Transcript Presentation Package - University of North Texas

chapter
18
Sex Differences
in Sport and
Exercise
Did You Know . . . ?
Performance differences between men and women
likely result from biological differences as well as
social and cultural restrictions placed on females
during their development and the fact that, historically,
fewer women have competed in athletic events than
men.
Body Size and Composition
• Major differences between boys and girls do not occur
until puberty.
• Puberty in girls—estrogen causes pelvis broadening,
breast development, fat deposition in hips and thighs,
and increased bone growth.
• Puberty in boys—testosterone causes increased bone
formation and muscle mass.
• After puberty, girls’ average relative body fat is 6% to
10% greater than that of boys.
Changes in Blood Concentrations of
Testosterone and Estrogen From Birth to
Adulthood
Reprinted, by permission, from R.M. Malina, C. Bouchard, and O. Bar-Or, 2004, Growth, maturation, and
physical activity, 2nd ed. (Champaign, IL: Human Kinetics), 414.
How Fat Is Stored
1. Estrogen increases activity of lipoprotein lipase, which
is produced by fat cells.
2. Lipoprotein lipase is bound to walls of capillaries.
3. Chylomicrons—major transporter of triglycerides—
pass by in the blood.
4. Lipoprotein lipase traps chylomicrons and transports
them to fat cells.
5. A decrease in lipolytic activity at the sites of fat
storage makes it difficult to lose fat.
Neuromuscular Responses
in Women
• Innate qualities of muscle and motor control are similar.
• For the same amount of muscle, strength is similar.
• Muscle fiber cross-sectional areas are smaller and
muscle mass is less.
• More muscle mass is distributed below the waist.
• Upper-body strength expressed relative to body weight
or fat-free mass is less.
No Sex Differences Are Seen When
Strength Is Expressed per Unit of Muscle
Cross-Sectional Area
Reprinted, by permission, from P. Schantz et al., 1983, "Muscle fibre type distribution, muscle cross-sectional
area and maximal voluntary strength in humans," Acta Physiologica Scandinavica 117: 219-226.
Distribution of Type I Fibers in the Vastus
Lateralis Muscle in Male and Female
Runners
Adapted, by permission, from B. Saltin et al., 1977, “Fiber types and metabolic potentials of skeletal muscles
in sedentary man and endurance runners,” Annals of the New York Academy of Sciences 301: 3-29.
Cardiovascular Responses
in Women
• Higher heart rate response for absolute levels of
submaximal exercise.
.
• Same HRmax and Q submaximal levels
• Lower SV due to smaller heart size and blood volume
• Less potential for increasing (a-v)O
2 diff
• Lower hemoglobin content
Comparison of Submaximal Heart Rate
(HR), Stroke
. Volume (SV), and Cardiac
Output (Q) Between Men and Women
Data from HERITAGE Family Study, 2001.
Respiratory Responses in Women
• Differences in response mostly due to differences in
body size
• More frequent breathing at maximal power output
• Smaller tidal volume
• Smaller ventilatory volume
Differences in Maximal Ventilatory
Volumes With Age in Untrained (UT) and
Trained (TR) Females and Males
Metabolic Responses in Women
.
• Average VO2max after puberty is 70% versus
average man’s 75%.
 More sex-specific essential body fat
 Lower hemoglobin levels
.
 Lower Q at maximal rates of work
.
• VO2 at same absolute rates of work are same as a
man’s.
• Relative lactate threshold values are similar.
Key Points
Adaptations to Acute Exercise
• For the same amount of muscle, there are no
differences in strength between the sexes.
• Women have smaller muscle fibers and less muscle
mass than men.
• Women have smaller left ventricles and lower blood
volume, which reduce stroke volume.
(continued)
Key Points (continued)
Adaptations to Acute Exercise
• Women have similar cardiac outputs as men for
the same rate of work, but that is achieved through
higher heart rates, which account for lower stroke
volumes.
• Women’s differences in respiratory response
during exercise are mostly due to their smaller
body size.
.
• VO2max values for women are generally lower than
men’s due to women’s extra essential body fat,
lower blood hemoglobin levels, and lower cardiac
output.
.
Range of VO2max for Female Nonathletes,
Male Nonathletes, Elite Female Athletes,
and Elite Male Athletes
Data from L. Hermansen and K.L. Andersen, 1965, "Aerobic work capacity in young Norwegian men and
women," Journal of Applied Physiology 20: 425-431.
.
VO2max Values for Elite Female and Male
Distance Runners Compared With Average
Values in Untrained Women and Men
Data from S. Robinson, 1938, "Experimental studies of physical fitness in relation to age," Arbeitsphysiologie 10: 251-323; I.
Astrand, 1960, "Aerobic work capacity in men and women with special reference to age," Acta Physiologica Scandinavica 49
(Suppl. 169); D.L. Costill and E. Winrow, 1971, "Maximal oxygen intake among marathon runners," Archives of Physical
Medicine and Rehabilitation 51: 317-320; M.L. Pollock, 1977, "Submaximal and maximal working capacity of elite distance
runners: Part I. Cardiorespiratory aspects," Annals of the New York Academy of Sciences 301: 310-322; RR. Pate et al., 1987,
"Cardiorespiratory and metabolic responses to submaximal and maximal exercise in elite women distance runners,"
International Journal of Sports Medicine 8 (Suppl. 2): 91-95; and J.H. Wilmore and C.H. Brown, 1974, "Physiological profiles
of women distance runners," Medicine and Science in Sports 6: 178-181.
