1. Sex Differences in Sport and Exercise
Chapter 19
Sex Differences in Sport and Exercise

2. Chapter 19 Overview Body size and composition
Physiological responses to acute exercise
Physiological adaptations to exercise training
Sport performance
Special issues

3. 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

4. Table 19.1

5. 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

6. Figure 19.1

7. 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

8. 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

9. Figure 19.2

10. 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

11. Figure 19.3

12. 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

13. Figure 19.4

14. 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

15. Figure 19.5

16. 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

17. Figure 19.6

18. Figure 19.7

19. 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

20. 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

21. 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

22. 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?

23. Figure 19.8

24. 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

25. 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

26. 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

27. Figure 19.9a

28. Figure 19.9b

29. Figure 19.9c

30. Figure 19.9d

31. Figure 19.9e

32. Figure 19.9f

33. Special Issues Menstruation, menstrual dysfunction Pregnancy
Osteoporosis
Eating disorders
Environmental factors

34. 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

35. Figure 19.10

36. 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

37. 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

38. Special Issues: 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

39. 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

40. 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

41. 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

42. 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.

43. 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

44. Table 19.2

45. 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

46. Figure 19.11a

47. Figure 19.11b

48. Figure 19.12

49. 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

50. 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)

51. 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

52. 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

53. Table 19.3

54. 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)

55. 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