BJMB
Brazilian Journal of Motor Behavior
Special issue:
“Fatigue issue in the performance of motor skills”
!
Lemos, Santos,
Carpes
2023
VOL.17
N.5
208 of 215
Sex differences in delayed onset muscle soreness induced by fatigue and measured by
different methods
ANDRESSA L. LEMOS | MILENA A. SANTOS | FELIPE P. CARPES
Applied Neuromechanics Research Group, Multicenter Graduate Program in Physiological Sciences, Federal University of Pampa, Uruguaiana, RS, Brazil
Correspondence to:!Felipe P Carpes, Ph.D.
Federal University of Pampa - Laboratory of Neuromechanics
97500-970, Uruguaiana, RS, Brazil
Phone office: +55 55 3911 0225
email: carpes@unipampa.edu.br
https://doi.org/10.20338/bjmb.v17i5.389
HIGHLIGHTS
DOMS assessed with a NRS is comparable between
men and women.
Absolute values of pressure pain thresholds were lower
in women.
Pressure pain thresholds data require normalization for
sex-comparisons.
ABBREVIATIONS
CPGS Chronic Pain Grade Scale
DOMS Delayed onset muscle soreness
GEE Generalized estimating equation
MPQ McGill Pain Questionnaire
NRS Numeric pain rate scale
PPT Pressure pain thresholds
RF Rectus femoris
VAS Visual Analog Scale
VL Vastus lateralis
PUBLICATION DATA
Received 21 08 2023
Accepted 26 09 2023
Published 30 09 2023
BACKGROUND: Controversial outcomes from different methods for assessment of delayed
onset muscle soreness (DOMS) in male and female may influence clinical decisions.
AIM: In this study, we determine sex differences in pain perception and pain thresholds in a
DOMS condition resultant of a fatigue protocol.
METHOD: 11 male and 15 female healthy adults were submitted to an exercise fatigue
protocol to induce DOMS in the quadriceps muscles. Pain perception was determined using a
numeric pain rate scale (NRS) and pressure pain thresholds (PPT) were determined by
mechanical pressure in the vastus lateralis (VL) and rectus femoris (RF) regions. Data were
compared between methods and sexes at baseline, immediately after (0h), and 48 h after
DOMS induction.
RESULTS: Results showed normalized lower PPT and higher NRS outcomes after fatigue,
without sex differences. Absolute values of PPT showed lower values in females comparing
both time and sex (VL and RF, baseline p = 0.002 and p = 0.009; 0h p = 0.002 and p = 0.001;
48h p<0.0001 and p<0.0001) with a mean difference for females and males on 0h and 48h of
from baseline VL 16,52% and 19.7%; -15.64% and -10.89%; RF 12.18% and 20.7%; -9.18%
and -1.97%. No correlations were found between the number of repetitions of exercise nor the
rate of perceived effort and DOMS outcomes.
CONCLUSION: Men and women show similar DOMS when NRS and normalized PPT
outcomes are considered. Absolute PPT values may lead to a confusing analysis of fatigue
exercise-induced DOMS if merging both sexes in the sample.
KEYWORDS: Muscle damage | Physical exercise | Pain perception | Pain thresholds
INTRODUCTION
Delayed onset muscle soreness (DOMS) is often experienced after intense physical exercise, an abrupt increase in exercise
load, or performance of exercises involving unusual movement amplitude and speed
1
. DOMS involves a painful sensation associated
with joint and muscle stiffness that appears when muscles are stretched or palpated, muscle swelling, and strength deficits
2,3
. These
symptoms become significant from 6 to 12 h after exercise, with peak values observed between 48 and 72 h after exercise
2
. Despite its
general progression to a condition of full recovery, the time course of DOMS can cause functional limitations and negatively impact
training and rehabilitation protocols.
Methods for assessment of pain intensity are diverse and results can be controversial, which can difficult clinical decisions.
Pressure algometry is a valid method to assess experimental pain. It involves the application of a known magnitude of force at specific
points to stimulate nociceptors and cause a painful sensation, allowing to determine the pressure pain threshold
4
. However, the need for
specialized instrumentation and time required for the assessment of pain thresholds often result in DOMS being assessed by a
unidimensional scale, such as a numeric rate scale (NRS). Using an NRS, the patient is requested to self-report the perceived pain. NRS
results show a strong correlation with results from other tools for pain assessment
5
. Other tools rely on subject report as well as the
Visual Analog Scale (VAS), McGill Pain Questionnaire (MPQ) and Chronic Pain Grade Scale (CPGS)
6
. However, sex differences
7
and
BJMB! ! ! ! ! ! ! ! !
