Psychobiology and Behavioral Strategies
WBE, Pain, and Physiological Adjustment to
Concentric and Eccentric Contractions
DANIEL B. HOLLANDER', ROBERT J. D U R ~ I ,
V. DANIEL CASTRACANE~, EDWARD P. HEBERTI, and ROBERT R KRAEMER'
JAMES L . TRYNICKI', DEBORAH LAROCK',
I Department of Kinesiology and Health -Studies. S&astern
Obstetrics and Gynecology, Texas Tech Universfty Health Science Center, Amarillo, TX
Louisiana Universiry, Harmrsolld, U;
and 2~eparanenr of
HOLLANDER, D. B., R. J. DURAND. J. L. TRYNlCKI, D. LAROCK, V. D. CASTRACANE, E. P. HEBERT. and R. R. KRAEMER.
WE. Pain, and Physiological Adjustment to Concentric and Eaamic Contractions Med Sci. Sporfs ~ T C . ,
1017-1025. 2003. Purpose: The purpose of the study was to compare perceptual (RPE and pain). cardiac (lean rate). lactate, and
endocrine (cortisol) responses with concentric (CON) and e c a m ~ c (ECC) resis~nce exarise prorocols using the same absolute
workload. Methods: Eight healthy men with resistance-training experience participated in the study. Subjects completed two
experimental trials consisting of either CON contractions or ECC contractions at the same absolute workload for each of four exercises:
bench press, leg extension, milimy press, and leg curl. Subjects performed four sets of 12 repetitions at 80% of l@RM with 90-s r e s t
periods. Blood samples were taken before. immediately after. and 15-min postexercise Resnlb: Thac was a sigdicant hiai effect f a
RPE, with CON exercise eliciting a higher RPE than ECC exercise(6.71 f . 051 and4.10 5 0.27, respectively). A significant trial effect
was also demonstrated for pain, with CON exercise producing a higher pain rating than ECC exercise (5.59 + 0.41 and 3.23 2 0.27,
respectively). Significantly higher heart rates and laaates wen also demonstrated &ring !he CON hial. -For cortisol, a significant
interaction was revealed between the pre- and M i
revealed a significant relationship between RPE a d pain for both aials. ~oncI&o& CON exercise &its greater perceptmi (hi*
W E and pain rating), cardiac, lactate and conk1 -rhan
ECC exercise at the sam absolute workload. Data demonstrate t h a t
relative to absolute load, RPE and pain respond to resistance exercise in a similr fastdon. Additionally, physiologicai cues are
consistent with these perceptual data. K e y Words. RESIS.TANCE EXERCISE, CORTISOL LAmATE. HEART RATE
monly associated with intense effort and pain. However,
few studies have investigated the link between rating of
perceived exertion (RPE) and pain, and we are unaware of
any studies investigating RPE and pain perceptions to re-
sistance exercise involving CON and ECC muscle actions.
Perceived exertion can be conceptualized as a sense of effoa
experienced while performing physical * or mental work
Borg has referred to this rating as a psychosomatic interac-
tion to assess changes in work, effort, and breathlessness to
produce an effort sense (5.23). Pain is typically defined as
Vol. 35, No. 6, pp.
but not an o v d trA effect. Comlational analyses
esistance exercise typically includes concentric
(CON) and eccentric (ECC) muscle contractions.
Moreover, strenuous resistance exercise is com-
i y unpleasant sensation that is a result of injury, disease,
emotional trauma, or distress (5).
The relationship between RPE and intensity of resistance
exercise appears to follow both a linear and quadratic model
(27). Gearhart et al. (10) demonstrated that when comparing
seven exercises at either five repetitions at a 90% of a 1-RM
or I5 repetitions at a 30% of a 1-RM, the higher intensity
protocol was perceived as more difficult despite requiring a
similar amount of relative work. Another investigation re-
vealed that at intensities of 30.60, and 90% of a 1-RM for
a biceps carl, RPE for both overall body and active muscle
increased as workload increased (21). These findings were
further validated by Lagally and colleagues (21), who dem-
onstrated that EMG increases paralleled the perception of
effoa changes during resistance exercise. Collectively, these
RPE is an effective
it^ of resistance exercise.
