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THE EFFECTS OF BIOLOGICAL SEX ON FATIGUE DURING AND RECOVERY FROM
RESISTANCE EXERCISE
Gregory Nuckols
A thesis submitted to the faculty at the University of North Carolina at Chapel Hill in partial
fulfillment of the requirements for the degree of Master of Arts in the Department of Exercise
and Sport Science (Exercise Physiology)
Chapel Hill
2019
Approved by:
Claudio L. Battaglini, Ph.D.
Anthony C. Hackney, Ph.D.
Erik D. Hanson, Ph.D.
ii
© 2019
Gregory Nuckols
ALL RIGHTS RESERVED
iii
ABSTRACT
Gregory Nuckols: The effects of biological sex on fatigue during and recovery from resistance
exercise
(Under the direction of Dr. Claudio L. Battaglini)
The purpose of this study was to investigate sex differences in fatigability and recovery
from resistance exercise. Male and female subjects with at least one year of bench press
experience (N = 21 males and 21 females) performed a fatigue protocol consisting of barbell
bench press with 75% 1RM loads for sets of 5 repetitions, with 90 seconds between sets, until
concentric failure. Recovery was monitored for the subsequent 72 hours using subjective ratings
of soreness and estimated 1RM strength derived from load-velocity profiles. The female
subjects completed more reps during the fatigue protocol (Females: 58.3 ± 27.3; Males: 29.6 ±
10.6; p = 0.0001), but post-training soreness and recovery of estimated 1RM strength did not
significantly differ between sexes. Results suggest that women fatigue slower than men during
multiple sets of bench press, and can recover from training at a similar rate despite completing a
larger relative workload.
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ACKNOWLEDGMENTS
I would like to thank my wife, Lyndsey Nuckols, for everything she’s done to help me
out over the past two years of grad school. Without her, I probably would have either failed out
of the program, died, or (probably) both. I’d like to thank Dr. Battaglini for his patience,
understanding, and mentorship thoughout my whole time in the Master’s program. I’d like to
thank the other members of my committee, Drs. Hackney and Hanson, for their help with
designing and refining the protocols used in this study. I’d like to thank the people who
participated in this study; they were all a joy to work with, and they were willing to sink several
hours of their lives into participating without any financial compensation. I’d like to thank all
my friends in the graduate program for the large amount of emotional support they may or may
not have realized they were providing, especially Stephanie Sullivan, Jordan Lee, Chad
Wagoner, and Eric Trexler. I’d like to thank Jason Beaulieu for allowing me to conduct data
collection in the women’s basketball weightroom. Finally, I’d like to thank Dale Keith for
helping me out with a lot of my research visits, purely out of the goodness of his heart.
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TABLE OF CONTENTS
LIST OF TABLES……………………………………………………………………………….vii
LIST OF FIGURES……………………………………………………………………………..viii
CHAPTER I: INTRODUCTION…………………………………….…………………………...1
Statement of Purpose……………………………………….……………………………..5
Hypotheses…………………………………….…………………………………………..6
Limitations…………………………………………………….…………………………..6
Delimitations……………………………………….……………………………………...7
Definition of terms…………………………………….……………...…………………...8
Assumptions…………….………………………………………………………………..10
Significance……………………..………………………………………………………..11
CHAPTER II: REVIEW OF LITERATURE………………………….………………..............12
Sex differences in fatigue…….…………………………………………………………..12
Sex differences in recovery.…………….………………………………………………..21
Other contributing factors…………………..……………………………………………25
Summary………………………………….……………………………...........................26
CHAPTER III: METHODS………………………….………………………………….............27
Subjects….…………………………….…………………………………………………27
Experimental Design………………………………………….………………………….27
Data Collection and Instrumentation………………………………….…………………28
Baseline Assessments…………….……...………………………………………………31
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Fatiguing Resistance Exercise Protocol………………………..………...........................33
Recovery Assessments………………………..………………………………………….33
Statistical Analyses………………….…………………………………...........................34
CHAPTER IV: RESULTS……………………………………………………………..………..37
CHAPTER V: DISCUSSION………………………………………………………...…………47
APPENDIX A: INFORMED CONSENT FORM……………………………............................55
APPENDIX B: SURVEYS AND QUESTIONNAIRES………………………………………..63
APPENDIX C: DATA COLLECTION SHEETS………………………………………………75
REFERENCES…………………………………………………………………………………..81
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LIST OF TABLES
TABLE 1: Descriptive Characteristics of the Subjects………………...……..…….……………44
TABLE 2: Performance and Training Characteristics……………………...……………………46
viii
LIST OF FIGURES
FIGURE 1: Sex Differences in Reps Completed……………….…………….………………….45
FIGURE 2: Recovery of Predicted 1RM Strength………………………………….…………...47
FIGURE 3: Soreness Following Fatigue Protocol……………………………………………….49
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CHAPTER I: INTRODUCTION
Resistance training is commonly employed by strength and conditioning professionals to
increase athletic performance, and by recreational athletes to increase strength and improve body
composition. Most guidelines for resistance training prescription, including those of the ACSM
(ACSM, 2014), do not consider sex, even though sex may influence responses and adaptations to
resistance training. Most research in exercise science is performed on men (Costello, 2014), so
the current resistance training guidelines may not be optimal for females.
Meta-analyses have demonstrated that higher training volumes are associated with larger
strength gains (Schoenfeld, 2017) and more muscular hypertrophy (Ralston, 2017). However,
some research indicates that excessive training volume can hinder strength gains (González-
Badillo, 2006) or muscular hypertrophy (Amirthalingham, 2017). It’s thought that excessive
training volume compromises positive adaptations by exceeding the body’s capacity to recover
from exercise. Thus, resistance exercise prescription must balance the benefits of higher
resistance exercise training volume, against the risk of decreasing adaptations by exceeding the
individual’s capacity to recover from training. If there are sex differences in the rate at which
men and women fatigue during a resistance training session, or the rate at which they recover
from resistance training, that may indicate that optimal resistance training volume differs
between the sexes.
Causes of fatigue during a resistance training session are not fully delineated. However, it
is believed that anaerobic metabolism and the associated drop in muscle pH and accumulation of
2
inorganic phosphate is a primary contributor (Metzger, 1990; Westerblad, 2002; Allen, 2012).
The anaerobic fatigue induced by resistance training is influenced by muscle blood flow. Intense
muscular contractions can partially occlude arteries (Hunter, 2001), limiting blood flow and
oxygen delivery; when this occurs, anaerobic glycolysis must increase to match the energetic
demands of exercise (Russ, 2003), leading to a drop in pH and accumulation of inorganic
phosphase. The drop in pH and accumulation in muscle phosphate attenuates Ca2+ release from
the sarcoplasmic reticulum, decreases the affinity of troponin C for Ca2+, and interferes with
cross bridge cycling, thus decreasing muscle force (Metzger, 1990; Westerblad, 2002; Allen,
2012; Wan, 2017). Since women have smaller muscles than men, on average, they experience
less arterial occlusion during forceful contractions, possibly decreasing the rate of fatigue during
resistance exercise (Hunter, 2014).
The factors contributing to neuromuscular recovery after a resistance training session are
not fully delineated, but it is known that full neuromuscular recovery takes longer to accomplish
in the presence of higher muscle damage (Byrne, 2004). This is illustrated by the fact that trained
lifters recover their strength after training faster than untrained lifters, due to the collection of
adaptations known as the repeated bout effect, which work to limit muscle damage (Hyldahl,
2017). It is thought that women experience less muscle damage than men after exercise, and that
women repair muscle damage after faster than men, as higher estrogen levels have been shown to
attenuate muscle damage and accelerate muscular regeneration. This evidence was summarized
by Enns and Tiidus (2010). However, this is not a unanimous finding in the literature (Stupka,
2000).
There is a considerable amount of research examining sex differences in acute fatigability
during resistance exercise. It was most thoroughly summarized by Hunter (Hunter, 2014; Hunter,
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2016). In general, women seem to fatigue more slowly than men during resistance exercise. The
primary mechanism seems to be greater preservation of muscle blood flow due to lower levels of
muscle mass (Hunter, 2001), but other potential reasons for lower fatigability in women include
a greater proportion of type I muscle fibers (Hunter, 2014), and a lower reliance on anaerobic
metabolism during submaximal exercise (Bunt, 1990; McCracken, 1994; Hackney, 1999;
Lundsgaard, 2014). However, most of the studies examining sex differences in fatigability
during resistance exercise involve the use of submaximal isometric contractions, which is not
reflective of typical practices in strength and conditioning. Less is known about sex differences
in fatigability during dynamic, isotonic resistance exercise. Of the studies examining sex
differences in fatigability during dynamic, isotonic resistance exercise, many confirm that
women are less fatigable (Lanning, 2017; Senefeld 2013; Maughan, 1986; Yoon, 2015; Ribeiro,
2014; Flanagan, 2014), while others find that men and women fatigue at similar rates
(Mendonca, 2018; Reynolds, 2006; Pincivero, 2004; Clark, 2003), though only one study with a
multi-set protocol has found that men are less fatigable than women (Monteiro, 2017).
There is less research examining sex differences in recovery from resistance exercise.
Several studies have examined sex differences in post-exercise muscle soreness and sex
differences in indirect markers of muscle damage, such as creatine kinase. Some find that men
and women either experience similar soreness and elevations in markers of muscle damage
(Benini, 2015; Flores, 2011), while others indicate that women experience less soreness and
smaller elevations in markers of muscle damage (Wolf, 2012; Amorim, 2014; Baggett, 2015).
However, studies examining sex differences in recovery of neuromuscular performance remain
scarce. One study found that women recovered 1RM strength sooner than men after a 5RM
testing session than men (Judge, 2010), while another study found that training volume
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performed during a full-body workout was similarly suppressed 24-hours after resistance training
in both men and women (Baggett, 2015). Finally a more recent study found that isokinetic
concentric knee extension torque and countermovement jump height were suppressed to a greater
extent in women than in men 24 hours after a squat training (Davies, 2018). Thus, it remains
unclear if men and women recover from resistance training at different rates.
One challenge when the studying recovery of strength after resistance exercise is that
maximal strength testing after fatiguing exercise imposes ethical and methodological dilemmas.
Testing 1RMs may be dangerous when a subject is already fatigued. Furthermore, any maximal
strength testing could also induce further fatigue, and thus repeated maximal testing to monitor
the progression of recovery could impact the rate of recovery after training, revealing a pattern of
recovery that differs the recovery rate that would have occurred had repeated maximal strength
testing not been performed. An alternate approach for monitoring strength recovery is the use of
submaximal testing, which should be safer for the subjects, and should not induce as much
additional fatigue as repeated maximal strength testing. Load-velocity profiles, established using
submaximal intensities, have been shown to accurately predict 1RM strength (Jidovtseff, 2011;
Pestaña-Melero, 2018), and within-lifter load-velocity profiles have been shown to be stable and
reliable (Banyard, 2018). Thus, changes in load-velocity profiles after a resistance training
session can be used to monitor strength recovery without the need for repeated maximal strength
testing.
In strength and conditioning contexts, resistance exercise is generally performed with
dynamic, isotonic exercises. Resistance training is often not performed to failure on every set, as
training to failure does not seem to enhance strength gains (Davies, 2016), and may increase
injury risk (Nóbrega, 2016). However, most of the literature examining sex differences in
5
fatigability and recovery, summarized by Hunter (2014), has either used isometric or isokinetic
exercise, or has employed training protocols where all sets are performed to failure. Thus, the
generalizability of this prior research to practice by strength and conditioning professionals is
limited. Therefore, this study will add to the literature by examining sex differences in
fatigability during resistance training and recovery from resistance exercise using a protocol that
is more reflective of current practices among strength and conditioning professionals.
STATEMENT OF PURPOSE
The primary purposes of this study were to determine if men and women fatigue at
different rates during a single resistance exercise session, and to determine if men and women
recover strength at different rates following a single resistance exercise session. The secondary
purpose of this investigation was to determine muscle soreness decreases at different rates in
men and women following a single fatiguing resistance training session, and if predicted 1RM
strength recovers at different rates following a single fatiguing resistance training session. A
tertiary purpose was to examine whether sex differences in fatigability could be explained by
differences in arm lean mass.
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HYPOTHESES
H1: Women will fatigue slower than men during a single resistance exercise session, as
assessed by completing more total reps when performing submaximal sets of resistance exercise
until the point of failure
H2a: If women fatigue slower than men during a single resistance exercise session, and
thus complete more reps during the session, they will recover from the session at the same rate as
men, as assessed by estimated 1RM returning to baseline and muscle soreness attenuating at a
comparable rate in both sexes.
