Effect of Pre-Exhaustion Exercise on Lower-Extremity Muscle Activation During a Leg Press Exercise

Abstract

The purpose of this study was to investigate the effect of pre-exhaustion exercise on lower-extremity muscle activation during a leg press exercise. Pre-exhaustion exercise, a technique frequently used by weight trainers, involves combining a single-joint exercise immediately followed by a related multijoint exercise (e.g., a knee extension exercise followed by a leg press exercise). Seventeen healthy male subjects performed 1 set of a leg press exercise with and without pre-exhaustion exercise, which consisted of 1 set of a knee extension exercise. Both exercises were performed at a load of 10 repetitions maximum (10 RM). Electromyography (EMG) was recorded from the rectus femoris, vastus lateralis, and gluteus maximus muscles simultaneously during the leg press exercise. The number of repetitions of the leg press exercise performed by subjects with and without pre-exhaustion exercise was also documented. The activation of the rectus femoris and the vastus lateralis muscles during the leg press exercise was significantly less when subjects were pre-exhausted (p < 0.05). No significant EMG change was observed for the gluteus maximus muscle. When in a pre-exhausted state, subjects performed significantly (p < 0.001) less repetitions of the leg press exercise. Our findings do not support the popular belief of weight trainers that performing pre-exhaustion exercise is more effective in order to enhance muscle activity compared with regular weight training. Conversely, pre-exhaustion exercise may have disadvantageous effects on performance, such as decreased muscle activity and reduction in strength, during multijoint exercise.

Full text

411
Journal of Strength and Conditioning Research, 2003, 17(2), 411–416
q2003 National Strength & Conditioning Association
Effect of Pre-Exhaustion Exercise on
Lower-Extremity Muscle Activation During
a Leg Press Exercise
J
ESPER
A
UGUSTSSON
,
1
R
OLAND
T
HOMEE
´
,
2
P
ER
H
O
¨RNSTEDT
,
3
J
ENS
L
INDBLOM
,
4
J
ON
K
ARLSSON
,
2
AND
G
UNNAR
G
RIMBY
,
1
1
Department of Rehabilitation Medicine, Go¨teborg University, Go¨teborg, Sweden 41345;
2
Department of
Orthopaedics, Go¨teborg University, Go¨teborg, Sweden 41345;
3
Odda Physical Therapy, Odda, Norway 5750;
4
Kroppsakuten Physical Therapy, Go¨teborg, Sweden 42750.
ABSTRACT
The purpose of this study was to investigate the effect of
pre-exhaustion exercise on lower-extremity muscle activation
during a leg press exercise. Pre-exhaustion exercise, a tech-
nique frequently used by weight trainers, involves combin-
ing a single-joint exercise immediately followed by a related
multijoint exercise (e.g., a knee extension exercise followed
by a leg press exercise). Seventeen healthy male subjects per-
formed 1 set of a leg press exercise with and without pre-
exhaustion exercise, which consisted of 1 set of a knee ex-
tension exercise. Both exercises were performed at a load of
10 repetitions maximum (10RM). Electromyography (EMG)
was recorded from the rectus femoris, vastus lateralis, and
gluteus maximus muscles simultaneously during the leg
press exercise. The number of repetitions of the leg press
exercise performed by subjects with and without pre-ex-
haustion exercise was also documented. The activation of the
rectus femoris and the vastus lateralis muscles during the
leg press exercise was significantly less when subjects were
pre-exhausted (p,0.05). No significant EMG change was
observed for the gluteus maximus muscle. When in a pre-
exhausted state, subjects performed significantly (p,0.001)
less repetitions of the leg press exercise. Our findings do not
support the popular belief of weight trainers that performing
pre-exhaustion exercise is more effective in order to enhance
muscle activity compared with regular weight training. Con-
versely, pre-exhaustion exercise may have disadvantageous
effects on performance, such as decreased muscle activity
and reduction in strength, during multijoint exercise.
Key Words: alternative weight training technique, elec-
tromyography, single-joint exercise, multijoint exercise
Reference Data: Augustsson, J., R. Thomee´, P. Ho¨rn-
stedt, J. Lindblom, J. Karlsson, and G. Grimby. Effect
of pre-exhaustion exercise on lower-extremity muscle
activation during a leg press exercise. J. Strength Cond.
Res. 17(2):411–416. 2003.
Introduction
I
n the initial stages of weight training for sports or
rehabilitation purposes, increases in strength are
quite rapid, mainly because of neural adaptation (17).