A consistent finding has been that lactate concentrations
are related to RPE during resistance exercise both in single
and multi-joint exercise prot~~ols
(17) demonstrated a clear progressive increase in RPE in a
multiple ser resistance exercise protocol utilizing three sets
of 10 repetitions for bench press, latissimus dorsi pull
downs. I q extensions, and leg curls with concomitant in-
Address for correspondence: Daniel 8. Hollander, I3.D.. - ,
ment of Kinesiology and Health Studies. Southeastern Louisiana Univer-
sity, SLU 10845. Hammond. LA 70402: E-mail: dhollan&&du.edu.
Submitted for publication August 2002.
Accepted for publication January 2003.
(17,21). Kraemer et al.
MEDICINE & SCIENCE IN SPORTS & EXERCISE,
Copyright 0 2003 by the American College of Spons Medicine
DOI: 10.1149101 .MSS.0000069749.13258.4E
crease in lactate. Another study reported significant corre-
lations between lactate and RPE in which subjects com-
pleted resistance exercise at 50 or 70% of a 1-RM (30).
Additionally, training may alter RPE and subsequent lactate
levels at a standard workload (25). Thus, the pattern of
increases in RPE with increases in intensity of resistance
exercise appears to be related to lactate concentrations and
these values can be attenuated after resistance exercise
Recently it was suggested that R E
markers of perceptual change because W E is related to
sense of effort whereas pain may be related to damage and
d i s t r e s s (5). Supporting this contention, a study that com-
pared W E
and leg pain in response tocycling suggested that
RPE is greater than leg pain on the same scale (CR-10) at
the same workload (6). Although prwious research indi-
cates the absolute scores for RPE are higher than pain, there
is evidence that the pattern of change in W E and pain to
ind workload is similar (6). The rationale for why
RPE and pain may be related can be seen in the physiolog-
ical marker of lactate. Several studies have been conducted
demonstrating the relationship between increased lactate
levels with higher workload and inaeased ratings for RPE
and pain (5,26,30). Additionally, when examining resistance
exercise, CON muscle actions in an absolute loading
scheme represent greater muscular stress than ECC ac-
tions, thus potentially eliciting higher lactate concentra- .
tions. Support for greater RPE and pain during CON.
muscle actions is inferred from research demonstrating
that maximal ECC strength is roughly 20-60% more than ;
maximal CON strength; thus, if identical absolute loads
are used for CON and ECC actions, ECC actions are .
performed at a lower relative intensity and may have iess
motor unit recruitment (2).
Cook et al. (7) compared the effects of progressive iso-
metric resistance exercise to fatigue on RPE and pain using
category ratio and standardized scales. A low correlation
was observed between RPE and pain. Perhaps the type of
muscle contraction (e.g., dynamic vs isometric) affects the
relationships between RPE and pain, as Borg et al. (6) found
that RPE and pain were related daring cycle ergometry.
Exploration of the effects of contraction type on the rela-
tionship between RPE and pain m l d illu~nate subtle
distinctions that may exist and are linked to physiological
changes (8,12,13.16,31). O'Connor et al. (25) examined the
relationship between RPE and pain responses to three dif-
ferent ECC resistance exercise protocols (80% of maximum
for 45 repetitions, 100% of maximum for 36 repetitions, and
120% of maximum for 30 repetitions of CON maximal
voluntary contraction). Elndirigs revealed a moderate rela-
tionship between RPE (during exercise) and pain (12-72 h
postexercise) that was probably due to the intensity of ECC
muscle work on skeletal muscle damage. The relationship
between W E and pain has yet to be examined during both
ECC and CON dynamic resistance exercise.
With regard to RPE and pain during resistance exercise,
if afferent feedback from the muscle or cognitive alterations
occurs. then it is plausible that cortisol, a neuroendocrine
and pain are distinct
marker of stress. w d d be altered (2). Additionally, if the
stressor of resistance exercise is perceived to be greater in
one muscular action versus another, then activity of the
hypothalamic-pituitary-adrenal (HPA) axis (as indicated by
cortisol levels) should mirror the perceptual changes. Tra-
ditionally, psychophysiological studies using cortisol as a
neuroendocrine marker have operated under the assumption
that perception of increased stress leads to a hormonal
cascade that results in increased cortisol bioavailability (32).
