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Purpose The female menstrual cycle (MC) is characterized by hormonal fluctuations throughout its different phases. However, research regarding its effect on athletic performance in high level athletes is sparse. The aim of this study was to (i) investigate the female MCs effect on strength and power performance in highly trained female team athletes throughout the MC and (ii) examine whether eumenorrheic participants with natural hormonal fluctuations displayed enhanced performance in the follicular phase (FP) versus the luteal phase (LP), compared to controls using hormonal contraceptives. Materials and Methods A total of 29 athletes (Age 21.2 ± 3.3 years; weight 65.6 ± 8.7 kg; height 170.2 ± 8.0 cm; and fat free mass 52.7 ± 7.1) completed the study after a 6-week testing period (8 eumenorrheic participants and 21 hormonal contraceptive controls). Participants were recruited from the team sports soccer, handball and volleyball. Testing protocol consisted of maximal voluntary isometric grip strength, 20-m sprint, countermovement jump and pneumatic leg-press. Based on self-reported use of hormonal contraceptives, participants were divided into non-hormonal contraceptive group and hormonal contraceptive group, the latter working as a control group. Differences in performance between the FP and LP were investigated. MC phase was confirmed by serum hormonal levels through venous blood samples in the non-hormonal contraceptive group. Results There were no statistically significant changes for the two different phases of the MC, in terms of physical performance for the whole group. Further, there was no significant difference between groups during the MC for any of the outcome variables, maximal voluntary isometric grip strength F (3.29) = 0.362; 20-m sprint F (3.24) = 0.710; countermovement jump F (3.26) = 2.361; and leg-press F (3.26) = 1.746. Conclusion In high level female team athletes, no difference in performance was observed based on hormonal contraceptive status. This suggests that the MC does not alter acute strength and power performance on a group level in high level team athletes.
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ORIGINAL RESEARCH
published: 22 February 2021
doi: 10.3389/fphys.2021.600668
Edited by:
Anthony C. Hackney,
University of North Carolina at Chapel
Hill, United States
Reviewed by:
Christoph Zinner,
Hessische Hochschule für Polizei und
Verwaltung, Germany
Xanne Janse de Jonge,
The University of Newcastle, Australia
*Correspondence:
Inger Haukenes
Inger.Haukenes@Uib.no
Specialty section:
This article was submitted to
Exercise Physiology,
a section of the journal
Frontiers in Physiology
Received: 30 August 2020
Accepted: 29 January 2021
Published: 22 February 2021
Citation:
Dasa MS, Kristoffersen M,
Ersvær E, Bovim LP, Bjørkhaug L,
Moe-Nilssen R, Sagen JV and
Haukenes I (2021) The Female
Menstrual Cycles Effect on Strength
and Power Parameters in High-Level
Female Team Athletes.
Front. Physiol. 12:600668.
doi: 10.3389/fphys.2021.600668
The Female Menstrual Cycles Effect
on Strength and Power Parameters
in High-Level Female Team Athletes
Marcus S. Dasa1, Morten Kristoffersen2, Elisabeth Ersvær3, Lars Peder Bovim4,
Lise Bjørkhaug3, Rolf Moe-Nilssen1, Jørn V. Sagen5,6 and Inger Haukenes1,7*
1Department of Global Public Health and Primary Care, University of Bergen, Bergen, Norway, 2Department of Sport, Food,
and Natural Sciences, Western Norway University of Applied Sciences, Bergen, Norway, 3Department of Safety, Chemistry,
and Biomedical Laboratory Sciences, Western Norway University of Applied Sciences, Bergen, Norway, 4Department
of Health and Functioning, Western Norway University of Applied Sciences, Bergen, Norway, 5Department of Clinical
Science, University of Bergen, Bergen, Norway, 6Department of Medical Biochemistry and Pharmacology, Haukeland
University Hospital, Bergen, Norway, 7Research Unit for General Practice, NORCE Norwegian Research Centre, Bergen,
Norway
Purpose: The female menstrual cycle (MC) is characterized by hormonal fluctuations
throughout its different phases. However, research regarding its effect on athletic
performance in high level athletes is sparse. The aim of this study was to (i) investigate
the female MCs effect on strength and power performance in highly trained female team
athletes throughout the MC and (ii) examine whether eumenorrheic participants with
natural hormonal fluctuations displayed enhanced performance in the follicular phase
(FP) versus the luteal phase (LP), compared to controls using hormonal contraceptives.
Materials and Methods: A total of 29 athletes (Age 21.2 ±3.3 years; weight
65.6 ±8.7 kg; height 170.2 ±8.0 cm; and fat free mass 52.7 ±7.1) completed
the study after a 6-week testing period (8 eumenorrheic participants and 21 hormonal
contraceptive controls). Participants were recruited from the team sports soccer,
handball and volleyball. Testing protocol consisted of maximal voluntary isometric grip
strength, 20-m sprint, countermovement jump and pneumatic leg-press. Based on self-
reported use of hormonal contraceptives, participants were divided into non-hormonal
contraceptive group and hormonal contraceptive group, the latter working as a control
group. Differences in performance between the FP and LP were investigated. MC
phase was confirmed by serum hormonal levels through venous blood samples in the
non-hormonal contraceptive group.
Results: There were no statistically significant changes for the two different phases of
the MC, in terms of physical performance for the whole group. Further, there was no
significant difference between groups during the MC for any of the outcome variables,
maximal voluntary isometric grip strength F(3.29) = 0.362; 20-m sprint F(3.24) = 0.710;
countermovement jump F(3.26) = 2.361; and leg-press F(3.26) = 1.746.
Conclusion: In high level female team athletes, no difference in performance was
observed based on hormonal contraceptive status. This suggests that the MC does not
alter acute strength and power performance on a group level in high level team athletes.
Keywords: menstrual cycle, female athletes, strength, power, hormones
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INTRODUCTION
Modern intermittent team sports require a wide range of
physiological attributes in order to meet the demands
of the given sport. Strength and power are important
characteristics in intermittent team sports, hence, compelling
attributes to research in relation to physical performance
(Drust et al., 2007;Lidor and Ziv, 2010;Póvoas et al.,
2014). Although gender equality has been more in focus
in recent years, related to exposure, conditions and
professionalism in sport, females are underrepresented in
the scientific literature. Findings from studies investigating
male physiology and performance does not necessarily
translate to females, as the female menstrual cycle (MC)
cause monthly changes in serum hormone levels (Reilly, 2000)
that may affect strength, power, and endurance (Hansen, 2018;
Thompson et al., 2020).
The role of the sex hormones (estradiol and progesterone)
in addition to the pituitary hormones regulating the gonadal
axis [i.e., lutenizing hormone (LH)- and follicle stimulating
hormone (FSH)], in developing strength and power, is not
fully understood. Studies suggest that estradiol, one of the
primary sex hormone during the reproductive MC, induce
anabolic, and muscle building processes in females (Lowe
et al., 2010;Hansen et al., 2012). Furthermore, hormone
replacement therapy using exogenous estrogen seem to attenuate
loss of muscle strength in peri and post-menopausal women
(Carter et al., 2001;Minahan et al., 2015). The impact of
estradiol on muscle strength is not necessarily accomplished
by increased muscle size through hypertrophy, but rather
by affecting the intrinsic quality of skeletal muscle, enabling
muscle fibers to generate greater force (Lowe et al., 2010).
