Sports Performance and the Menstrual Cycle
By Frank Horwill
A number of old wives' tales have percolated down the years on this subject: "My mother says I mustn't have a bath or go swimming while I'm like it,"..."My mother says I mustn't wash my hair during a period." Even the great physiologist, Olaf Astrand, wrote, "Women should not swim during menstruation because of the possibility of infection."
This is not very encouraging news to an Olympic swimmer who qualifies in the heats for an Olympic final which coincides with the "curse".
The exact timing of the menarche is affected by genetic, racial, socio-economic and climatic factors. At the menarche, the duration of blood loss may be from two to nine days, but limited. The duration gradually decreases until by the age of 16 years, it lasts for an average of six days. The normal adult menstrual cycle varies from 21 to 25 days and is rarely the often-quoted 28 days. In fact, 20% of 16 year olds still have menstrual cycles exceeding 40 days.
Stress can either shorten or lengthen the menstrual cycle. All sport is a stress, and usually lengthens it. Females who go to altitude to compete or train, have an added stress due to the lack of oxygen, which usually shortens the cycle. It is important for a sportswoman and her advisers to know what is going on in her body and at what stage the cycle is at.
In case you didn't know...
An ovum (egg) is released each month from one or other ovary (ovulatior) and finds its way to the adjacent fallopian tube. The ovum ripens before release in a sort of shell, the graafian follicle. The ovum is released, leaving the follicle remains behind in the ovary, and grows into a small endocrine gland, a corpus luteum. This produces a hormone, progesterone, that stimulates the uterus lining to form a thick layer with additional blood supply ready to receive an embryo if the ovum becomes fertilised. If the ovum is not fertilised, the corpus luteum withers in two weeks and the uterus, deprived of progesterone, sheds its lining (the period). The average loss is about two ounces (60cc). As soon as this ceases, the uterine lining regenerates and some two weeks later the cycle begins again with the release of another ovum. The interval between ovulation and the period, i.e. the life span of the corpus luteum – if there is no pregnancy – is nearly always two weeks. But the interval between the period and the next ovulation varies individually, and also from month to month in the same individual. The whole cycle may last from three to five weeks or more.
Hormones and PMS – a matter of timing?
The concentration of hormones in the body during this cycle affects sportswomen differently. The follicle-stimulating hormone rises gradually from the first day after the cessation of the period to a peak around the 14th day in tandem with the luteinising hormone. But the oestrogen hormonal rise precedes this by 2 days and tapers off for 2 days only to slightly rise again 5 days after around the 22nd day of the cycle, then declines. Progesterone climbs steadily after ovulation on the 15th day and reaches a peak on the 21st day and declines rapidly thereafter.
Oestrogen and progesterone are steroids. It is the pre-menstrual fall in these that in some women cause the phenomena of pre-menstrual syndrome (PMS). However, while both decline to the 14th day, progesterone climbs to a peak on the 20th day and it is that this hormone is the major cause of PMS. The sportswoman and her coach have for many years searched for the ideal time in the menstrual cycle when performance will be at its peak. And, have also searched for natural ways of neutralising any psychological and physical handicaps caused by PMS and the actual period.
Some research in 1993 (Menstrual Cycle Phase and Running Economy, Medicine and Science in Sports and Exercise, Vol 25(5), pS74, 1993) goes some way towards solving part of the equation. Eight fit, normally menstruating females were asked to run at intensities of 55% and 80% VO2 max during different stages of their menstrual cycles. This intensity approximates to 70% and 88% of the maximal heart rate, respectively. The mid-luteal phase of the cycle (about a week after ovulation , i.e. a week before actual menstruation), turned out to be a time when exercise became more difficult and psychological health took a nosedive (depression, fatigue and confusion increased while feelings of vigour declined). However, the lactate threshold - the exercise intensity above which large amounts of lactate begin to accumulate in the blood – was not influenced by the menstrual cycle phase. In further research at Springfield College, Massachusetts, eight female distance runners were asked to run at close to top speeds for short periods of time and also ran as far as possible at tan intensity of 85% VO2 max, about 90% of maximal heart rate. None of the variables measured – VO2 max, blood lactate, lactate threshold, maximal heart rate and fat oxidation – were different at any stage of the menstrual cycle.
For unknown reasons, the mid-luteal phase is a potentially low-performance time for female competitors. But there is a bonus side to this phase - it is a potent time for muscle glycogen storage in the legs. Recent research reveals that glycogen storage is 22% higher in the leg muscles of females in the mid-luteal phase, compared to before ovulation, and total endurance performance – measured as the ability to continue pedalling a bicycle at an intensity of 70% VO2 max (marathon pace) tended to be about 10% greater! This suggests that female marathoners should seek a marathon race during this phase because the added glycogen store in the legs could lead to increased speed over the final 6 miles (10K).
But, the exact opposite is the case if a speedy activity is contemplated, such as a swimming, cycling or running sprint event. The ideal time for these is the two weeks before ovulation, when economy and mood are better and ventilation isn't so expansive.