However, the relationship between cortisol, RPE and pain in
response to different muscle actions has not been clearly
Therefore, the purpose of this investigation was to exam-
ine perceptual (WE and pain), cardiac (heart rate), lactate,
and cortisol responses to CON and ECC resistance exercise
protocols using the same absolute workload. Additionally,
we sought to examine the relationship between RPE and
pain during resistance exercise. Our hypotheses were that
CON muscle actions would produce higher RPE and pain
ratings on the CR-10 scale than ECC muscle actions; HR,
lactate, and cortisol responses would also be higher in re-
sponse to CON muscle actions; and RPE and pain would be
related. The expectation that RPE and pain would be related
was predicated on the previous work of Borg and colleagues
demonstrating at moderate intensities of work, WE, and
pain ratings were moderately related and became more
correlated as maximum workloads were approached (5).
-Understanding.the reiatid&ip &tween RPE and pain as
well as physiological markers related t o these perceptual
changes for standard, absolute load resistance exercise could
aid in the development of resistance exercise prescriptions
to improve the exercise experience while capitalizing on the
psychophysiological benefits of exercise.
Subjects. Eight healthy men with resistance-training
experience were reuuited and gave written consent for
participation in the investigation. Subjects were determined
to be eligible if they engaged in recreational weight lifting
for a minimum of 1 yr and were between 18 and 30 yr of
age. The subjects were well-trained recreational athletes
who were not involved in sport but whose normal training
regimen consisted of bodybuilding type workouts (i.e.,.mul-
tiple sets, high-repetition training). A health history ques-
tionnaire was administered to rule out 1) participation in
competitive body building or weight lifting for the previous
year; 2) smoking; 3) taking medications that could alter test
results (e-g., anabolic steroids, sympathoadrenal drugs, etc.);
4) history of pituitary, renal, hepatic, cardiovascular, or
metabolic disease; 5 ) adherence to a reduced calorie or low
fat diet, or ketogenic diet that could affect hormone levels;
and 6) use of commial ergogenic aids in the past 6
months such as creaaine monohydrate, androstenedione,
DHEA, or ephedra. The mean +- SE for age, height, weight.
and body com~osition were 24.88 2 1.36 yr, 178.28 + 2.49
cm, 84.72 5 6.27 kg. and 17.00 t 1.78%. respectively. The
study was approved by the Southeastem Louisiana Univer-
Official Journal of the American College of Sports Medicine
sity Institutional Review Board and was conducted in ac-
cordance with the policies of the American College
Experimental design. Subjects completed three test-
ing trials: 1) a preexperimental trial, 2) a CON-only exercise
trial. and 3) an ECC-only exercise trial. The CON and ECC
trials were ~~IIducted in a Counterbalanced fashion. Most
resistance training protocols investigating CON and ECC
contractions and RPE have used either the same relative
load or did not employ both muscular actions (14,25). We
employed conventional resistance exercise that involved the
performance of dynamic, full range-of-motion conmctions
against a constant external load.