H2b: If women do not fatigue slower than men during a single resistance exercise
session, and thus complete a comparable number of reps during the session, they will recover
from the session faster than men, as assessed by estimated 1RM returning to baseline sooner and
muscle soreness attenuating faster in women than in men.
H3: Differences in arm lean mass will explain the sex differences in fatigability.
LIMITATIONS
• Recovery was assessed by estimating 1RM from load-velocity profiles
using a submaximal test, not by actually testing 1RM.
• Reported delayed onset muscle soreness (DOMS) is a subjective
assessment, and may be subject to differing perceptions of pain between sexes.
• Bench press reps were performed with a brief pause on the chest, which
some subjects were not be familiar with, potentially compromising performance during
the fatiguing exercise session in some subjects more than others.
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• Since the subjects needed to be available for testing on four consecutive
days, it was not possible to test all subjects at the same time of day for every session due
to scheduling conflicts. Thus, diurnal fluctuations in strength may not be fully controlled
for.
• Hormonal contraception usage and menstrual cycle phase for the female
subjects was not controlled.
DELIMITATIONS
• All subjects had at least one year of bench press experience but were not
required to be high-level bench pressers, and thus the results of this study may not
generalize to untrained lifters or elite-level lifters.
• All subjects were between the ages of 18-35 years old, and thus the results
may not generalize to younger or older lifters.
• Load-velocity profiles can be used to estimate 1RM and velocity with
submaximal loads. However, ability to maintain force output over multiple reps may
recover at a different rate, so strength recovery should not be assumed to reflect recovery
of all aspects of neuromuscular performance.
• Differences in metabolic profiles and muscle blood flow may underpin
differences in acute fatigability between sexes, and muscle biopsies would be required to
directly assess muscle damage, which may underpin differences in recovery. Other
research will be required to investigate those potential mechanisms.
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DEFINITION OF TERMS
• Fatigability - the rate at which performance declines during exercise, or
the total decrease in performance observed following a prescribed workload.
• Repeated bout effect - a set of physiological and neurological adaptations
to exercise which limit muscle damage when the same exercise stimulus is repeated.
• Creatine kinase - an enzyme that aid in bonding creatine and inorganic
phosphate. Assessments of creatine kinase are used as indirect indicators of muscle
damage.
• DOMS - delayed onset muscle soreness. The feelings of muscle soreness
that generally peak 24-48 hours after exercise.
• Load-velocity profile - the relationship between resistance exercise
intensity and mean concentric velocity. Load-velocity profiles can be used to estimate
1RM strength from submaximal testing.
• Isometric contraction - a muscle contraction that occurs without the
muscle changing in length.
• Isokinetic contraction - a muscle contraction performed at a fixed speed,
generally aided by the use of a dynamometer.
• Isotonic contraction - a muscle contraction performed against the same
external force, but (typically) with varying speeds throughout the contraction. Isotonic
exercise generally involves an eccentric and concentric component.
• Eccentric contraction - a muscle contraction during which the muscle
lengthens
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• Concentric contraction - a muscle contraction during which the muscle
shortens
• Muscle perfusion - blood flow to the muscle
• Type I muscle fiber - a muscle fiber type characterized by high aerobic
metabolism, low anaerobic metabolism, low fatigability, and slow shortening velocity.
• Type II muscle fiber - a muscle fiber type characterized by low aerobic
metabolism, high anaerobic metabolism, higher fatigability, and fast shortening velocity.
• Aerobic metabolism - the production of ATP in mitochondria in the
presence of oxygen. Aerobic metabolism is associated with a slower rate of fatigue
accumulation during exercise than anaerobic metabolism
• Anaerobic metabolism - the production of ATP within the sarcoplasm
without the use of oxygen. Anaerobic metabolism is associated with a faster rate of
fatigue during exercise than aerobic metabolism.
• Lactate threshold - the exercise intensity at which lactate appearance in
the blood exceeds lactate clearance. Exceeding the lactate threshold indicates increased
reliance on anaerobic metabolism.
• Vasodilation - an increase in blood vessel circumference.
• Occlusion - decreasing blood flow through a blood vessel by increasing
the external pressure on the vessel.
• Fatigue Index - a measure of fatigue accumulated during resistance
exercise, based on the relationship between volume load completed during the first set of
an exercise, and volume load completed during the last set of an exercise. A higher
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fatigue index indicates a greater decrease in volume completed from the first set to the
last set, and thus greater fatigue accumulation.
• Visual analog scale - a scale that can be used for subjective assessments
of various perceptions. In this study, visual analog scales will be used to assess perceived
soreness. Higher values will indicate more soreness, and lower values will indicate less
soreness.
• Sarcolemma - the cell membrane of a muscle fiber.
• Macrophage - an immune cell. When macrophage levels increase in a
muscle, it generally indicates that muscle damage has occured and that local
inflammation is present.
• DEXA - dual energy x-ray absorptiometry. DEXA scans can be used to
assess body composition with relative ease, and considerably accuracy compared to most
other methods of assessing body composition.
ASSUMPTIONS
• It is assumed that subjects were not using supplements or pharmacological
agents that could enhance or decrease performance while enrolled in this study. They
were asked about their usage of such substances, but lab testing was not performed to
guarantee their honesty.
• It is assumed that subjects put forth their full effort and reached true
concentric failure during the fatiguing exercise session. They were reminded and
encouraged to do so.
• It is assumed that subjects were honest about their training history.
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SIGNIFICANCE
Resistance exercise prescription should be informed by the rate at which lifters fatigue
during a resistance training session, and the rate at which they recover from exercise. These
factors inform differing recommendations for untrained versus trained lifters, and for young
versus older adults. However, sex is rarely considered when making guidelines for exercise
prescription, thought there may be sex differences in fatiguability during resistance training or
recovery from resistance training.
Current research, summarized by Hunter (2014), indicates that women may fatigue at a
slower rate during resistance training than men, though research has typically not used protocols
that reflect typical practice in strength and conditioning. Research comparing rates of recovery
from resistance training in men and women is scant and inconclusive. The results of this study
will help clarify whether sex differences in fatigue during resistance training still exist with more
ecologically valid training protocols (dynamic, isotonic exercise, without every set performed to
failure), and will add to the sparse body of literature examining the effects of sex on strength
recovery following resistance training. These results will help guide lifters and strength and
conditioning practitioners when determining whether resistance exercise volume prescriptions
should be moderated by sex.
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CHAPTER II: REVIEW OF LITERATURE
This literature review is organized into three sections. The first section reviews the
research on sex differences in fatigue during resistance exercise. The second section discusses
the research on sex differences in recovery from resistance exercise. The last section addresses
the ways in which training background, muscle mass, sleep, and stress can affect fatigue during
resistance training and recovery from resistance training.
SEX DIFFERENCES IN FATIGUE DURING RESISTANCE TRAINING
Potential mechanisms
Women tend to fatigue during resistance training at a slower rate than men (Hunter,
2014). Sex differences in fatigue may be driven differences in fiber type, differences in reliance
on anaerobic metabolism, and differences in muscle perfusion.
Many studies have compared fiber type ratios in men and women (Simoneau, 1985;
Simoneau, 1989; Miller, 1993; Esbjörnsson-Liljedahl, 1999; Staron, 2000; Carter, 2001;
Esbjörnsson-Liljedahl, 2002; Porter, 2002; Toft, 2003; Roepstoroff, 2006; Maher, 2009;
Esbjörnsson, 2012). Hunter quantitatively assessed these studies, finding that roughly 10% more
of womens’ total muscle mass is composed of type I fibers (p<0.05) (Hunter, 2014). Type I
muscle fibers have greater mitochondrial content and greater aerobic capacity than type II fibers,
and are thus more fatigue resistant (Zierath, 2004). Hickson et al. found that proportion of type I
muscle fibers was significantly associated with reps completed in the back squat with 40% and
13
60% of 1RM, but not 80% of 1RM (Hickson, 1994). However, Terzis et al. found no relationship
between proportion of type I muscle fibers and leg press reps to failure with 75% and 85% of
1RM (Terzis, 2008). Thus, there is mechanistic reason to believe that women may be less
fatigable during resistance training, in part, due to a higher proportion of type I muscle fibers, but
research directly investigating the relationship between muscle fiber type and fatigability during
resistance training is equivocal.
Differences in reliance on anaerobic metabolism may contribute to women being less
fatigable during resistance training than men. Increased anaerobic energy production is
associated with decreases in muscle pH and accumulation of inorganic phosphate, which
interfere with muscle contraction (Metzger, 1990; Westerblad, 2002; Allen, 2012). In studies on
aerobic exercise, women are found to have a lower reliance on anerobic metabolism at
submaximal exercise intensities (Bunt, 1990; McCracken, 1994; Hackney, 1999; Lundsgaard,
2014). This is consistent with the finding that during isometric muscle contractions, the relative
sex difference in fatigability is larger with low-intensity contractions, and lower with higher
intensity contractions (Hunter, 2014). Furthermore, research on athletes with different training
backgrounds shows that endurance trained athletes, who would likely have a lower reliance on
anaerobic metabolism at submaximal exercise intensities due to aerobic exercise adaptations, are
capable of completing more reps to failure than strength trained athletes with the same relative
load. Richens and Cleather found that endurance trained athletes could complete, on average,
39.9 reps with 70% of their leg press 1RM and 19.8 reps with 80%1RM, compared to 17.9 and
11.9 reps for resistance trained subjects (Richens, 2014). However, this difference may have also
been driven by other divergent adaptations to endurance versus resistance training, and likely
isn’t solely attributable to reliance on anaerobic metabolism. Another study by Morris et al.
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found that force declines during a prolonged isometric contraction were negatively associated
with lactate threshold, providing more direct evidence that decreased reliance on anaerobic
metabolism decreases fatigability during resistance exercise (Morris, 2008).
Finally, differences in muscle perfusion influence sex differences in fatigability during
resistance training. When muscles contract, they partially occlude arterial blood flow (Hunter,
2001). Men generally have considerably larger muscles than women, and thus occlude their
arteries to a greater extent during submaximal muscle contractions (Hunter, 2001; Hunter, 2014).
However, during maximal contractions, occlusion is similar, and rates of fatigue are similar in
men and women (Hunter, 2001). Furthermore, in studies where the groups of men and women
are matched for strength, which is associated with muscle mass, rate of fatigue during isometric
contractions is more similar than when the men and women are not strength-matched (Hunter,
2004a, Hunter 2006), though other studies show that women are still less fatigable even when
strength-matched with men (Fulco, 1999; Hunter, 2004b). Women may also have a greater
vasodilatory response to resistance exercise than men (Parker, 2007), and may have a greater
density of capillaries per unit of muscle cross-sectional area due to having smaller muscle fibers
and a greater proportion of type I muscle fibers (Hunter, 2008; Reopstorff, 2006; Høeg, 2009),
though neither of these are unanimous findings (Porter, 2002). The combination of less muscle
mass (and thus less mechanical compression of arteries), potentially greater vasodilatory
response, and potentially greater capillary density may all lead to greater muscle perfusion in
women during resistance exercise, and thus lower rates of fatigue.
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Studies investigating sex differences in fatigue
More than 60 studies have examined sex differences in fatigue during resistance exercise.
However, as discussed, most of the protocols used have low ecological validity. Most of the
studies employed isometric exercise, and most of the studies using dynamic exercise used either
concentric or eccentric isokinetic exercise. Fifteen studies were found that examined sex
differences in fatiguability during resistance training using dynamic, isotonic exercise.
Furthermore, two more studies employing isokinetic exercise will be discussed, as they were
important when designing the protocol for this study.
In a study by Reynolds et al., the subjects were 34 men and 36 women with “varied
degrees of resistance training experience” (Reynolds, 2006). The exercise protocol involved
working up to each individual's 1RM, 5RM, 10RM, and 20RM chest press and leg press on
different days. Each multi-rep max was a similar percentage of 1RM in both sexes for both chest
press and leg press, indicating that if there are sex differences in fatigability during isotonic
resistance exercise, they may not be related to fatigability during a single set of resistance
exercise taken to failure.
Similarly, a study by Pincivero et al. had 15 male and 15 female subjects perform as
many knee extension repetitions and possible with 50% of 1RM (Pincivero, 2004). There was no
significant difference in the number of reps performed.
A study by Clark et al. had similar findings (Clark, 2003). Ten male and 10 female
subjects performed isotonic truck extensions with a load equal to 50% of maximum voluntary
contraction force. There was no significant difference in the number of reps performed.
However, within the same study, isometric trunk extensions against 50% of MVC force were
also performed, and women had a significantly longer time to task failure than men (146.0 versus
16
105.4 seconds). This illustrates the importance of differentiating between isometric and isotonic
contractions.