However, the role of estradiol during acute hormonal changes,
as seen amid the MC is not fully understood (Chidi-Ogbolu
and Baar, 2019). A second hormone playing an important
role during the female MC is progesterone. A decline in
progesterone levels (and estradiol levels) signals shedding of
the endometrium resulting in menstrual bleeding. Related to
sports, progesterone has been associated with protein catabolism,
conceivably attenuating muscle strength (Oosthuyse and Bosch,
2010). Indeed, studies have demonstrated ameliorated strength
levels during both the follicular phase (FP) and luteal phase
(LP) (Phillips et al., 1996;Birch and Reilly, 2002). These
conflicting finding makes understanding of potential superior
performance allocated to a specific MC phase speculative.
Sung et al. (2014) demonstrated increased muscle strength
and muscle diameter through strength training periodized to
the FP, compared to LP (Sung et al., 2014). Wikström-Frisén
et al. (2017) confirmed this finding and reported increased
power and strength gains through FP periodized training
(Wikström-Frisén et al., 2017). Despite this, several studies
within this field of research are hampered with insufficient
methodology, by lacking biological documentation of the MC
phase, which is seen as the gold standard (Allen et al.,
2016;Janse et al., 2019;Thompson et al., 2020). Studies with
unsatisfactory biological methodology also report increased
muscular performance through changes in serum hormonal
levels during and shortly prior to menstrual bleeding (Sarwar
et al., 1996;Bambaeichi et al., 2004).
A recently published systematic review investigating the effect
of MC and oral contraceptives on acute responses and chronic
adaptations to resistance training, concluded that the effects of
both the MC and oral contraceptive use on acute responses
to resistance training remain unclear (Thompson et al., 2020).
To summarize some findings of this review: (i) One of the 17
studies found no significant differences in acute responses to a
resistance training session over the natural MC, while four studies
did find changes (Thompson et al., 2020). (ii) For the responses
to a resistance training program, three studies reported FP -
based training to be superior to LP -based training or regular
training, while one study reported no differences (Thompson
et al., 2020). Finally, (iii) when assessing the differences in
acute responses between the oral contraceptive and MC groups,
two studies reported oral contraceptives to have a positive
influence, whilst four studies reported that oral contraceptive
users had a delayed recovery, higher levels of markers of
muscle damage, or both (Thompson et al., 2020). Some of the
conclusions made by this review is that FP -based resistance
training programs appear to result in better responses than LP
based and regular training programs. Furthermore, this review
highlights the need for further experimental research in this area
(Thompson et al., 2020).
We argue that more research is needed to investigate whether
hormonal fluctuations during the MC may alter performance
and in such have implications for periodic training and
competition. Furthermore, no studies have investigated the
effect of female sex hormone fluctuations on performance in
high-level team athletes, a sub-group where small changes
may have major impact. The aim of the study was therefore
(i) to examine potential changes in performance in high
level female team athletes during different phases of the MC
and (ii) to examine whether eumenorrheic participants, with
natural hormonal fluctuations during the MC display enhanced
performance during the FP versus the LP (due to higher relative
concentrations of circulating estradiol), compared to participants
using hormonal contraceptives.
MATERIALS AND METHODS
Participants
Women from six high-level teams from the Hordaland County
of western Norway, Norway, were invited to participate in the
study. Team sports invited were soccer, handball and volleyball,
competing at the top two national levels. Twelve players were
currently representing their national team. Five teams accepted
the invitation; one team declined due to logistics. Inclusion
criteria were (i) 18 years of age, (ii) competing at a national
level in their respective team sport, and (iii) free of any injury
or disease prohibiting testing. All participants satisfying inclusion
criteria (n= 55) received a baseline questionnaire via email
before the start of the intervention period. Of these, nine
team-members dropped out before testing, leaving the final
participant number at 46.
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During the testing period, additional five participants were
lost to follow up due to time commitment, school, or injury.
Four participants were excluded post hoc as they did not self-
report onset of menstruation during the 6-week testing period.
Additionally, eight participants were excluded as they did not
provide at least two test weeks from both FP and LP. Thus, the
total number of participants completing the study was Figure 1
(Age 21.2 ±3.3 years; weight 65.6 ±8.7 kg; height 170.2 ±8.0 cm;
and fat free mass 52.7 ±7.1). Group specific descriptive data are
presented in the section “Results.”
This study was approved by the Regional Ethics Committee
Norway (REK2018/1529).
Study Design
A prospective cohort study with repeated measures over 6-
weeks was executed. Exposure was hormonal contraceptive
(HC) status. Hormonal contraceptive group (HCG) and non-
hormonal contraceptive group (NHCG) were defined post hoc
(the participants HC status was unknown during the 6-week
testing period). The MC phases (FP and LP) were confirmed
through serum hormonal levels in blood samples taken at every
visit during the 6-week testing period, in the NHCG, to ensure
correct group assignment and validity of self-reported menstrual
phase. This validation procedure (hormonal values in serum
samples) was not performed in the HCG, as confirmation of
MC phase through blood samples is not possible due to a
steady flow of contraceptive specific exogenous sex hormones
throughout the MC (Allen et al., 2016). Self-reported onset of
menstruation was used in this group for assignment of FP and
LP phases. Guidelines provided by Sims and Heather (2018)
were used to choose test weeks included in the statistical analysis
for the HCG (Sims and Heather, 2018). More specifically, we
strived to test participants in the HCG using monophasic oral
contraceptives in the active pill phase. Blood samples of subjects
in the HCG were, however, drawn, but for other analytical
purposes (parallel study). HC types were recorded at baseline in
the HCG (Supplementary Table 3). Weekly outcome measures
(see testing procedure) were compared between the HCG and
NHCG. For this, four out of six testing weeks were selected
for statistical analysis to represent the FP and LP phases (FP
week 1/2 and LP week 3/4). Six weeks of consecutive testing
was performed to secure a minimum of two measurements in
both FP and LP, thus minimizing exclusion based on failure
to fulfill this requirement (e.g., week 1-4 and week 5-2 etc.).
This variation of included test weeks reduced the chance of a
systematic learning effect.
Testing Procedures
At baseline, all participants completed the LEAF-Q
questionnaire: a screening tool for the identification of female
athletes at risk for the female athlete triad. The questionnaire
comprises questions of age, height, weight, and BMI, as well
as more comprehensive information (sleep, nutrition, and
metabolism) for purposes beyond the scope of this study
(Melin et al., 2014).
On the day of testing, participants were encouraged to
eat approximately the same type and amount of food and
liquid throughout the testing period. They were also instructed
to avoid any caffeine consumption 12 h preceding testing,
due to the possible ergogenic effects related to physical
performance (Goldstein et al., 2010;Grgic et al., 2019a).
When arriving at the facility for testing, participants were
asked to complete a self-administered questionnaire regarding
MC, nutrition, training, injuries/pain, and test-day form
(expectations on test influence). Weight and body composition
were measured using multi-frequency bioelectrical impedance
(IN-body 720, Biospace, Tokyo, Japan), along with venous blood
samples for determination of menstrual phase. Before physical
testing, participants performed a 15-min standardized warm
up (100 watts) using the Wattbike ergometer (Wattbike Ltd.,
FIGURE 1 | Flow chart displaying the drop-out rate and exclusion during the study. N, number of participants; HC, hormonal contraceptive user; NHC, non-hormonal
contraceptive user. HC status for drop out prior to the start of the study is not included, due to incomplete questionnaires from some of the participants.
