Sex Differences and Exercise Performance

Eumenorrhea

a normal pattern of timing between menses

Delayed menarche has been reported in most

elite female athlete populations (requiring strength and endurance), compared to the normal population. Theorized to be influenced by factors such as nutritional status, genetics, family size, groupings with other females and/or birth order, and -perhaps- physical training.

What is the key linking factor to all the components of the female athlete triad

estrogen

What is key to the disruption of estrogen production?

low energy

In the female athlete triad and RED-S, one major consequence of disordered eating that links to the other factors of the triad is

menstrual dysfunction, caused by caloric restriction / low energy availability, resulting in a reduction in estrogen production.

Theories of why later maturers tend to make up a larger percentage of elite athletes:

• Physical: Later maturers tend to be leaner, more linear, higher strength to weight ratio. (note: no differences in motor ability) • Social: Early maturing females tend to be socialized away from sports, via social- and status-related motives. • Psychological: Since later maturing females are older at menarche, they may be better able to cope with competitive pressures of sport and receive greater motivation with success in athletics.

Four theoretical clinical concerns with exercise and pregnancy:

--Reduced blood flow to the uterus, leading to fetal hypoxia --Possibility of miscarriage or premature labor --Fetal hyperthermia --Effect on birth weight and future health of the child

The menstrual cycle is divided into two phases

--The follicular phase - starts with the beginning of menses (bleeding) and ends with ovulation --The luteal phase - starts with ovulation until the beginning of menses During the follicular phase, estrogen levels rise gradually from the end of menses, peaking at about 6 times baseline levels just prior to ovulation.

Osteoporosis is believed to be influenced by three primary factors

-estrogen deficiency (the biggest one) -inadequate calcium intake (a low factor) -inadequate physical activity (particularly weight bearing activity)

Key physiological factors that are significantly different between sexes

1. Decreased hemoglobin concentration in women 2. Smaller cross sectional muscle fiber areas in women 3. Smaller heart volumes (particularly LV volume) in women Women will typically have the same Q as men for a given submaximal workload, however, typically HR will be higher and SV will be lower. Due to smaller left ventricle size and smaller total blood volume. 4. Lower relative VO2max values in women. The difference is reduced when expressed as ml/kg LBM/min, but still lower than men (mainly due to lower Hb levels). 5 Reduced strength levels in women -primarily due to less muscle mass. -However, no difference in strength between sexes for the same amount of muscle mass. 6. Similar rates of strength gain with training between sexes, however women tend to gain more strength through neural adaptations and less through muscle mass gain (testosterone)

The Panel agreed that indications for obtaining a DXA scan for BMD testing in an athlete should follow the Triad risk stratification (see Clearance and Return to Play section) and include the following:

1. ≥1 'High risk' Triad Risk Factors: ▸ History of a DSM-V diagnosed ED ▸ BMI ≤17.5 kg/m2, <85% estimated weight, OR recent weight loss of ≥10% in 1 month▸ Menarche ≥16 years of age▸ Current or history of <6 menses over 12 months ▸ Two prior stress reactions/fractures, one high-risk stress reaction/fracture (see figure 4), or a low-energy nontraumatic fracture ▸ Prior Z-score of < -2.0 (after at least 1 year from baseline DXA) OR 2. ≥ 2 "Moderate risk" Triad Risk Factors: ▸ Current or history of DE for 6 months or greater ▸ BMI between 17.5 and 18.5, <90% estimated weight, OR recent weight loss of 5-10% in 1 mo ▸ Menarche between ages 15 and 16 years ▸ Current or history of 6-8 menses over 12 months ▸ One prior stress reaction/fracture ▸ Prior Z-score between -1.0 and -2.0 (after at least 1 year interval from baseline DXA) 3. In addition, an athlete with a history of ≥1 non-peripheral or ≥2 peripheral long bone traumatic fractures (non-stress) should be considered for DXA testing if there are one or more moderate or high-risk Triad risk factors

In women, after about the age of _____, there is a sharp decline in the ability to lay down bone mass and minerals. In women who maintain adequate nutrition and exercise, problems with osteoporosis usually surface only after _______ (end of menstrual function with aging, accompanied by reduced estrogen levels).

30 menopause

Low BMD (bone mineral density) can be diagnosed by a

DXA scan

Osteoporosis

Defined as a decreased bone mineral content, causing increased bone porosity (brittle bones)

Recovery of energy, menstrual, and bone mineral density status

Energy status: takes days Menstrual status: takes months Bone mineral density: takes years

How does exercise affect birth weight?

In the second half of pregnancy, there was a low volume of exercise - the birth weight was higher than normal (increase % of body fat) When they did moderate to high intensity exercise in the second exercise, the birth weight decreased (decrease % body fat)

How do you measure "maturational pace?"