Similar results were obtained in a study by Mendonca et al (Mendonca, 2018). This study
tested decrements in maximal isometric elbow flexion force in 31 men and 31 women following
four sets of ten repetitions with 75% of 1RM. Absolute torque decrements were significantly
larger in men, but the men were also significantly stronger than the women. Relative (%)
decrements were similar between the sexes.
A study by Lanning et al. had equivocal findings (Lanning, 2017). Eight male and 9
female subjects completed 200 reps of plantar flexion against a load equal to 30% of maximum
voluntary contraction force. Post-exercise decreases in maximum voluntary force were similar
between sexes, but peak power decreased significantly less (~15%) in women.
A study by Senefeld et al. also had equivocal findings (Senefeld, 2013). Sixteen men and
19 women completed 90 reps of biceps curls and knee extensions with a load equal to 20% of
maximal voluntary isometric contraction force. Maximal isometric force for the elbow flexors
decreased in both sexes to a similar degree pre- to post-exercise, but knee extension force
decreased to a significantly greater degree in men than women.
A study by Maughan et al. found that exercise intensity influences sex differences in
fatigability (Maughan, 1986). Twelve untrained men and 11 untrained women completed as
many reps as possible in the biceps curl with 50%, 60%, 70%, 80%, and 90% of 1RM. Women
completed significantly more reps with 50%, 60%, and 70% of 1RM, but there were no
significant differences at 80% or 90% of 1RM.
A study by Yoon et al. also found lower fatigability in women with low intensity
resistance exercise (Yoon, 2015). This study on 25 men and 29 women tested time to task failure
17
using 3-second isotonic biceps curls with a load equal to 20% of elbow flexion MVIC. Time to
task failure was significantly longer is women than men (9.7 versus 6.1 minutes).
Ribeiro et al. found sex differences in fatigability with higher loads using a multi-set
protocol (Ribeiro, 2014). The subjects were 58 untrained men and 65 untrained women. The
testing protocol involved 4 sets of bench press to failure with 80% of 1RM before and after a
training intervention. A similar number of bench press reps were performed across 4 sets both
pre- and post-training in both sexes. Significantly more arm curl reps were performed in women
than in men (20.2 vs. 15.4 pre-training and 19.7 vs. 15.8 post-training). Fatigue index - a
measure of how many fewer reps could be performed on the last set of an exercise, relative to the
first set of that exercise - was lower in women for both exercises both pre- and post- training,
indicating lower fatigability.
Fatigue index is calculated: Fatigue index = [(volume load of the first set – volume load
of the last set)/volume load of the first set]*100.
Volume load is calculated: Volume load = reps performed * absolute external resistance
used.
Flanagan et al. found that sex differences in fatigability may depend on the type of
muscular action performed (Flanagan, 2014). The subjects were 10 men and 10 women with at
least 6 months of training experience. The testing protocol involved single sets concentric-only,
eccentric-only, and full reps (with both an eccentric and concentric phase) to failure with 85%
1RM. There were no sex differences during the squat with any muscle action. For bench press,
women performed significantly more concentric-only (4.1 vs. 3.3) and eccentric-only (13.9 vs.
10.5) reps, while men performed more full reps (6.6 vs. 6.2). It’s unclear why women would be
capable of performing more concentric-only and eccentric reps, but fewer full reps. However, it
18
may be related to sex differences in the ability to utilize the stretch shortening cycle (Miyaguchi,
2009; Edwén, 2014), as men may make greater use of the stretch shortening cycle than women.
Häkkinen found that when men and women performed 20 1RM squats within a single
training session, decrements in squat 1RM and isometric knee extension force were similar
between sets (Häkkinen, 1993).
In a separate study, Häkkinen also found that after performing 10x10RM squats, women
had a significantly smaller decrease in isometric knee extension torque than men (Häkkinen,
1994). To ensure that each set would be a 10RM, loads were adjusted throughout the training
session. Changes in those loads weren’t statistically analyzed, but the decrease in 10RM loads
used from the first set to the tenth set was likely significantly greater in men (-27.2% for men
versus -14.5% for women).
Salvador et al. examined the decrease in reps completed in the bench press, curl, and
squat from the first set to the fourth set to failure with 80% 1RM loads (Salvador, 2005). Women
had a significantly smaller decrease in bench reps performed than men, but there were no
significant differences for the squat or curl.
Miller et al. used a protocol consisting of curls and knee extensions with 60% of 1RM,
with a fixed cadence of six reps per minute (Miller, 1993). Time to task failure for biceps curls
was greater for women, but there was no significant difference between the sexes for knee
extensions.
Finally, Monteiro et al. found that, during a full resistance training session, women may
actually be more fatigable than men (Monteiro, 2017). The subjects were 16 men and 12 women
with at least 12 months of experience. The testing protocol involved 4 sets to failure with 10RM
load for bench press and leg press, arranged in four different configurations (altering which
19
exercise came first, and whether a rest interval was allowed between exercises). When pooling
across all four conditions, the decrease in reps from the first to fourth sets was 25.5% smaller for
bench, and 24.5% smaller for leg press in men.
Moving on to studies using isokinetic exercise that are relevant to the protocol for this
study, Hill et al. found that sex differences in fatigability during dynamic contractions may be
driven by baseline differences in muscle mass and strength (Hill, 2018). The subjects were 12
men and 12 women with >6 months of resistance training experience. The exercise protocol
involved 50 isokinetic concentric contractions at 65% MVIC and 60 deg/sec. Elbow flexion peak
torque significantly decreased more in men (23.8%) than women (18.5%) from the beginning to
end of the protocol. However, this difference was no longer significant when covarying for peak
torque values, indicating the higher baseline strength and muscularity in the men explained the
majority of the difference. The other studies finding that sex differences in fatigability were
driven by differences in muscle mass and/or strength used isometric exercise; this study is
significant for finding this same relationship with dynamic resistance exercise.
Lastly, Gentil et al. demonstrated that fatigability during resistance exercise is affected by
training status, which is why this study will be restricted to only trained subjects (Gentil, 2017).
The subjects were 34 men and 34 women. Half of the subjects had at least 6 months of training
experience, while half were untrained. The exercise protocol involved 30 maximal isokinetic
repetitions at 180 deg/sec. Fatigue index was lowest for trained women (37.86%), followed by
untrained women (45.74%) and trained men (45.89%), with untrained men (51.92%) having the
highest fatigue index. In terms of significant differences, resistance trained women had a
significantly lower fatigue index than all other groups, untrained women and trained men had
20
similar fatigue indices that were significantly lower than untrained men, and untrained men a
fatigue index higher than all other groups.
Of the studies using isotonic exercise, two found that at least one measure of fatigability
was lower in men (Monteiro, 2017; Flanagan, 2014), nine found that at least one measure of
fatigability was lower in women (Lanning, 2017; Senefeld, 2013; Maughan, 1986; Yoon, 2015;
Ribeiro, 2014; Flanagan, 2014; Miller, 1993; Salvador, 2005; Häkkinen, 1994), and twelve found
no sex differences in fatigability during isotonic resistance training in at least one measure
(Reynolds, 2006; Pincivero, 2004; Clark, 2003; Mendonca, 2018; Lanning, 2017; Senefeld,
2013; Maughan, 1986; Ribeiro, 2014; Flanagan, 2014; Miller, 1993; Häkkinen, 1993; Salvador,
2005). Thus, while there is clear evidence that women are less fatigable than men during
isometric exercise, the literature using dynamic exercise, and isotonic dynamic exercise in
particular, is much less clear. Furthermore, most of the studies using isotonic exercise employed
either a single set to failure, multiple sets to failure, or very low loads. The sole exception was
the study by Mendonca et al. (4 sets of 10 reps with 75% of 1RM). However, the authors of that
study report that not all subjects could complete all four sets, and that some subjects were given
assistance on their final reps, while other subjects could complete the protocol without assistance
(Mendonca, 2018). Thus, actual execution of the protocol differed between subjects, which
harms the internal validity of the study. None have examined fatigability using a multi-set
protocol where not all sets are performed to failure, and termination of the protocol is determined
by the subject’s individual rate of fatigue.
21
SEX DIFFERENCES IN RECOVERY FROM RESISTANCE TRAINING
Potential mechanisms
There is much debate about whether women experience less muscle damage than men,
and whether women recover faster than men after resistance training. On one hand, mechanistic
evidence reviewed by Enns and Tiidus (2010) indicates that estrogen is protective against muscle
damage by helping to stabilize the sarcolemma, that it limits macrophage infiltration after
damaging exercise, and that it may promote skeletal muscle recovery after exercise by increasing
satellite cell activation. On the other hand, direct evidence in humans tends to indicate that
women do not experience less muscle damage after eccentric exercise than men (Stupka, 2000;
Stupka, 2001, and that men and women recover strength at a similar rate following eccentric
exercise (Sayers, 2001; Sewright, 2008). Eccentric exercise is typically used, as it causes more
muscle damage than concentric exercise (Proske, 2001). However, studies on eccentric exercise
may not be directly relevant in strength and conditioning contexts involving isotonic exercises
employing both eccentric and concentric components. Performance in such contexts will by
limited by concentric strength, as muscles can produce more force eccentrically than
concentrically. Women have higher eccentric:concentric strength ratios than men (Colliander,
1989; De Ste Croix, 2007). Thus, studies using eccentric-only exercise have women training with
a higher percentage of their concentric 1RM than men. So, when men and women train utilizing
the same percentage of their eccentric strength, muscle damage and rates of recovery are similar.
However, during isotonic exercise with an eccentric and concentric component, women would be
training with a lower percentage of their maximal eccentric strength, and may thus experience
less muscle damage and recover faster from training.
22
Furthermore, muscle damage after exercise is attenuated by training through a collection
of adaptations known as the repeated bouts effect (Hyldahl, 2017). Many of the studies assessing
muscle damage and recovery after resistance exercise used untrained subjects. However,
epidemiological studies consistently show that men have higher rates of leisure time physical
activity than women (Azevedo, 2007; Beville, 2014), and are more likely that women to have
jobs that involve manual labor (Gabriel, 2007). Thus, in subjects who aren’t specifically
resistance-trained, men may, on average, have a greater baseline level of the repeated bout effect
adaptations that protect against muscle damage. Consistent with this idea, a larger proportion of
untrained women demonstrate extreme reductions in maximal contractile force (>70%) following
eccentric exercise (Sayers, 2001). Studies on resistance-trained male and female subjects
mitigate this possible confounder.
Studies using conventional isotonic resistance exercise and resistance-trained subjects
Eight studies using isotonic resistance exercise and trained subjects that assessed sex
differences in muscle damage or recovery after resistance training were identified in this review
and are presented below:
Judge et al. investigated recovery after resistance exercise in 6 men and 6 women who
were highly trained (Judge, 2010). The exercise protocol involved working up to 5RM bench
press. It took 48hr for 1RM strength to return to baseline in men. In women, strength was not
significantly suppressed post-exercise at any time point, indicating that one set with a 5RM load
was sufficient to suppress performance for up to 48 hours in men, but was insufficient to
suppress performance in women.
Wolf et al. indirectly assessed post-resistance training muscle damage in 8 trained men
and 7 trained women (Wolf, 2012). The exercise protocol involved 6 sets of 5 squat reps with
23
90% of 1RM. Men experienced a larger increase in creatine kinase levels at 6 and 24hr post-
training than women. Creatine kinase in an indirect marker of muscle damage.
Amorim et al. also assessed sex differences in creatine kinase after resistance exercise
(Amorim, 2014). Eleven trained men and eleven trained women completed an exercise circuit
involving 17 different resistance exercises for 3 sets of 12 reps. Creatine kinase activity
increased more in men than in women post-exercise, and the difference was still present up to 72
hours post-training.
In contrast, Benini et al. had 8 recreationally trained male and 8 recreationally trained
female subjects complete 3 sets of 8-10 reps for 10 different exercises (Benini, 2015). This study
found no sex differences in creatine kinase levels 24 hours post-training.
Baggett et al. assessed soreness and performance recovery in 14 trained men and 14
trained women (Baggett, 2015). The exercise protocol involved 3 sets of 8-12 reps for 3 upper
body and 3 lower body exercises for two sessions, separated by 24 hours. There were similar
decreases in reps performed in the second session in both sexes. Delayed onset muscle soreness
24 hours after the first workout was significantly higher in men than women, but both sexes
reported similar discomfort during the second workout.
In two separate studies, Häkkinen et al. assessed recovery of isometric knee extension
force in men and women. In one study (Häkkinen, 1993), the exercise protocol consisted of 20
1RM squats, and in the other study (Häkkinen, 1994), the protocol was 10x10RM squats. In the
first study, maximal force recovered more in women during the first hour of recovery, but was
similar between sexes at 24 and 48 hours post-training. In the second study, maximal force
recovered more in women during the first 2 and 24 hours post-training, but was similar between
sexes at 48 hours post-training.