Preexperimental trial (session 1). Subjects com-
~leted a preexperimental session to obtain anthropometric
and muscular strength measurements. Fist, height and
weight were determined. Next, body composition was as-
sessed with a skinfold caliper using a four-site equation (15)
(abdomen, suprailiac, triceps, and thigh) (Lange, Beta Tech-
nology Inc., Santa Cruz, CA). Subjects were then tested to
determine the 10-RM for each of the four exercises: bench
press (BP), leg extension (LE), military press (MP), and leg
curl (LC). Before each subject was tested, two 48-inch (10
lb each) steel pipes were bolted on top of the machine bench
and military press. The steel rods were placed on the ma-
chine before the 10-RM to simulate the conditions of the
CON and ECC trials. The 10-RM was a modification of a
1-RM protocol by Kraemer et al. (20). Briefly, a 2-3 set
warm-up was performed with 5-10 repetitions that rep- ,
sented 40-60% of a perceived maximal exertion.'-E&6
warm-up set was perfonned in a linear progression. Subjects
were instructed to perform $e next 1-2 sets for 5 repetitions'
at a weight that was approximately 80% of perceived 10-
RM. Immediately after these sets, subjects were instructed
to perform a 10-RM; if the 10-RM was not achieved, a
heavier weight was chosen. Rest periods between a l l sets
were 3-5 rnin. A f t e r determining the 10-RM on each exer-
cise, the validity of this measurement was tested by having
each subject perform as many repetitions as possible with
the determined 10-RM weight after a 10-min rest period. All
subjects reached their 10-RM within three trials after their
warm-up sets were performed. Ten-repetition maximum
strength measurements have been accepted as a suitable
secondary choice for determining appropriate training loads
when maximal strength testing is not possible (2). The
position of all benches, seats, bars, and subject handgrip
alignment were recorded and kept constant for each exer-
cise. For each exercise, the distance the weight was dis-
placed was determined with a metal meter stick and pointers
mounted to the resistance exercise equipment in an effort to
maintain constant work per repetition in subsequent ses-
sions. The maximal lifts determined for the BP, LE. MP, and
LC used in the ECC and CON trials were (mean + SE)
116.48 2 8.6 kg, 42.05 + 3.lkg, 68.75 2 7.4 kg, and 21.02
+ 1.5 kg, respectively.
Sessions 2 and 3 (CON and ECC trials). Seven and
14 d after the preexperimental trial. the subjects returned to
the iveight room for session 2 or 3 after an 8-h fast. For both
sessions, the same procedures were followed except one
session was CON-only and the other session was ECC-only
resistance exercise. At 8 : 0 0 a.m., the subject was seated
quietly for 20 min. A baseline blobd sample was collected
from an antecubital vein via venipuncture. During this rest
period, subjects filled out a state anxiety quationmire.
Subjects then performed four sets of 12 repetitions of the
four exercises at 80% of the preMously determined 10-RM
in following order: BP, LE, MP, and LC. During piloting
of h e study, we determined that four sets of 10 repetitions
at 80% of a 1-RM load was too strenuous for researchers
posisbning the weight (in a timely manner) and for some
subjects to complete the CON protocol. Four sets of 12
repetitions at 80% of the 10-RM load (approximately 60-
65% of 1-RM, see reference 2) were found to be optimal to
produce a substantial stimulus and ensure completion of the
protoco1. After each set, the subject's heart rate, RPE, and
pain level were recorded. During the CON trial, subjects
lifted the weight for each repelition, whereas technicians
using a pulley or steel bar extensions performed the lower-
ing of the weight. During the ECC trial, technicians lifted
the weight stack with a pulley or steel bar extensions, and
then the subject lowered the weight. All repetitions were
performed to the rhythm of a metronome; the weight was
lifted in 2 s and lowered in 2 s. Subjects rested 90 s between
all sets and exercises. A rest period of 90 s was chosen
because this interval is indicative of high-intensity weight-
naining sessions commonly performed (19). A f t e r comple-
tion of the fourth set of LC, a blood sample was immediately
collected, and another blood sample was taken 15-min pos-
texercise. For each blood sample, blood was collected into
a 10-mL whole-blood tube for hormone analysis and a 3-mL
tube with sodium fluoride and potassium oxalate for lactate
determination. The 10-mL t u b e s were allowed to sit at room
temperature for 10 rnin for clot formation and refrigerated
for 25 min before centrifugation (500 X g ) . Serum was
diquoaed and samples were stored a t - 80°C until hormone
assays were performed.
State anxiety inventory. A state anxiety questionnaire
that is a measure of how anxious a subject is at the moment
(the state portion from Spielberger's State-Trait Anxiety
Inventory (STAI)) was employed as a control variable to
ensure that anxiety did not disrupt perceptions of exertion or
pain (29). Previous research has demonstrated a relationship
be-tween state anxiety and RPE during exercise (9,24). Our
god was to control for potential effects of state anxiety on
RPE and pain during resistance exercise. The state portion
of the STAI asks individuals to respond to a series of
questions regarding their thoughts and feeling "at this mo-
ment" to examine context and current levels of anxiety.
RPE and pain instruments. For instructing the sub-
jects to rate perceived exertion during CON and ECC trials,
we quoted the exact instructions recommended by Borg (5).