In women - ask age at menarche (can be done retrospectively) In men - typically do serial x-rays to see when growth plate fuse (must be done prospectively)

Factors that can lead to secondary amenorrhea

Inadequate nutrition / low energy availability / disordered eating Low body weight (in particular, low body fat %) High volume and intensity of training Stress Prior history of menstrual dysfunction Hormonal alteration

In general, the benefits of exercise during pregnancy appear to far outweigh the risks. A sampling of general recommendations:

Most favorable long term health outcomes for the child are likely to result from a modest reduction in average birth weight or a reduction in LGA (large for gestational age), without a significant increase in SGA (small for gestational age). Potential health benefits of maternal exercise for the child may the greatest in overweight / obese mothers, who have a greater risk of delivering a large baby with increased risk for obesity in childhood. Care should be taken in the first trimester, where incidence of miscarriage are greatest. Moderation in volume and intensity, focus on hydration, and awareness of heat dissipation are key factors during this time. Mild to moderate exercise at least 3 days per week can give significant health benefits to mother and fetus Exercise early in pregnancy has stimulatory effects on placental growth and function, which could have the less desirable effect of promoting excess fetal growth in overweight and obese mothers. In these populations, it may be best to initiate an exercise program at week 20 to prevent excess fetal growth - however this recommendation is not universally accepted and further research is needed.

The Female Athlete Triad

Relates low energy availability, menstrual dysfunction, and osteoporosis

With many researchers, there is a preference to move to a concept called RED-S, which stands for

Relative Energy Deficiency Syndrome, versus the term "Female Athlete Triad." (more inclusive of men who also show the syndrome)

Possibility of miscarriage or premature labor

Research here is unclear. Many studies show benefits with exercise during pregnancy, such as reduced maternal weight gain, fewer C sections, easier vaginal deliveries, reduction in fetal complications due to labor, reduced incidence of high blood pressure and quicker post-partum recovery.

Does training delay menarche?

Results from our laboratory at Indiana University would suggest that training does not delay menarche - as long as nutritional needs are adequate.

Risk for too high and too low percent fat

Risks for too low Obesity Type 2 DM Risks for too high Cardiovascular disease Type 2 DM Metabolic Syndrome

However, women athletes have typically experienced greater improvements in athletic performances over the last 20-40 years, compared to men. Why?

Social factors The greater improvement in female athletes during this time is likely based on social factors, more so than physiological factors.

Maturation in junior athletes and elite (adult) level

The Junior athletes were early maturers. Successful athletes at the elite (adult) level tend to be later maturers

Does a (naturally) delayed menarche predispose the individual to success in athletics? Is the success of females with delayed menarche a result of physiological or sociological factors?

The data suggest that it is more appropriate to say that menarche in elite female athletes naturally occurs later rather than saying that training delays menarche.

The most "level playing field" between sexes?

Ultra type events (triathlon) Long endurance activities aren't dependent on strength, they are dependent on the ability to preserve over time (women also have more fat reserve to depend on)

Reduced blood flow to the uterus, leading to fetal hypoxia

Uterine blood flow can fall by as much as 25% during strenuous exercise. It is unclear if the drop in uterine blood flow leads to fetal hypoxia. Because fetal blood has a much higher affinity than maternal blood, fetal hypoxia should not occur.

Fetal hyperthermia

When you exercise, you get hot and could this increase the temp of the fetus

Oligomenorrhea

an irregular patten of timing between menses

Non-weight bearing exercises are encouraged

as this form is better tolerated by obese women, and to minimize potential injury or accidental trauma to the abdomen.

In individuals with disordered eating or amenorrhea, there is often a greater risk of reduced

bone mineral stores (i.e. bone mineral loss), primarily due to estrogen deficiency. In addition, it appears that the resumption of normal menstrual function does not totally reverse the bone mineral loss.

Disordered eating

describes patterns of eating that are not considered normal, but do not meet specific diagnostic criteria for an eating disorder.

Estrogen production therapy problem

can lead to cancer

Eating disorders

must meet specific criteria that meet medical/psychological definitions for the condition. The most common eating disorders are anorexia nervosa and bulimia nervosa, with a third type - anorexia athletica - gaining status.

Anorexia athletica:

people who lose weight, thinking it will benefit their performance

Women will not outrun a man due to

testosterone

Amenorrhea

the absence of menstruation

Secondary amenorrhea

the absence of menstruation after menarche

Primary amenorrhea

the absence of menstruation because menarche has not occurred

Menarche

the first menses

Disruption of this rise in estrogen production has a strong effect on

the regular pattern of menstruation.

Exercise in the second half is beneficial, there is a slight weight reduction in offspring which in most cases tend to lead to better health outcome (t/f)

true