24
In the most recently study in this topic of research, Davies et al. assessed multiple
markers of fatigue and recovery in 11 men and 8 women (Davies, 2018). The exercise protocol
involved squatting 5 sets of 5 reps with 80% of 1RM, followed by one set to failure. Isometric,
concentric, and eccentric knee extension strength, countermovement jump height, creatine
kinase, and lower body muscle pain were assessed for three days following the training session.
Women had larger decrements than men in concentric isokinetic knee extension strength and
countermovement jump height at 24 hours post-training, and no other measures were
significantly different between the sexes.
Of these studies, five looked at performance recovery (Häkkinen, 1993; Häkkinen, 1994;
Judge, 2010; Baggett, 2015; Davies, 2018), and five examined indirect markers of muscle
damage (Wolf, 2012; Amorim, 2014; Benini, 2015; Baggett, 2015; Davies, 2018). Judge et al.
found that 1RM strength recovered significantly faster in women, Baggett et al. found that
performance during an entire exercise session was similarly suppressed 24 hours post-training in
both men and women, and Davies et al. found that concentric strength and countermovement
jump height were suppressed more in women 24 hours following a squat training session.
However, Judge et al. only used a single set of resistance exercise, and Baggett et al. only
assessed performance recovery at a single time point, 24 hours post-training. Wolf et al., Baggett
et al., and Amorim et al. found that indirect markers of muscle damage – creatine kinase or
delayed onset muscle soreness – were elevated to a greater degree in men than women. However,
Benini et al. did not find any sex differences in creatine kinase response to training, and Davies
et al. did not find significant differences in either creatine kinase or muscle pain.
25
FACTORS BEYOND SEX THAT MAY AFFECT FATIGUE OR RECOVERY
Other factors beyond sex and training status may influence fatigue during resistance
exercise and recovery from resistance exercise. Assessing these possible confounders will help
with determining whether any significant differences observed in this study are truly driven by
sex, rather than some other factor.
Research is surprisingly mixed concerning the effects of sleep restriction on exercise
performance, and the weight of the evidence suggests that sleep restriction does not negatively
impact strength acutely (Knowles, 2018). However, some studies do show that sleep restriction
or sleep deprivation negatively impacts time to exhaustion during isometric resistance exercise
(Arnal, 2016), or volume that can be completed during isotonic exercise (Reilly, 1994; Cook,
2012). Furthermore, a study on rowers found a positive relationship between sleep disturbances
and elevation in pro-inflammatory cytokines (Main, 2010), which may be related to
compromised muscular recovery from exercise. The relationship between sleep and fatigue
during resistance training or recovery from resistance training isn’t clear. However, some
evidence indicates that insufficient sleep may negatively impact resistance training performance
or recovery.
Only one study investigating the relationship between perceived psychological stress and
recovery from resistance exercise was found (Stults-Kolehmainen, 2014). It monitored recovery
of maximum isometric leg press force after a fatiguing resistance training session, and it found
that those experiencing less perceived stress recovered from resistance training significantly
faster than those experiencing a high degree of perceived stress. Thus, it’s worthwhile to assess
the stress levels of the subjects in this study to ensure that there aren’t sex differences in
26
perceived stress that could moderate the relationship between sex and recovery from resistance
exercise.
It’s a consistent finding that high-repetition training increases strength endurance
(Anderson, 1982; Campos, 2002; Schoenfeld, 2015). This is in line with the tenants of training
specificity and the SAID (specific adaptations to imposed demands) principle. Collecting data on
the subjects’ training backgrounds, with an emphasis on training volume and frequency of high-
repetition training, will help us determine if any of the potential sex differences in fatigability
may be moderated by differences in approaches to resistance exercise.
SUMMARY
While the totality of the resistance exercise literature indicates that women are less
acutely fatigable than men during resistance exercise, research utilizing isotonic resistance
exercise has yielded mixed results. In both isometric and isotonic exercise, there’s evidence that
resistance exercise intensity affects the sex difference in fatigability, such that the sex difference
decreases as intensity increases. However, the current research uses protocols that are not
reflective of typical training practices in strength and conditioning. Research on eccentric
exercise shows that men and women may experience similar muscle damage after resistance
exercise and recover at similar rates; however, research using isotonic resistance exercise has
mostly indicated that women experience less muscle damage, though research examining
performance recovery is equivocal. The discrepancy may be explained by sex differences in
eccentric:concentric strength ratios. Finally, other factors, including sleep, psychological stress,
and training style may affect fatigue during resistance training or recovery from resistance
training.
27
CHAPTER III: METHODS
SUBJECTS
The subjects were 22 males and 22 females, aged 18-35 years old. To be included in the
study, the subjects must have had at least one year of consecutive bench press experience.
Subjects were free of any injury within the past six months that would have dpreclued them from
safely participating or putting forth their best effort during 1RM bench press testing or during a
fatiguing bench press protocol. Furthermore, female subjects were pregnancy tested to verify that
they were not pregnant. Due to the prevalence of hormonal contraceptive usage in the target
population, hormonal contraceptive usage was not an exclusion criterion for female subjects.
EXPERIMENTAL DESIGN
This was a quasi-experimental study utilizing a parallel groups design, as group
assignment was based on sex, not random allocation, but both groups underwent the same
intervention and testing.
The study included six visits to the lab, over a span of 8-11 days. The first two visits
involved baseline assessments, the third visit was for the fatiguing resistance exercise protocol,
and the fourth, fifth, and six visits were to monitor recovery following the resistance exercise
protocol. The first visit included informed consent, pregnancy screening, completion of surveys,
anthropometric measurements, 1RM testing for the bench press, and load-velocity profile testing
for the bench press. The second visit took place 48-96 hours after the first visit, and included
28
1RM testing, load-velocity testing, and assessment of reps to failure with 75% of 1RM. The third
visit took place 48-96 hours after the second visit, and involved blood lactate assessments, the
fatiguing exercise protocol, and load-velocity profile testing. The fourth through sixth visits took
place 24 hours after the preceding visit, and involved load-velocity profile testing and
assessments of muscle soreness. To the greatest extent as was feasible, visits took place within a
four-hour time window for each subject in order to minimize fluctuations in performance that
could be attributed to diurnal fluctuations in strength.
DATA COLLECTION AND INSTRUMENTATION
Forms
Informed consent was obtained using the form in Appendix A. Sleep quality was assessed
using the Pittsburgh Sleep Quality Index (Buysse, 1988). Nutritional intake was assessed using
3-day food records. Stress was assessed using the Perceived Stress Scale (Cohen, 1983). Training
practices were assessed using a simple questionnaire. Soreness was assessed using 100mm visual
analog scales. (Appendix B). Data collection forms for all sessions are in Appendix C.
Measurements during sessions 1 and 2
Height measurements were made using a stadiometer that measures height to the nearest
millimeter (Detecto, Webb City, MO, USA).
Body mass was recorded to the nearest quarter pound using a calibrated (Detecto, Webb
City, MO, USA). Weights were then converted into kilograms for analysis.
The pregnancy test was accomplished using strips that detect elevations of luteinizing
hormone in the subject’s urine (Clinical Guard, Atlanta, CA, USA). The subject was asked to
29
urinate in a cup in order to collect the urine, and a member of the research team used the testing
strip.
Arm lean mass was assessed via DEXA (Hologic, Inc., Bedford, MA). The arm segment
was separated from the torso segment of the DEXA scan by ensuring that the line that separates
these segments passes directly through the axilla and the midpoint of the acromioclavicular joint.
Sleep duration and quality were estimated using the Pittsburgh Sleep Quality Assessment
(Chronbach’s α = 0.83). The subject was asked to fill out the assessment, and the assessment was
scored using the scoring scale recommended by the assessment.
Stress levels were estimated using the Perceived Stress Questionnaire (reliability: r =
0.84-0.86). The subject was asked to fill out the questionnaire, which was scored using the
scoring scale recommended by the questionnaire.
Aspects of the subjects’ training histories were assessed via questionnaire. The subject
were asked to fill out the questionnaire. Each question was assessed independently.
Dietary intake was assessed via 3-day food logs. Subjects were instructed about how to
fill out the food logs, told to include portion sizes and brand names whenever possible, and asked
to record two week days and one weekend day of nutritional intake. This data was collected to
help with the interpretation of the results if there were large differences in recovery rate, to
ensure those differences were not due to drastic sex differences in nutrient intake.
1RM bench press testing was performed on a standard bench press (Life Fitness,
Rosemont, IL, USA) using a standard 20.4kg Olympic barbell (Rogue Fitness, Columbus, Ohio,
USA) and commercial-quality weight plates (Rogue Fitness, Columbus, Ohio, USA), primarily.
However, if a subject bench pressed less than 68kg, their first warm-up sets were performed
using a 15kg Olympic barbell (Eleiko, Halmstad, Sweden). For a repetition to be counted, the
30
subject’s shoulders and gluteal region needed to maintain contact with the bench, and their feet
needed to remain on the floor and not move throughout the repetition. The bar started at full
elbow extension, was lowered until it made contact with the chest, was paused briefly on the
chest, and was then pressed until full elbow extension was attained.
Bench press load-velocity profiles were assessed using the GymAware Power Tool
(Kinetic Performance Technology, Canberra, Australia), measuring mean concentric velocity.
This device has been shown to have excellent validity and reliability with the loads used to
establish load-velocity profiles in this study (relationship with gold-standard measure r > 0.9; CV
< 10%) (Banyard, 2017; Banyard, 2018). Criteria for a successful bench press rep was the same
as for 1RM testing. The subjects were instructed to press each repetition as fast and hard as
possible. Estimated 1RM was assessed by calculating a linear trendline for the load-velocity
profile, and solving for load when velocity is equal to the observed velocity during that subject’s
1RM (Jovanović, 2014).
Bench press reps to failure were performed using 75% of the subject’s 1RM. The criteria
for a successful rep was the same as for 1RM testing. This test was terminated when a subject
failed to complete a rep.
Measurements in session 3
Load-velocity testing and estimated 1RM were assessed as previously described
(Jovanović, 2014).
The fatiguing resistance exercise protocol was completed using 75% of the subject’s
1RM. The subjects performed sets of 5 repetitions with 90 sets of rest between sets. Criteria for a
successful bench press rep was the same as for 1RM and load-velocity profile testing. The
31
protocol was terminated when concentric failure occurred. Total reps completed during the
protocol were then counted.
Blood lactate levels were assessed using a Lactate Plus blood lactate analyzer (Sports
Resource Group, Hawthorne, NY, USA), requiring blood from a fingerstick.
Vertical displacement of the barbell each rep was measured by the GymAware. Average
vertical displacement for each subject was calculated by averaging all reps during sets that were
completed successfully during the fatigue protocol.
Measurements in sessions 4-6
Load-velocity testing and estimated 1RM were assessed as previously described.
Soreness of the bench press prime movers (pectoralis major, triceps brachialis, and
anterior deltoid) were assessed using a visual analog scale (Kanda, 2013).
VISITS 1 AND 2: BASELINE ASSESSMENTS
On a subject 's first visit, they were informed about the study protocol, screened for
eligibility for participation by a member of the research team, and asked to provide informed
consent. On a female's first visit, they were then asked to provide a urine sample for a pregnancy
test after informed consent was obtained. All subjects provided urine samples for all sessions in
order to verify that they were adequately hydrated. Urine specific gravity was required to be
between 1.00 and 1.02, assessed via refractometry. After this, their height and body mass were
obtained using a stadiometer and calibrated scale, and all subjects underwent a DEXA scan.
Following the DEXA scan, they filled out questionnaires regarding their training, sleep, and
stress. Following these pre-testing assessments, the subject began a five-minute self-selected
warm-up of stretching and/or light calisthenics. After the warm-up, the subject was asked to
32
estimate their one-repetition maximum (1RM) bench press. The initial load used for testing was
30% of estimated 1RM if possible, or 33lbs if 30% of estimated 1RM was less than 33lbs. Load
was increased in increments of 10% of estimated 1RM until reaching approximately 80% of
1RM estimated. At 80% of 1RM, smaller load increases took place, until a 1RM has been
attained, ideally within 5 attempts. Subjects rested for 2-3 minutes between each warm-up set,
and for 2-5 minutes between each 1RM testing attempt until a 1RM was achieved. Subjects
performed 3 repetitions per set until reaching 80% of their estimated 1RM, and performed single
repetitions with all loads above 80% of estimated 1RM in order to minimize fatigue, which could
hinder 1RM performance. Each rep was performed through a full range of motion, touching the
chest at the bottom of the rep, and locking out the elbows at the top of the rep. There needed to
be a clear pause between eccentric and concentric portions of the rep, and the butt and shoulders
needed to maintain contact with the bench at all times. If subjects struggled with sufficiently
pausing the bar on their chest, they were told to wait for a “press” command, provided by a
member of the research team. The subjects were instructed to control the eccentric portion of
each repetition, and to perform the concentric portion of each repetition as fast as possible. At the
end of this visit, subjects were given 3-day food logs with instructions for how to fill them out,
and were asked to record two week days and one weekend day of eating and drinking.