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Nottingham, United Kingdom). The weekly testing protocol
consisted of maximal voluntary isometric grip strength (MVIGS),
20-m sprint, Counter movement jump (CMJ) and leg-press.
Testing was completed once a week, at approximately the
same time each weekday to control for circadian variations
(±2 days/±2 h on the testing day). To minimize potential
bias through a learning effect, participants were given two
experimental attempts for every test, before recording started.
Maximal Voluntary Isometric Grip
Strength (MVIGS)
Isometric grip strength of the dominant hand was measured
using a digital pinch/grip analyzer (MIE, Medical research
Ltd, Leeds, United Kingdom). Standard instructions before and
during the test: (i) to be seated with a slight forward bend of
the trunk, elbow resting on the thigh with 90elbow flexion,
(ii) exert maximal force for 3–5 s, (iii) two attempts with a 30 s
break between. If deviation from the instructions the attempt was
disallowed. If the force production in their last attempt exceeded
the previous with >5%, a new attempt was performed. The best
recording was used for statistical analysis. MVIGS is shown to
be a repetitive measure, with ICC-scores classified as very good
(Vassilis, 2012).
20-M Sprint
Sprint performance was assessed over a 20-m track, made
from portable non-slipping surface (Hitashita international, ON,
Canada). Times were recorded at 5, 10, and 20-m using single
beam photocells (Brower timing systems, Utah, United States).
Photocells were fixed at 120 cm height, apart from the first pair,
which were fixed at 10 cm height to ensure similar photocell
interception. participants were instructed to a stationary start
with the dominant leg behind and a slight forward bend of
the trunk. Participants decided when to start their effort, with
recording being initiated by interception of the first photocell
beam. Each subject carried out two attempts, separated by 2 min
of rest. If the second attempt was >5% faster than the previous,
a new attempt was performed. The best total 20-m sprint time
was used for statistical analysis. 20-m sprint is shown to be a
repetitive measurement, with ICC-scores classified as very good
(Shalfawi et al., 2012). This method is also reviewed as reliable
in a comprehensive review of sprint performance monitoring
(Haugen and Buchheit, 2016).
Countermovement Jump
Counter movement jump performance started from an upright
position and the participants were instructed to descend to
a self-chosen depth, followed by a maximal vertical jump
effort. Participants were instructed to use a hand on hips
position throughout the entire movement. Maximum jump
height (cm) was calculated using Kistler Measurement, Analysis
and Reporting Software (MARS, 2015, S2P, Ljubljana, Slovenia).
Participants performed at least two attempts or continued
until performance declined. The best attempt was selected for
statistical analysis. CMJ is shown to be a repetitive measure, with
ICC-scores classified as very good (Slinde et al., 2008).
Leg Press
Relative peak power (RPP) was estimated using a progressive
maximal pneumatic resistance seated leg press test on a Keiser
A420 (Keiser, Fresno, CA, United States). An estimated 1-
Repetition maximum (1 RM) was chosen based on participants
self-reported training history, bodyweight, sport and previous
internal testing. Participants completed a 10-repetition
incremental step test toward peak of 1 RM on last repetition. The
test protocol is well established and described in detail elsewhere
(Redden, 2019). RPP was estimated using all 10 repetitions, and
each participant was to use the same protocol at every test point.
RPP measured and estimated with pneumatic leg press is shown
to be a repetitive measure, with ICC-scores classified as good
(Redden et al., 2018).
Serum Hormone Analysis
To provide hormonal confirmation of MC phase, participants
provided non-fasted venous blood samples before testing at every
visit, in order to avoid effect of physical strain on hormonal
levels. Blood was collected using eclipse blood collection needles
(BD vacutainer, Franklin Lakes, NJ, United States) in EDTA-
vials by qualified biomedical laboratory scientists. After 30 min,
blood samples were centrifuged at 2000×gfor 10 min (Thermo
Fisher Scientific SL1R centrifuge, Thermo Fisher Scientific,
Waltham, MA, United States). Serum was isolated and stored
at 80C until all samples were collected during the 6-week
testing period prior to hormonal analysis. Serum samples were
analyzed for progesterone, estradiol, FSH, LH, and Sex hormone-
binding globin (SHBG). Analysis of progesterone and estradiol
levels were performed using Liquid Chromatography-Mass
Spectrometry (LC-MS/MS) (progesterone by the LC-system by
Agilent (Santa Clara, CA, United States) and MS-system: SICX,
while estradiol by LC-MS/MS by Waters). FSH, LH and SHBG
was analyzed by chemical luminescence on the Immulite 2000
XPi (Siemens, Erlangen, Germany). All hormone analyses were
performed at the Hormone Laboratory, Department of medical
biochemistry and pharmacology, Haukeland University Hospital.
All analyses are accredited according to NS-EN ISO 15189:2012.
Reference values used by the laboratory are presented in
Supplementary Table 4.
We performed a dichotomous division for FP and LP,
respectively. A progesterone value <0.5 nmol/L was considered
true FP whereas a value >5.5 nmol/L was considered true LP. In
some instances, we identified progesterone levels between 0.5 and
5.5 nmol/L. For these cases we evaluated the preceding and the
following weeks progesterone values. If the week prior presented
a progesterone value of >5.5 nmol/L, both weeks were considered
to be LP. In other cases, a low but measurable progesterone
value appeared, followed by a spike in progesterone. These cases
were labelled mid-cycle and were not included in the statistical
analysis, since it is difficult to conclude whether the value is
actually late FP or early LP.
Statistical Analysis
Descriptive statistics were used to examine the distribution of
subject characteristics across exposure groups. We calculated
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Dasa et al. Strength Performance in Female Athletes
interclass correlation coefficients (ICC, random model) as
measures of reliability, based upon the four weekly measurements
chosen for analysis of performance during the MC. The results
are presented as mean ±standard deviation (SD). One-way
repeated measures analysis of variance (ANOVA) were used
to analyze for between group differences, between the average
results of two FP measures and two LP measures. ANOVA
was also conducted separately for the HCG and NHCG to
investigate potential within group chances between the FP and
LP. Bonferroni correction was conducted post hoc to reduce
the chance of type one error with significant ANOVAs. An
alpha level of P<0.05 was set a priori. Participants with
incomplete hormonal or performance data were excluded from
the statistical analysis. Between groups comparison is based on
the interaction between hormonal statusmenstrual cycle (time).
Statistical analysis was performed using IBM SPSS 25 (IBM,
Armonk, NY, United States).
RESULTS
A total of 29 participants were included in the study, 21 and
8 individuals in the HCG and NHCG, respectively. Mean age,
height, weight, fat free mass, and monthly training volume are
presented in Table 1. There was no statistical difference between
the two groups for any of these measures.
Self-reported onset of menstruation was registered in the
NHCG (n= 8) and compared with hormonal analyses to
investigate the accuracy of self-reported onset of menstruation.
We found deviating results in the self-reported data in two
individual cases (ID: D16, H3). Range of analyses in the different
phases of MC are presented in Supplementary Table 1. Reference
values for FP and LP are presented in Supplementary Table 4.
Repeated measures reliability was assessed as satisfactory
to excellent, with the following ICC vales; 0.75 for
countermovement jump, 0.80 for leg press, 0.88 for MVIGS, and
0.91 for 20-m sprint performance.
There were no statistically significant changes for the two
different phases of the MC, in terms of physical performance
for the whole group. Further, the interaction effect between
contraceptive status and time (MC phase) were compared. There
were no statistically significant group differences between the
HCG and NHCG for any outcome measures throughout the
TABLE 1 | Descriptive data showing mean values ±standard deviation of subject
characteristics in the hormonal contraceptive group and non-hormonal
contraceptive group.
