Docstoc

Sex Differences

Document Sample
Sex Differences Powered By Docstoc
					PHYSIOLOGICAL DIFFERENCES
   by SEX with EXERCISE
Parameters to consider

    w body composition
    w testosterone:development of strength and
      fat-free mass.
    w Upper and lower body strength
     w VO2max differences
        .
     w Does menstrual cycle affects athletic
       performance and Does athletic performance
       affects the menstrual cycle?
    w Eating disorders, amenorrhea, and bone
      mineral loss.
    w Differences in their exercise responses to
      altitude, heat, humidity, and cold.
Issues regarding comparing men and women


 •   Women have higher body fat ~10%
 •   Training history differences
 •   Socio-cultural
 •   Hormonal fluctuations (women) and
     menstrual state
Biological versus Social Differences

 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

 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
SEX DIFFERENCES IN FAT-FREE MASS
Effects of Estrogen on Fat Storage

 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.
Relative Body Fat Values for Average, Untrained
Women and Men of Various Ages


                             Relative body fat %
     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
Strength Differences—Women and Men

 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 Type I fibers are largest in women whereas IIA
    fibers are largest in men
Table 3. Effect of age and gender on resistance exercise training responses


                                                  18-19 years old        20-31 years old

                                                     (N=45∞)                   (N=109#)
                                                                                               P              P
                                                                                             (age)          (gen
                              Gender              Mean         SD             Mean    SD
                                                                                                            der)
    Lean Mass Gain (kg)       Men                  2.6         1.9            1.5     1.7      0.006    0.007
                              Women                1.5         1.7            0.9     1.3


    Lean Mass Gain (%)        Men                  4.1         3.4            2.3     2.8   0.003       0.420
                              Women                3.5         3.7            2.0     2.8


    Arm Circ gain (%)         Men                  5.9         3.9            3.4     4.5   0.006       0.497
                              Women                4.8         2.7            3.5     3.5


    Leg Circ gain (%)         Men                  2.1         3.6            0.7     3.8   0.032       0.852
                              Women                1.8         3.8            0.8     3.7


    Arm strength gain* (%)    Men                  35          21              30     17    0.648      <0.001
                              Women                56          27              58     30


    Leg strength gain* (%)    Men                  34          20              35     20    0.739       0.042
                              Women                41          22              44     23
MEN’S vs WOMEN’S STRENGTH
ST FIBER DISTRIBUTION
MEN’S vs WOMEN’S STRENGTH
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 Same HRmax but lower Qmax because of lower SVmax
 w Lower SV at rest and at all exercise intensities due to
   smaller heart size and smaller blood volume
                                   –
 w Less potential for increasing a-vO diff because of the
                                     2
  lower arterial O2 content (lower Hb concentration)

 w Are woman more suited for ultraendurance exercise?
                        .
SUBMAXIMAL HR, SV, AND Q
   Same absolute power    Same relative power
                                      .
      output (50 W)      output (60% VO2max)
Respiratory Responses in Women

 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 ventilatory rate
 w Smaller ventilatory volume during maximal exercise due to
   smaller lungs
Metabolic Responses in Women

           .
 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

           .
w Estrogen enhances glucose uptake during exercise
                .

w Progesterone impairs glucose uptake and may block
  estrogens effects (gestational diabetes)
w Progesterone .is a metabolically inflexible state
  whereas estrogen enhances both glucose and fat
  oxidation (glycogen sparing)
         .
RANGE OF VO2MAX VALUES
                      Pronghorn antelope:
                      272 ml/kg/min




                  77 ml/kg/min: Female
                  Russian x-country skier


                        * ml/kg/min: Male
                        94
                        Norwegian x-country skier

                                 *
                                        p. 579
                         .
VO2max: Elite Distance Runners and Untrained
Subjects
              Ultraendurance
•   Metabolic substrate selection
•   Muscle oxidative stress
•   Muscle damage
•   Thermoregulation
              Fat Metabolism
• Women higher fat, higher gluteal/femoral fat
  (Android, Gynoid fat patterns)
• Larger gluteal adipocytes (higher lipolytic rates)
• Catechol mediated leg fatty acid release lower in
  women
• Fat oxidation at rest is lower in females
• Post-prandial fat deposition higher in viscera in
  men, sub-Q in women
• But, proportion of fat oxidized during exercise
  higher in women
             Fat Metabolism
• β1, β2, β3 adrenoreceptors stimulate lipolysis
• α2 adrenoreceptors inhibit lipolysis
• Women have higher α2 in gluteal
• Rate of appearance of glycerol higher in women
  during submax exercise- why?
• Lower RER, higher fat oxidation, lower glucose
  uptake by muscle, lower glycogen use in women
• Higher PFK/3-HaCoA DH in muscle of men
  indicating greater proportion of carb use.
• Higher Trigs in muscle of women
           Protein metabolism
• Leucine oxidation may differ both at rest and
  during exercise
• Little difference in overall protein synthesis
• Ovarian hormones may inhibit protein synthesis
  (18% higher leucine oxidation in luteal but
  progesterone is high?)
• Estrogen inhibits PS in vitro
• Must control fitness level, fat free mass, age,
  dietary intake, menstrual cycle, birth control meds
• Methods may not be sensitive enough
Training and Body Composition in Women

 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.
Strength Training Adaptations in Women

 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 may be because of lower
   testosterone levels.
World Olympic Weight-Lifting Records
Totals are for the two
Olympic lifts, snatch and
clean and jerk. The
highest weight
classification records are
not included.
Menstrual Cycle Effects on Performance

 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.
MENSTRUAL CYCLE PHASES
           Menstrual Effects
• Metabolism
  – luteal increase in glycogen and change in
    glucose kinetics
  – Higher protein oxidation in luteal (18%)
• Thermogenesis (luteal +0.5 C)
Cause or Effect?

 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?
Normal and Abnormal Menstrual Function

 Menarche—the first menses (can be delayed)
 Eumenorrhea—normal menstrual function
 Oligomenorrhea—abnormally infrequent or scant
 menstruation
 Amenorrhea—absence of menstruation
 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
Menstrual Dysfunction—Amenorrhea

 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
Possible Causes of Menstrual Dysfunction

 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
 w Probably 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

 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.
Anorexia Nervosa

 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 Amenorrhea
Bulimia Nervosa

 w Recurrent episodes of binge eating; >2/week for 3 months
 w A feeling of lack of control during these binges
 w Purging behavior—self-induced vomiting, laxative use,
   and/or diuretic use

 w Non-purging type: fasting or excessive exercise
Anorexia Athletica

 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
Female Athlete Triad

 w Disordered eating
 w Secondary amenorrhea
 w Bone mineral disorders
Factors Contributing to Osteoporosis

 w Bone mineral loss with aging (especially in women)
 w Estrogen deficiency
 w Inadequate calcium intake before early 30s
 w Inadequate physical activity
 w Amenorrhea
 w Anorexia nervosa
HEALTHY AND OSTEOPOROTIC BONE
BONE MINERAL CONTENT
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.

				
DOCUMENT INFO
Shared By:
Categories:
Tags:
Stats:
views:2
posted:3/30/2013
language:English
pages:45