The instructions included a paragraph of basic instruction
and separate scaling instructions for RPE and pain. The
instmtions to the subjects for rating RPE were: "We want
you to rate your perception of exertion, that is, how heavy
and strenuous the exercise feels to you. The perception of
RPE, PAIN, AND MUSCLE ACTION
Medicine 8 Science in Sports & Exercise*
TABLE 1. Borg CRlO scale 1998 (5).
Nothing at all "No P"
m n g Heavy
Absolute maximum Highest possible
exertion depends mainly on the strain and fatigue in your
muscles and on your feeling of breathlessness or aches in the
chest. We want you to use this scale from 0 to 10 and "*,
where 0 means 'no exertion at all' and 10 means 'extremely
strong-max P,' that is, the maximal exertion you have
previously experienced" (Table 1).
For instructing the subjects to rate pain during CON and
ECC trials, we quoted the exact instructions recommen~
by Borg (5). The instructions to the subjects for rating pain
were 'What are your worst experiences of pain? If you use
10 as the strongest exertion you have ever experienced oi
can think of, how strong would you say that your three worst
pain experiences have been (5)Y
"10 'Extremely strong-max
reference. It is anchored in your previously experienced
worst pain, which you just described, the 'max P'."
''@The worst pain that you have experienced, the 'max P'
may not be the highest possible level of pain. There may- be
a level of pain that is still stronger than your 10, you will say
11 or 12. If it is much stronger, e-g., 1.5. times, 'Max P,' you
will say 15! Any questions (5)?"en
to scale their pain using the CR-10 scale as shown above.
Additionally, subjects were told that W E and pain were
different sensations in that RPE should relate to fatigue and
strain, whereas pain should be considered as unpleasant
feelings related t o muscle damage or potential muscle dam-
age. Subjects were asked to confmn that they recognized the
differences in the ratings. These directions enabled subjects
to have perceptions anchored by the worst pain they bad
ever experienced and compare the pain with the type and
quality of pain they were experiencing during the resistance
exercise trial. The rationale for employing the CR-10 scales
for overall body RPE and pain was to remain consistent with
past research that had employed overall body W E ratings
when using multiple joint movements such as those em-
ployed in the bench press and military press for the present
study (3,17,30). In addition, because a specific muscle ac-
tion was not targeted in the present study, overall body RPE
and pain ratings were deemed most appropriate. Moreover,
although active muscle RPE has been employed in pat
research, it was important for our experiment to employ
whole-body RPE to match whole-body ratings of pain.
Then, instructions were given that followed Borg's recom-
P,' is your main point of'
subjects were asked
mendations on pain scaling (4). Category-ratio scales (CR-
10) for both rating of perceived exertion and pain were
selected based on high concurrent and predictive validity.
Specificallyl carepry-ratio scales for RPE and pain em-
ployed during multiple workloads of cycle ergometry re-
vealed high correlation coefficients (correlation coefficients
between pain and exertion and workload magnitude estima-
tions r = 0.66 (5) as well as perception of exertion and pain
and maximal workload capacity (r = 0.56) (5)). Further-
more, reliability coefficients using split-half analyses have
demonstrated high coefficients with both types of scales
during bicycle ergometry testing (Spearman-Brown carre-
latlons were re (exertion) = 0.96, r, (pain) = 0.96, heart rate
r = 0.97, and blood lactate r = 0.98 (5)). These scales were
also consistent with recommendations related to psycho-
physiological scaling (5).
Heart rate and blood analyses. All blood samples
were analyzed for lactate and cortisol. Lactate was deter-
mined using an enzymatic method (Sigma Chemical, St.
Louis, MO). Cortisol concentrations were determined using
a sensitive chemiluminescent enzymatic imrnunoassay (Im-
mulite: Diagnostic Products Corp., Los Angeles, CA). The
interassay coefficient of variation was 5.44%. and the intra-
assay coefficients of variation were < 5.0%.