Total HCG NHCG
N29 21 8
Age 21.2±3.3 20.48 ±2.5 22.5±4.2
Weight (kg) 65.6±8.7 66.9±8.3 63.1±9.3
Height (cm) 170.2±8.0 170 ±7.6 168.8±8.9
Fat free mass (FFM) 52.7±7.1 53.4±6.7 52.3±7.9
Training volume (monthly hours) 52.8±14.2 52.7±14.9 52.9±13.7
N, number of participants.
4 weeks chosen for analysis, although both groups showed
variation in performance (Figure 2 and Supplementary Table 2).
Additionally, no significant changes were observed when
investigating the MC cycle in both groups separately.
Despite non-significant findings, In terms of maximal
isometric grip strength both groups demonstrated weekly
variations in MVIGS, displaying the highest isometric grip
strength values for both groups in the LP with a mean of
31.3 ±5.6 kg in the HCG and 28.7 ±3.6 in the NHCG,
respectively (Figure 2 and Supplementary Table 2). Further,
both groups showed consistent measures for sprint performance
throughout the 4 weeks of the MC, with results ranging
from 3.194 ±0.132 s to 3.209 ±0.123 s in the HCG and
3.165 ±0.121 s to 3.191 ±0.116 s in the NHCG, respectively
(Figure 2 and Supplementary Table 2). With respect to counter
movement jump the CMJ displayed a greater between group
difference compared to the other tests, with means ranging from
32.9 ±6.3 cm to 30.7 ±4.3 cm in the HCG and 33.5 ±4.7 cm
to 30.7 ±2.7 cm in the NHCG, respectively (Figure 2 and
Supplementary Table 2). Finally, the NHCG displayed greater
variation between weeks in leg press compared to the HCG; means
ranging from 24.4 ±2.9 W/kg to 23.3 ±2.0 W/kg in the NHCG
compared to 23.6 ±2.6 W/kg to 23.2 ±2.8 W/kg in the HCG
(Figure 2 and Supplementary Table 2).
DISCUSSION
The aim of this study was to examine potential changes in
performance due to hormonal changes during the MC. This was
done by comparing test results from FP and LP between a NHCG
and HCG, the latter serving as controls over a 6-week period.
When comparing eumenorrheic participants with controls using
HC, we found no statistically significant differences for the MC
overall. Further, no statistically significant differences were found
for the FP when comparing the two groups. These findings
suggest that HC status does not alter strength and power
performance on a group level in high-level female team athletes,
when tested in a controlled environment throughout one MC.
Our findings are in line with several studies reporting no
difference in strength or power performance throughout the
different phases of the MC (Lebrun et al., 1995;Jonge et al.,
2001;Fridén et al., 2003;Bushman et al., 2006;Abt et al., 2007;
Julian et al., 2017;Romero-Moraleda et al., 2019). However,
there are studies reporting altering effects on strength and power
performance following periodized training regiments, adjusting
for hormonal fluctuations in the different MC phases (Thompson
et al., 2020). For instance, Sung et al. (2014) reported increased
muscle strength in participants following a FP periodized training
regimen, compared to a LP periodized training regiment, over a
total of three MC’s (Sung et al., 2014). Possibly, this procedure,
in contrast to acute performance as investigated in our study,
could better utilize the proposed mechanisms behind estradiol’s
ameliorating effects in muscle strength (Lowe et al., 2010). Our
study was cross-sectional, and we did not follow any specific
strength intervention and only provided data for one MC. This
might explain why the NHCG did not display any significant
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FIGURE 2 | Mean values through the menstrual cycle with 95% confidence intervals for (A) maximal voluntary grip strength, (B) 20-m sprint, (C) leg press, and (D)
countermovement jump. Week 1–4 (week 1/2 FP; week 3/4 LP) are based on serum hormonal levels.
alterations in their performance relative to the HCG. Further,
Phillips et al. (1996) reported up to 10% increase in maximal
voluntary force of the adductor pollicis during the FP of the
MC (Phillips et al., 1996). These findings contradict our result,
although we used MVIGS with a handheld dynamometer, which
is comparable with maximal voluntary force of the adductor
pollicis. Although not significant, in the current study, MVIGS
demonstrated small weekly variations in performance for both
groups with the greatest variations between FP and LP for both
groups. As the weeks are based on self-reported menstruation and
confirmation with hormonal analyses, representing the biological
week of the MC and not chronological test week, a systematic
learning effect can be ruled out. The fact that both groups showed
similar variations in their results, suggests that the MC was not
the impacting factor in the NHCG.
Counter movement jump displayed slight weekly non-
significant variations in the NHCG throughout the MC. In
contrast, the HCG showed a substantial deviation with a mean
difference of 2.2 cm between week two and four, which is a
6.9% difference. This manifested itself with a FP peak before
declining in the LP and can be viewed as a meaningful difference,
considering the marginal differences in high level sport. If
estradiol indeed does ameliorate muscle strength and power,
this increase in performance would be plausible. However, with
HC agents providing a steady supply of exogenous hormones
throughout the MC, minimizing the hormonal fluctuations, this
weekly difference in the HCG was unexpected. As highlighted
by Myllyaho et al. (2018), different HC agents may exert varying
effects of performance (Myllyaho et al., 2018). Hence, this might
be a line of investigation interesting to follow in future studies, by
separating groups of different HC agents.
Relative peak power showed weekly variations, with the
NHCG displaying the greatest change between week one and two,
with a mean difference of 1.1 w/kg. For this outcome, the greatest
value manifested itself in the FP. This is in line with previous
research, demonstrating superior performance in the FP (Phillips
et al., 1996;Greeves et al., 1997). However, the outcome measures
of both these studies are quite reductionistic. Further, MC phase
was not necessarily verified through serum blood samples, giving
these results low validity (Allen et al., 2016).
A total of 20-m sprint displayed the least variation in
both groups. Since repeated measures ICC was high for sprint
measures, these results cannot be explained as uncertainty of
the measurement method to detect small changes, but rather
demonstrates stable performance across the testing period.
Further, it is possible 20-m was too short of a distance to measure
any meaningful difference, as results were very marginal.
Although no significant findings were detected between
groups, several variables showed substantial weekly variations in
performance in both the HCG and NHCG. As small changes
in performance may impact results in high level sport, our
findings indicate that the time of testing could yield different
results for high level female athletes in general. However,
these variations cannot directly be contributed to hormonal
fluctuations occurring during the MC. One plausible explanation
for the weekly variations observed in this study is individual
physiological load. Indeed, Andersson et al. (2008) demonstrated
that full match recovery in female soccer players can last up
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Dasa et al. Strength Performance in Female Athletes
to 72 h. The recovery time from handball is also proven to be
substantial (Ronglan et al., 2006;Andersson et al., 2008).
Our study contradicts the suggestion that estradiol acutely
ameliorates muscle strength and power, supporting the findings
of Jonge et al. (2001), showing no correlation between estradiol
serum hormonal levels and muscle strength, fatiguability, and
contractile properties (Jonge et al., 2001). Serum estradiol levels
varied in the range from 35 pmol/L to 1122 pmol/L. As
highlighted by Jonge et al. (2001), the large variations seen in
serum estradiol levels is partly caused by secretory pulses of
these hormones. In addition, the MC is highly individual in their
length, thus, the participants may have been in different stages of
their respective cycles. This is in line with Greeves et al. (1997)
who demonstrated that supraphysiological doses of estradiol
did not significantly increase muscle strength, questioning the
findings of Phillips et al. (1996), and Sarwar et al. (1996),
suggesting that acute changes in estradiol ameliorates muscular
strength (Phillips et al., 1996;Sarwar et al., 1996).