During the second testing visit, scheduled to take place 48-96 hours after the first testing
visit, the same 1RM testing procedures were repeated, beginning with the 5-minute self-selected
warm-up. After attaining a 1RM, the subject rested for 5 minutes before beginning a reps-to-
failure test. The bar was loaded with 75% of the subject's highest 1RM attained during the first
two sessions, and the subject performed as many repetitions as possible, until they failed a rep or
were unable to complete another rep with proper technique. 48-96 hours was determined to be an
33
adequate interval between sessions. Judge et al. found that 48 hours was long enough for bench
press strength to return to baseline in both men and women after maximal strength testing
(Judge, 2010), and allowing up to 96 hours allowed for more scheduling flexibility.
VISIT 3: FATIGUING RESISTANCE EXERCISE PROTOCOL
During the third visit, the subjects were put through a fatiguing exercise protocol. This
visit began with a finger prick to assess pre-exercise lactate concentrations. Following a five-
minute self-selected general warm-up, the subjects worked up from 30% of 1RM to 80% of their
1RM, performing sets of 3 repetitions, with 2-3 minutes between sets. Then, the bar was loaded
to 75% of the subject's 1RM, and they performed sets of 5 repetitions, with 90 seconds between
sets, until they reached the point of concentric failure. Five minutes after the end of the last set,
there was another finger prick to assess post-exercise blood lactate. Ten minutes after the end of
the last set, the subjects again worked up from 30% of 1RM to 80% of their 1RM, performing
sets of 3 repetitions, with 2-3 minutes between sets.
VISITS 4-6: RECOVERY ASSESSMENTS
For three consecutive days following the fatiguing exercise protocol, recovery from the
fatiguing exercise protocol was assessed. The subjects began with a five-minute self-selected
warm-up, and worked up from 30% of 1RM to 80% of their 1RM in 10% increments,
performing sets of 3 repetitions, with 2-3 minutes between sets. This protocol should not induce
any substantial degree of additional fatigue; rather, it will be used to gauge recovery of velocity
output (with lower loads) and force output (with heavier loads). This was followed by
34
questionnaires to assess their sleep duration, sleep quality, and the soreness of their pectoral
muscles, triceps, and anterior deltoids.
STATISTICAL ANALYSES
All data were reduced and analyzed using SPSS Version 25.0 for Microsoft Windows
(SPSS, Inc., Chicago, IL) or JASP version 0.8.6.0. Means and 95% confidence intervals are
reported for all major variables.
Total reps completed during the fatiguing exercise protocol was compared between sexes
using both Welch’s t-test and a 1x2 ANCOVA, covarying for arm lean mass. The t-test was used
to determine whether there's a difference in acute fatigability between sexes; since there was a
significant difference, the ANCOVA was used to assess whether differences in baseline arm lean
mass account for a significant proportion of those differences. Previous research (Hill, 2018) has
used a similar statistical approach.
Slope of the load/velocity curve and predicted 1RM from the subjects' load/velocity
profile was analyzed using 2x5 ANOVAs, with two levels of sex (male and female), and five
time points (pre-exercise, post-exercise, 24-hours post, 48-hours post, and 72-hours post).
Perceived muscle soreness was analyzed using a 2x3 ANOVA, with the same factors and the
levels for sex, but only three time points (24-hours post, 48-hours post, and 72-hours post). A
Greenhouse-Geisser correction was applied to all ANOVAs in an effort to limit the false
discovery rate.
If a significant group x time interaction was detected by any of the ANOVAs, a
Bonferroni post hoc test was used to identify those interactions.
35
All other data collected (training histories, sleep, stress, etc.) were only be used for
exploratory analyses, for descriptive purposes, or for sensitivity analyses to ensure that any
significant findings remain significant after covarying for other factors that could conceivably
influence fatigability or recoverability.
To detect a group x time interaction in any of the recovery measures, a sample size of
40 subjects (20 per group) would be sufficient to detect a partial eta squared effect size of 0.03,
given a power of 0.8, an alpha of 0.05, and a correlation among within-subject measures of 0.5
(GPower ver. 3.1). For reps completed during the fatigue protocol, we anticipated that women
would complete approximately 15 more reps than men, and we anticipated that the standard
deviation within each sex would be approximately 10 reps. Given a sample size of 20 men and
20 women, we anticipated that the SE for both sexes would be approximately 2.24 reps, and the
standard error for the difference between sexes would be approximately 3.2 reps.
Effect sizes are reported to contextualize results and group differences. For descriptive
characteristics and the t-tests, effect sizes are reported as Cohen’s d. For correlations, effect
sizes are reported as Pearson’s r. For ANOVAs, effect sizes are reported as ηp2.
• H1: Women will fatigue slower than men during a single resistance
exercise session, as assessed by completing more total reps when performing submaximal
sets of resistance exercise until the point of failure
• H2a: If women do not fatigue slower than men during a single resistance
exercise session, and thus complete a comparable number of reps during the session, they
will recover from the session faster than men, as assessed by estimated 1RM returning to
baseline sooner and muscle soreness attenuating faster in women than in men.
36
• H2b: If women fatigue slower than men during a single resistance exercise
session, and thus complete more reps during the session, they will recover from the
session at the same rate as men, as assessed by estimated 1RM returning to baseline and
muscle soreness attenuating at a comparable rate in both sexes.
• H3: Differences in arm lean mass will explain the sex differences in
fatigability.
37
Chapter IV: Results
The primary purpose of this study was to examine whether women fatigue at a slower
rate than men when performing submaximal sets of bench press, consisting of sets of 5
repetitions at 75% of 1RM with 90 seconds between sets. The secondary purpose was to examine
whether men and women recover from fatiguing exercise at different rates by assessing muscle
soreness and estimated 1RMs for 72 hours following the fatiguing exercise session.
Subjects
A total of 44 subjects – 22 men and 22 women – were enrolled in the study. One male
subject dropped out of the study after the second visit due to shoulder pain, and one female
subject was found to not meet all inclusion criteria. Thus, the final sample consisted of 21 men
and 21 women. Nine of the male subjects and five of the female subjects reported that their
primary reason for bench pressing was to build muscle, two male and three female subjects
reported that their primary reason for bench pressing was to improve strength endurance, and ten
of the male and thirteen of the female subjects reported that their primary reason for bench
pressing was to increase strength. Descriptive characteristics for the subjects can be seen in
Table 1.
38
Table 1: Descriptive Characteristics of the Subjects
Men (N=21)
Women (N=21)
Variable
mean ± SD
Range
mean ± SD
Range
p-value
Effect size (d)
Age (years)
24.5 ± 4.1
(18.9 - 31.9)
24.0 ± 3.7
(19.7 - 34.2)
0.666
0.14
Weight (kg)*
83.4 ± 9.7
(66.9 - 108.4)
72.7 ± 10.3
(55.3 - 88.5)
0.001
1.07
Height (cm)*
174.5 ± 6.6
(162.5 - 187.6)
166.7 ± 8.5
(145.0 - 184.5)
0.002
1.03
BMI
27.4 ± 3.3
(22.7 - 35.3)
26.2 ± 3.8
(19.5 - 33.0)
0.278
0.34
DXA LBM (kg)*
65.7 ± 6.1
(55.5 - 78.4)
51.4 ± 6.6
(40.5 - 63.3)
<0.001
2.24
DXA body fat percentage*
19.9 ± 5.3%
(12.5% - 31.4%)
28.1 ± 5.2%
(21.5% - 38.5%)
<0.001
-1.56
DXA arm lean mass (kg)*
9.2 ± 1.2
(7.0 - 11.9)
5.8 ± 1.1
(3.7 - 7.8)
<0.001
3.01
PSQI seven component score
4 ± 2
(0 - 6)
3 ± 2
(0 - 10)
0.312
0.32
PSQ score
19 ± 6
(8 - 29)
20 ± 6
(6 - 28)
0.676
-0.13
Training years
7.2 ± 4.4
(1.5 - 17.0)
6.2 ± 5.3
(1.5 - 27.0)
0.542
0.19
Bench press years*
6.6 ± 4.2
(1.5 - 17.0)
4.1 ± 2.3
(1.0 - 10.0)
0.026
0.72
All data are mean ± SD (range). * denotes a statistically significant difference between sexes (p<0.05). A positive effect size (Cohen's d) indicates
a larger value for the male subjects. BMI = body mass index. DXA = Dual Energy X-Ray Absorptiometry. LBM = Lean body mass. PSQI =
Pittsburgh Sleep Quality Index. PSQ = Perceived Stress Questionnaire.
The males were taller, heavier, had more lean body mass, a lower body fat percentage,
more arm lean mass (p<0.01 for all), and more years of bench press experience (p = 0.03).
However, age, indicators of sleep quality (PSQI scores) and stress (PSQ scores), years of
resistance training experience, all variables related to the subjects’ habitual bench press training,
and scaled strength (IPF points) were not significantly different between sexes (p>0.05).
The men and women completed a similar number of reps during a single set to failure
with 75% of 1RM in session 2 [women: 9.0 ± 2.0; men: 8.6 ± 1.7; t(39.035)=0.743; p=0.462;
d=0.23, 95% CI = -0.38-0.84; Table 2].
39
Hypothesis 1: Women will fatigue slower than men during a single resistance
exercise session, as assessed by completing more total reps when performing submaximal
sets of resistance exercise until the point of failure.
The women completed more total reps during the fatigue protocol in session 3 [women:
58.3 ± 27.3; men: 29.6 ± 10.6; t(25.923)=4.489; p=0.0001; d=1.39 95% CI = 0.66-2.09]. The
mean difference was 28.7 reps (95% CI = 15.5-41.8; Figure 1). One outlier was detected in the
female cohort (reps completed > Q3 + 1.5 x IQR). The difference was still significant with this
data point removed [t(26.26)=4.447; p=0.0001; d=1.40 (0.66-2.10)], though the mean difference
decreased to 25.4 reps (95% CI = 13.7-37.1). Table 2 presents the performance and training
characteristics of the subjects. Figure 1 is a graphic representation of the results of the analyses
for hypothesis 1.
Figure 1. *** denotes p<0.001. Individual data points, 95% CI, and box and whisker
plot presented for both sexes.
40
Table 2: Performance and Training Characteristics
Men (N=21)
Women (N=21)
Variable
mean ± SD
Range
mean ± SD
Range
p-value
Effect size (d)
Bench press 1RM (kg)*
106.4 ± 27.8
(68.0 - 183.7)
57.0 ± 16.2
(30.4 - 87.1)
<0.001
2.17
IPF points
432.3 ± 99.7
(256.4 - 628.7)
455.2 ± 99.0
(295.0 - 656.9)
0.459
-0.23
Bench press frequency
2.0 ± 0.9
(1.0 - 4.0)
1.6 ± 0.6
(1.0 - 3.0)
0.124
0.49
Bench press sets per week
9.8 ± 4.0
(4.0 - 20.0)
8.0 ± 4.3
(3.0 - 20.0)
0.165
0.44
Bench press sets of <5 reps
23 ± 19%
(0% - 90%)
35 ± 29%
(0% - 100%)
0.108
-0.51
Bench press sets of 5-15 reps
74 ± 19%
(10% - 100%)
62 ± 29%
(0% - 100%)
0.129
0.48
Bench press sets of >15 reps
3 ± 7%
(0% - 25%)
3 ± 6%
(0% - 25%)
0.728
0.11
Reps completed with 75% to failure
8.6 ± 1.7
(6 - 11)
9.0 ± 2.0
(5 - 14)
0.462
-0.23
Reps completed during fatigue protocol*
29.6 ± 10.6
(13 - 54)
58.3 ± 27.3
(19 - 124)
<0.001
-1.39
Pre-training lactate (mmol/L)
1.4 ± 0.7
(0.5 - 2.9)
1.1 ± 0.4
(0.5 - 2.1)
0.081
0.56
Post-training lactate (mmol/L)*
7.2 ± 1.3
(4.9 - 10.1)
4.7 ± 1.2
(2.9 - 7.6)
<0.001
2.05
Change in lactate (mmol/L)*
5.8 ± 1.5
(3.6 - 9.1)
3.6 ± 1.3
(1.7 - 6.6)
<0.001
1.62
Bench stroke vertical displacement (cm)
37.6 ± 4.5
(28.3 - 44.3)
35.3 ± 5.6
(23.4 - 46.7)
0.147
0.46
All data are mean ± SD (range). * denotes a statistically significant difference between sexes (p<0.05). A positive effect size
(Cohen's d) indicates a larger value for the male subjects. The bench press sets <5 reps, 5-15 reps, >15, and >5 reps are proportions
of weekly sets within those respective rep ranges. Bench press frequency is sessions per week. IPF Points = bench press scoring
system of the International Powerlifting Federation.
