Transcript Slide 1

Sex Differences in Sport
and Exercise
CHAPTER 19 Overview
• Body size and composition
• Physiological responses to acute exercise
• Physiological adaptations to exercise training
• Sport performance
• Special issues
Introduction to Sex Differences in
Sport and Exercise
• For decades, culture, athletic governing
bodies, and PE curricula perpetuated the
myth that girls and women should not
compete in sport
• Last 30 to 40 years, girls and women have
achieved great athletic feats
– Sex differences in performance still exist
– Separating biological versus other factors
Table 19.1
Body Size and Composition
• Testosterone leads to
–  Bone formation, larger bones
–  Protein synthesis, larger muscles
–  EPO secretion,  red blood cell production
• Estrogen leads to
–  Fat deposition (lipoprotein lipase)
– Faster, more brief bone growth
– Shorter stature, lower total body mass
–  Fat mass, percent body fat
Figure 19.1
Body Size and Composition
• Distinct female fat deposition pattern
• Rapid storage on hips and thighs due to 
lipoprotein lipase activity
•  Lipolytic activity makes regional fat loss
more difficult
• Lipoprotein lipase , lipolysis  during
third trimester of pregnancy, lactation
Physiological Responses
to Acute Exercise
• Muscle strength differs between sexes
– Upper body: women 40 to 60% weaker
– Lower body: women 25 to 30% weaker
– Due to total muscle mass difference, not difference
in innate muscle mechanisms
• No sex strength disparity when expressed
per unit of muscle cross-sectional area
Figure 19.2
Physiological Responses
to Acute Exercise
• Causes of upper-body strength disparity
– Women have more muscle mass in lower body
– Women utilize lower body strength more
– Altered neuromuscular mechanisms?
• Women: smaller cross-sectional areas
• Similar fiber-type distribution
• Research indicates women more fatigue
resistant
Figure 19.3
Physiological Responses
to Acute Exercise
• Cardiovascular function differs greatly
• For same absolute submaximal workload
– Same cardiac output
– Women: lower stroke volume, higher HR
(compensatory)
– Smaller hearts, lower blood volume
• For same relative submaximal workload
– Women: HR slightly , SV , cardiac output 
– Leads to  O2 consumption
Figure 19.4
Physiological Responses
to Acute Exercise
• Women compensate for  hemoglobin via
 (a-v)O2 difference (at submaximal
intensity)
– (a-v)O2 difference ultimately limited, too
– Lower hemoglobin, lower oxidative potential
• Sex differences in respiratory function
– Due to difference in lung volume, body size
– Similar breathing frequency at same relative
workload
– Women  frequency at same absolute workload
Figure 19.5
Physiological Responses
to Acute Exercise
• Women’s VO2max < men’s VO2max
• Untrained sex comparison unfair
– Relatively sedentary nonathlete women
– Relatively active nonathlete men
• Trained sex comparison better
– Similar level of condition between sexes
– May reveal more true sex-specific differences
Figure 19.6
Figure 19.7
Physiological Responses
to Acute Exercise
• Can scale VO2max to other body variables
– Height, weight, FFM, limb volume
– Sex difference minimized or gone with scaling
• Simulated women’s fat mass on men
– Reduced sex differences in treadmill time,
submaximal VO2 (ml/kg), VO2max
– Women’s additional body fat major determinant of
sex-specific difference in metabolic responses
Physiological Responses
to Acute Exercise
• Women’s lower hemoglobin limits VO2max
• Women’s lower cardiac output limits VO2max
– SVmax limited by heart size, plasma volume
– Plasma volume loading in women helps
– Submaximal absolute VO2: no sex difference in SV
• Sex differences in lactate, threshold
– Peak lactate concentrations lower in women
– Lactate threshold occurs at same percent VO2max
Physiological Adaptations
to Exercise Training
• Body composition changes
– Same in men and women
–  Total body mass, fat mass, percent body fat
–  FFM (more with strength vs. endurance training)
• Weight-bearing exercise maintains bone
mineral density
• Connective tissue injury not related to sex
Physiological Adaptations
to Exercise Training
• Strength gains in women versus men
– Less hypertrophy in women versus men, though
some studies show similar gains with training
– Neural mechanisms more important for women
• Variations in weight lifted for equivalent
body weight
– For given body weight, trained men have more FFM
than trained women
– Fewer trained women
– Factors other than FFM?
