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Medicine & Science in Sports & Exercise® Published ahead of Print contains articles in unedited manuscript form that have been peer reviewed and accepted for publication. This manuscript will undergo copyediting, page composition, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered that could affect the content.
Copyright © 2017 American College of Sports Medicine
Muscle Strength Influences Pressor Responses to Static Handgrip
in Men and Women
Karambir Notay
1, Jordan B. Lee
1, Anthony V. Incognito
1,
Jeremy D. Seed1, Adam A. Arthurs
1, and Philip J. Millar
1,2
1Department of Human Health and Nutritional Sciences, University of Guelph, Guelph,
Ontario, Canada; 2
Toronto General Research Institute, Toronto General Hospital,
Toronto, Ontario, Canada
Accepted for Publication: 6 November 2017
Muscle Strength Influences Pressor Responses to Static Handgrip in Men and
Women
Karambir Notay1, Jordan B. Lee
1, Anthony V. Incognito
1,
Jeremy D. Seed1, Adam A. Arthurs
1, and Philip J. Millar
1,2
1Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario,
Canada; 2
Toronto General Research Institute, Toronto General Hospital, Toronto, Ontario,
Canada
Address for Correspondence and requests for reprints:
Philip J. Millar, PhD
ANNU 348A, 50 Stone Road East, Guelph, Ontario, Canada, N1G2W1
Telephone: 519-824-4120 x54818
Email: [email protected]
This research was supported by a Natural Science and Engineering Research Council of Canada (NSERC)
Discovery Grant (P.J.M. #06019), the Canada Foundation for Innovation (P.J.M. #34379), and the
Ontario Ministry of Research, Innovation, and Science (P.J.M. #34379). An Ontario Graduate
Scholarship (OGS) supported J.B.L. A Queen Elizabeth II Graduate Scholarship in Science and
Technology supported A.V.I. The authors declare no conflicts of interest relevant to the content of this
study. The authors declare that the results of the study are presented clearly, honestly, and without
fabrication, falsification, or inappropriate data manipulation and do not constitute endorsement by the
American College of Sports Medicine.
Medicine & Science in Sports & Exercise, Publish Ahead of Print DOI: 10.1249/MSS.0000000000001485
Copyright © 2017 by the American College of Sports Medicine. Unauthorized reproduction of this article is prohibited.
Abstract
Purpose: Whether differences in absolute muscle strength impact blood pressure (BP) responses
to relative intensity static exercise remains controversial but could contribute to known sex-based
differences and influence the interpretation of cross-sectional data. Methods: One hundred
thirty-two healthy participants (66 men and 66 women, age: 22±3yrs) underwent continuous
seated measurements of BP (Finometer) and heart rate (electrocardiography) during baseline rest
and two minutes of static handgrip (30% maximal voluntary contraction [MVC]). BP and heart
rate responses were quantified in 30-second epochs during exercise and compared between men
and women with and without statistical adjustment (ANCOVA) for differences in baseline BP
(or heart rate), forearm girth, and handgrip MVC. Within each sex, BP and heart rate responses
were compared also between tertiles of handgrip MVC (n=22 per group). Results: Men had
larger systolic, diastolic, and mean arterial pressure responses during static handgrip than women
(interaction term, All P<0.0005), though heart rates responses were similar (interaction term,
P=0.25). These sex-based BP differences persisted following statistical adjustment for
differences in baseline BP or forearm girth, however, controlling for handgrip MVC abolished
differences in BP responses during static handgrip exercise between men and women (interaction
term, All P>0.35). In men, BP responses were smaller within the lowest tertile of handgrip MVC
(interaction term, All P<0.006), while in women, BP responses were larger within the highest
tertile of handgrip MVC (interaction term, All P<0.04). Conclusion: Our findings suggest an
important between- and within-sex role of absolute handgrip strength in mediating the BP
response to static handgrip exercise and highlight the importance of controlling for inter-
individual differences in future work.