Hypothesis 2a: If women fatigue slower than men during a single resistance exercise
session, and thus complete more reps during the session, they will recover from the session
at the same rate as men, as assessed by estimated 1RM returning to baseline and muscle
soreness attenuating at a comparable rate in both sexes.
A 2×5 (sex × time) ANOVA for predicted 1RM found significant time [F(2.772,110.880)
= 11.842; p<0.001; ηp2 = 0.228] and sex [F(1,40) = 42.290; p<0.001; ηp2 = 0.514] effects, but no
significant sex × time interaction ([F(2.772,110.880) = 2.131; p = 0.105; ηp2 = 0.051). When
41
normalizing predicted 1RMs to the predicted 1RMs recorded prior to the fatigue protocol in
session 3, there was still a significant main effect for time [F(3.491,139.640) = 15.096; p<0.001;
ηp2 = 0.274; Figure 2], but no main effect for sex [F(1,40) = 0.837; p = 0.366; ηp2 = 0.020] nor a
sex × time interaction [F(3.491,139.640) = 0.907; p = 0.452; ηp2 = 0.022]. Normalized predicted
1RM was significantly lower at the post-exercise time point in session 3 than at the pre-exercise
time point in session 3 (pbonf = 0.01), or sessions 5 and 6 (pbonf < 0.001). It was also significantly
lower in session 4 than in sessions 5 and 6 (pbonf < 0.001). Figure 2 depicts the recovery of
normalized predicted 1RM strength in males and females.
Figure 2. Data are presented as mean and 95% CI for each of the five time points. *
denotes a significant difference from 10 Minutes Post, and + denotes a difference from 24 Hours
Post.
42
A 2×5 (sex × time) ANOVA for slope of the load-velocity relationship found a
significant main effect for time [F(3.373,134.909) = 3.740; p = 0.010; ηp2 = 0.086], but no main
effect for sex [F(1,40) = 3.330; p = 0.075; ηp2 = 0.077] and no significant sex × time interaction
([F(3.373,134.909) = 2.254; p = 0.078; ηp2 = 0.053). Post-hoc testing revealed that the slope of
the load-velocity relationship was steeper 24 hours post-training than immediately post-training
(pbonf = 0.010).
Multiple 2×3 (sex × time) ANOVAs for perceived muscle soreness found significant
main effects for time for all three muscles examined (pectorals, triceps, and anterior deltoids) and
for the summed soreness of all three muscles (p<0.01 for all; ηp2 = 0.524 for pectorals, 0.174 for
triceps, 0.365 for anterior deltoids, and 0.531 for summed soreness). For the pectoral, anterior
deltoids, and summed measures, soreness was significantly greater during session 4 than sessions
5 and 6, and significantly greater in session 5 than session 6 (pbonf < 0.05). For the triceps, there
was no significant difference in soreness between sessions 4 and 5 (pbonf = 0.355), but soreness
was significantly lower in session 6 than in sessions 4 and 5 (pbonf < 0.05). There were no
significant main effects for sex nor any significant sex × time interactions for the three muscles
examined, nor for the summed soreness measures. Figure 3 provides a visual representation of
the level of soreness following the fatigue protocol between the male and female subjects in this
study.
43
Figure 3. Summed soreness of the pectorals, triceps, and anterior deltoids assessed
using a 100mm visual analog scale. Data are mean and 95% CI. * denotes a significant
difference from 24 hours post-exercise, and + denotes a significant difference from 48 hours
post-exercise.
Hypothesis 2b: If women do not fatigue slower than men during a single resistance
exercise session, and thus complete a comparable number of reps during the session, they
will recover from the session faster than men, as assessed by estimated 1RM returning to
baseline sooner and muscle soreness attenuating faster in women than in men.
This hypothesis was predicated on the assumption that men and women would complete
a similar number of reps during fatiguing exercise protocol. This assumption was not correct.
However, when removing the results from the 10 women who completed more reps than any of
them men (i.e. comparing all 21 male subjects to the 11 female subjects who completed 54 reps
or fewer during the fatigue protocol), there still was not a main effect for sex (p = 0.672), nor a
sex × time interaction (p = 0.281) for recovery of normalized predicted 1RM. There were also
44
no significant main effects for sex, nor any sex × time interactions for any of the soreness
assessments (p > 0.10 for all). Thus, it appears hypothesis 2a would have been incorrect, had its
assumption been met.
Hypothesis 3: Differences in arm lean mass will explain the sex differences in
fatigability.
Due to high collinearity between sex and arm lean mass (r = 0.839) and lack of
relationship between arm lean mass and reps completed during the fatigue protocol in the male
and female samples independently (men: r = -0.25; p = 0.27; women: r = -0.22; p = 0.34), an
ANCOVA covarying for arm lean mass was deemed inappropriate. However, since it was pre-
specified in the data analysis plan, this ANCOVA was still run. Neither sex nor arm lean mass
were significant predictors of reps performed during the fatigue protocol when included in the
same ANCOVA model (p = 0.184 for sex, and p = 0.194 for arm lean mass).
Exploratory Analyses
In spite of completing more reps during session 3, post-training lactate was lower in the
women than the men [women: 4.7 ± 1.2; men: 7.2 ± 1.3; t(39.337)=6.636; p<0.0001; d=2.05
95% CI = 1.29-2.79]. The pre- to post-training increase in blood lactate was also smaller in
women [women: 3.6 ± 1.3; men: 5.8 ± 1.5; t(39.371)=5.251; p<0.0001; d=1.62 95% CI = 0.91-
2.32]. There was not a significant correlation between reps completed in session 3 and post-
training lactate (r = 0.06 in men; r = -0.07 in women) or change in lactate (r = 0.07 in men; r = -
0.20 in women) in either sex. However, post-training lactate (r = 0.719; p < 0.001) and change in
lactate (r = 0.642; p < 0.001) were significantly correlated with 1RM bench press within the
45
entire cohort, and post-training lactate was non-significantly correlated with 1RM bench press in
both sexes independently (men: r = 0.42; p = 0.06; women: r = 0.36; p = 0.11), though the
relationships between bench press 1RM and change in lactate were weaker (men: r = 0.35; p =
0.12 ; women: r = 0.29; p = 0.20).
In an effort to see whether any other variables contributed to reps completed during the
fatigue protocol, all background training variables were individually tested as covariates in a
multiple regression model also accounting for sex. Bench press sets per week was the only
background training variable that was significantly predictive of reps completed during the
fatigue protocol (p=0.029) when also accounting for sex.
Reps completed during a single set to failure at 75% 1RM was significantly, albeit
weakly, associated with reps completed during the fatigue protocol (r = 0.352; p = 0.022).
Similar correlations were seen within each sex independently, though they were not significant
since the degrees of freedom were lower (r = 0.41; p = 0.06 for men and r = 0.37; p = 0.10 for
women).
Using summed soreness and relative decreases in predicted 1RM 24 hours post-training
as proxies for the stress imposed by the fatigue protocol, soreness was significantly, albeit
weakly, positively associated with hours of sleep the preceding night (r=0.366; p=0.017), though
that’s likely a spurious correlation (as it’s unlikely that sleeping for longer would be predictive of
greater soreness). For the male subjects, soreness 24 hours post-training was moderately
associated with reps completed during the fatigue protocol (r=0.49; p=0.025); however, there
was not a significant association for the female subjects (r=0.05; p=0.81). The relative decrease
in predicted 1RM 24 hours post-training was not significantly associated with any baseline
variables or sleep the preceding night.
46
Velocity loss during each set of the fatigue protocol increased as the subjects approached
failure. During the first set, average velocity loss per rep was 0.030 ± 0.014 m/s. During the last
successful set, average velocity loss per rep was 0.047 ± 0.015m/s. This was a significant
difference [t(41)=6.912; p<0.001; d=1.07 95% CI = 0.68-1.44].
The load-velocity profiles of the men and women were similar, including velocities at 30-
80% 1RM, velocity with 1RM loads, and the slope of their load-velocity profiles (all p>0.05).
47
Chapter V: Discussion
The key findings of this study were that male and female lifters completed a similar
number of reps to failure with 75% of their 1RM, but women completed almost twice as many
total reps during a fatigue protocol consisting of sets of 5 reps with 75% of 1RM and 90 seconds
between sets, taken to the point of failure. In spite of completing more reps during the fatigue
protocol, recovery following the fatigue protocol was similar between the sexes, assessed via
muscular soreness and predicted 1RMs from load-velocity profiles.
The finding that male and female lifters completed a similar number of reps to failure
during a single set with 75% of their 1RM is consistent with previous literature (Flanagan, 2014;
Maughan, 1986; Reynolds, 2006). Women tend to complete more reps during a single set to
failure or have a longer time to task failure during isometric exercise when using low loads (<
70% of 1RM or MVIC), but the difference between the sexes is not significant with heavier
loads.
Hypothesis 1
The fatigue protocol used in this study is unique in the literature, as it consisted of
multiple sets of a fixed number of reps, stopping shy of failure on all sets except for the final set.
Similar research has primarily used protocols consisting of a fixed number of sets with all sets
taken to failure (Reynolds, 2006; Pincivero, 2004; Clark, 2003; Maughan, 1986; Yoon, 2015;
Ribeiro, 2014; Flanagan, 2014; Monteiro, 2017; Miller, 1993; Häkkinen, 1993; Häkkinen, 1994;
48
Salvador, 2005), or it has prescribed a predetermined workload (Mendonca, 2018; Lanning,
2017; Senefeld, 2013) while assessing decrements in performance pre- to post-exercise. Since
resistance trainees do not always train to failure, it is important to know whether men and
women fatigue at different rates during submaximal training stopping shy of concentric failure.
While some research indicates that women complete more reps during sets to failure or
experience smaller decrements in strength after completing a fixed relative workload (Lanning,
2017; Senefeld, 2013; Maughan, 1986; Yoon, 2015; Ribeiro, 2014; Flanagan, 2014; Miller,
1993; Salvador, 2005; Häkkinen, 1994), most studies find no difference between the sexes
(Reynolds, 2006; Pincivero, 2004; Clark, 2003; Mendonca, 2018; Lanning, 2017; Senefeld,
2013; Maughan, 1986; Ribeiro, 2014; Flanagan, 2014; Miller, 1993; Häkkinen, 1993; Salvador,
2005), and two studies found more reps were completed by men during sets to failure (Flanagan,
2014; Monteiro, 2017).
The sex difference in total reps performed in the current study was considerably larger
than has been observed in prior research using protocols consisting of multiple sets to failure.
There are possibly a few hypotheses for why that may be the case. First, it may be that women
recover faster between sets than men, allowing for large differences in total reps performed to
arise when sets aren’t taken to failure, and the number of sets that can be performed is not
predetermined. In this study, the average velocity loss from the fastest rep to the slowest rep
within each set of the fatigue protocol was similar between sexes (0.152 ± 0.051 m/s for men and
0.157 ± 0.052 m/s for women), but the recovery of velocity from the slowest rep of one set to the
fastest rep of the next set was greater in women (0.123 ± 0.045 m/s for men and 0.146 ± 0.053
m/s for women). Thus, using within-set velocity loss as a proxy for fatigue, and between-set
velocity increase as a proxy for recovery, men were approximately 81% recovered, an average,
49
set-to-set, while women were approximately 93% recovered. Using a protocol that allows for
more sets, women are able to better advantage of their superior set-to-set recovery.
If women recover faster between sets than men, the difference may be due to differences
in metabolism and substrate utilization. In spite of completing almost twice as many sets during
the fatigue protocol, post-exercise lactate was substantially lower in the female subjects,
suggesting less reliance on anaerobic glycolysis. This may be related to differences in fiber type
composition (Hunter, 2014) or the effects of estrogen (Bunt, 1990; McCracken, 1994; Hackney,
1999; Lundsgaard, 2014). However, the sex differences in lactate may instead by driven by
strength difference between the sexes since less total work is required to lift lighter loads, though
the lack of significant relationship between post-training lactate and bench press 1RM within
each sex calls this explanation into question. Finally, the difference may be due to more efficient
clearance of metabolic waste between sets in women. In a prior pair of studies using strength-
matched men and women (Hunter 2004a; Hunter 2004b), time to task failure was the same
between the sexes during continuous isometric contractions, but time to task failure was
significantly greater for women during intermittent isometric contractions, even though the rest
interval between contractions was only four seconds. If this was due to metabolic differences,
one would expect a difference in time to task failure during continuous isometric contractions as
well; the difference may instead by due to the women clearing the metabolic byproducts related
to fatigue and force decrements – including hydrogen ions and free phosphate – more effectively
than men, even during very limited rest intervals.