Figure 19.8
Physiological Adaptations
to Exercise Training
• Cardiorespiratory changes not sex specific
• Aerobic, maximal intensity
–  Qmax due to  SVmax ( preload, contractility)
–  Muscle blood flow, capillary density
–  Maximal ventilation
• Aerobic, submaximal intensity
– Q unchanged
–  SV,  HR
Physiological Adaptations
to Exercise Training
• VO2max changes not sex specific
– ~15 to 20% increase
–  Qmax,  muscle blood flow
– Depends on training intensity, duration, frequency
• Lactate threshold 
• Blood lactate for given work rate 
• Women respond to training like men do
Sport Performance
• Men outperform women by all objective
standards of competition
– Most noticeable in upper-body events
– Gap narrowing
• Women’s performance drastically improved
over last 30 to 40 years
– Leveling off now
– Due to harder training
Figure 19.9a
Figure 19.9b
Figure 19.9c
Figure 19.9d
Figure 19.9e
Figure 19.9f
Special Issues
• Menstruation, menstrual dysfunction
• Pregnancy
• Osteoporosis
• Eating disorders
• Environmental factors
Special Issues: Menstruation
• Normal menstrual function
– Menstrual (flow) phase
– Proliferative phase (estrogen)
– Ovulation—follicle stimulating hormone (FSH),
luteinizing hormone (LH)
– Secretory phase (estrogen, progesterone)
• Cycle length ~28 days, can vary
Figure 19.10
Special Issues: Menstruation
• No reliable data indicate altered athletic
performance across menstrual phases
• No physiological differences in exercise
responses across menstrual phases
• World records set by women during every
menstrual phase
Special Issues:
Menstrual Dysfunction
• Menarche: first menstrual period
– May be delayed in certain sports (e.g., gymnastics)
– Delayed menarche: after age 14
• Delayed-menarche athletes self-select?
– Sport may not  delayed menarche
– Small, lean athletic girls (delayed menarche
candidates) may gravitate to sport
Special Issues:
Menstrual Dysfunction
• Menstrual dysfunction
–
–
–
–
–
Seen more in lean-physique sports
Eumenorrhea: normal
Oligomenorrhea: irregular
Amenorrhea (primary, secondary): absent
Can affect 5 to 66% of athletes
• Menstrual dysfunction ≠ infertility
Special Issues:
Menstrual Dysfunction
• Secondary amenorrhea—caused by energy
deficit (inadequate caloric intake)
–  LH pulse frequency
–  T3 secretion
–  Estrogen, progesterone
– May also involve GnRH, leptin, cortisol
• As long as caloric intake adequate, exercise
does not  secondary amenorrhea
Special Issues:
Pregnancy Concerns
1. Acute reduction in uterine blood flow
(shunt to active muscle)  fetal hypoxia
2. Fetal hyperthermia from increase in
maternal core temperature
3. Maternal CHO usage , thereby  CHO
availability to fetus
4. Miscarriage, final outcome of pregnancy
Special Issues:
Pregnancy Research
•  Uterine blood flow may not  hypoxia
– Uterine (a-v)O2 difference  may compensate
– Fetal HR  due to maternal catecholamines
• Fetal hyperthermia: unresolved
• CHO availability: unresolved
• Miscarriage, final pregnancy outcome
– Data scarce, conflicting
– Many studies show favorable (or no) effects
Special Issues:
Pregnancy Recommendations
• Mild-to-moderate exercise 3 times/week
• No supine exercise after first trimester
• Stop when fatigued
• Non-weight-bearing exercise preferable
• No risk of falling, loss of balance, etc.
Special Issues:
Pregnancy Recommendations
• Ensure adequate caloric intake
• Dress and hydrate to avoid heat stress
• Prepregnancy exercise routine should be
gradually resumed postpartum
• No scuba diving
• Benefits > risks if cautiously undertaken
Table 19.2
Special Issues:
Osteoporosis
• Osteopenia versus osteoporosis
– Risk greater in women especially after menopause
– Slowed and retarded by weight-bearing exercise
• Major contributing factors
–
–
–
–
Estrogen deficiency
Inadequate calcium intake
Inadequate physical activity
Amenorrhea, anorexia nervosa
Figure 19.11a
Figure 19.11b
Figure 19.12
Special Issues:
Osteoporosis
• Estrogen supplementation
– Originally prescribed to reverse osteoporosis
– Higher risk of cancer, stroke, heart attack
• Bisphosphonates
– Antiresorptive medication
– May slow, stop bone degeneration
• Preventive
– Diet, lifestyle
–  Ca2+, vitamin D intake
– Exercise, maintain eumenorrhea
Special Issues:
Eating Disorders
• Anorexia nervosa
– Refusal to maintain minimal normal weight
– Distorted body image, fear of fatness
– Amenorrhea
• Bulimia nervosa
– Recurrent binge eating
– Lack of control during binges
– Purging behaviors (vomiting, laxatives, diuretics)
Special Issues:
Eating Disorders
• Young women at highest risk
• Eating disorder versus disordered eating
• Worse in certain sports
–
–
–
–
Appearance sports: diving, figure skating, ballet
Endurance sports: distance running, swimming
Weight-class sports: jockeys, boxing, wrestling
Perfectionists, competitive, under tight control
• Self-reporting underestimates prevalence
Special Issues:
Eating Disorders
• Eating disorders considered addictions
–
–
–
–
Behavior reinforced by media, parents, coaches
Very difficult to treat
Often accompanied by denial
Life threatening, expensive to treat
• Must seek out trained clinical specialist
Table 19.3
Special Issues:
Female Athlete Triad
• Syndrome of interrelated conditions
– Energy deficit  secondary amenorrhea  low
bone mass
– Disordered eating may (not) be involved
• Three disorders can occur alone or in
combination, must be addressed early
• Treatment:  caloric intake,  activity (in
some cases)
Special Issues:
Environmental Factors
• Heat stress issues
– Women:  sweat production
– No sex differences in thermal tolerance
• Cold stress issues
– Women: better insulated ( subcutaneous fat)
– Men: better shivering thermogenesis ( FFM)
• Altitude stress issues
– VO2max decreases
– No sex differences in altitude tolerance