Indeed, several studies have shown estradiol hormone
replacement therapy to be beneficial in decreasing attenuation
of muscle strength in peri and post-menopausal women, as
summarized by Chidi-Ogbolu & Baar (Chidi-Ogbolu and Baar,
2019). Lowe et al. (2010) hypothesize that estradiol alters myosin
function during muscle contractions through estradiol receptors
in a typical steroid manner (Lowe et al., 2010). As described
by the aforementioned authors, skeletal muscle is an estradiol
receptive tissue, working through the estradiol receptor. This may
help explain why studies adopting periodized training protocols,
utilizing elevated circulating estradiol levels over time have
demonstrated increased muscle strength, as opposed to more
modest results displayed when measuring acute performance.
Exploiting a preferable milieu may promote strength gains over
time, as adaptations in skeletal muscle may need time to manifest
themselves, even if estradiol alone also improves the intrinsic
quality of contractile fibers. Individual estrogen receptor content
may therefore be partly indicative of muscle strength gains
and performance.
As highlighted by Sims and Heather (2018), HC users are
proposed as suitable controls when measuring the effects of
the MC (Sims and Heather, 2018). However, several types
of contraceptive agents, with different active ingredients and
exogenous hormones were administered in the HCG. Thus, the
impact on performance may vary, depending on the type of
contraceptive agent being used. To our knowledge, there is no
study investigating the effect on different type of HC’s related
to athletic performance in high level athletes. Considering the
current lack of knowledge related to different HC agents and
performance, we would like to re-emphasize the need for future
research regarding this manner.
Methodological Considerations and
Limitations
This study highlights the possibility of conducting prospective
research on female athletes, which is often considered
problematic due to training and competition schedule,
paired with female physiology. A further strength is the
prospective study design, were we measured 6 weeks and
chose 4 weeks, representing the MC based on self-reported
onset of menstruation and hormonal confirmation. However,
measurements over several MC’s would have provided increased
validity, due to individual variation in MC length and onset.
Comparing self-reported onset of menstruation to hormonal
analysis, revealed deviating results in four participants.
Although some of these variations may be contributed to
survey misunderstandings, the results indicate that some
caution should be made when interpreting studies exclusively
applying this method for MC phase determination. Although
no statistical difference was observed between the two groups,
some interindividual variability was present in both groups.
With a relatively small sample size, it is possible that the results
would approach being statistically significant with a larger
population. Further, a potential limitation is small variations
in test procedures. Testing was originally scheduled for the
same day (±2 days) and time (±2 h) throughout the study
period to account for circadian variations. However, due to
national team obligations and training/competition schedules
being fluctuant in pre-season, some participants were tested
outside these frames at one or several time points. This could
have impacted the results, as circadian rhythm has been shown
to affect performance in strength and power endeavors (Grgic
et al., 2019b). Grgic et al. (2019b) reported that expression of
strength is greater in the evening, versus the morning. On the
other hand, the circadian effects on test results also depend on
athletes normal training schedule (Grgic et al., 2019b). Thus, the
impact of variation in test procedures on the final results is not
fully known. Indeed, the relatively low sample size limits external
validity. On the other hand, the participants were selected based
on stringent criteria’s before entering the study, increasing the
likelihood of being representative for high level female team
athletes within the relevant sports. As described earlier, HCG
testing weeks was selected based on self-reported menstruation.
Although we strived to follow guidelines presented by Sims and
Heather (2018), this method of validation should be interpreted
with caution (Sims and Heather, 2018). Finally, we chose to limit
testing to FP and LP exclusively. Ideally, hormonal validation
of MC phase should have included ovulation. Further, FP and
LP could have been divided to include early and late FP and LP.
Due to time and financial reasons, this was not done. Hence, this
limits our result, due to variations in serum hormonal levels in
different parts of FP and LP, respectively.
CONCLUSION
In this study, there was no statistically significant changes
for the two different phases of the MC, in terms of
physical performance in high level female team athletes.
Further, testing of strength and power performance
parameters were not significantly affected by HC status
when comparing an HCG and NHCG during the MC. These
findings suggest that MC phase should not be of major
consideration for athletic testing or competition, emphasizing
strength and power performance. However, interindividual
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Dasa et al. Strength Performance in Female Athletes
variability in results and hormonal levels, together with a
small sample size makes firm guidelines arduous. Based on
our study and the current literature, possible alterations to
strength and power performance elicited by the MC are
more likely to occur during long term MC phase dependent
training interventions, rather than acute testing of performance.
Our findings should be interpreted with caution, due to the
limitations of the study.
DATA AVAILABILITY STATEMENT
The raw data supporting the conclusions of this article will be
made available by the authors, without undue reservation.
ETHICS STATEMENT
The studies involving human participants were reviewed and
approved by Regional Committees for medical and health
research ethics (2018/1529). The patients/participants provided
their written informed consent to participate in this study.
AUTHOR CONTRIBUTIONS
MD: planning, data collection, statistical analysis, and writing.
MK and LPB: planning and data collection. EE: planning and
writing. LB: planning, data collection, and writing. RM-N:
statistical analysis. JS: writing and hormonal data analysis. IH:
planning, statistical analysis, and writing. All authors contributed
to the article and approved the submitted version.
ACKNOWLEDGMENTS
The authors gratefully thank the participants for their time and
effort. The authors would also like to thank the students at
Western Norway University of Applied Science, who participated
in the data collection, making this project possible.
SUPPLEMENTARY MATERIAL
The Supplementary Material for this article can be found
online at: https://www.frontiersin.org/articles/10.3389/fphys.
2021.600668/full#supplementary-material
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Conflict of Interest: The authors declare that the research was conducted in the
absence of any commercial or financial relationships that could be construed as a
potential conflict of interest.
Copyright © 2021 Dasa, Kristoffersen, Ersvær, Bovim, Bjørkhaug, Moe-Nilssen,
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... Another recent systematic review by Blagrove et al. (4) came to a similar conclusion. Studies that have investigated the effect of the MC on performance parameters in women have either reported no significant difference in strength performance during the MC (5)(6)(7)(8)(9)(10)(11)(12) or greater muscle strength just before ovulation (13)(14)(15). The lack of consensus could be due to methodological differences and limitations in the individual studies (16). ...
... Measurement of sex hormones is essential for confirmation of MC phases, but has not been performed in several of the previous studies (13,14,17). In the majority of studies, the number of participants has been <20 (5)(6)(7)(8)(9)(10)(11)(12)(13)(14), and the number of test days completed during an MC has been ≤3 (5-10,12). Furthermore, including trained women as participants may create bias through prior training sessions in the days leading up to the testing confounding the results, as well as increasing the incidence of suppressed female sex hormone levels and irregular MC (18,19). ...
... This was followed by the midfollicular phase (MF; days 6-10), which is characterized by a slow increase in estrogen and a low progesterone level. The following late follicular phase (LF; ovulation phase; days [11][12][13][14] is characterized by a rapid increase in estrogen and luteinizing hormone (LH) reaching their peaks just before ovulation. After LF, the early luteal phase (EL; days [15][16][17] follows, where estrogen initially declines; hereafter, both estrogen and progesterone levels slowly increase. ...
