Women are not small men: Factors to consider for performance
By Dr. Stacy Sims
While the participation of women in sports has increased significantly over the
last several decades, research of women in sports has lagged behind that of men. Until
the 1980’s, it was widely assumed that the physiological responses to exercise did not
truly differ between men and women; thus all the training, nutrition, recovery schedules
I’ve seen, (and for the most part still exist), are recommendations that have been
generalized to women- without really questioning if this direct transfer was viable. Why
has research of women in sports lagged behind that of men? Primarily because women
have been deemed “too difficult” to be included in research because of these hormone
fluctuations, or the research that has been done occurs when the women are in the first
14 days of their cycle, when hormone levels are low and women’s responses are very
close to men’s. Additionally, the variations in how long a woman’s natural menstrual
cycle lasts further complicates determining accurate exercise testing days between
subjects. Although there is lots of research addressing how exercise affects the menstrual
cycle (women becoming irregular or ammenoheric), less is known about how the
menstrual cycle affects women’s performance in sport. These cyclic hormone changes
can affect physical and psychological potentials and ultimately influence sports
performance although experiences are highly individual. This article will look at some of
the research on how exercise performance is affected by the menstrual cycle and include
recommendations on how to best train and compete in phases of your cycle.
The Menstrual Cycle
Before we can address the topic, readers need to have a clear understanding of the major
phases of the menstrual cycle. The typical menstrual cycle is 28 days long, with the first
day of menses considered Day 1. Menstruation is usually completed by Day 5 -7, and the
mucosal lining (endometrium) of the uterus once again begins to proliferate in
preparation for an egg. The phase from Day 1 to ovulation, which is normally Day 14-15,
is called the follicular phase. The luteal phase is from ovulation until the day before
menses, normally about Day 2. With a triphasic oral contraceptive pill, the first active
hormone pill is taken on Day 1, with low hormone levels lasting from Day 1-5, moderate
levels lasting from Day 6 – 10, and the highest hormone levels lasting from Day 11 -21,
with a sugar pill or no pill taken for Day 22 – 28, allowing for breakthrough bleeding to
mimic a period. Due to the varying hormone concentrations with OCP, there is not a
follicular or a luteal phase, just low and high hormone phases (Figure 1).
Serum Concentrations (ug)
Triphasic OCPs vs Endogenous Hormones
ethinyl-E
progestin
oestrogen
progesterone
150
135
120
105
90
75
60
45
30
15
0
1
4
7
10
13
16
19
22
25
28
Time (days)
Figure 1. Triphasic OCP vs Natural menstrual cycle hormone concentrations
As most women know, symptoms that accompany menstrual cycles vary considerably.
Some women do not experience any symptoms; others may suffer slight discomfort to
severe pre- or initial-flow discomfort. Changes in exercise performance during the
menstrual cycle vary as well. Many women report impaired performance and just as
many not. There are a number of women who have won Olympic medals while
menstruating. Some women may experience some minor discomfort but merely push
themselves forward during participation. Because most variations in performance are
due to the high hormone levels, let’s look at how high levels of estrogen and
progesterone, both natural and from oral contraceptives have an effect on women and
performance.
METABOLIC CHANGES-a.k.a FUELING
One important factor to note is recent research on oral contraceptives has illustrated a
rise in naturally produced estrogen during the sugar pill week. Thus, although almost
every article and text out there describes the sugar pill week as being “low hormone”
this is not necessarily the case. Van Heusen and Fauser (1999) observed significantly
higher concentrations of follicle stimulating hormone (FSH) and natural estrogen at the
end of the pill-free interval, and the higher the amount of estrogen in the OCP, the less
natural estrogen was secreted in the pill free week (Creinin et al. 2001, Schlaff et al.
2003). What does this mean, to the casual reader and female athlete?
Estrogen decreases the reliance on liver glycogen, increases the use of fat, and decreases
amino acid breakdown during exercise. These fuel responses have been attributed to a
sex difference between catecholamine responses during exercise (men release a larger
amount of catecholamines at a given moderate-high intensity exercise load than women
who have similar training status). This glycogen sparing, increased fat use is even
greater during the high hormone phase (luteal phase) of the menstrual cycle- when
estrogen is at its highest concentrations.
How does this translate to everyday practical use? Women have a greater capacity for
burning fat and sparing glycogen (both in the liver and the muscle) in the high hormone
phase. To maintain the capacity to hit intensities, women should look to stay ontop of
carbohydrate intake during exercise; BUT during the low hormone phase, women can
afford to ingest less exogenous carbohydrate than her age and fitness matched male
counterpart (think: 45-55g per hour as opposed to the 65-80g per hour).
“So does this mean I need to eat more fat?” Actually, not necessarily….Researchers have
looked at the recovery phase in men and women. Although women metabolize and use
more fatty acids during prolonged exercise (and we have greater fat stores than men),
women have a greater ability to maintain energy substrate stores during exercise and
during recovery. Three hours post-exercise, men still have higher rates of blood glucose
fluctuations and lower glycogen stores, whereas women are relatively close to the preexercise state (side note- this also contributes to the harder-to-get-lean factor many
women face- less of a window of elevated metabolic state and fatty acid use at rest).
What about protein use during exercise?
Women also oxidize less protein and leucine than men even though there is no sex
difference in the muscle enzyme that controls the intramuscular use of branch-chained
amino acids. But, during the high hormone phase of the menstrual cycle, progesterone
(or a lower estrogen to progesterone ratio) increases the use of protein during exercise.
This phase difference is important to note for recovery- amino acids are key to immune
function as well as muscle adaptations to stress.
“Okay, ok, so there ARE sex differences in how my body fuels itself for exercise; but
how do I take all this info and apply it?”
Key points to take onboard:

Women have greater fat stores and access fat to a greater degree during exercise;
sparing liver glycogen.

Women don’t oxidize as many branch-chained amino acids during exercise as
men, but in the high hormone phase of the menstrual cycle, there is a greater
reliance on protein during exercise and at rest, thus recovery protein intake is
critical for muscle synthesis and recovery

The post-exercise recovery phase: three hours post-exercise, a woman’s
metabolism is pretty close to pre-exercise/baseline levels; so the 2-hour recovery
window after the first of a 2xday exercise session needs to be carefully planned,
in order to restore the muscles’ fuel stores.

The quick return to baseline metabolism also contributes to the reduced ability to
“lean up” in women- again, need to take advantage of the 2-hour window to
promote body composition change and glycogen/fat store recovery.
What about HYDRATION?
Plasma volume is the watery component of blood that reduces the thickness of the blood
and allows blood to flow quickly to working tissues. When we begin to sweat, it is the
plasma volume that is lost first, as it is this fluid that helps make up the sweat. We sweat
to remove heat. As women, we have an elevation of our resting core temperature in the
luteal phase of the natural menstrual cycle, and in the last 15 days of OCP use, due to
elevated progesterone concentrations. The increased progesterone stimulates the phrenic
nerve, increasing respiration and it also acts to increase sweat production later than in
the low hormone times of the menstrual cycle. So, with elevated progesterone, there is a
natural resetting of the baseline body temperature by as much as 0.3 -0.5 °C. Coupled
with an increased time to sweating during the luteal (high hormone) phase, it can be
seen that athletic performance is compromised in the luteal phase due to higher body
temperature and less ability to get rid of the heat. What’s more, is the high estrogen and
progesterone act on the kidney’s hormones to reduce plasma volume, a drop of up to 8%
from ovulation to the mid-luteal phase, and this fluid goes between the cells; causing the
bloating often associated with PMS. In general, during the luteal phase and the high
hormone phase of the menstrual cycle, women are less able to cope with the heat and
have a reduced ability to sweat to remove the heat from deep inside the body.
How do I compensate for this shift in temperature and body water?

Pre-hydrate! Using a sodium based hyper-hydration drink before high
intensity or race situations will help slow down the rate of dehydration
(water alone won’t work, you need a bit of sodium to help pull fluid into
the vascular spaces of the body)

If you’re not racing or training high intensity, be sure to stay on top of
your hourly drinking- I recommend fluid intake based on body weight:
0.15- .018 ounces per pound of body weight per hour (lower intake for
slower and cooler conditions).

