C H A P T E R 18. SEX DIFFERENCES IN SPORT AND EXERCISE. w Learn how trained and untrained females' VO 2 max values differ from trained and untrained males. . (continued). Learning Objectives.
SEX DIFFERENCES IN SPORT AND EXERCISE
w Learn how trained and untrained females' VO2max values differ from trained and untrained males.
w Differentiate between the body composition of females and males and between female and male athletes and nonathletes.
w Discover the role of testosterone in the development of strength and fat-free mass.
w Find out the differences in upper and lower body strength between men and women.
w Learn if the menstrual cycle affects athletic performance and if athletic performance affects the menstrual cycle.
w Find out if there are risks to exercising during pregnancy.
w Examine the relationship among eating disorders, amenorrhea, and bone mineral loss.
w Discover if women and men differ in their exercise responses to altitude, heat, humidity, and cold.
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.
w Major differences between boys and girls do not occur until puberty
w Puberty in girls—estrogen causes pelvis broadening, breast development, fat deposition in hips and thighs, increased bone growth, and faster closure of growth plates
w Puberty in boys—testosterone causes increased bone formation and muscle mass
w After puberty, girls’ average relative body fat is about 10% greater than boys
w Men not only have a greater muscle mass, but they carry a higher percentage of their muscle mass in the upper body compared to women
1. Estrogen increases activity of lipoprotein lipase (LPL—produced by fat cells), particularly in the hips and thighs.
2. LPL is bound to walls of capillaries.
3. Chylomicrons—major transporters of triglycerides—pass by in the blood.
4. LPL removes FFA from triglycerides in chylomicrons and they are taken up by fat cells where most of the fat is stored.
5. There is a decrease in lypolytic activity in the sites of fat storage in the hip and thigh areas making it difficult to lose fat in these areas.
Age group (years) Women Men
15-19 20-24 13-16
20-29 22-25 15-20
30-39 24-30 18-26
40-49 27-33 23-29
50-59 30-36 26-33
60-69 30-36 29-33
Relative Body Fat Values for Average, Untrained Women and Men of Various Ages
w Innate qualities of muscle and motor control are similar
w For the same amount of muscle, strength is similar
w Muscle fiber cross-sectional areas are smaller and muscle mass is less in women
w More muscle mass is proportionately distributed below the waist in women
w Upper-body strength expressed relative to body weight or fat-free mass is less in women
w Same HRmax but lower Qmax because of lower SVmax
w Less potential for increasing a-vO2 diff because of the lower arterial O2 content (lower Hb concentration)
Cardiovascular Responses in Women
w Higher heart rate response at rest and for same absolute levels of submaximal exercise (about the same Q as men)
w Lower SV at rest and at all exercise intensities due to smaller heart size and smaller blood volume
SUBMAXIMAL HR, SV, AND Q
Same absolute poweroutput (50 W)
Same relative poweroutput (60% VO2max)
w Differences in response from men are mostly due to smaller body size
w Higher respiratory rate at given ventilatory rate
w Smaller tidal volume at given ventialtory rate
w Smaller ventilatory volume during maximal exercise due to smaller lungs
w Average VO2max after puberty is 70% to 75% of the average man’s VO2max—much closer before puberty
– More sex specific body fat
– Lower hemoglobin levels and lower total blood volume
– Smaller heart size, thus lower Qmax
w VO2 at same absolute rate of work is similar to a man's
w Relative lactate threshold values are similar (i.e., % of VO2max)
Metabolic Responses in Women
RANGE OF VO2MAX VALUES
77 ml/kg/min: Female
Russian x-country skier
94 ml/kg/min: Male
Norwegian x-country skier
VO2max: Elite Distance Runners and Untrained Subjects
w Decreases in fat mass and increases in fat-free mass (FFM), though women generally gain less FFM than men.
w Losses in body mass are more related to energy expenditure than to the participant's gender.
w Density of weight-bearing bones increases equally in both sexes.
w Endurance training strengthens connective tissue in both sexes.
w Women's magnitude of strength gained from resistance training (% increase) is similar to men's.
w Women generally don't gain as much muscle size as men from resistance training.
w Less muscle mass development is because of lower testosterone levels.
Totals are for the two Olympic lifts, snatch and clean and jerk. The highest weight classification records are not included.
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 their menstrual cycle.
Menarche (the first menses) tends to come later in highly trained elite athletes in sports or activities 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 the elite athlete?
w Primary—absence of first menses in women 18 and older
w Secondary—absence of menstruation sometime after first menses, for at least three consecutive cycles
Normal and Abnormal Menstrual Function
Menarche—the first menses (can be delayed)
Eumenorrhea—normal menstrual function
Oligomenorrhea—abnormally infrequent or scant menstruation
w May occur in 2% to 12% of women in general population
w May occur in up to 40% of female athletes, depending on the sport and the level of competition
w Risk increases with increased duration or intensity of training
w Amenorrhea does not necessarily prevent pregnancy, even though some athletes believe amenorrhea is a method of birth control
w Prior history of menstrual dysfunction
w Acute stress (anxiety, depression, etc.)
w High training volume or intensity
w Low body weight or body fat; fat converts pre-estrogen steroids into estrogen, so low body fat might affect estrogen levels
w Hormonal alterations; e.g., training reduces LH and FSH secretion
wProbably the most important factor: inadequate nutrition (energy deficit) and disordered eating; thus training can contribute to the energy deficit; Study: 8 of 13 amenorrheic runners had eating disorders, compared with 0 of 19 eumenorrheic runners
Eating disorders are more serious than “disordered eating” (abnormal eating patterns), but both are causes for concern. The prevalence for both are higher for female athletes than male, especially in appearance, endurance, or weight-classification sports.
w Refusal to maintain more than the minimal normal weight based on age and height
w Distorted body image
w Intense fear of fatness or gaining weight
w Recurrent episodes of binge eating; >2/week for 3 months
w A feeling of lack of control during these binges
w Not yet clinically recognized as an eating disorder
w Intense fear of gaining weight or fat though underweight
w A weight loss of at least 5% accomplished by energy deficit
w Use of bingeing, self-induced vomiting, laxatives, or diuretics
w Disordered eating
w Secondary amenorrhea
w Bone mineral disorders
w Bone mineral loss with aging (especially in women)
w Estrogen deficiency
w Inadequate calcium intake before early 30s
w Inadequate physical activity
w Anorexia nervosa
1. Will reduced uterine blood flow lead to insufficient oxygen to fetus, i.e., competition for maternal Q?
2. Will the fetus suffer from hyperthermia due to increased maternal body temperature?
3. Will there be reduced carbohydrate availability to the fetus because of increased maternal CHO metabolism?
4. Are there dangers of miscarriage and the final outcome of pregnancy because of mechanical factors associated with the exercise (e.g., the shocks or jolts from running?
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.
Environment and Performance
w Women have lower sweat rates due to lower sweat production, but this does not appear to inhibit their ability to tolerate heat.
w Women have more insulating subcutaneous fat than men and, thus, a slight advantage over men during cold exposure, but not in high temperatures.
w Women’s smaller muscle mass limits their ability to generate as much body heat as men through shivering.
w Women and men have a similar response during exercise at altitude.