Key Words: Hemodynamic; Sex differences; Maximal voluntary contraction; Muscle mass;
Exercise
Copyright © 2017 by the American College of Sports Medicine. Unauthorized reproduction of this article is prohibited.
Introduction
Exercise is considered a valuable, non-invasive perturbation to uncover physiologically-
relevant differences in cardiovascular or autonomic function between groups that are not
apparent at rest (1,2). One of the most studied exercise modes involves submaximal static
handgrip contractions (i.e. 20-50% of maximal volitional contraction [MVC]) completed for a set
duration (e.g. 1 to 3 minutes) (3–10) or until failure (11–19). Static exercise produces
reproducible increases in heart rate and blood pressure (BP) through cardiac parasympathetic
withdrawal and sympathetic activation (20,21), though large inter-individual variability in
pressor responses exist (9).
The magnitude of cardiovascular responses to static exercise are thought to be governed
primarily by both the relative intensity and duration of the contraction, independent of the
amount of contracting muscle mass or absolute tension generated (22). However, the latter
assertions remain controversial as numerous small-scale studies have reported differences in BP
responses during similar relative intensity static handgrip and leg exercise (i.e. differences in
muscle mass) (23–25) or within participants when comparing the dominant to the non-dominant
leg with different absolute strength (24). Sex-based differences in absolute muscle strength (26)
parallel also observations that men demonstrate larger BP responses to fixed-duration (e.g. 2 - 3
minutes) 30% MVC static handgrip contractions than women (3–7). Unfortunately, prior studies
examining sex comparisons did not address specifically whether controlling for baseline
differences in muscle mass or strength ameliorated differences between men and women in
hemodynamic responses during static handgrip exercise. Additionally, men and women routinely
present with different resting BP values (15), which may impact responses due to regression to
the mean (27).
Copyright © 2017 by the American College of Sports Medicine. Unauthorized reproduction of this article is prohibited.
Supporting an important contribution of muscle strength in determining hemodynamic
responses to static handgrip exercise, inter-individual differences in relative force are negatively
correlated to static handgrip time-to-failure (12–14). As a result, even when completing a static
contraction at the same relative intensity those with higher target forces will fatigue earlier
causing intensity differences between participants during prolonged contractions. In prior work,
normalizing for static handgrip time-to-failure has abolished sex-based differences in BP
responses during 20-40% MVC static handgrip exercise in some (12,14,16,18,19) but not all
(11,13,15,17) studies. A major limitation of assessing static handgrip time-to-failure is that it can
be influenced by perception of effort through somatosensory, neurocognitive (e.g. learned
experience), psychological, and hedonistic (e.g. forearm discomfort/pain) inputs in order to reach
true physiological failure (28–30). Early termination of a contraction (due to disinterest or
discomfort) would confound normalization of BP and heart rate responses.
Therefore, the purpose of the study was to investigate, in a large cohort of 132 healthy
young men and women, potential sex differences in hemodynamic responses to 30% MVC static
handgrip exercise, with and without adjustment for differences in resting baseline BP, forearm
girth, and handgrip strength. To further probe the confounding role of handgrip strength, we
compared, within each sex, the hemodynamic responses to static handgrip exercise within tertiles
of handgrip MVC. We hypothesize that 1) males will have larger BP responses to static handgrip
than women but that these differences will be abolished following adjustment of baseline
covariates; and 2) within each sex, differences in BP responses will be detected across tertiles of
muscle strength.
Copyright © 2017 by the American College of Sports Medicine. Unauthorized reproduction of this article is prohibited.
Methods
Participants
One hundred thirty-two young healthy recreationally active men (n=66) and women
(n=66) were studied between January-August 2017 after providing informed written consent. All
of the women self-reported that they possessed a regular 28-day menstruation cycle and were
studied during the early follicular phase (between days 1-5). If women reported taking oral
contraception (n=29), they were studied similarly during the first five days of their placebo pills
to align with the early follicular phase. All participants where free of known cardiovascular or
metabolic disease and did not consume any chronic medications other than oral contraception.