The second potential explanation for the relatively large sex difference in performance
during a fatigue protocol in this study compared to prior research relates to the effects of training
to failure during the testing protocol. When sets are taken to failure or closer to failure, lifters
50
take longer to recover from training, compared to stopping sets prior to failure or further from
failure (Morán-Navarro, 2017; Pareja-Blanco, 2018). This may be related to muscle damage as a
result of neuromuscular fatigue and technique alterations as lifters approach failure. If the set-to-
set decrements in performance in studies that involve training to failure are driven by muscle
damage, and if the women in the present study were able to outperform men by recovering more
between sets due to metabolic differences, training to failure may nullify (or at least decrease)
the effects of that metabolic advantage.
The third hypothesis for why the sex difference in performance during a fatigue protocol
was larger in this study compared to prior studies relates to the similarity between the sexes in
reps performed during a single set to failure with relatively high loads. Multi-set fatigue
protocols are ultimately testing both strength endurance and recovery between sets, but different
protocols are affected to different degrees by those two factors. In a protocol like the one used in
this study where the workload in each set is fixed but the number of sets is flexible, a subject
completes more reps by completing more sets, and thus recovery between sets plays a large role.
In a protocol consisting multiple sets to failure, strength endurance plays a larger role. If two
people have similar strength endurance when unfatigued, but one individual recovers a bit faster
between sets, the two may ultimately complete a the same number of reps during a single set to
failure, and the marginal advantage for the person who recovers faster may only be a rep or two
per set on subsequent sets, and this advantage will be somewhat offset by simply performing
more reps per set than his or her counterpart after the first set. As such, performance with this
sort of protocol relies more on strength endurance and less on between-set recovery, when
compared to a protocol such as the one used in this study. If there’s a sex difference in between-
51
set recovery but not strength endurance, a protocol like the one used in this study will be more
likely to find large sex differences in performance during the fatigue protocol.
Hypothesis 2
In spite of the fact women completed nearly twice as many reps as men during the fatigue
protocol, recovery of predicted 1RM and post-training muscular soreness was similar between
the sexes. While much of the prior research suggests that women recover faster than men (Judge,
2010; Häkkinen 1994; Wolf, 2012; Amorim, 2014; Baggett, 2015) or that men and women
recover at similar rates (Baggett, 2015, Häkkinen, 1993, Benini), all of those studies equated
either the reps or sets performed by the subjects, meaning this is a novel finding.
It may be that reaching the point of failure has an outsized effect on training-induced
fatigue and muscle damage. Since all subjects only reached failure once, that may explain the
similarities in recovery between the sexes. However, that seems to be an unlikely explanation, as
the variability in soreness and changes in projected 1RM was relatively high within the cohort.
Furthermore, soreness 24 hours post-training was significantly associated with the total reps
performed during the fatigue protocol in men, suggesting that training volume – not just reaching
the point of concentric failure – also influences post-training fatigue in men. However, there
wasn’t any relationship between reps performed in session 3 and post-training soreness in
women. We also did not find any significant differences between the male and female cohorts in
their bench press training variables (sets per week, training frequency, reps per set, or rest
intervals), not did any of those variables seem to correlate with soreness 24 hours after the
fatigue protocol, nor with decreases in predicted 1RM 24 hours after the fatigue protocol, so it
seems unlikely that differences in training prior to the study influenced these results. As such, the
52
similarities in recovery, in spite of large difference in reps performed, may simply be due to
intrinsic differences between the sexes, due to the protective effects of estrogen.
However, the results of this study contrast with those of Davies et al. (2018). They found
that men recovered faster after five sets of five squats with 80% of 1RM, followed by one set to
failure, as assessed by concentric knee extension torque and countermovement jump height. The
difference may be due to the different exercises used. Women may recover faster from bench
press per unit of training volume, while men may recover faster from squats. More research is
needed to clarify these conflicting results.
Load-Velocity Profiles
Finally, though this was not a primary outcome of this study, the similarities in load-
velocity profiles between the sexes warrants mentioning, as this finding contrasts with prior
research (Torrejón, 2018; Askow, 2019). Other studies have found that men have a steeper load-
velocity relationship – driven by greater velocities with light loads – and lower velocities with
1RM loads. In this study, velocity at 1RM, slope of the load-velocity relationship, and absolute
velocities with all loads from 30% to 80% of 1RM were similar between the sexes. The male and
female subjects seemed to be roughly equally well-trained for the bench press. Total years of
resistance training experience was similar between the sexes, and while the men had been bench
pressing for significantly longer, the women still had over four years of bench press experience,
on average. Furthermore, both sexes were similarly skilled at bench pressing, according to the
International Powerlifting Federation’s formula for comparing relative bench press strength
across sex and weight classes. Prior research has found that trained lifters’ load-velocity profiles
differ from those of untrained lifters (Banyard, 2018; Zourdos, 2018; Ormsbee, 2019), and that
53
more highly trained lifters have lower velocities with 1RM loads. In the studies that have found
sex differences in load-velocity profiles, the male subjects tend to have more training experience
and tend to be more proficient benchers. For example, a study by Torrejón et al. (Torrejón, 2018)
included male subjects with an average of 6.2 years of bench press experience, compared to 1.2
years for women, and the average female bench press was just 39.9kg; the sex differences in that
study may have been driven by differences in bench press experience moreso than sex.
Conclusions
In spite of completing a similar number of reps during a single set to failure at 75% of
1RM, women were able to complete almost twice as many total reps during a fatigue protocol
resembling normal resistance training practice. In spite of the fact that women completed more
reps during the fatigue protocol, recovery of muscle soreness and predicted 1RM following
training was similar between sexes. In aggregate, these findings suggest that women engaged in
resistance training can likely train the bench press with higher per-session relative training
volumes than men, while still recovering at approximately the same rate. Since this study used a
fatigue protocol that differed considerably from prior research, further studies are warranted to
confirm or refute these findings using similar protocols, so training practices can by optimized
for both sexes.
Recommendations for Future Research
There are several directions for extending the findings of this study. More research is
needed to understand the mechanisms underpinning the large difference in performance between
the males and females in this study during the fatigue protocol. Monitoring RER to assess
54
substrate utilization and using NIRS to examine local oxygen kinetics, especially during the
recovery periods, would help with gaining insight into the physiology driving the differences.
Further measurements could also provide a more holistic view of the recovery process. For
soreness assessments, an algometer could be used to identify the pressure-pain threshold, instead
of relying on subjective assessments. Furthermore, assessments of cortisol, pro-inflammatory
cytokines, and more direct markers of muscle damage like creatine kinase, myoglobin, and cell-
free DNA could add to the current findings.
To make the results more useful for sports coaches, a lower body exercise could be used
for the fatigue protocol, and sport-specific recovery assessments such as sprints, jumps, or agility
tests could be used to monitor recovery. Future research should also use this sort of protocol to
examine the effects of the menstrual cycle and contraceptives on fatigue during and recovery
from training. Furthermore, future studies could test variations on this protocol, manipulating
load, reps per set, and rest intervals. Also, future research should examine whether these findings
generalize to other exercises, and particularly lower body exercises.
Lastly, longitudinal training studies could employ protocols resembling the fatigue
protocol used in this study to personalize training loads. If female lifters can do more sets than
men and still recover just as fast, it should be determined if that allows them to use higher
training volumes and attain more hypertrophy and larger strength gains than are currently seen in
the literature.
55
APPENDIX A: Informed Consent Form
University of North Carolina at Chapel Hill
Consent to Participate in a Research Study
Adult Participants
Consent Form Version Date: October 23, 2018
IRB Study # 18-1635
Title of Study: The Effects of Biological Sex on Fatigue During and Recovery From Resistance
Exercise
Principal Investigator: Gregory Nuckols
Principal Investigator Department: Exercise and Sport Science
Principal Investigator Phone number: 336-793-6381
Principal Investigator Email Address: gnuckols@live.unc.edu
Co-Investigators: Anthony C. Hackney, Erik Hanson
Faculty Advisor: Claudio Battaglini
Faculty Advisor Contact Information: (919) 843-6045
_________________________________________________________________
What are some general things you should know about research studies?
You are being asked to take part in a research study. To join the study is voluntary.
56
You may refuse to join, or you may withdraw your consent to be in the study, for any reason,
without penalty.
Research studies are designed to obtain new knowledge. This new information may help people
in the future. You may not receive any direct benefit from being in the research study. There
also may be risks to being in research studies. Deciding not to be in the study or leaving the
study before it is done will not affect your relationship with the researcher, your health care
provider, or the University of North Carolina-Chapel Hill. If you are a patient with an illness,
you do not have to be in the research study in order to receive health care.
Details about this study are discussed below. It is important that you understand this information
so that you can make an informed choice about being in this research study.
You will be given a copy of this consent form. You should ask the researchers named above, or
staff members who may assist them, any questions you have about this study at any time.
What is the purpose of this study?
The current study seeks to determine whether men and women fatigue at different rates during
resistance exercise, or recover at different rates from resistance exercise. This will be
accomplished by having trained men and women complete a standardized bench press workout,
observing the number of reps completed during the workout, and monitoring performance
recovery and sor3ness for the subsequent three days.
You are being asked to be in the study because you fit the following inclusion criteria below:
• You are between 18 and 35 years of age;
• You have at least one year of continuous experience with the bench press exercise;
• You have not had any injury within the past six months that would preclude you from
safely participating or putting forth your best effort in any aspect of the study.
Are there any reasons you should not be in this study?
You should not be in this study if you have any medical condition that affects the skeletal bones,
or skeletal muscles, or if you have any current injuries or limitations that affect your ability to
57
bench press. You should not be in this study if your doctor has warned against participation in
strenuous exercise.
How many people will take part in this study?
There will be approximately 40 people in this research study.
How long will your part in this study last?
You will be asked to report to the laboratory a total of 6 times regarding testing and resistance
training sessions during the span of approximately 8-10 days. Visits 1 and 2 (initial testing) will
last approximately 45 minutes, visit 3 (the exercise protocol) will last approximately one hour,
and visits 4-6 (monitoring recovery) will last approximately 30 minutes. The overall length of
time that you will approximately participate in this study will be 4 hours.
What will happen if you take part in the study?
Participation in this study will require you to report to the Exercise Oncology Research
Laboratory (EORL) and women’s basketball weight room (WBWR). The EORL is located in
Fetzer Hall, and the WBWR is located in Woollen Gym at the University of North Carolina at
Chapel Hill. All study procedures are a requirement of participation in the study.
Laboratory Visit 1:
The purpose of the first laboratory visit is to provide you with an overview of the study, give you
an opportunity to ask questions, sign this informed consent form, retrieve demographic
information about you, provide questionnaires about your sleep, stress, and training habits,
perform anthropometric testing, and perform strength testing. Specific procedures are outlined
below:
1. Provide opportunity to ask any questions you may have about the study;
2. Sign informed consent form;
3. Fill our surveys about training practices, sleep, and stress;
4. Undergo body composition testing (DEXA scan);
5. Perform a 1 repetition-maximum (1RM) bench press test
58
When arriving to the EORL for the initial visit, you will be screened for participation in the
study, given an opportunity to ask questions about the study, and sign the informed consent form
if you choose to participate. After the form is signed, your height and weight will be assessed,
and you will be given questionnaires assessing your stress, sleep habits, and training practices.
Once these questionnaires are completed, you will undergo a DEXA scan to assess body
composition.
Lastly, you will undergo a 1RM assessment for the bench press exercise in order to determine
training load during the fatiguing exercise session during visit 3. You will be instructed on
proper form, and complete six warm-up sets prior to 1RM attempts. During these warm-up sets,
consisting of sets of 3 repetitions with 30%, 40%, 50%, 60%, 70%, and 80% of 1RM, you will
be instructed to lift every rep as explosively as possible, in order to assess your load-velocity
profile. The 1RM value will be defined as the maximum amount of weight that can be lifted once
with proper form.
Before leaving the laboratory, you will be given a three day food log, and instructions on how to
accurately fill it out.