In contrast, at the intermediate and advanced stages
of weight training progress is markedly slower. By
then, weight training for athletic purposes is often
characterized by performance plateaus or even decre-
ments (3, 4). However, a number of empirically based
strategies have been developed through the years to
maintain a positive response to long-term weight
training (2, 13). Thus various systems, such as peri-
odization (i.e., organization of training into distinct pe-
riods), and methods, such as supersets, forced reps,
power factor training, and pre-exhaustion exercise, are
used to avoid performance to plateau and for bringing
about optimal gains in strength and muscle hypertro-
phy (1–3, 18, 20–22).
The practice of pre-exhaustion exercise has been
made popular by Eastern European weight lifters and
by body builders in the United States (2). Pre-exhaus-
tion exercise involves working a muscle or a muscle
group to the point of fatigue using a single-joint ex-
ercise, immediately followed by a related multijoint ex-
ercise (2, 18, 21). For example, a weight trainer might
pre-exhaust his or her quadriceps muscles by perform-
ing a knee extension exercise, then follow that exercise
immediately with either a barbell squat exercise or a
leg press exercise (2). In nonscientific weight training
literature, authors advocate this method to overcome
‘‘sticking points’’ or for ‘‘bringing a ‘weak’ body part
up to speed’’ by providing the pre-exhausted muscle
with a greater training stimulus compared with reg-
ular weight training (12).
The effects of fatigue on muscle function and the
implications of this on strength and muscle hypertro-
phy acquisition is not well documented, and existing

412 Augustsson, Thomee´, Ho¨rnstedt, Lindblom, Karlsson, and Grimby
data on whether fatigue may stimulate strength and
muscle volume development is contradictory. Rooney
et al. (16) reported that fatiguing, continuous repeti-
tions resulted in greater strength gains compared with
when rest was taken between repetitions. Similarly,
Schott et al. (19) demonstrated greater strength gains
and muscle hypertrophy following strength training
using long, fatiguing activations compared with short,
intermittent activations. Also, Tesch (22) noted that
body builders, who display large muscularity and
mass, must ‘‘punish themselves’’ (i.e., perform sets to
exhaustion in their training programs) in order to see
progress. Conversely, Pincivero et al. (15) examined
the influence of rest intervals on strength gains sub-
sequent to high-intensity training and reported that a
longer rest period between sets resulted in greater im-
provement in muscle strength. The results obtained by
Pincivero et al. (15) is supported by the observation
that development of fatigue is not desired in power
lifting where the major training goal is to optimize
maximal strength (2). Taken together, it is still not
clear whether accumulation of fatigue during exercise
may be of importance if the objective is to bring about
maximal muscle hypertrophy and strength gains.
Although weight trainers frequently use pre-ex-
haustion exercise, this training technique has, to our
knowledge, not been the subject of a scientific study.
Weight trainers using this method believe pre-exhaus-
tion exercise would result in greater muscle activation
for the subsequent multijoint exercise because presum-
ably the pre-exhausted muscle is engaged in both ex-
ercises (12). To test this hypothesis, we decided to use
the knee extension and the leg press as test exercises
to gain a stress profile of the pre-exhaustion method
and to compare this technique to regular weight train-
ing. Thus the purpose of this study was to investigate
the effect of pre-exhaustion exercise on lower-extrem-
ity muscle activation during a leg press exercise.
Methods
Experimental Approach to the Problem
To test the hypothesis presented in the Introduction,
electromyography (EMG) was recorded from 3 lower-
extremity muscles with and without pre-exhaustion
exercise (knee extensions) during the leg press exer-
cise. The number of repetitions of the leg press exercise
performed by subjects with and without pre-exhaus-
tion exercise was also documented. The collection of
these acute data may suggest whether pre-exhaustion
exercises have a greater potential for producing
strength and muscle size gains compared with regular
weight training.
Subjects
Seventeen healthy male subjects with a mean (6SD)
age, body mass, and height of 26 64 years, 77 66
kg, and 182 66 cm, respectively, volunteered to par-
ticipate in the study. All subjects were recreational
weight trainers with an average (6SD)of5.564 years
of resistance training experience. None of the subjects
had a recent or remote history of significant lower-
extremity injury. Before participation in this study,
each subject provided informed consent approved
through the Ethics Committee of the Faculty of Med-
icine, Go¨teborg University, Sweden.
Determination of 10 Repetitions Maximum
Each subject performed a pretest 4 to 5 days before
testing began. At this time the experimental protocol
was reviewed and the subjects were given the oppor-
tunity to ask questions. In addition, each subject’s 10
repetitions maximum (10RM) was determined for a
knee extension exercise and a leg press exercise by us-
ing the maximum weight that could be lifted for 10
consecutive repetitions. The weight lifted for each trial
was incremented by 5–10 kg until failure occurred.