The University of Guelph Research Ethics Board approved all procedures.
Experimental Protocol
Prior to the testing visit participants were asked to refrain from caffeine, alcohol, and
vigorous exercise for a minimum of 24 hours. Participants were studied for a single visit in a
light and temperature controlled laboratory. Following voiding and collection of anthropometric
measurements, participants were positioned upright on a comfortable chair with their feet up on
an ottoman for the duration of the study. To determine MVC, participants were asked to execute
two maximal handgrip contractions (Lafayette Instrument, Lafayette, LA) in their left hand. Nine
participants were left-handed (5 men; 4 women). Each contraction lasted ~3 seconds and was
separated by at least 30 seconds of rest. The highest value was taken as MVC. Forearm girth was
measured as the point of greatest circumference around the proximal quarter of the left forearm
using a measuring tape to the nearest tenth of a centimeter (31).
Copyright © 2017 by the American College of Sports Medicine. Unauthorized reproduction of this article is prohibited.
After instrumentation (~10 minutes), continuous measures of heart rate and BP, as well
as discrete minute-to-minute brachial BP were collected simultaneously over a five minute
resting baseline. Following the rest protocol, participants underwent continuous measurements of
heart rate and BP during a two minute baseline and two minute static handgrip contraction at
30% MVC.
Measurements
Single-lead electrocardiography (Lead II) was used to obtain beat-to-beat HR
(ADInstruments Pty Ltd, Australia). Discrete resting BP was measured from the left brachial
artery on a minute-to-minute basis using an automated sphygmomanometer (BPTru Medical
Devices, Coquitlam, Canada). Continuous beat-to-beat BP was recorded from the right middle
finger using photoelectric plethysmography (Finometer MIDI, Finapres Inc, Netherlands) to
monitor hemodynamic responses during static handgrip. All continuous data was digitized and
stored with LabChart (PowerLab, ADInstruments, Colorado Springs, CO) at a sampling
frequency of 1000 Hz.
Data and Statistical Analysis
Heart rate and BP measurements were averaged over the two minute baseline and in 30-
second epochs during static handgrip exercise; the changes from baseline were used for
statistical analyses. To examine the effects of handgrip strength on heart rate and BP responses
within men and women separately, each sex underwent division into tertiles (n=22 in each
group) based on handgrip MVC.
Copyright © 2017 by the American College of Sports Medicine. Unauthorized reproduction of this article is prohibited.
Statistical analyses were performed using IBM SPSS Statistics 24 (Armonk, NY) and
GraphPad Prism (GraphPad Software, La Jolla, CA). The Shapiro-Wilk test was used to assess
normality; only heart rate responses to static handgrip exercise were not normally distributed and
underwent mathematical transformation to achieve normality. Baseline characteristics between
men and women were assessed using unpaired two-tailed t-tests. Two-way mixed model
repeated measure analyses of variance (ANOVA) were used to evaluate the changes in
hemodynamic variables during static handgrip exercise both between sexes, and within male and
female tertiles separately. Similar two-way ANOVAs were used to compare directly heart rate
and BP responses between men and women matched for handgrip MVC. Significant main effects
and interactions were probed using Bonferroni post-hoc tests. To control for sex differences in
baseline BP (or heart rate), forearm girth, and/or handgrip MVC on heart rate and BP responses
to static handgrip exercise, data were analyzed using an analysis of covariance (ANCOVA). We
completed three ANCOVA models to test the effects of each covariate independently. Model one
was used to covariate baseline BP (or heart rate); model two to covariate forearm girth; and
model three to covariate handgrip MVC. Significance was considered P<0.05. Data presented as
mean ± SD, unless otherwise stated.
Results
Baseline participant characteristics comparing men and women are found in Table 1.
Participants were matched for age, body-mass index, diastolic BP, and mean arterial pressure
(All P>0.05), though height, body weight, handgrip MVC, and forearm girth were all larger in
men (All P<0.0001). Compared to women, men also had higher resting systolic BP (P=0.0009)
and lower resting heart rate (P<0.0001).