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Purpose: We aimed to study variations in strength and power performance during the menstrual cycle (MC) in eumenorrheic young women and during the pill cycle in oral contraceptives (OC) users. Methods: Forty healthy, normal-weight women between 18 and 35 yr (n = 30 eumenorrheic women; n = 10 OC users) completed this prospective cohort study. Seven to nine times during the MC/pill-cycle, the participants completed a physical performance test series, a questionnaire about psychological well-being, blood sampling, and determination of body mass. The physical tests included isometric handgrip strength, elbow flexor strength, countermovement jump (CMJ) height, and a 10-s Wingate bike test. Results: No direct correlation was observed between the variations in sex hormones and physical performance parameters. However, positive correlations were observed between physical performance outcomes and self-reported motivation, perception of own physical performance level, pleasure level, and arousal level. CMJ was 6% lower in the late luteal phase (LL) compared with the midluteal phase (ML) (P = 0.04). Wingate peak power was 3% lower in early follicular (EF) compared with the ML (P = 0.04). Furthermore, Wingate average power was 2%-5% lower in LL compared with all other MC phases. In line with these observations, physical pain was higher in EF and LL, and the pleasure level was lower in EF compared with the other MC phases. In OC users, we observed no variation in performance and self-reported parameters between the placebo-pill phase and the OC-pill phase. Conclusions: Impairments in CMJ and Wingate performance were observed at the end and start of MC compared with other MC phases, which were associated with lower psychological well-being, but not the sex hormone fluctuations.
... This work neither found differences in performance comparing these three phases (bleeding, follicular and luteal phases), which concur with our main findings for similar outcomes. Lastly, our results are also in line with a recent study with high-level team sport players, which did not show differences among MC phases in CMJ performance in eumenorrheic athletes, analyzed with serum hormonal levels by blood sample [35]. Therefore, the current study confirms the lack of MC effect on vertical jumping performance and, as a novelty, provides information about the dynamic of the F-v relationship parameters over the different phases of MC. ...
... Likewise, in an experiment performed outdoors (i.e., on field testing) [16], the authors found no differences in 30 m linear sprint time during the different phases of MC in female soccer players. Another recent study found differences in 20 m linear sprint with high-level team sport players [35]. However, as previously indicated, the authors of these studies only compared the follicular phase with the luteal phase, dismissing the bleeding phase, one of the most important physiological moments of the MC due to the lower concentrations of estrogen and progesterone [8,9]. ...
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The aim of this study was to examine the effects of the menstrual cycle on vertical jump, sprint performance and force-velocity profiling in resistance-trained women. A group of resistance-trained eumenorrheic women (n=9) were tested in 3 phases over the menstrual cycle: bleeding phase, follicular phase, and luteal phase (i.e., days 1-3, 7-10, and 19-21 of the cycle, respectively). Each testing consisted of a battery of jumping tests (i.e., squat jump [SJ], countermovement jump [CMJ], drop jump from a 30 cm box [DJ30], and the reactive strength index) and 30 m sprint running test. Two different applications for smartphone (My Jump 2 and My Sprint) were used to record the jumping and sprinting trials, respectively, at high-speed (240 fps). The repeated measures ANOVA reported no significant differences (p0.05, ES<0.25) in CMJ, DJ30, reactive strength index and sprint times between the different phases of the menstrual cycle. A greater SJ height performance was observed during the follicular phase compared to the bleeding phase (p=0.033, ES=-0.22). No differences (p0.05, ES<0.45) were found in the CMJ and sprint force-velocity profile over the different phases of the menstrual cycle. Vertical jump, sprint performance and the force-velocity profiling remain constant in trained women, regardless the phase of the menstrual cycle.
... Recently, it was reported that 36% of high-performance female athletes stated that their menstrual cycle impacted negatively on their performance for at least some or most of the time (Heather et al., 2021). In contrast, it did not a ect the production of muscle strength and power (McNulty et al., 2020;Dasa et al., 2021). Furthermore, we recommend to future research could consider the confounding influence of physical fitness levels of participants. ...
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This study aimed to examine sex differences in oxygen saturation in respiratory (SmO 2-m.intercostales) and locomotor muscles (SmO 2-m.vastus lateralis) while performing physical exercise. Twenty-five (12 women) healthy and physically active participants were evaluated during an incremental test with a cycle ergometer, while ventilatory variables [lung ventilation (VE), tidal volume (Vt), and respiratory rate (RR)] were acquired through the breath-by-breath method. SmO 2 was acquired using the MOXY R devices on the m.intercostales and m.vastus lateralis. A two-way ANOVA (sex ⇥ time) indicated that women showed a greater significant decrease of SmO 2-m.intercostales, and men showed a greater significant decrease of SmO 2-m.vastus lateralis. Additionally, women reached a higher level of 1SmO 2-m.intercostales normalized toVE (L·min 1) (p < 0.001), whereas men had a higher level of 1SmO 2-m.vastus lateralis normalized to peak workload-to-weight (watts·kg 1 , PtW) (p = 0.049), as confirmed by Student's t-test. During an incremental physical exercise, women experienced a greater cost of breathing, reflected by greater deoxygenation of the respiratory muscles, whereas men had a higher peripheral load, indicated by greater deoxygenation of the locomotor muscles.
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The aim of this study was to examine the effects of the menstrual cycle on vertical jumping, sprint performance and force-velocity profiling in resistance-trained women. A group of resistancetrained eumenorrheic women (n = 9) were tested in three phases over the menstrual cycle: bleeding phase, follicular phase, and luteal phase (i.e., days 1–3, 7–10, and 19–21 of the cycle, respectively). Each testing phase consisted of a battery of jumping tests (i.e., squat jump [SJ], countermovement jump [CMJ], drop jump from a 30 cm box [DJ30], and the reactive strength index) and 30 m sprint running test. Two different applications for smartphone (My Jump 2 and My Sprint) were used to record the jumping and sprinting trials, respectively, at high speed (240 fps). The repeated measures ANOVA reported no significant differences (p � 0.05, ES < 0.25) in CMJ, DJ30, reactive strength index and sprint times between the different phases of the menstrual cycle. A greater SJ height performance was observed during the follicular phase compared to the bleeding phase (p = 0.033, ES = −0.22). No differences (p � 0.05, ES < 0.45) were found in the CMJ and sprint force-velocity profile over the different phases of the menstrual cycle. Vertical jump, sprint performance and the force-velocity profiling remain constant in trained women, regardless of the phase of the menstrual cycle.
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The importance of defining sex differences across various biological and physiological mechanisms is more pervasive now than it has been over the last 15-20 years. As the muscle biology field pushes to identify small molecules and interventions to prevent, attenuate or even reverse muscle wasting, we must consider the effect of sex as a biological variable. It should not be assumed that a therapeutic will affect males and females with equal efficacy or equivalent target affinities under conditions where muscle wasting is observed. With that said, it is not surprising to find that we have an unclear or even a poor understanding of the effects of sex or sex hormones on muscle wasting conditions. Although recent investigations are beginning to establish experimental approaches that will allow investigators to assess the impact of sex-specific hormones on muscle wasting, the field still has not established enough published scientific tools that will allow the field to rigorously address critical hypotheses. Thus, the purpose of this review is to assemble a current summary of knowledge in the area of sexual dimorphism driven by estrogens with an effort to provide insights to interested physiologists on necessary considerations when trying to assess models for potential sex differences in cellular and molecular mechanisms of muscle wasting.
