.8* 71.7 T4.6* 72.8 T5.1* 72.3 T6.4*
Values are presented as mean TSD.
*PG0.05 vs PRE.
4RF, four exercises training to repetition failure group; 4NRF, four exercises training not
to failure group; 2NRF, two exercises training not to failure group; C, control group;
FFM, fat-free mass; PRE, before intervention; POST, after 8 wk of training.
FIGURE 1—BP (A) maximal strength (1RM
BP
) and (B) maximum
power obtained from all loads examined (W
max
BP
). *PG0.05 from
pretraining. #PG0.05 from the relative change between groups. Data
are presented as mean and SD.
FIGURE 2—Mean TSD muscle power output in the concentric BP
action at different loads of individual maximal 1RM in 4RF (A),
4NRF (B), and 2NRF (C) group. *PG0.05 from corresponding value
at pretraining. Data are presented as mean and SD.
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ranged from 0.75 to 0.80. The PG0.05 criterion was used
for establishing statistical significance.
RESULTS
Body composition. At the beginning of the training
program, no significant differences were observed between
groups in age, training experience, height, body mass, body
fat mass, or FFM. A significant decrease in body mass,
body fat, and FFM was observed after training in 4RF and
4NRF groups. After the intervention, a significant decrease
was also observed for 2NRF and control groups in body
mass and FFM, whereas no significant differences were
observed in body fat (Table 2).
Maximal strength and muscle power output. At
baseline, no significant differences were observed between
groups in maximal strength (1RM
BP
), maximal power at all
loads (from 15% to 90% of 1RM
BP
;WmaxBP ), and power
output index in BP (WindexBP ). In the control group, no
significant changes were observed from PRE to POST for
any of the maximal strength and muscle power variables
analyzed. After the training period, significant increases were
observed in 1RM
BP
,Wmax BP ,andWindex BP butonlyinthe
4NRF group. Significant group time interaction was
observed for the 1RM
BP
, with a significantly larger magni-
tude of increase for 4NRF (4.6%) than that found in 4RF and
2NRF (2.1% and 0.6%, respectively) (Fig. 1A). Significant
group time interaction was observed for the Wmax BP
and Windex BP with a significantly larger (PG0.05) magni-
tude of increase for 4NRF (6.4% and 5.2%, respectively)
than that recorded in 4RF (j1.2% and j0.6%) and 2NRF
(j0.3% and 2.2%) (Fig. 1B).
Significant increases were observed in muscle power
output at 75% and 85% of 1RM
BP
for the 4NRF group
(Fig. 2B). A significant group time interaction was ob-
served in muscle power output at 75% and 85% of 1RM
BP
,
with a significantly larger (PG0.05) magnitude of increase
for 4NRF (6.6% and 6.7%) than those recorded in 4RF
(j3.1% and j2.7%) and 2NRF (0.8% and 1.4%) from
PRE to POST training (Fig. 2, A–C).
At baseline, no significant differences were observed in
muscle power output with an absolute load corresponding
to the 70% of 1RM
BP
. During the 8 wk of intervention, sig-
nificant increases were observed in muscle power output
with an absolute load corresponding to 70% of 1RM
BP
at
pretraining for 4NRF and 2NRF (Fig. 3), whereas no sig-
nificant changes were observed in the 4RF group. In the
control group, significant decreases (j2.6%) were observed
from PRE to POST for this variable. Significant group
time interaction was observed in muscle power output with
an absolute load corresponding the 70% of 1RM
BP
at pre-
training, with a significantly larger (PG0.05) magnitude of
increase for 4NRF (13.1%) than that recorded in 4RF and
2NRF groups (1.3% and 7.9%, respectively) (Fig. 3).
Performance in rowing ergometer. At baseline, no
significant differences were observed between groups in
FIGURE 3—Mean TSD muscle power output with an absolute load
corresponding to the 70% of 1RM
BP
during experimental period.
*PG0.05 from week 1.
a
PG0.05 from corresponding value of 4RF.
b
PG0.05 from corresponding value of 2NRF.
FIGURE 4—Mean TSD power output of 10 strokes (W
10strokes
) (A),
which elicited a blood lactate concentration of 4 mmolIL
j1
(B), and
during 20 min of all-out test (W
20min
) (C) attained in rowing ergometer
during the experimental period. *PG0.05 from pretraining. #PG0.05
from relative change between the groups.
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rowing ergometer performance variables (i.e., W
4mmolIL
j1
and W
20min
). W
10strokes
increased significantly only in the
4NRF and 2NRF training groups. Significant group time
interaction was observed in W
10strokes
, with a significantly
larger magnitude of change for 4NRF and 2NRF (3.6% and
5%) than that found for the 4RF (j0.1%) and control
groups (j0.8%) (Fig. 4A).
W
4mmolIL
j1
significantly (PG0.05) increased in all
groups after 8 wk of intervention period (Fig. 4B). No
significant differences were observed in the magnitude of
the change between groups (4NRF 6.2%, 4RF 5.3%, 2NRF
6.8%, and C 4.5%).