Copyright © 2017 by the American College of Sports Medicine. Unauthorized reproduction of this article is prohibited.
Effect of sex
Heart rate and BP increased during static handgrip exercise (time effect, all P<0.0001).
Systolic BP responses were different between men and women at 60 seconds (P=0.003), 90
seconds (P<0.0001), and 120 seconds (P<0.0001); diastolic BP responses were different at 90
seconds (P=0.0005) and 120 seconds (P=0.0001); and mean arterial pressure responses were
different at 60 seconds (P=0.04), 90 seconds (P=0.0001), and 120 seconds (P<0.0001). Heart
rate responses were not different between men and women (interaction term, P=0.25) (Figure 1).
Table 2 displays P-values for the main effect of sex and the interaction term after
adjusting for baseline differences in baseline BP (or heart rate), forearm girth, or handgrip MVC.
Statistical adjustment for baseline BP and forearm girth had no effect on the observed differences
in BP responses between men and women. In contrast, adjustment for handgrip MVC abolished
all sex-based differences in BP responses. To confirm this observation, we matched the 12
weakest men and 12 strongest women (MVC: 37 ± 3 kg vs. women: 36 ± 2 kg, P=0.54) and
found no significant main effects of sex (All P>0.16) or sex*time interactions (All P>0.35) for
heart rate and BP responses to static handgrip exercise.
Across the entire cohort, handgrip MVC was positively associated with systolic BP
(r=0.42; P<0.0001), diastolic BP (r=0.37; P<0.0001), mean arterial pressure (r=0.40; P<0.0001),
and to a lesser extent heart rate (r=0.22; P=0.01).
Influence of handgrip MVC on static handgrip responses in men
In men, the mean handgrip MVC was 39 ± 4 kg (range: 32-43 kg) in the first tertile, 46 ±
2 kg (range: 43-49 kg) in the second tertile, and 58 ± 7 kg (range: 50-75 kg) in the third tertile.
Systolic BP responses were larger in tertile two and three compared to tertile one during 60
seconds (P=0.01 and P=0.005, respectively), 90 seconds (P=0.003 and P=0.001, respectively),
Copyright © 2017 by the American College of Sports Medicine. Unauthorized reproduction of this article is prohibited.
and 120 seconds (Both P<0.0001). Diastolic BP responses were higher in tertile two compared to
tertile one at 60 seconds (P=0.04), while both tertile two and three were greater than tertile one at
90 seconds (P=0.002 and P=0.006, respectively) and 120 seconds (Both P<0.0001). Mean
arterial pressure responses were higher in tertile two and three compared to tertile one at 60
seconds (P=0.01 and P=0.02, respectively), 90 seconds (Both P=0.001) and 120 seconds (Both
P<0.0001). Heart rate responses were also greater in tertile two and three at 90 seconds
compared to tertile one (Both P=0.02) and tertile three was greater than tertile one at 30 seconds
(P=0.02), at 60 seconds (P=0.03), and 120 seconds (P=0.01). There were no differences between
tertile two and three for any variable (Figure 2).
Influence of handgrip MVC on static handgrip responses in women
In women, the mean handgrip MVC was 21 ± 4 kg (range: 13-25 kg) in the first tertile,
27 ± 1 kg (range: 25-29 kg) in the second tertile, and 34 ± 3 kg (range: 29-41 kg) in the third
tertile. Systolic BP responses were greater in tertile three compared to tertile two during 60
seconds (P=0.001), and greater than both tertile one and two at 90 seconds (P=0.03 and
P<0.0001, respectively) and 120 seconds (P=0.001 and P<0.0001, respectively). Diastolic BP
responses were higher in tertile three compared to tertile two at 60 seconds (P=0.02) and 90
seconds (P=0.008) and greater than both tertile one and two at 120 seconds (P=0.02 and P=0.01,
respectively). Mean arterial pressure responses were higher in tertile three compared to tertile
one and two at 60 seconds (P=0.048 and P=0.005, respectively) and 120 seconds (P=0.002 and
P=0.003, respectively). Additionally, tertile three had a greater mean arterial pressure response
than tertile two at 90 seconds (P=0.0009). Heart rate was not different between any of the
tertiles. There were no differences between tertile one and two for any variable (Figure 3).