Pre and post exercise cooling: Pre-cooling with the ingestion of cold
drinks (if possible, use this technique on the bike as well) Post-Exercise:
cool water or cool towel against the skin (not icy!) to facilitate blood flow
back to the muscles to reduce heat and facilitate recovery
INJURY??
Something else to think about is musculoskeletal and joint injuries. There is a higher
incidence of these types of injuries right before your period comes. But, we aren’t sure
exactly why, as there is little definitive research indicating the exact causes. One theory
is a relationship of increased relaxin levels and increased flexibility and elasticity of
connective tissue in and around the joints. Relaxin is a hormone that is thought to be
responsible for softening and relaxation of the ligaments in joints. Although still poorly
understood in humans, relaxin levels highly correlate with relaxing of the pubic bones
allowing for birth in females of several mammal species. Relaxin is thought to create
joint laxity, which allows the pelvis to accommodate the enlarging uterus. This may also
weaken the ability of for the lumbar spine to withstand impact and twisting forces. Thus
low back and knee injuries from stepping down wrong and twisting are common during
PMS and menstruation.
What about the POST-Menopausal Athlete?
As more and more women are staying highly active and competitive into their late 40s
and beyond, there are specifics for the post menopausal athlete.
A few key points to remember when the hormone flux is taken away (aka menopause)1) Blood vessels are less compliant (meaning blood pressure changes are slower)
2) There is less core temperature flux tolerance (meaning you can't handle hot
very well)
3) You sweat later in activity and vasodilate longer (i.e. your body tries to get rid
of heat by sending more blood to the skin instead of relying on sweating to cool
you off for a longer period of time)
4) There is greater sensitivity to carbohydrate (more blood sugar swings and less
need for carbohydrate overall)
5) The body uses protein less effectively (meaning that the type and quality of
protein you eat and when you eat it becomes very important for building lean
mass and holding onto it)
6) Less power production (thus train for power, not for endurance!- on the bike
and in the gym!)
Potential solutions!
For 1 and 2: Cooling post exercise is a great way to facilitate blood flow for
recovery. Using cool towels or cool water immersion to get a bit of skin
constriction- pushing the blood back into central circulation. During exercise,
consume cool foods and fluid (if possible).
For 3: Focus on hydration- food in the pocket, hydration in the bottle. Using the
pre-hydration technique before racing will help.
4: Aim for 40-50g carbohydrate per hour; not 60-90g. Upping your calorie needs
with mixed macronutrient foods
5: Take 15g whey isolate or 9g branch chained amino acids 30 min before
training; and definitely 25 g mixed whey isolate and casein within 30 min post
exercise. (NOT soy as there is not enough leucine for post menopausal women to
promote muscle synthesis). For recovery: another 20-25g mixed whey+casein 2
hours post training with another ~10- 15 grams protein before bed!!!
6: Focus on power training- the speed and strength of muscle contractions tends to
diminish with age; thus power and speed becomes an essential aspect of the postmenopausal woman’s training arsenal.
In a nutshell
Research on women and athletic performance is lagging, but there is information
available to maximize training for performance. Knowing that the high levels of
estrogen and progesterone associated with the luteal phase, and OCP use affect
metabolism, blood flow, thermoregulation, and overall performance can allow women
to alter their racing schedule to maximize performance. Moreover, although OCP use is
lessening, there are still many women athletes who use the pill to alter their cycles. I
have several women athletes who regularly compete in the hot Hawaii and Spanish
environments. I have found that by altering their cycles to compete 2 – 3 days post-bleed
has produced excellent performances. This can be attributed to controlled low levels of
estrogen and progesterone leading to increased aerobic and anaerobic capacity, lower
core temperature, greater plasma volume, and a greater ability to sweat as compared to
the later stages of their cycles. It is impossible to alter the training and racing cycles to
maximize the benefits of low hormones. However, you can schedule your training to be
able to maximize your session in accordance to the phase of your menstrual cycle. For
example, schedule your high intensity sessions during the low hormone phases, while
scheduling longer recovery and steady state (low to moderate intensity) weeks during
the high hormone phases of your cycle. You can begin by keeping a training log and
monitoring your cycle versus your performance. From this, you will be able to establish
the strongest and best training days and when to back off. This will facilitate modifying
a training schedule by planning for strenuous sessions, peak training and when rest is
needed.