Significant increases were observed in W
20min
for all
groups (Fig. 4C). Significant group time interaction was
observed in W
20min
, with a significantly larger (PG0.05)
magnitude of increase for 4NRF and 2NRF (7.6% and 9%)
than those recorded in 4RF (4.6%) and control groups
(4.5%).
DISCUSSION
The two major findings of this study were that after 8 wk
of combined resistance and endurance training, 1) the 4NRF
group experienced larger gains in maximal strength and
maximal power output, in absolute and relative terms, when
compared with both 4RF and 2NRF groups; and 2) the
4NRF and the 2NRF groups improved W
10strokes
and W
20min
to a greater extent than the 4RF group, whereas no sig-
nificant differences between groups were observed in the
magnitude of changes in rowing power associated with a
[La
j
] of 4 mmolIL
j1
. These data seem to indicate that short-
term resistance training using a moderate volume of repeti-
tions not to failure enables a favorable environment for
achieving greater enhancements in strength, muscle power,
and rowing performance compared with higher training
volumes of repetitions to failure. Therefore, our results sug-
gest that to improve performance in sports with great demands
of both muscle strength and aerobic endurance, a combined
program of endurance and resistance exercise characterized
by not training to repetition failure and performing only a
moderate number of repetitions in each training session may
be an effective and safe option for highly trained athletes.
Few studies have examined the different possibilities of
manipulating resistance training volume for the concurrent
development of strength and endurance in sports with great
requirements of both fitness components (e.g., rowing). As
already mentioned, moderate increases in training volume
have been shown to lead to further improvement in strength
(1,11,12,20,33). However, It appears that once a given
‘‘optimal’’ volume is reached, a further increase in training
volume does not yield more gains and can even lead to
reduced performance in experience resistance-trained sub-
jects (11,12). The results of the present study tend to
support this because only the 4NRF group led to significant
increases in maximal strength and relative muscle power
during a concurrent strength and aerobic training. In con-
trast, 2NRF and 4RF approaches did not provide an ade-
quate stimulus for improving upper-body maximal strength
and power during concurrent strength and endurance
training, despite the training volume in 2NRF being 25%
of that performed in 4RF. This seems to indicate that during
concurrent strength and endurance training (i.e., row train-
ing), an optimal resistance training volume should be one
that that elicits not only maximal strength and power gains
but also an improvement in specific rowing performance.
Thus, it is likely that performance could be compromised if
this threshold volume were surpassed or drastically reduced,
perhaps suggesting that moderate-volume high-intensity
stimuli are needed to induce further power gains in highly
trained athletes when the concurrent development of both
strength and endurance are important.
Short-term isolated strength training programs (G9 wk)
consisting of repetitions performed to failure have shown to
lead to greater strength gains (6,34) compared with ap-
proaches not leading to failure in untrained subjects. On the
contrary, other studies have shown that training to failure
may not be necessary for optimal training gains (8,25,37).
Several factors such as differences in the manipulation of
volume and intensity of training, dependent variable se-
lection, muscle groups involved, and initial training status
of the subjects may explain the contradictory results of
these studies. Recently, Izquierdo et al. (20) reported that
training to failure and training not to failure resulted in
similar gains in 1RM strength and muscle power output of
the arm and leg muscles. That study was performed in a
strength-trained population with a carefully equated and
controlled volume and training intensity in the experimental
groups. However, after a preceding peaking phase, training
not leading to failure resulted in higher gains in muscle
power compared with a training leading to failure approach.
To the authors’ knowledge, no studies have isolated the
effects of performing sets leading to failure (or the number)
in a multigroup experimental design while controlling other
variables in a long-term training protocol in sports where
both endurance and strength need to be simultaneously en-
hanced to optimize performance. The results of the present
study suggest that short-term combined endurance and re-
sistance training leading to failure do not provide an ad-
vantage for improving upper-body maximal strength and
muscle power in highly trained rowers. In contrast, in the
present combined training program, a not leading to failure
and moderate training volume approach resulted in greater
increases in maximal strength and muscle power gains of the
upper-body musculature. This moderate increase (4%–6%)
in maximal strength and muscle power was observed in
spite of significant losses (È1.6%) in FFM in response to
the combined endurance and resistance training intervention
in all treatment groups (i.e., 4RF, 4NRF, and 2NRF). This
pattern of results may be due to the very high physical demands
placed on the athletes during the short-term high-intensity
combined endurance rowing and strength training program.
TRAINING AND OPTIMIZING ROWING PERFORMANCE Medicine & Science in Sports & Exercise
d
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Our findings are consistent with those of a previous study
performed in trained subjects (24), which reported that
combining strength and endurance training attenuates the
muscle fiber hypertrophy produced by resistance training
alone. Nevertheless, further research is required to optimize
maximal strength and power development in the context of
combined strength and endurance training.