Copyright © 2017 by the American College of Sports Medicine. Unauthorized reproduction of this article is prohibited.
Discussion
The present study sought to examine the effect of sex on BP and heart rate responses to
static handgrip exercise with and without statistical adjustment for differences in baseline BP (or
heart rate), forearm girth, and handgrip MVC. In support of our hypothesis, men had greater BP
responses to static handgrip exercise than women, though no differences in heart rate responses
were observed. After controlling for differences in baseline BP or forearm girth, these sex-based
differences in BP responses persisted. However, following adjustment for differences in
handgrip MVC, the differences in BP responses between men and women were abolished. The
examination of a large data set also permitted a novel examination of the effect of handgrip
MVC on within-sex BP and heart rate responses. These results demonstrate that, in men, BP
responses were smaller within the lowest tertile of handgrip MVC compared to the two stronger
groups, while in women, BP responses were larger in the strongest tertile of handgrip MVC
compared to the two weaker groups. Overall, these results demonstrate the importance of
absolute muscle strength in determining the pressor response to static handgrip exercise and
emphasize the need to control for inter-individual differences.
Prior studies investigating the effect of sex on hemodynamic responses between men and
women during fixed-duration static handgrip exercise failed to account for differences in
baseline BP, muscle strength, or muscle mass, and in some cases restricted analysis to only mean
arterial pressure or failed to account for different phases of the menstrual cycle in women (3–7).
Each of these studies concluded that men demonstrate greater BP responses during static
handgrip compared to women. In an effort to control for confounding effects of muscle strength,
a number of studies have normalized data to account for differences in static handgrip time-to-
failure, which in some studies has eliminated these sex differences (12,14,16,18,19), though
inconsistently as others reported that larger BP responses in men persisted (11,13,15,17).
Copyright © 2017 by the American College of Sports Medicine. Unauthorized reproduction of this article is prohibited.
Additionally, in two studies, females did not possess longer static handgrip time-to-failure
responses, even though they had a lower absolute handgrip MVC than men (15,19). In one of
these studies men demonstrated a greater BP response (15), while the other study showed no BP
differences between men and women (19). This inconsistency in results, combined with time-to-
failure exercises not being comfortable and requiring great motivation to reach true fatigue (28),
potentially makes handgrip to fatigue a non-ideal measure for normalizing between groups.
The primary finding in the present study was that adjustment for handgrip MVC, but not
baseline BP or forearm girth, abolished sex-based differences in BP responses during a 30%
MVC 2-minute static handgrip contraction. This finding emphasizes the importance of absolute
strength on BP responses when performing a relative intensity fixed duration static handgrip
contraction between men and women. Moreover, a second novel finding was that within both
men and women, BP responses differed based on tertile groupings of handgrip MVC. This
finding further supports the notion that absolute strength can impact BP responses during static
handgrip. Interestingly, examination of the strength-based tertiles across the entire cohort
identified three distinct bands of BP responses. The first band consisting of the two weakest
female tertiles, the second consisting of the strongest females and weakest males, and the third
consisting of the two strongest male tertiles. The present study did not investigate the
mechanism(s) responsible for the confounding effects of handgrip MVC on BP responses,
however, we speculate that differences in skeletal muscle fibre type distribution may be
involved. In support of this hypothesis, a higher proportion of fast-twitch brachioradialis muscle
fibres was correlated positively with mean arterial pressure responses (r=0.89) at the end of a two
minute 40% MVC static handgrip contraction (32). Similarly, the diastolic blood pressure
response to two minutes of electrically-evoked static plantar flexion at 30% MVC was related to
fast isomyosin content of the lateral gastrocnemius and soleus (33). Fast-twitch muscle fibres
Copyright © 2017 by the American College of Sports Medicine. Unauthorized reproduction of this article is prohibited.
have been associated with higher rates of metabolite production during static exercise (32,34),
which would stimulate metabolically-sensitive group III/IV skeletal muscle afferents (32,35) that
relay peripheral afferent feedback to increase central sympathetic outflow and ultimately BP
(20,21).