Each subject’s knee-flexing and knee-extending ca-
dence was not fixed during the knee extension and the
leg press exercise, rather each subject was allowed to
use a self-selected tempo while performing the exer-
cises. Five minutes of rest was allowed between trials.
EMG Electrode Preparation
The exercise session began with EMG electrode prep-
aration. Each electrode site was shaved, abraded, and
cleaned with alcohol to facilitate electrode adherence
and conduction of EMG signals. Bipolar surface elec-
trodes with a diameter of 9 mm (Red Dot, 3M Medica,
Borken, Germany) were placed over the bellies of the
rectus femoris, vastus lateralis, and gluteus maximus
muscles using a standardized method described by Is-
ear et al. (10).
A Tubigrip (Seaton Healthcare Group, Oldham,
England) compression wrap was applied to the test
extremity (right leg) to maintain electrode placement.
Heavy adhesive tape was used to secure electrode
placement on the gluteus maximus muscle. All test
sites were identified and prepared by the same inves-
tigator.
Instrumentation
The EMG signal was preamplified with a gain of
1,000, an impedance of more than 0.5 MOhm at 50 Hz,
and a band width of 0.5–400 Hz by an HDX-82 (Chat-
tanooga Group Inc., Hixson, TN) and was thereafter
band pass-filtered between 7 and 490 Hz by a KC-
EMG (Chattanooga Group). The EMG was sampled
with a frequency of 1,250 Hz by an NB-MIO-16L9 (Na-
tional Instruments Corporation, Austin, TX) on a Mac-
intosh computer with software developed in Lab View
(National Instruments) by Punos Electronics AB, Go¨-
teborg, Sweden. The EMG signal was rectified and the
average of the amplitude was calculated using the root
mean square (RMS) method. During testing, RMS
EMG signals were monitored on the computer. Before

Effect of Pre-Exhaustion Exercise on Muscle Activation
413
Figure 1. Testing setup: Subjects performed a knee
extension exercise (pre-exhaustion) immediately followed
by a leg press exercise. Both exercises were performed at a
10 repetition maximum (10RM) load.
each testing session began, calibration of the EMG ap-
paratus was performed according to the specifications
outlined in the manufacturer’s service manual.
The Maximal Voluntary Isometric Activation Proce-
dure
The maximal voluntary isometric activation (MVIA)
was recorded for each muscle and was used as a ref-
erence value for comparison of muscle activity with
and without pre-exhaustion exercise during the leg
press exercise. Three MVIAs were performed against
a fixed resistance for each muscle in the following po-
sitions: the rectus femoris muscle and the vastus later-
alis muscle—seated with the hip at 908and the knee
at 608of flexion; and the gluteus maximus muscle—
prone with the hip at 108of extension and the knee at
more than 908of flexion. Each activation was held for
4 seconds with a 10-second rest period between rep-
etitions. Each EMG sample included the entire MVIA
interval of 4 seconds’ duration. The largest RMS value
of the 3 MVIAs was designated the reference EMG and
used for normalization.
The Pre-Exhaustion Exercise Procedure
Subjects were then placed in the knee extension and
leg press station (Figure 1). Before testing commenced,
each subject was instructed in the proper technique for
each exercise (i.e., the importance of mental concentra-
tion during the performance of the exercise) and using
a controlled movement for both the concentric as well
as the eccentric phase of the exercise. Warm-up con-
sisted of 2 submaximal (not in excess of 40% of their
10RM pretest weight) sets of 10 repetitions of the knee
extension and leg press exercises.
The starting and ending positions for the knee ex-
tension exercise were seated with approximately 1208
knee flexion angle. From the starting position, each
subject extended the knees and returned to the start-
ing position. The pad supporting the back was ad-
justed for each subject so that the axes of the knee
joints were aligned with the axis of the knee extension
machine resistance arm. The footpad was positioned
at approximately 5 cm proximal to the lateral malle-
olus.
The beginning and ending position for the leg
press was with the knee in full extension. Subjects
were assisted to the beginning position of the leg press
exercise by 1 investigator; thus in this position data
collection was initiated. In a continuous motion the
subject descended to maximum knee flexion (1208)and
then ascended back to the starting position. Visual
feedback of the 1208knee flexion angle position for
each subject was enabled through markers, which were
attached onto the leg press machine. Subjects used a
standardized 40-cm stance width on the leg press plat-
form, with the feet at 208of external rotation.