However, non-menstruating sportswomen and those who are taking oral contraceptives, which usually provide low, steady doses of progesterone, don't have a normal mid-luteal phase, and therefore do not have to worry about negative psychological and physical changes.
The dangers of preventing menstruation
Generally speaking, a girl's body fat content has to reach about 17% before menstruation will begin. Romanian gymnasts are kept at half this percentage and either do not start their periods or cease them once the required weight is reached. The medical profession is divided over this condition – on the one hand, one school of thought forecasts infertility if this is prolonged. On the other hand, another view is that it is nature's way of telling the female she is too thin to have children. But the non-appearance of menstruation has been strongly linked with osteoporosis (weakening of the bones) and possible chronic undermining of bone structure. A high calcium intake is recommended in such cases, of around 1,200mg daily. Good dietary sources are: milk, cheese, broccoli, legumes, green, leafy vegetables, nuts, seeds, peas, beans and lentils. Because milk is associated with many allergic reactions with some people, it should not be relied upon as the main calcium source. A new finding is that an obscure mineral – boron, found in fruits and nuts – if lacking in the diet, will hamper calcium metabolism. Also implicated in calcium absorption is the mineral manganese, a glass of pineapple juice two or three times a week will suffice. It should be noted that nuts provide all three minerals (calcium, boron and manganese).
There is little doubt that taking the contraceptive pill not only eradicates or alleviates many of the unwelcome incidents of PMS, but can be used to manipulate the menstrual cycle so that a period does not occur at the same time as a major sporting event. However, where endurance events are concerned, its major drawback is weight gain, fluid retention and a major cancelling out of the entire vitamin B complex. The first two are unwanted handicaps in any activity that continues for more than an hour. The last will affect carbohydrate absorption which is the main fuel for physical activity. A diminution of vitamin B12's role will reduce the manufacture of new red blood cells. None of these is a happy state of affairs for the keen sports woman.
James G Penland, PhD, a psychologist at the US Department of Agriculture, carried out research on a group of females with severe PMS and menstruation problems. Half were given 600mg of calcium for six months, the rest were given 1,300mg a day. Those on the low dose suffered as before. The others on the high dose had reduced mood swings, less physical pain before and during their period. Calcium deficiency has long been linked to muscular cramps. It is utterly illogical that a sportsperson who has trained for months or even years for the greatest moment in her sporting life, such as for the Olympics or Commonwealth Games, and possibly her one and only opportunity to do so, should have that occasion marred by possible PMS and or menstrual problems. However, one study of 80 females in the 1964 Tokyo Olympics revealed that gold medals were won during all phases of the menstrual cycle.
Dealing with PMS
While there are some drugs available to alleviate PMS, and also period pain, many of them also affect performance by interfering with the Krebs Cycle (the conversion of energy in to oxygen), in particular, the barbiturates. Research suggests that PMS sufferers cannot efficiently metabolise the essential fatty acid, linoleic acid – which is mainly found in good quality vegetable oils – into its normal by-products, possibly because of the subtle interaction between derivatives of linoleic acid and certain menstrual hormones. This barrier could occur because of dietary deficiencies of nutrients essential for its conversion which include: vitamin B6, magnesium, zinc, vitamin C, vitamin B3 and chromium. Research has shown that countries with a high intake of fruit and vegetable produce tend to have a lower incidence of PMS.
Poor blood sugar control (chromium helps with this) is often a problem in women with PMS. Many notice an increase in appetite and/or food or sugar craving in the week o so before the period, and this may contribute to their weight gain and fluid retention.
The following treatments are either proven or accepted by a significant number of medical experts:
- Limit the consumption of refined sugar, salt, red meat and alcohol
- Eat fish, poultry, whole grains and legumes as major sources of protein and rely less on red meat and dairy produce.
- No smoking
- Minimal amounts only of coffee, tea, chocolate, and cola-based drinks.
- Avoid saturated fats (animal fats, fried food, butter).
- Eat plenty of complex carbohydrates (fruit, all kinds of vegetables).
- Train in the morning in order to keep weight down.
- If sugar and food craving is experienced, eat every 4 hours on the dot only; nuts, seeds, peas, beans and lentils, fish and eggs (all high quality protein foods).
- Take a multivitamin supplement providing the RDA of all the vitamins and most of the minerals, especially magnesium.
Primrose oil – 500mg capsules, 4-8 per day, taken during the two weeks
before the period is due, but if not effective it should be tried
throughout the month.
Warning: If symptoms do not improve or are very severe, a doctor must be consulted. Some hormonal problems can have similar symptoms to those of PMS yet require medical or surgical treatment.
Suslov, the former national coach for distance running in the former USSR, wrote in Track Technique Annual 1981, "Female sports competitors are encouraged to train normally through all phases of their menstrual cycle. The exception being with weight-training, where heavy weights were substituted for lighter weights with many repetitions. Our experience is that in the 4 days before and after a period, there is a higher incidence of injury when using heavy weights."