The present findings have important implications for the interpretation of past and future
studies, demonstrating a critical need to control for muscle strength when performing cross-
sectional designs with between-group differences in handgrip MVC. Studies drawing
conclusions from groups with different handgrip MVC may show attenuated hemodynamic
responses or underestimate a true difference in responses between groups. For example,
attenuated BP responses during a two minute static handgrip at 30% MVC were reported in
individuals with down syndrome, although this group had lower absolute handgrip MVC (11.6 ±
1.6 kg) compared to the control group (27.4 ± 2.8 kg) without down syndrome (10). Whether a
true physiological attenuation in BP responses exists may be confounded by the difference in
absolute strength between the two groups. In contrast, Sterns et al. reported no differences in BP
responses during two minutes of static handgrip at 30% MVC between patients with heart failure
and a healthy control group (8). The heart failure group again had weaker absolute handgrip
MVC (38 ± 3 kg) compared to the healthy controls (45 ± 2 kg). This difference in absolute
strength may ultimately underestimate the true difference in BP responses between these two
groups. Therefore, based on the findings from the present study, controlling for differences in
absolute handgrip MVC are essential when comparing between participants.
We acknowledge several limitations in the present study. We studied only young healthy
males and females, which may limit the generalizability to older or diseased cohorts. Similarly,
whether BP responses to larger muscle mass exercise exhibit the same patterns as small muscle
mass handgrip exercise warrants further work. The specific duration and intensity may also
impact the observed findings. We selected the two minute, 30% MVC static handgrip contraction
Copyright © 2017 by the American College of Sports Medicine. Unauthorized reproduction of this article is prohibited.
as it represents one of the most commonly used exercise modes in the literature (3,4,6,8,10),
however, whether similar findings are present with alternative protocols is unclear. Future
studies are required to test BP responses to a variety of relative and absolute intensities to
confirm these results. We also acknowledge that circumferential measurements of forearm girth
provide an indirect estimate of muscle mass (36). Finally, using handgrip MVC to determine
each individual’s relative exercise intensity may not be the best indicator of underlying
metabolic activity (37) and future studies should consider the use of forearm critical force.
Nevertheless, the present results demonstrate that the use of already collected MVC data may
suffice in controlling for inter-individual differences in handgrip strength.
In conclusion, our results demonstrate that the larger BP responses to static handgrip
exercise observed consistently in men compared to women are abolished after adjustment for
handgrip MVC but not baseline BP or forearm girth. Further, we show that differences in
handgrip MVC also are associated with variability in BP responses within both men and women
separately. These findings underscore the importance of controlling for inter-individual
differences in absolute muscle strength when examining cardiovascular responses to exercise.
Acknowledgements
This research was supported by a Natural Science and Engineering Research Council of Canada
(NSERC) Discovery Grant (P.J.M. #06019), the Canada Foundation for Innovation (P.J.M.
#34379), and the Ontario Ministry of Research, Innovation, and Science (P.J.M. #34379). An
Ontario Graduate Scholarship (OGS) supported J.B.L. A Queen Elizabeth II Graduate
Scholarship in Science and Technology supported A.V.I. The authors declare no conflicts of
interest relevant to the content of this study. The authors declare that the results of the study are
presented clearly, honestly, and without fabrication, falsification, or inappropriate data
manipulation and do not constitute endorsement by the American College of Sports Medicine.
Copyright © 2017 by the American College of Sports Medicine. Unauthorized reproduction of this article is prohibited.