Pre-assessment guidelines for this visit are as follows:
1. Be at least 8 hours fasted
2. Void completely before testing.
3. Maintain proper hydration prior to testing.
4. Please wear appropriate clothing/shoes for testing (close-toes shoes, and clothes that do not
restrict movement)
5. No upper body exercise 48 hours prior to testing.
6. No alcohol consumption 24 hours prior to testing.
7. No caffeine consumption 8 hours prior to testing.
Laboratory Visit 2
This visit will take place 48-72 hours after visit 1. The purpose of this visit is to confirm the
results of the strength assessment on visit 1. This visit will begin by retesting 1RM and load-
velocity profile. Following a five-minute recovery interval, you will then complete as many reps
as possible with 75% of your 1RM from either visit 1 or visit 2 (whichever is higher).
Laboratory Visit 3
Visit 3 will take place 48-72 hours after visit 2. The visit will begin with a finger prick to assess
blood lactate levels. After this, we will retest load-velocity profile. Then, the fatiguing exercise
59
protocol will take place. It will consist of sets of 5 repetitions with 75% of 1RM with 90 seconds
between sets. You will perform sets until you can no longer complete another repetition with
proper technique. Five minutes after the completion of this test, there will be another finger prick
to assess blood lactate levels. Ten minutes after the completion of the test, we we retest load-
velocity profile.
Laboratory Visits 4-6
Visits 4-6 will consist of recovery assessments. We will begin with an assessment of soreness in
the chest muscles, triceps, and front deltoids. We will also ask you about your perceived stress
levels, and about sleep duration and quality for the previous night. To assess performance
recovery, we will test load-velocity profile. The three-day food log will be returned during one of
these sessions once it is completed.
For all visits except visit 1, you will be expected to have eaten within 2 hours of the start of the
visit. You will be expected to have abstained from caffeine for at least 8 hours prior to testing.
What are the possible benefits from being in this study?
Research is designed to benefit society by gaining new knowledge. The benefits to you from
being in this study may be the opportunity to have your body composition assessed during visit
1. Further, you will be able to see the strength of your upper body strength, endurance,
explosiveness, and recovery rate. Due to the expensive nature of some of these testing
procedures, most fitness professionals (coaches, personal trainers, etc.) do no have the ability to
access these types of test, and therefore, will not be able to precisely determine your body
composition, recovery rate, and load-velocity profile as accurately as we will be able to. The
ultimate benefit from this study is that you will be able to leave with a better idea of your
performance capacity and recovery rate when planning future resistance training.
What are the possible risks or discomforts involved from being in this study?
Physiological and psychological risk/harm is very minimal and would not cost you physical or
emotional loss. Despite this, there is always the chance that exercise participation may result in
soreness or injuries to the muscles, joints, and bones. Possible injuries from exercise can include
muscle or joint aches, torn muscles, or sprained ligaments. If an unlikely injury does occur while
participating in the study, members of the research team will assess the injured area and take
appropriate actions for medical care if necessary. In the event that any uncommon or previously
unknown risks surface, you should inform a member of the research team.
60
What if we learn about new findings or information during the study?
You will be given any new information gained during the course of the study that might affect
your willingness to continue your participation.
How will information about you be protected?
You will not be identified in any report or publication about this study. Although every effort
will be made to keep research records private, there may be times when federal or state law
requires the disclosure of such records, including personal information. This is very unlikely, but
if disclosure is ever required, UNC-Chapel Hill will take steps allowable by law to protect the
privacy of personal information. In some cases, your information in this research study could be
reviewed by representatives of the University, research sponsors, or government agencies (for
example, the FDA) for purposes such as quality control or safety.
All data obtained from you throughout the course of the study will be coded using a research ID
number. Only members of the research team will have access to these codes. Data collection
sheets will be stored in a locked cabinet within the EORL that can only be opened by key card
access. Access will only be given to those of the research team. Study databases will not have
any identifiable information that will cause subjects to be identified by anyone other than a
member of the research team.
What will happen if you are injured by this research?
All research involves a chance that something bad might happen to you. This may include the
risk of personal injury. In spite of all safety measures, you might develop a reaction or injury
from being in this study. If such problems occur, the researchers will help you get medical care,
but any costs for the medical care will be billed to you and/or your insurance company. The
University of North Carolina at Chapel Hill has not set aside funds to pay you for any such
reactions or injuries, or for the related medical care. You do not give up any of your legal rights
by signing this form.
What if you want to stop before your part in the study is complete?
You can withdraw from this study at any time, without penalty. The investigators also have the
right to stop your participation at any time. This could be because you have had an unexpected
reaction, you have become ill, you use a medication that may influence the outcome variables
within the study, you are not able to complete required exercise sessions, you fail to show up or a
laboratory visit, or because the study as a whole has been terminated. In the even that you decide
61
to withdraw from the study, all collected data from you will be destroyed and not used in the data
analysis process.
Will you receive anything for being in this study?
You will receive a written report of your body composition testing during visit 1. After data
collection for the study is completed, we can send you information about your load-velocity
profile, fatigue rate, and recovery rate.
Will it cost you anything to be in this study?
The cost of transportation to the lab will not be provided. However, parking will be provided to
you for free, and it is located right behind Fetzer Hall, just a few meters (approximately 50
meters) from the laboratories where the study will be conducted.
What if you have questions about this study?
You have the right to ask, and have answered, any questions you may have about this research. If
you have questions about the study (including payments), complaints, concerns, or if a research-
related injury occurs, you should contact the researchers listed on the first page of this form.
What if you have questions about your rights as a research participant?
All research on human volunteers is reviewed by a committee that works to protect your rights
and welfare. If you have questions or concerns about your rights as a research subject, or if you
would like to obtain information or offer input, you may contact the Institutional Review Board
at 919-966-3113 or by email to IRB_subjects@unc.edu.
62
Participant’s Agreement:
I have read the information provided above. I have asked all the questions I have at this time. I
voluntarily agree to participate in this research study.
_____________________________________________________
Signature of Research Participant
_________________
Date
_____________________________________________________
Printed Name of Research Participant
_____________________________________________________
Signature of Research Team Member Obtaining Consent
_________________
Date
_____________________________________________________
Printed Name of Research Team Member Obtaining Consent
63
APPENDIX B : Surveys and Questionnaires
PITTSBURGH SLEEP QUALITY INDEX
64
PERCEIVED STRESS QUESTIONNAIRE
SUBJECT ID_____________________________
The questions in this scale ask you about your feelings and thoughts during the last month. In
each case, you will be asked to indicate how often you felt or thought a certain way. Although
some of the questions are similar, there are differences between them and you should treat each
one as a separate question. The best approach is the answer each question fairly quickly. That is,
don’t try to count up the number of times you felt a particular way, but rather indicate the
alternative that seems like a reasonable estimate.
For each question, choose from the following alternatives :
1. Never
2. Almost never
3. Sometimes
4. Fairly often
5. Very often
65
1) In the last month, how often have you been upset because of something that happened
unexpectedly? _____________
2) In the last month, how often have you felt that you were unable to control the important things
in your life? _____________
3) In the last month, how often have you felt nervous and “stressed”? _____________
4) In the last month, how often have you dealt successfully with irritating life hassles? -
_____________
5) In the last month, how often have you felt that you were effectively coping with important
changes that were occurring in your life? _____________
6) In the last month, how often have you felt confident about your ability to handle your personal
problems? _____________
7) in the last month, how often have you felt that things were going your way? _____________
8) In the last month, how often have you found that you could not cope with all the things that
you had to do? _____________
9) In the last month, how often have you been able to control irritations in your life? -
_____________
10) In the last month, how often have you felt that you were on top of things? _____________
11) In the last month, how often have you been angered because of things that happened that
were outside of your control? _____________
66
12) In the last month, how often have you found yourself thinking about things that you have to
accomplish? _____________
13) In the last month, how often have you been able to control the way you spend your time? -
_____________
14) In the last month, how often have you felt difficulties were piling up so high that you could
not overcome them? _____________
Cohen S, Kamarck T, Mermelsetein R. A Global Measure of Perceived Stress. Journal of Health and Social Behavior. 1983, 24(4): 385-96.
67
BASELINE TRAINING ASSESSMENT
Subject ID:__________
Date:____________
Years of resistance training:
Years of bench pressing:
Bench press frequency (sessions per week):
Bench press sets per week:
Estimated proportion of bench press sets of <5 reps:
Estimated proportion of bench press sets of 5-15 reps:
Estimated proportion of bench press sets of >15 reps:
Estimated rest intervals between sets of bench press:
Primary goal when bench pressing (circle one):
Muscle growth Strength Endurance Strength gains
68
Recovery Assessments
Subject ID: ____________
Date: _____________
Session Number: ______________
Days post-workout: ______________
Sleep duration (hours): ______________
Sleep Quality
_______________________________________________
The worst sleep imaginable Perfect Sleep
69
Pectoral Soreness
_______________________________________________
No Soreness Maximal Soreness
70
Triceps Soreness
_______________________________________________
No Soreness Maximal Soreness
71
Anterior Deltoid Soreness
_______________________________________________
No Soreness Maximal Soreness
72
FOOD RECORD
Subject ID: ____________
Food record day: _____________
Date: ______________
Week day or weekend? ______________
Food, beverage, or supplement
Amount
Time
Food, beverage, or supplement
Amount
Time
73
Instructions:
Fill in the food record as soon as you can after consuming a food item, beverage, or supplement.
When possible, include brand names (e.g. “Campbell’s chicken noodle soup” rather than just
“chicken noodle soup”). If you don’t know the brand name, be as specific as possible.
When possible, include the weight or volume measurement of the food or beverage you consume
(e.g. “4 oz. of chicken” not “1 serving of chicken” or “12 oz of Coke” not “1 can of Coke”)
Don’t forget dressings and condiments, or things you add to foods or beverages (for example,
sugar and cream in coffee).
Don’t forget cooking oils or butter.
When possible, be as specific as possible about the way a food was prepared (e.g. “baked
chicken thigh without skin” or “fried chicken breast with the skin on,” not just “chicken”)
74
APPENDIX C: Data Collection Sheets
DATA COLLECTION FORM, SESSION 1
Informed consent? ____________
Subject ID:__________
Date:____________
Weight (kg): ____________
Height (cm): ____________
Pregnancy test? ____________
DEXA completed? ____________
Arm lean mass: ____________
PSQI completed? ____________
PSQ completed? ____________
Training history completed? ____________
3-day food log given? ____________
75
Visit 1
Load-velocity testing
Estimated 30% 1RM load: ____________ MCV: ____________
40%: ____________ MCV: ____________
50%: ____________ MCV: ____________
60%: ____________ MCV: ____________
70%: ____________ MCV: ____________
80%: ____________ MCV: ____________
1RM testing
1RM attempt 1: ____________
Attempt 2: ____________
Attempt 3: ____________
Attempt 4: ____________
Attempt 5: ____________
Best completed attempt: ____________
MCV at 1RM: ____________
76
DATA COLLECTION FORM, SESSION 2
Visit 2
Subject ID: ____________
Date: ____________
Load-velocity testing
30% 1RM load: ____________ MCV: ____________
40%: ____________ MCV: ____________
50%: ____________ MCV: ____________
60%: ____________ MCV: ____________
70%: ____________ MCV: ____________
80%: ____________ MCV: ____________
1RM testing
1RM attempt 1: ____________
Attempt 2: ____________
Attempt 3: ____________
Attempt 4: ____________
Attempt 5: ____________
Best completed attempt: ____________
MCV at 1RM: ____________
Reps to failure
77
75% 1RM load: ____________
Reps completed: ____________
DATA COLLECTION FORM, SESSION 3
Visit 3
Subject ID: ____________
Date: ____________
Pre-exercise blood lactate: ____________
Load-velocity testing pre
30% 1RM load: ____________ MCV: ____________
40%: ____________ MCV: ____________
50%: ____________ MCV: ____________
60%: ____________ MCV: ____________
70%: ____________ MCV: ____________
80%: ____________ MCV: ____________
Fatiguing exercise protocol
75% 1RM load: ____________
Sets completed:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21
Reps completed on failure set: ____________
Post-exercise blood lactate: ____________
78
Load-velocity testing post
30% 1RM load: ____________ MCV: ____________
40%: ____________ MCV: ____________
50%: ____________ MCV: ____________
60%: ____________ MCV: ____________
70%: ____________ MCV: ____________
80%: ____________ MCV: ____________
79
DATA COLLECTION FORM, SESSIONS 4-6
Visit 4 5 6 (circle one)
Subject ID: ____________
Date: ____________
VAS completed? ____________
Load-velocity testing
30% 1RM load: ____________ MCV: ____________
40%: ____________ MCV: ____________
50%: ____________ MCV: ____________
60%: ____________ MCV: ____________
70%: ____________ MCV: ____________
80%: ____________ MCV: ____________
3 day food log returned? ____________
80
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