Training and Body Composition in
Women
• Decreases in fat mass and increases in fat-free mass
(FFM), though women generally gain less FFM than
men.
• Losses in body mass are more related to energy
expenditure than participant’s sex.
• Density of weight-bearing bones increases equally in
both sexes.
• Endurance training strengthens connective tissue in
both sexes.
Neuromuscular Adaptations
in Women
• Women’s magnitude of strength gained from resistance
training is similar to men’s.
• Women generally don’t gain as much muscle size as
men do from resistance training.
• Less muscle mass is a result of lower testosterone
levels.
Men’s and Women’s World Weightlifting
Records as of 2006 for the Total Amount of
Weight Lifted
Key Points
Adaptations to Exercise Training
• Women generally gain less FFM than men.
• Women can gain considerable strength but not
large increases in muscle bulk.
• Cardiovascular and respiratory changes do not
appear to be sex specific.
• Women
experience the same relative increases in
.
VO2max as men.
(continued)
Key Points (continued)
Women’s Athletic Performance
• Men have more of an advantage than women in
sports using upper body strength.
• The gap between men’s and women’s world
records is narrowing.
• Since the 1970s more women are participating in
sports and are being trained as hard as their male
counterparts.
Phases of the Menstrual Cycle
Did You Know . . . ?
Some female athletes have reportedly set world
records during the flow phase while other women
report that their performance is inhibited during this
phase of the menstrual cycle. No general pattern has
been found concerning the ability of women to
achieve their best athletic performances during any
specific phase of the menstrual cycle.
Cause or Effect?
Menarche (the first menses) tends to come about 2
yrs later in higher-trained athletes in sports such as
gymnastics and ballet than in other girls. Does intense
training to achieve the level of elite athlete delay
menarche, or does a later menarche provide an
advantage that contributes to the success of an elite
athlete?
Types of Menstrual Dysfunction
Eumenorrhea is normal menstrual function.
Oligomenorrhea is abnormally infrequent or scant
menstruation.
Amenorrhea is absence of menstruation.
• Primary amenorrhea is absence of first menses in
women 18 and older.
• Secondary amenorrhea is absence of menstruation
sometime after first menses.
Menstrual Dysfunction
• May occur in 2% to 12% of general population.
• May occur in 5% to 40% of female athletes.
• Risk increases with increased duration or intensity of
training.
• Athletes can become pregnant while amenorrheic.
Possible Causes of Menstrual
Dysfunction
•
•
•
•
•
History of menstrual dysfunction
Acute stress
High training volume or intensity
Low body weight or body fat
Inadequate nutrition (energy deficit) and disordered
eating
• Hormonal alterations
Concerns of Exercising During
Pregnancy
1. Reduced uterine blood flow leading to insufficient
oxygen to the fetus
2. The fetus could suffer from hyperthermia due to
increased exercising temperature
3. Reduced carbohydrate availability to the fetus
4. The possibility of miscarriage and other dangers to
the final outcome of pregnancy
Did You Know . . . ?
The benefits of a properly prescribed exercise
program during pregnancy outweigh the potential
risks. It is important that the exercise program during
pregnancy be coordinated with the woman’s
obstetrician.
Cardiovascular Responses
in Women
•
•
•
•
•
•
Bone mineral loss with aging (especially in women)
Estrogen deficiency
Inadequate calcium intake before early 30s
Inadequate physical activity
Amenorrhea
Anorexia nervosa
Did You Know . . . ?
Disordered eating is not the same thing as eating
disorders, yet both are causes for concern. The
prevalence of both is higher among female athletes
than male, especially in appearance, endurance, or
weight-classification sports.
(a) Healthy Bone, and (b) Bone Showing
Increased Porosity Resulting From
Osteoporosis
Reproduced from Journal of Bone and Mineral Research 1986, 1:15-21 with permission of the American
Society for Bone and Mineral Research. Photos provided courtesy of D.W. Dempster.
Bone Mineral Content of Female Runners
and Untrained Women Who Are
Amenorrheic (Am) and Eumenorrheic (Eu)
Unpublished data from Dr. Barbara Drinkwater.
Anorexia Nervosa
• Refusal to maintain more than the minimal normal
weight based on age and height (<1%)
• Distorted body image
• Intense fear of fatness or gaining weight
• Amenorrhea
Bulimia Nervosa
• Recurrent episodes of binge eating (1-4%)
• A feeling of lack of control during binges
• Purging behavior—self-induced vomiting, laxative use,
and/or diuretic use
Anorexia Athletica
• Not yet clinically recognized as eating disorder
• Intense fear of gaining weight or fat though
underweight
• A weight loss of at least 5% accomplished by energy
deficit
• Use of bingeing, self-induced vomiting, laxatives, or
diuretics
Female Athlete Triad
• Disordered eating
• Secondary amenorrhea
• Bone mineral disorders
Key Points
Environment and Performance
• Women have lower sweat rates due to lower sweat
production, but this does not appear to inhibit their
ability to tolerate heat.
• Women have more insulating subcutaneous fat
than men and thus a slight advantage over men
during cold exposure.
• Women’s smaller muscle mass limits their ability to
generate as much body heat as men through
shivering.
• Women and men have a similar response during
exercise at altitude.