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Figure Legends
Figure 1. Systolic blood pressure (A), diastolic blood pressure (B), mean arterial pressure (C), and
heart rate (D) responses during 2 minutes of 30% MVC static handgrip in men (n=66) and women
(n=66); *, P<0.05; **, P<0.01; ***, P<0.001; ****, P<0.0001 vs. women. Mean ± SEM.
Figure 2. Systolic blood pressure (A), diastolic blood pressure (B), mean arterial pressure (C), and
heart rate (D) responses during 2 minutes of 30% MVC static handgrip in men (n=66) divided by
tertiles of handgrip MVC (n=22 in each group). *, P<0.05; **, P<0.01; ***, P<0.001; ****,
P<0.0001 vs. tertile 2. †, P<0.05; ††, P<0.01; †††, P<0.001; ††††, P<0.0001 vs. tertile 3. Mean ±
SEM.
Figure 3. Systolic blood pressure (A), diastolic blood pressure (B), mean arterial pressure (C), and
heart rate (D) responses during 2 minutes of 30% MVC static handgrip in women (n=66) divided by
tertiles of handgrip MVC (n=22 in each group). *, P <0.05; **, P <0.01; ***, P <0.001; ****, P
<0.0001 vs. tertile 1. †, P <0.05; ††, P <0.01; †††, P <0.001; ††††, P <0.0001 vs. tertile 2. Mean ±
SEM.
Copyright © 2017 by the American College of Sports Medicine. Unauthorized reproduction of this article is prohibited.
Copyright © 2017 by the American College of Sports Medicine. Unauthorized reproduction of this article is prohibited.
Copyright © 2017 by the American College of Sports Medicine. Unauthorized reproduction of this article is prohibited.
Copyright © 2017 by the American College of Sports Medicine. Unauthorized reproduction of this article is prohibited.
Table 1. Resting baseline characteristics in men and women.
Characteristic Men (n=66) Women (n=66)
Age (years) 22 ± 3 [18 – 30] 21 ± 2 [18 – 29]
Height (cm) 178 ± 7 [163 – 196] 165 ± 7 [147 – 182]****
Weight (kg) 77 ± 13 [52 – 124] 63 ± 9 [44 – 86]****
Body mass index (kg/m2) 24 ± 3 [18 – 35] 23 ± 3 [17 – 33]
Heart rate (bpm) 63 ± 10 [44 – 92] 71 ± 12 [52 – 101]****
Systolic blood pressure (mmHg) 107 ± 8 [91 – 133] 102 ± 9 [83 – 123]***
Diastolic blood pressure (mmHg) 64 ± 7 [50 – 79] 66 ± 8 [51 – 87]
Mean arterial pressure (mmHg) 79 ± 7 [64 – 97] 78 ± 8 [62 – 99]
Maximal volitional contraction (kg) 48 ± 9 [32 – 75] 27 ± 6 [13 – 41]****
Forearm circumference (cm) 27 ± 2 [22 – 31] 23 ± 2 [19 – 27]****
Mean ± SD [Range]. *, P<0.05; **, P<0.01; ***, P<0.001; ****, P<0.0001 vs. men.
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Table 2. P-values of unadjusted and adjusted models for sex (group) and sex*time (interaction)
effects.
Variable Unadjusted Model 1
Model 2 Model 3
Sex Sex*Time Sex Sex*Time Sex
Sex*Time Sex Sex*Time
Systolic blood pressure <0.0001 <0.0001 <0.0001 <0.0001 0.03
0.01 0.68 0.59
Diastolic blood pressure 0.001 0.0005 0.002 0.001 0.03
0.03 0.43 0.35
Mean arterial pressure 0.0003 <0.0001 0.0003 <0.0001 0.03
0.01 0.47 0.50
Heart rate 0.53 0.25 0.78 0.25 0.74
0.29 0.04 0.07
Model 1 covariates baseline blood pressure or heart rate; Model 2 covariates forearm girth;
Model 3 covariates handgrip maximal volitional contraction.
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