Previous studies have also shown that short-term high-
intensity concurrent resistance and endurance training may
compromise the magnitude of strength and power develop-
ment (7,15,24). The attenuated strength improvement
usually observed in concurrent training has been attributed
to the development of residual fatigue in the neuromuscular
system (15) because of the high volume and training fre-
quency (4–6 dIwk
j1
) typical of these combined programs,
even during short-term training periods (G12 wk) (7,15,24).
A trend toward attenuated strength adaptations with con-
current training could be also observed when a demanding
amount of training volume and/or frequency was performed
over a long period (3,13). However, when the training
frequency is low (2–3 dIwk
j1
), there may be a synergistic
effect between strength and endurance training in the ob-
served increase in maximal strength during both short-term
(G12 wk) (4,19,28) and long-term training periods (920 wk)
(13). Research has also documented that short-term re-
peated high-intensity training can lead to overtraining (9).
Thus, residual fatigue from a previous aerobic session could
cause a reduction in the quality of subsequent strength
training by compromising the ability of the neuromuscular
system to rapidly develop force (26) and/or by reducing the
absolute volume of strength training that could be per-
formed in such condition (10,35,36). Therefore, it appears
that the manipulation of training volume and/or intensity is
critical to avoid potential interferences in concurrent training
(5,10,19), especially when high-intensity resistance training
is performed concurrently with regular endurance rowing in
well-trained athletes.
Tracking weekly time-course changes in the upper-body
muscle power output developed with an absolute load
corresponding to 70% 1RM pretraining value is a unique
aspect of the present study that provides meaningful data
for resistance training design during concurrent strength and
endurance training. A moderate-volume training program
performing each set not to muscular failure (i.e., 4NRF
group) led to greater gains in power output, whereas no
significant weekly gains in power were observed for the
high-volume training to repetition to failure (i.e., 4RF)
approach. These data indicate that training to failure for
improving absolute upper-body muscle power may not
provide a positive stimulus for optimal power development
during concurrent training. Conversely, a moderate volume
of training sets not performed to muscle failure made it
possible to attain high power output values during a few
selected repetitions and to minimize fatigue so that near-
maximum neuromuscular drive and force could be applied
to each repetition (20,21).
An interesting finding of the present study was that the
periodized strength training program not leading to failure
with moderate-volume (4NRF) and low-volume (2NRF)
approaches induced greater gains in anaerobic rowing per-
formance (e.g., W
10strokes
) and average power during the
20-min all-out test (e.g., W
20min
) than high-volume training
to failure approach (4RF) or endurance only (control group).
In addition, no significant differences between groups were
observed in the magnitude of changes in stroke power
associated with a blood lactate concentration of 4 mmolIL
j1
(W
4mmolIL
j1
). These results are partially in agreement with
those of previous studies, which showed that the addition of
resistance training to ongoing exercise regimens of well-
trained endurance athletes is beneficial and results in im-
proved endurance performance (10,16,30,31). Similarly, it
has recently been reported that a periodized training program
can be effectively used for simultaneously developing
strength and aerobic endurance in elite kayakers (10). Fur-
thermore, our results also suggest that when training resis-
tance volume is carefully controlled, high-volume program
leading to failure does not yield improved aerobic gains and
can even negatively affect rowing performance in highly
trained endurance athletes. In contrast, this result may sug-
gest that alternating exercise modes of moderate- or low-
volume resistance training not leading to failure (e.g., 4NRF
or 2NRF groups) combined with endurance training may
help to increase training-induced aerobic gains compared
with single endurance mode of training. Therefore, in the
context of an 8-wk concurrent resistance and endurance
rowing training cycle, highly trained rowers can enhance
endurance gains by performing 50% or less of the maximum
number of repetitions performed that could be completed in a
given set while improving also neuromuscular function. By
doing so, a moderate-volume training program performing
each set not to muscular failure (i.e., 4NRF group) could be
more efficient for also improving maximal strength and
relative muscle power as well as providing a better stimulus
for improving endurance performance during a concurrent
strength and aerobic training cycle.
In conclusion, an 8-wk linear periodized concurrent
strength and endurance training program using a moderate
number of repetitions not to failure provides a favorable
environment for achieving greater enhancements in strength,
muscle power, and rowing performance when compared with
higher training volumes of repetition to failure in experienced
highly trained rowers. By contrast, both muscle strength and
rowing performance could be compromised if a given thresh-
old volume is surpassed or drastically reduced during a short-
term training program, especially when both strength and
aerobic endurance need to be concurrently enhanced.
No funding was received for this work from any of the following
organizations or any other institution: National Institutes of Health
(NIH), Wellcome Trust, and Howard Hughes Medical Institute
(HHMI).
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by the American College of Sports Medicine. Unauthorized reproduction of this article is prohibited.Copyright @ 2010
This study was supported by the Ministry of Education (National
Plan of R&D+i 2004–2007. Key Action ‘‘Sport and Physical Activity’’
(DEP2006-56076)). The results of the present study do not constitute
endorsement by the American College of Sports Medicine.
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