Sex Differences in Sport and Exercise. CHAPTER 19 Overview Body size and composition Physiological...

Sex Differences in Sport and Exercise

CHAPTER 19 CHAPTER 19 OverviewOverview

• Body size and composition

• Physiological responses to acute exercise

• Physiological adaptations to exercise training

• Sport performance

• Special issues

Introduction to Sex Differences in Introduction to Sex Differences in Sport and ExerciseSport 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 19.1Table 19.1

Body Size and CompositionBody 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 19.1Figure 19.1

Body Size and CompositionBody 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 Physiological Responses to Acute Exerciseto 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


• 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


• 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


• 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


• 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


• 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


• 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 Physiological Adaptations to Exercise Trainingto 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


• 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?


• 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


• 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 PerformanceSport 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 19.9Figure 19.9aa

Figure 19.9Figure 19.9bb

Figure 19.9Figure 19.9cc

Figure 19.9Figure 19.9dd

Figure 19.9Figure 19.9ee

Figure 19.9Figure 19.9ff

Special IssuesSpecial Issues

• Menstruation, menstrual dysfunction

• Pregnancy

• Osteoporosis

• Eating disorders

• Environmental factors

Special Issues: MenstruationSpecial 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

Special Issues: MenstruationSpecial 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:Special Issues:Menstrual DysfunctionMenstrual 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


• 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


• 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:Special Issues:Pregnancy ConcernsPregnancy 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:Special Issues:Pregnancy ResearchPregnancy 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:Special Issues:Pregnancy RecommendationsPregnancy 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:Special Issues:Pregnancy RecommendationsPregnancy 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

Special Issues:Special Issues:OsteoporosisOsteoporosis

• 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 19.11Figure 19.11aa

Figure 19.11Figure 19.11bb

Special Issues:Special Issues:OsteoporosisOsteoporosis

• 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:Special Issues:Eating DisordersEating 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)


• 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


• 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

Special Issues:Special Issues:Female Athlete TriadFemale 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:Special Issues:Environmental FactorsEnvironmental 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

Sex Differences in Sport and Exercise. CHAPTER 19 Overview Body size and composition Physiological...

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