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Background Resistance training is well known to increase strength and lean body mass, and plays a key role in many female athletic and recreational training programs. Most females train throughout their reproductive years when they are exposed to continuously changing female steroid hormone profiles due to the menstrual cycle or contraceptive use. Therefore, it is important to focus on how female hormones may affect resistance training responses. Objective The aim of this systematic review is to identify and critically appraise current studies on the effect of the menstrual cycle and oral contraceptives on responses to resistance training. Methods The electronic databases Embase, PubMed, SPORTDiscus and Web of Science were searched using a comprehensive list of relevant terms. Studies that investigated the effect of the menstrual cycle phase or oral contraceptive cycle on resistance training responses were included. Studies were also included if they compared resistance training responses between the natural menstrual cycle and oral contraceptive use, or if resistance training was adapted to the menstrual cycle phase or oral contraceptive phase. Studies were critically appraised with the McMasters Universities Critical Review Form for Quantitative Studies and relevant data were extracted. Results Of 2007 articles found, 17 studies met the criteria and were included in this systematic review. The 17 included studies had a total of 418 participants with an age range of 18–38 years. One of the 17 studies found no significant differences in acute responses to a resistance training session over the natural menstrual cycle, while four studies did find changes. When assessing the differences in acute responses between the oral contraceptive and menstrual cycle groups, two studies reported oral contraceptives to have a positive influence, whilst four studies reported that oral contraceptive users had a delayed recovery, higher levels of markers of muscle damage, or both. For the responses to a resistance training program, three studies reported follicular phase-based training to be superior to luteal phase-based training or regular training, while one study reported no differences. In addition, one study reported no differences in strength development between oral contraceptive and menstrual cycle groups. One further study reported a greater increase in type I muscle fibre area and a trend toward a greater increase in muscle mass within low-androgenic oral contraceptive users compared with participants not taking hormonal contraceptives. Finally, one study investigated androgenicity of oral contraceptives and showed greater strength developments with high androgenic compared with anti-androgenic oral contraceptive use. Conclusions The reviewed articles reported conflicting findings, and were often limited by small participant numbers and methodological issues, but do appear to suggest female hormones may affect resistance training responses. The findings of this review highlight the need for further experimental studies on the effects of the menstrual cycle and oral contraceptives on acute and chronic responses to resistance training.
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This study aimed to investigate the fluctuations of muscle performance in the Smith machine half-squat exercise during three different phases of the menstrual cycle. Thirteen resistance-trained and eumenorrheic women volunteered to participate in the study (58.6 ± 7.8 kg, 31.1 ± 5.5 years). In a pre-experimental test, the half-squat one-repetition maximum (1RM) was measured. Body mass, tympanic temperature and urine concentration of the luteinizing hormone were estimated daily for ~30 days to determine the early follicular phase (EFP), the late follicular phase (LFP), and the mid-luteal phase (MLP) of the menstrual cycle. On the second day of each phase, performance of the Smith machine half-squats was assessed using 20, 40, 60 and 80% of one repetition maximum (1RM). In each load, force, velocity, and power output were measured during the concentric phase of the exercise by means of a rotatory encoder. The data were analyzed using one-way repeated measures ANOVA coupled with magnitude-based inferences. Overall, force, velocity and power output were very similar in all menstrual cycle phases with unclear differences in most of the pairwise comparisons and effect sizes >0.2. The results of this investigation suggest that eumenorrheic females have similar muscle strength and power performance in the Smith machine half-squat exercise during the EFP, LFP, and MLP phases of the menstrual cycle.
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Objective To systematically review, summarise, and appraise findings of published meta-analyses that examined the effects of caffeine on exercise performance. Design Umbrella review. Data sources Twelve databases. Eligibility criteria for selecting studies Meta-analyses that examined the effects of caffeine ingestion on exercise performance. Results Eleven reviews (with a total of 21 meta-analyses) were included, all being of moderate or high methodological quality (assessed using the AMSTAR 2 checklist). In the meta-analyses, caffeine was ergogenic for aerobic endurance, muscle strength, muscle endurance, power, jumping performance, and exercise speed. However, not all analyses provided a definite direction for the effect of caffeine when considering the 95% prediction interval. Using the GRADE criteria the quality of evidence was generally categorised as moderate (with some low to very low quality of evidence). Most individual studies included in the published meta-analyses were conducted among young men. Summary/Conclusion Synthesis of the currently available meta-analyses suggest that caffeine ingestion improves exercise performance in a broad range of exercise tasks. Ergogenic effects of caffeine on muscle endurance, muscle strength, anaerobic power, and aerobic endurance were substantiated by moderate quality of evidence coming from moderate-to-high quality systematic reviews. For other outcomes, we found moderate quality reviews that presented evidence of very low or low quality. It seems that the magnitude of the effect of caffeine is generally greater for aerobic as compared with anaerobic exercise. More primary studies should be conducted among women, middle-aged and older adults to improve the generalisability of these findings.
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Estrogen has a dramatic effect on musculoskeletal function. Beyond the known relationship between estrogen and bone, it directly affects the structure and function of other musculoskeletal tissues such as muscle, tendon, and ligament. In these other musculoskeletal tissues, estrogen improves muscle mass and strength, and increases the collagen content of connective tissues. However, unlike bone and muscle where estrogen improves function, in tendons and ligaments estrogen decreases stiffness, and this directly affects performance and injury rates. High estrogen levels can decrease power and performance and make women more prone for catastrophic ligament injury. The goal of the current work is to review the research that forms the basis of our understanding how estrogen affects muscle, tendon, and ligament and how hormonal manipulation can be used to optimize performance and promote female participation in an active lifestyle at any age.
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New findings: What is the topic of this review? We review methodological considerations for the inclusion of women in sex and menstrual cycle phase comparison studies. What advances does it highlight? Improving the methodological design for studies exploring sex differences, menstrual cycle phase differences and/or endogenous versus exogenous female sex hormones will help to close the gap in our understanding of the effects of endogenous and exogenous hormones on exercise science and sports medicine outcomes. Abstract: In recent years, the increase in scientific literature exploring sex differences has been beneficial to both clinicians and allied health science professionals, although female athletes are still significantly under-represented in sport and exercise science research. Women have faced exclusion throughout history though the complexities of sociocultural marginalization and biomedical disinterest in women's health. These complexities have contributed to challenges of studying women and examining sex differences. One underlying complexity to methodological design may be hormonal perturbations of the menstrual cycle. The biphasic responses of oestrogen and progesterone across the menstrual cycle significantly influence physiological responses, which contribute to exercise capacity and adaptation in women. Moreover, oral contraceptives add complexity through the introduction of varying concentrations of circulating exogenous oestrogen and progesterone, which may moderate physiological adaptations to exercise in a different manner to endogenous ovarian hormones. Thus, applied sport and exercise science research focusing on women remains limited, in part, by poor methodological design that does not define reproductive status. By highlighting specific differences between phases with regard to hormone perturbations and the systems that are affected, methodological inconsistencies can be reduced, thereby improving scientific design that will enable focused research on female athletes in sports science and evaluation of sex differences in responses to exercise. The aims of this review are to highlight the differences between endogenous and exogenous hormone profiles across a standard 28-32 day menstrual cycle, with the goal to improve methodological design for studies exploring sex differences, menstrual cycle phase differences and/or endogenous versus exogenous female sex hormones.