Statistical analysis. A preliminary t-test was r u n on
state anxiety measures for each trial to ensure that anxiety
was similar in each protocol. If the t-tests were significant,
anxiety would be entered as* mvariatti in subsequent and-
jses. WE, pain; and heart rate were analyzed using 2 (Trial:
. _ CQN and ECC) X 16 (Time of measurement) ANOVA with
. , &at4 measures. For lactate and cortisol, 2 (Trial: CON
.and ECC) X 3 (Time: pre, immediately post, and 15 min
postexercise) ANOVA with repeated measures were per-
formed. Finally, Pearson product moment correlation coef-
ficients were computed to examine relationships between
RPE and pain as well as these perceptual variables and HR,
ladate, and cortisol. All comparisons were considered sta-
tisically significant at P < 0.05. Post hoc tests were applied
where appropriate. ANOVA analyses were followed by the
calculation of eta-squared and post hoc power analysis to
determine the statistical probability of detecting differences
of the obse~ed sizes as significant given the design char-
acteristics and number of subjects in the study.
The t-test comparing anxiety before CON and ECC trials
revealed no significant difference. Therefore, anxiety was
not entered as a covariate in the ANOVA analyses.
WE. Analysis of RPE data revealed a significant trial
effect (P < 0.01) with CON exercise eliciting a higher RPE
than ECC exercise (6.71 2 0.51 and 4.10 t- 0.27, respec-
tively). A main effect for time was also demonstrated (P <
0.001). This factor was further investigated using post hoc
analyses that compared each exercise time point to the
previous time point. Significant differences were demon-
strared between bp 1 -bp2, bp2-bp3, bpdrlel, le2-le3, mpl-
mp2, mp2-mp3, mp4-lcl, lcl-lc2, lc2-lc3, and lc3-lc4 (P <
Official Journal of the American College of Sports Medicine
bpi bp2 bp3 bp4 lei
le2 le3 le4 mpl mp2 mp3 mp4 1 ~ 1 lc2 lc3
FIGURE 1-Data represent mean -c SE RPE values for the concentric (CON) and eccentric (ECO trials. * Represents a significantly dafemtt (P
< 0.05) value of CON trial when compared with the same time point in the ECC trhl. For sls 1-4: bp, bench press; 1% leg extension; mp, military
press; Ic, leg curl.
0.01) time points. As shown in Figure 1, RPE increased on
each subsequent set of each exercise then decreased at the
start of each new exercise. A significant trial x time inkc-
action effect was demonstrated as well for RPE (P < 0.01).
Post hoc contrasts indicated significant differences existed -
between CON and ECC tiials'f6r a l l but the following time
points, le3,le4, mpl, and lcl, suggesting that RPE changed
at a different rate for CON as compared with ECC muscle
actions (see Fig. 1). Eta-squared values indicated most of the
variance in RPE was due to the time factor (0.60) and trial
factor (0.48). Power to detect differences for these two
factors as significant were greater than 0.90. The interaction
eta-squared value was substantially smaller (0.15) and
power to detect differences for this interaction was 0.64.
Pain. The pattern of changes in pain across trials was
similar to RPE. Pain increased with each subsequent set of
an exercise and decreased between exercises (see Fig. 2).
Analysis of pain between CON and ECC trials demonstrated
a significant trial effect (P < 0.01) with CON contractions
eliciting a higher pain rating than ECC contractions (5.59 2
0.56 and 3.26 2 0.56, respectively). Additionally, a signif-
icant time effect was demonstrated (P < 0.0001); post hoc
comparisons revealed sigGficant time differences between
sets bp 1 -bp2, bp2-bp3, bpblel, le 1 -1e2, le2-le3, mpl -rnp2,
mp2-mp3, mp4-lcl, lc1-1c2,1~2-1~3.
The interaction failed to reach significance. Eta-squared and
observed power for trial, time, and the interaction respec-
tively were 0.3810.77, 0.5511.00, and 0.0910.40. These val-
ues indicate that pain primarily varied as a function of time
and trial, and that power was adequate to detect these
and lc3-lc4 (P < 0.01).