Brazilian(Journal(of(Motor(Behavior(
(
Lemos, Santos,
Carpes
2023
VOL.17
N.5
209 of 215
Special issue:
Fatigue issue in the performance of motor skills
small variations in the perceived pain are difficult to identify when using unidimensional scales
5,8
.
Additionally, there are physiological differences between sexes related to exercise adaptations and pain. Males are more
susceptible to experiencing exercise-induced muscle damage or fatigue than women
9
. Females can be less fatigable at higher intensity
isometric exercise, they can sustain a long time to task failure, and may have more type I fibers and a higher density of capillaries per unit
of skeletal muscle in the vastus lateralis than males
10
. Additionally, females show a higher prevalence and sensitivity for pain compared
to males
1113
. Hormonal differences between males and females may also account for differences in pain outcomes, such as the higher
levels of androgen hormones and testosterone in males that appear to be protective against chronic pain
14
. On the other hand, estrogen
hormones have analgesic and hyperalgesia effects in females
15
.
These physiological differences may suggest that pain perception outcomes could differ between males and females
depending on the measure tool, and baseline conditions. However, sex differences regarding exercise-induced pain are considered in a
few studies. It appears that when pain outcomes are compared between sex, even healthy females show lower pressure pain thresholds
considering absolute values
16
and higher perception of pain using a visual analog scale
17
. This could be relevant information to be
considered when comparing sexes, since the absolute values could lead to a misinterpretation on results. For instance, studies are not
clear regarding data normalization considering baseline measures, which would be sound considering sex differences
18
. In this study, we
determine whether there are differences in pain outcomes measured using an NRS and between absolute and normalized values using
pressure algometry in females and males submitted to physical exercise to induce DOMS in the lower limbs. We hypothesized that
females would report higher pain intensity and exhibit lower pressure pain thresholds than males. Also, we suggest that sex-based
differences in pain perception may be influenced by the methods used to normalize pressure pain measurements.
METHODS
Participants and experimental design
This observational study was approved by the local institution's Ethics Committee. Participants were recruited from the local
community through flyers posted in social media and signed a consent term agreeing to participate. Twenty-six participants, 15 females,
and 11 males were included (see Table 1 for participant characteristics). They answered an anamnesis questionnaire to collect
information about their physical activity routine. Leg preference was assessed by the Waterloo questionnaire
19
. Participants were adults
of age between 18 and 40 years old, enrolled with recreational physical exercise, without lower limb injuries at least six months before the
assessment, and not performing plyometric training. Data collection involved two visits to the laboratory. Participants were requested to
refrain from physical exercise 24 h before each visit to the laboratory and not use any medication with anti-inflammatory properties or
techniques for analgesia during the study participation. In the first visit, the pain was measured before and immediately after the exercise
to induce the fatigue and delayed onset muscle soreness considering pain perceived using an NRS, and pressure pain thresholds using
a digital algometer. After 48 h they visited the laboratory again to be evaluated for the presence of DOMS considering pain perceived
using the NRS, and pressure pain thresholds using the digital algometer. Figure 1 illustrates the experimental design.
Figure 1. Experimental design.
BJMB! ! ! ! ! ! ! ! !
Brazilian(Journal(of(Motor(Behavior(
(
Lemos, Santos,
Carpes
2023
VOL.17
N.5
210 of 215
Special issue:
Fatigue issue in the performance of motor skills
DOMS induction protocol
To induce quadriceps DOMS, participants completed an exercise protocol for fatigue with maximum squat repetitions to
exhaustion with their body weight as workload
20
. A researcher demonstrated how squat movements should be performed in terms of
amplitude and movement speed. From the upright posture, the squat movement should be performed by flexing the knees to 90° and
returning to the upright position again. To ensure that the participants performed a 90º degree knee flexion, an adjustable height bench
was used, and whenever they felt the bench touching their thighs, they should return to the standing position. Participants were instructed
to maintain their feet and knees aligned with the shoulders and avoid a knee valgus movement. They performed the maximal number of
squats, as fast as possible, for repeated 1-min sets. The 1-min sets were repeated with a 15-s interval in between, until exhaustion.