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Introduction: The aim of this review is to provide methodological recommendations for menstrual cycle research in exercise science and sports medicine based on a review of recent literature. Research in this area is growing, but often reports conflicting results and it is proposed that some of this may be explained by methodological issues. Methods: This review examined the menstrual cycle verification methodologies used in recent literature on exercise performance over the menstrual cycle identified through a literature search of PubMed and SportDiscus from 2008 until 2018. Results: Potential changes over the menstrual cycle are likely related to hormone fluctuations, however, only 44% of the selected studies measured the actual concentrations of the female steroid hormones estrogen and progesterone. It was shown that the likely inclusion of participants with anovulatory or luteal phase deficient cycles in combination with small participant numbers has impacted results in recent menstrual cycle research and consequently our understanding of this area. Conclusion: To improve the quality of future menstrual cycle research it is recommended that a combination of three methods is used to verify menstrual cycle phase: the calendar-based counting method combined with urinary luteinizing hormone surge testing and the measurement of serum estrogen and progesterone concentrations at the time of testing. A strict luteal phase verification limit of >16 nmol·L for progesterone should be set. It is also recommended that future research focusses on the inclusion of the late follicular estrogen peak. It is envisaged that these methodological recommendations will assist in clarifying some of the disagreement around the effects of the menstrual cycle on exercise performance and other aspects of exercise science and sports medicine.
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The present paper endeavored to elucidate the topic on the effects of morning vs. evening resistance training on muscle strength and hypertrophy by conducting a systematic review and a meta-analysis of studies that examined time of day-specific resistance training. This systematic review was performed in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines with searches conducted through PubMed/MEDLINE, Scopus, and SPORTDiscus databases. The Downs and Black checklist was used for the assessment of the methodological quality of the included studies. Studies that examined the effects of time of day-specific resistance training (while equating all other training variables, such as training frequency and volume, between the groups) on muscle strength and/or muscle size, were included in the present review. The random-effects model was used for the meta-analysis. Meta-analyses explored: (1) the differences in strength expression between morning and evening hours at baseline; (2) the differences in strength within the groups training in the morning and evening by using their post-intervention strength data from the morning and evening strength assessments; (3) the overall differences between the effects of morning and evening resistance training (with subgroup analyses conducted for studies that assessed strength in the morning hours and for the studies that assessed strength in the evening hours). Finally, a meta-analysis was also conducted for studies that assessed muscle hypertrophy. Eleven studies of moderate and good methodological quality were included in the present review. The primary findings of the review are as follows: (1) at baseline, a significant difference in strength between morning and evening is evident, with greater strength observed in the evening hours; (2) resistance training in the morning hours may increase strength assessed in the morning to similar levels as strength assessed in the evening; (3) training in the evening hours, however, maintains the general difference in strength across the day, with greater strength observed in the evening hours; (4) when comparing the effects between the groups training in the morning vs. in the evening hours, increases in strength are similar in both groups, regardless of the time of day at which strength assessment is conducted; and (5) increases in muscle size are similar irrespective of the time of day at which the training is performed.
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Measurement of lower limb strength, power and asymmetries of soccer players is important for monitoring physical development and injury risk. The aim of the present study was to establish the reliability and limits of meaningful change of single and double leg maximal strength, power and bilateral imbalance measures in elite soccer players using a pneumatic resistance based seated leg press. Thirteen participants undertook an incremental resistance leg press test on three separate testing days within a seven day period. Paired t-tests established no significant differences (p > 0.156) between consecutive tests, whilst 'good' reliability (intraclass correlation coefficient-ICC >0.762) and acceptable typical percentage errors (< 6.9%) were observed for maximal resistance, velocity and force pushed as well as average and peak power outputs. Imbalance variables accounting for left and right leg average power output across all repetitions were established as the most reliable imbalance variables, with 'good' reliability (ICC > 0.874) and absolute typical error values of 2.1%. Imbalance variables calculated using peak power output or average power output from the last 4 repetitions resulted in weaker reliability (ICC < 0.657) and significant differences between tests, and therefore were considered less suitable for applied use. Subsequently, to better inform the practitioner, limits of meaningful change were calculated for all strength, power and imbalance variables. The current study shows that lower limb strength, and power output variables and average imbalance measures of soccer players assessed through a seated leg press protocol show acceptable levels of reliability, and provides practitioners with limits of meaningful change around parameters to better evaluate test results.
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Myllyaho, MM, Ihalainen, JK, Hackney, AC, Valtonen, M, Nummela, A, Vaara, E, Häkkinen, K, Kyröläinen, H, and Taipale, RS. Hormonal contraceptive use does not affect strength, endurance, or body composition adaptations to combined strength and endurance training in women. J Strength Cond Res XX(X): 000-000, 2018-This study examined the effects of a 10-week period of high-intensity combined strength and endurance training on strength, endurance, body composition, and serum hormone concentrations in physically active women using hormonal contraceptives (HCs, n = 9) compared with those who had never used hormonal contraceptives (NHCs, n = 9). Training consisted of 2 strength training sessions and 2 high-intensity running interval sessions per week. Maximal bilateral isometric leg press (Isom), maximal bilateral dynamic leg press (one repetition maximum [1RM]), countermovement jump (CMJ), a 3,000-m running test (3,000 m), body composition, and serum hormone levels were measured before and after training between days 1-5 of each subject's menstrual cycle. Both groups increased 1RM and CMJ: HC = 13.2% (p < 0.001) and 9.6% (p < 0.05), and NHC = 8.3% (p < 0.01) and 8.5% (p < 0.001). Hormonal contraceptive improved 3,000 m by 3.5% (p < 0.05) and NHC by 1% (n.s.). Never used hormonal contraceptive increased lean mass by 2.1% (p < 0.001), whereas body fat percentage decreased from 23.9 ± 6.7 to 22.4 ± 6.0 (-6.0%, p < 0.05). No significant changes were observed in body composition in HC. No significant between-group differences were observed in any of the performance variables. Luteinizing hormone concentrations decreased significantly (p < 0.05) over 10 weeks in NHC, whereas other hormone levels remained statistically unaltered in both groups. It seems that the present training is equally appropriate for improving strength, endurance, and body composition in women using HC as those not using HC without disrupting hypothalamic-pituitary-gonadal axis function.
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Due to increased longevity, women can expect to live more than one-third of their lives in a post-menopausal state, which is characterised by low circulating levels of oestrogen and progesterone. The aim of this review is to provide insights into current knowledge of the effect of female hormones (or lack of female hormones) on skeletal muscle protein turnover at rest and in response to exercise. This review is primarily based on data from human trials. Many elderly post-menopausal women experience physical disabilities and loss of independence related to sarcopenia, which reduces life quality and is associated with substantial financial costs. Resistance training and dietary optimisation can counteract or at least decelerate the degenerative ageing process, but lack of oestrogen in post-menopausal women may reduce their sensitivity to these anabolic stimuli and accelerate muscle loss. Tendons and ligaments are also affected by sex hormones, but the effect seems to differ between endogenous and exogenous female hormones. Furthermore, the effect seems to depend on the age, and as a result influence the biomechanical properties of the ligaments and tendons differentially. Based on the present knowledge oestrogen seems to play a significant role with regard to skeletal muscle protein turnover. Therefore, oestrogen/hormonal replacement therapy may counteract the degenerative changes in skeletal muscle. Nevertheless, there is a need for greater insight into the direct and indirect mechanistic effects of female hormones before any evidence-based recommendations regarding type, dose, duration and timing of hormone replacement therapy can be provided.