Subjects performed 1 set of pre-exhaustion exercise
of the quadriceps muscles to the point of fatigue using
the knee extension exercise at a load of 10RM. Imme-
diately following that exercise, EMG was recorded
from the rectus femoris, vastus lateralis, and gluteus
maximus muscles simultaneously during 1 set of the
leg press exercise performed at a load of 10RM. After
a 20-minute rest period, EMG was recorded as subjects
once again performed 1 set of the leg press exercise
(without pre-exhaustion exercise) at a load of 10RM.
Subjects terminated the exercise sets on the completion
of 10RM or muscle failure. One investigator monitored
the exercise to ensure that the correct technique was
maintained while using strong verbal commands and
encouragement. EMG samples were collected for all
repetitions of the leg press exercise set. The range of
motion for collecting the EMG was from 08to 1208
knee flexion, and both the concentric and the eccentric
phases of the exercise were examined. The mean RMS
value for the leg press exercise set under each condi-
tion was then calculated. The number of repetitions of
the leg press exercise performed by subjects with and
without pre-exhaustion exercise was documented. The
order of performing the leg press exercise (with and
without pre-exhaustion exercise) was randomly as-
signed for subjects. Prior to testing all subjects per-
formed a pre-exhaustion exercise procedure session for
familiarization purposes, with a minimum of 4 days
between tests.
Statistical Analyses
Muscle activation amplitude obtained during the pre-
exhaustion exercise procedure was normalized relative
to the MVIA (test EMG amplitude/EMG amplitude of
MVIA multiplied by 100). Paired-samples t-test was
used to compare the average RMS values collected
during the leg press exercise with and without pre-
exhaustion exercise. The number of repetitions of the
leg press exercise performed by subjects with and
without pre-exhaustion exercise was compared using

414 Augustsson, Thomee´, Ho¨rnstedt, Lindblom, Karlsson, and Grimby
Figure 2. Mean and SEM of electromyography (EMG)
activity (expressed as percent of maximal voluntary
isometric activation) during a leg press exercise with
compared to without pre-exhaustion exercise for the rectus
femoris, vastus lateralis, and gluteus maximus muscles,
respectively. *Difference (p50.034) from pre-exhausted
condition. **Difference (p50.001) from pre-exhausted
condition.
a paired-samples t-test. An alpha level of 0.05 was
used for all comparisons.
Results
Significantly lower EMG activity during the leg press
exercise set was noted for the rectus femoris (p5
0.001) and the vastus lateralis (p50.034) muscles with
pre-exhaustion exercise compared to without pre-ex-
haustion exercise. No significant difference of gluteus
maximus muscle activity was observed between the
pre-exhausted condition and the non–pre-exhausted
condition (p50.755; Figure 2). Subjects performed
significantly (p50.001) less repetitions of the leg press
exercise with compared to without pre-exhaustion ex-
ercise; the mean (6SD) number of repetitions was 7.9
(61.4) and 9.3 (62.3), respectively.
Discussion
Our study showed that pre-exhaustion exercise had
the exact opposite effect on muscle activation as sug-
gested by weight trainers using this technique. In our
study, pre-exhaustion exercise (a single-joint knee ex-
tension exercise) resulted in decreased, rather than in-
creased, activation of the quadriceps muscle during a
multijoint leg press exercise. Subjects also performed
less repetitions of the leg press exercise when in a pre-
exhausted state. Thus the lower muscle activity and
reduction of strength when using pre-exhaustion ex-
ercise compared with regular weight training implies
the pre-exhaustion technique may be less effective in
muscle development and strength acquisition.
By using pre-exhaustion exercise the muscle activ-
ity, in theory, may increase, as studies have demon-
strated that EMG activity consistently increases during
exercise performed at a constant load (6, 7, 14). How-
ever, this was not the case in our study, as pre-ex-
haustion exercise of the knee extensor muscles resulted
in decreased EMG amplitude of the rectus femoris and
vastus lateralis muscles during the leg press exercise.
One possible explanation for this result might be mus-
cle substitution, i.e., that the fatigue of the quadriceps
muscle may have dictated greater use of synergistic
muscle. Although our data showed no significant
change of gluteus maximus muscle activation as a re-
sult of pre-exhaustion exercise, it is possible that there
was different activation of other hip extensors, such as
the adductor muscles, or plantar flexion muscles, such
as the gastrocnemius (which also has potential func-
tion at the knee) and soleus muscles.
Another method of pre-exhaustion described in the
literature involves fatiguing synergistic or stabilizing
muscles, rather than prime mover agonistic muscles,
before performing the primary exercise movement (2).