Exhaustion was defined by the participant being no longer able to perform the squat movements or when movement technique
deteriorated, for example, reducing the range of motion. The rate of perceived exertion was reported at the end of the exercise using the
Borg scale of 6-20
21
.
DOMS assessment
DOMS was estimated using a numeric rating scale ranging from 0 (left side, absence of pain) to 10 (right side, most intense
pain) presented to participants in the pre, immediately after (0 h), 24 h, and 48 h post-DOMS induction. For NRS assessment the
participants were seated, at rest, and should consider the pain only in the lower limbs as a result of the exercise.
DOMS was also determined by the pressure pain threshold (PPT) measured in the pre (baseline), immediately after (0 h), and
48 h post-DOMS induction, using a digital algometer (Instrutherm DD-200, Portable Digital Dynamometer) with a resolution of 0.01 N and
a flat tip with an area of 1 cm
2 22
. The PPT assessment was done in two days because of the peak DOMS occurs between 48 and 72
hours after the exercise
2
, and we chose just two days with presential assessment because of the difficulty to bring the participants to the
lab. For bilateral assessment of PPT, patients were in the supine position, with muscles relaxed. The algometer was pressed
perpendicularly to the skin surface over the muscle belly of the rectus femoris (RF) and vastus lateralis (VL). For familiarization with the
assessment, the algometer was first pressed on the anterior region of the deltoid, a non-exercised body region evaluated to reduce
sensitization by systemic factors
23
. The algometer was gradually pressed against the sore region causing discomfort, and the participants
were instructed to notify the evaluator when this discomfort became painful
22,23
. Participants were previously advised on how to report the
moment when the sensation of pressure became uncomfortable pain. The PPT was recorded in N/cm
2
, and the same researcher
performed all assessments. Pre-exercise PPT measurement (baseline) was considered as a reference to normalize the subsequent PPT
measures. Absolute and normalized values (%baseline) were considered.
Statistical analysis
The normality of data distribution was checked by the Shapiro-Wilk test. Levene’s test was used to check the homogeneity.
Nonparametric data are presented as median and interquartile intervals and parametric as mean and standard deviation. Qualitative data
are reported by frequency and percentage among participants. The age, height, body mass index, the number of squat repetitions, and
rate of perceived effort were compared between males and females using the Mann-Whitney U test. Body mass was compared using an
independent t-test. Leg preferences were compared with a Pearson Chi-square test. PPT was compared between the preferred and non-
preferred legs using a paired t-test. As leg differences were not found, the legs average was used for posterior PPT analyses. A
generalized estimating equation (GEE) was used to compare sexes (males vs. females) and time (pre vs. 0 h vs. 48 h) for normalized
and non-normalized values of PPT at vastus lateralis, rectus femoris and deltoid and NRS points. A delta was calculated considering the
difference between baseline and the 48h absolute and normalized measures of PPT, and NRS. Mann-Whitney U test was used to
compare this delta between males and females, except for the Vastus Lateralis normalized PPT compared by independent t-test.
Pearson or Spearman’s correlations were used to verifying the correlations between the rate of perceived exertion, squat repetitions, and
PPT (normalized/non-normalized) and NRS outcomes, considering a pool of data from all participants. All analyzes considered a
significance level of 0.05 and were performed using a commercial statistical package (version 26.0. IBM SPSS Statistics for Windows
Armonk, NY: IBM Corp).
RESULTS
Table 1 summarizes the participants' characteristics and the exercise outcomes. Females showed lower body mass, body
mass index, and height than males.
Numerical rate scale outcomes
NRS values (points, Figure 2) did not differ between females and males at baseline (0.80 ± 0.31 and 0.64 ± 0.34, p = 0.727, for
females and males, respectively), 0 h (4.77 ± 0.52 and 5.27 ± 0.70, p = 0.567) and 48 h post DOMS induction (4.0 ± 0.78 and 3.47 ±
0.84, p = 0.649; Figure 2). The time course of NRS did not differ between females and males, with lower values in baseline compared to