. Heart rate. Heart rate increased during both trials with
eliciting higher HR than the ECC triai (see
' Fig. 3). The ANOVA revealed a si&cant
0.001) with higher mean HR values (128.85 + 3.01 bpm)
'for CON exercise as compared with ECC exercise (9455 +
.. 1'13 1 bpm). Significant time effects were evident as w e l l (P
< 0.001). Post hoc analyses comparing each exercise time
point to the previous time point indicated si@cant
ences between the bp3-bp4, le4-mpl, and mprllcl (P <
0.01). Additionally, a significant interaction effect was dem-
onstrated between CON and ECC hem rates (P < 0.0001).
comparisons at each exercise time point indicated
that HR during the CON ma1 was higher than that during the
ECC mal at every time point except the first. Examination
of post hoc power estimates indicated that HR primarily
varied as a function of trial (eta-squared = 0.66, observed
power = 1.00) and time (eta-squared = 0.55, observed
power = 1.00). The interaction accounted for 21% of HR .
variance and observed power for this factor was 0.88.
Lactate. Lactate increased during both CON and ECC
trials with the greatest increase evident in the CON trial
immediately post and 15 min postexercise (see Fig. 4). Data
analysis revealed a significant trial effect (P < 0.0001) with
CON resistance exercise exhibiting a higher lactate than
ECC resistance exercise. Also, a significant time effect was
demonstrated (P < 0.0001); follow-up comparisons of each
exercise time point to the previous time point indicated
significant differences between pre to immediate post to 15
min postexercise. In addition, a significant interaction was
revealed (P < 0.001), indicating lactate changed at differing
rates during the CON and ECC trial. Post hoc comparisons
trial effect (P <
RPE, PAIN. AND MUSCLE ACTION
Medicine 8 Science in Sports & Exerci*
b p l bp2 bp3 bp4 lel le2 le3 le4 mpl mp2 mp3 mp4
E x e r c i s e
FIGURE >Data represent mean i SE pain values for the concentric (CON)
for ratings of pain but no interaction effects were demonstrated. For sets 1-4: bp, bench press; le, leg extension; mp, military press; 1% leg curl.
and eccentric (ECC) trhls. Overall CON was greater than ECC trials
indicated lactate was significantly different between trials
immediately and 15 rnin postexercise, Eta-squared and-oh
served power for trial, time, and the interaction respectively
were 0.6711.0, 0.7411.0, and 0.6411.0.
Cortisol. Cortisol declined for both mals with thi-. '
greater decline in the ECC trial (see Fig. 5). The ANOVA '
revealed no significant trial effect. However, a significant
time effect as well as an interaction effect was revealed (P
< 0.05). Post hoc comparisons of each exercise time point
to the previous time point demonstrated a significant main
effect for time at pre to immediately postexercise for cortisol
iP < 0.01). These comp&i~oris iiiaicated cortisol did not
change significantly during the CON trial. But a significant
dqline during the ECC trial was observed from pre to
. , ..
bpl bp2 bp3 bp4 lei
le4 mpl mp2 mp3 mp4
FIGURE ?---Data represent mean k SE heart rate values for the concentric (CON)
(P < 0.05) value compared with the same time point in the ECC trial. For Sets 1-4: bp, bench press; le, leg extension; mp, military press; Ic, leg
and eccentric (ECC)
trials. * Represents a significantly different
Official Journal of the American College of Sports Medicine
FIGURE 4-Data represent mean r+ SE lactate values for the con-
tric (CON) and eccentric (ECC) trials. * Reprksents a significantly
different (P < 0.05) value compared with the same time point in the
immediately postexercise. Examination of post hoc power
estimates indicated that cortisol primarily varied as a func-
tion of time (eta-squared = 0.64, observed power = 1.00).
Comparatively, the interaction and trial factors had lower
eta-squared values (0.25 and 0.09, respectively), and the
ability to detect significant differences was reduced (0.66
Comparison of RPE and pain perceptions. Data
indicated that RPE and pain perceptions followed similar
patterns over each trial (Fig. 6). However, RPE scores were
slightly higher than pain during exercise. Correlations be-
tween RPE and pain were computed for each set. Relation-
ships observed ranged from 0.71 to 0.86, all significant &$.