An example of this strategy is performing lat pull-
downs or military presses prior to performing the
bench press exercise. It is theorized that the fatigued
smaller muscles will contribute less to the movement
of the later exercises, thereby placing greater stress on
the large muscle groups (2). Our data, where the fa-
tigued knee extensor muscles contributed less during
the subsequent leg press exercise, support the idea of
pre-exhausting small synergistic muscles, rather than
prime mover agonistic muscles. Therefore, to meet the
goal of increased quadriceps muscle activity during a
leg press exercise, we speculate that pre-exhaustion ex-

Effect of Pre-Exhaustion Exercise on Muscle Activation
415
ercise should consist of a hip extension exercise, rather
than a knee extension exercise. Theoretically, this
would force the quadriceps muscles to increased activ-
ity because the synergistic hip extensor muscles would
probably contribute less during the leg press exercise.
However, the advantages and disadvantages of differ-
ent pre-exhaustion exercise combinations in optimiz-
ing strength and muscle size need further study.
The vastus lateralis muscle demonstrated higher
EMG activity than that of the rectus femoris muscle
during the leg press exercise both when subjects were
in a non-fatigued and a fatigued state (;75% vs.
;100% of MVIA; Figure 2). We believe that this dif-
ferent EMG amplitude pattern represents the biartic-
ular nature of the rectus femoris muscle, which also
functions at the hip joint. This requires the rectus fe-
moris muscle to decrease its activity since the rectus
femoris muscle is a hip flexor, not a hip extensor.
Subjects performed significantly (p,0.001) less
repetitions of the leg press exercise when in a pre-ex-
hausted state. This is in accordance with the observa-
tions of Fleck and Kraemer (2) who compared the
workout logs of subjects when barbell squats were
placed in the beginning of the workout with those
when squats were placed at the end of the workout.
Significantly heavier resistances were used when
squats were performed first.
Although no training studies have been performed
on the effects of pre-exhaustion exercise, it appears un-
likely, based on the acute stresses measured in our
study, that pre-exhaustion exercise would result in
greater gains in muscle strength or hypertrophy than
regular weight training.
Although most weight trainers use a multiple-set
system when performing the pre-exhaustion method,
only 1 set of each exercise was used experimentally in
our study. A multiple-set protocol would not have al-
lowed sufficient recovery from prior pre-exhaustion
and non–pre-exhaustion exercise sets to allow an ac-
curate comparison between conditions.
The movement velocity during the knee extension
exercise was not controlled in our study. This is due
to the fact that the cadence consistently decreases from
the first to the last repetition for a subject during a set
of heavy weight training exercise (11).
When applied to the quadriceps muscle, the pre-
exhaustion technique involves a knee extension exer-
cise combined with either a leg press or a barbell squat
exercise (2). The weight machine leg press exercise was
preferred in our study because of advantages such as
greater control over technique and extraneous body
movement (5), which may have facilitated measure-
ment reliability and objectivity. The free weight bar-
bell squat exercise could be considered more of an
overall body movement, and is in addition probably
more difficult to perform correctly due to greater de-
mands for coordination and balance (5).
Empirically, the resistance used when performing
pre-exhaustion exercise is in the 10RM range. With the
intent of reproducing normal training conditions, pre-
exhaustion exercise sets in our study were therefore
performed at a load of 10RM, which approximates
80% of 1RM strength (8, 9). Consequently, quadriceps
muscle force fell to about 80% of maximal strength as
a result of knee extension pre-exhaustion exercise. The
use of different RMs (lighter or heavier resistance than
10RM) when performing pre-exhaustion exercise may
have produced different results.
Practical Applications
Despite the widespread use of pre-exhaustion exercise
by weight trainers as a technique to increase the acti-
vation of the targeted (fatigued) muscle during mul-
tijoint exercise, pre-exhaustion exercise may have dis-
advantageous effects on muscle performance, i.e., de-
creased activation of the fatigued muscle. Also, sub-
jects performed less repetitions of the leg press
exercise when in a pre-exhausted state. Therefore our
data imply that weight trainers using this method
should reconsider its effectiveness in producing
strength and muscle size gains.
Future research in this area should address the ef-
fect of a reversed pre-exhaustion strategy, as our data
support the notion of pre-exhausting small synergistic
muscles, rather than prime mover agonistic muscles.
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Acknowledgments
This study was supported by a grant from the Swedish
National Centre for Research in Sports.
Address correspondence to Jesper Augustsson, jesper.
augustsson@rehab.gu.se.