Relationships between physiological variables
and subjective perceptioiis. To assess the relationshi;
between physiological variables and subjective perceptions,
correlations were computed between the final ratings of pain
and RPE and immediate postexercise HR. lactate, and cor-
tisol. High positive correlations were demonstrated between
the last rating of RPE and immediate postexercise lactate (r
= 0.73, P < 0.001), cortisol (r = 0.51, P < 0.05), and heart
rate (r = 0.76, P < 0.001). Relationships between the last
pain rating and immediate postexercise lactate (r = 0.61, P
= 0.012), cortisol (r = 0.56, P < 0.05), and heart rate (r =
0.76, P < 0.001) were also strong and positive.
centric (CON) and eccentric (ECC) trials. * Represents a significant
time different (P < 0.05) from the previous time point-
represent mean rl: SE cortisol values for the con-
F I -
CR-10 scale * All correlations were signi6caut at the P c 0.01.
6--Data represent mean * SDbetween RPEad pain- the
We hypothesized that CON muscle contractions would
produce higher RPE, pain ratings, heart rate, lactate, and
cortisol concentrations at the same absolute workload than
ECC muscle contractions. Moreover, we hypothesized that
RPE and pain ratings would be related for each muscle
action. These hypotheses were tenable. O u r data revealed
that at a constant load, RPE and pain: 1) were higher in
response to CON than ECC contractions, 2) provided con-
stant perceptual markers of resistance exercise stress, and 3)
w v significantly related. Additionally, heart rate, lactate,
a d cortiql concentrations were higher in the CON trial
than th6ECC trial corroborating greater physiological stress
' ocamed in the CON trial. Data indicated t h a t RPE and pain
were associated with the same physiological cues assessed
.in the present study. To our knowledge, this is the first study
to document either RPE or pain responses to both types of
muscle actions during resistance exercise. Moreover, this is
the-first study to examine RPE and pain -tion
CON and ECC muscle actions separately at a constant load.
Although this study had a relatively small sample size,
dependent measures were taken s e v d times in the re-
peated measures design, which resulted in increasing power.
Post hoc power analyses indicated that when eta-squared
values were greater than 0.40, power was > 0.90.
T k heart rate data in the present study showed a clear
cumulative effect of resistance exercise during CON muscle
actions. For instance, HR rose 41% from baseline in the
CON trial versus only 17% in the ECC trial. Thus, HR data
demonstrated a greater cardiac demand during CON actions
compared with ECC muscle actions at the same absolute
workload. The increases in cardiac demand during CON
mmck actions could be related t o the higher pePcentage of
absofute maximal force employed for the CON trial as
compared with the ECC trial (2). With regard to lactate, it
was also clear that CON muscle actions produced higher
levels than ECC muscle actions. Higher lactate concentra-
tions would be expected from greater recruitment of fast-
twitch muscle fibers and greater glycogenolytic activity.
Our fmdings support previous research suggesting lactate
comntrations are also related to RPE and pain (5) and that
higher rating of these perceptual markers are induced, in
Medicine & Science in Sports & Exercise?, 1023
RPE. PAIN. AND MUSCLE ACTION
part, by lactate (23). Thus, present data support that differ-
ences in lactate levels induced by CON and ECC muscle
actions were associated with differences in perceptions of
effort sense and pain.
Decreased cortisol levels in the present study reflect nor-
mal morning decline consistent in pattern and magnitude
with previous research (18). A lesser decrease in cortisol
was evidenced for the CON as compared with the ECC
muscle actions during our study. The attenuated cortisol
decline during &e CON trial compared with the ECC ma1
was probably doe to greater effort andlor pain that awld
stimulate the P A axis. This supposition seems tenable as
researchers have proposed a l i n k between pain, fatigue, and
heighten HPA-axis stimulation (1.5).
In the present investigation, overall body RPE and pain
were assessed using a category-ratio technique. Resdts
showed similar patterns of response between these per-
ceptual constructs but revealed a trend of greater absolute
values of RPE than pain. These results are similar to
previously reported RPE and pain responses to cycle
The present study did not provide specific cues for pain
ratings such as stinging, throbbing, or burning sensations.
Gearhart and Robertson have recommended specific s c h g
of RPE for resisrarm exercise and have noted that this type
of scaling can benefit the coachttrainer in monitoring a h a
perceptions and enable the exerciserlathlete to become
aware of the effects of perception on power output
(3,11,22,28). Additionally, it is quite possible for pain to .
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RPE, PAIN, AND MUSCLE ACTION
Medicine & Science in Sports & E x -