The Pill may be the most effective contraceptive and the best way to manipulate your cycle for important events, but are you aware of its physiological effects and their impact on performance?

By Andrew Harrison  for peak performance

The oral contraceptive pill (OCP) is the form of contraception most widely used by women in general and sportswomen in particular. Undoubtedly, the main reason for its popularity with both groups is its high effectiveness in preventing pregnancy.

Female athletes may also choose the Pill on the basis of other perceived benefits, including bone health, the ability to manipulate the menstrual cycle and control of premenstrual symptoms.

However, the impact of the Pill goes further than that, and the purpose of this article is to make sportswomen and their coaches fully aware of its physiological effects, both positive and negative, and their impact on performance and health?

An OCP is made up of hormones which can be combined in four different ways, defined by the ratio of oestrogen to progesterone:

  • The monophasic pill has a low oestrogen content and the dose of both hormones remains constant throughout the cycle, allowing for easy manipulation of cycles when competing and travelling; 

  • The triphasic pill provides three different dosages of hormones during the cycle. Because it contains less total progesterone (and therefore a lower overall dose of hormones) than the monophasic pill, it is thought to mimic the ‘natural’ cycle more closely than other types of OCP. It is recommended for women who experience side effects, such as weight gain, when using the monophasic pill. However, the varying dosages employed throughout the cycle make cycle manipulation more difficult; 

  • The biphasic pill maintains a constant oestrogen dose throughout the cycle, with a change in progesterone mid-cycle. It offers no particular advantage over the other two preparations and is not often prescribed; 

  • The ‘minipill’ contains progesterone only and is recommended for new mothers and those who are sensitive to the oestrogen component of other pills. Its main drawback is that it has a higher failure rate than the other formulations.

The manner and extent to which these combinations affect athletic performance is far from clear. Some investigators have reported reductions in VO2max associated with the use of the OCP.

A recent Canadian trial, involving 14 female athletes with average VO2max values of over 50 ml/kg/min, demonstrated a mean reduction in aerobic capacity of 4.7% following two months of OCP usage.

Similarly, another research group reported a 5% reduction in VO2max in a group of élite subjects after two months on OCPs. Other performance variables measured, including maximum heart rate and endurance at 90% VO2max, were not affected by OCP usage. And both sets of researchers concluded that the observed reductions in VO2max were reversible following cessation of medication, typically within 4-6 weeks.

However, other researchers have observed no negative impact of the OCP on performance. One recent study found no differences in exercsie performance between an OCP and control group despite differences in blood lactate and temperature. In another, a low-dose OCP taken over a single cycle was found to have no effect on breathing rate, VO2max during a treadmill assessment, or an endurance running test. These findings have been echoed by numerous other studies investigating the effect of the OCP on aerobic and anaerobic variables.

Even if the OCP does lead to a slight drop in VO2max, it is unclear whether this would translate to a fall-off in performance. And against this possibility should be balanced the known supplementary benefits of the OCP. For example, a reduction in pre-menstrual symptoms, which is a confirmed effect of OCP usage, might well outweigh a slight drop in VO2max during training or competition.

Another benefit of OCPs is that they reduce menstrual blood loss by up to 50%, so also reducing the risk of iron deficiency anaemia posed by heavy menstrual loss combined with inadequate dietary iron intake. Increased stroke volume, blood volume and cardiac output have also been reported with OCP usage, potentially increasing oxygen delivery to the muscles.

How the Pill impacts on body weight and muscle strength

The issue of weight gain is of great concern to athletes and often of even greater concern to their coaches. This is particularly the case in power:weight ratio-dependent sports such as distance running, light weight rowing and gymnastics.

Individual responses to the hormones in the OCP may include some weight gain as a result of either fluid retention or, possibly, appetite stimulation. Nevertheless, contrary to popular belief, most population studies indicate no overall effect on body weight while taking the OCP. This is particularly the case with the newer low-dose pills.

Few studies have investigated the effects of OCP on muscle strength in female athletes, and those which have been carried out have found no significant differences in the strength of various muscle groups with OCP usage. Fluctuations in muscle strength have been noted during a normal menstrual cycle, and these appear to relate to changes in levels of oestradiol, the major female sex hormone produced by the ovaries. Increased strength has been reported late in the follicular (pre-ovulatory) phase of the cycle, corresponding to increases in oestradiol before ovulation, with reduced strength reported in the luteal (pre-menstrual) phase, possibly due to increases in deep muscle tissue.

The point about OCP usage is that it appears to eliminate these natural fluctuations in muscle strength.

Adverse effects on risk factors for cardiovascular disease have been highlighted with higher dose OCPs. However, researchers have hypothesised that exercsie itself may counteract these potentially negative effects.

Substrate utilisation during exercsie has also been studied in relation to the Pill. In one study, a group of women on OCPs was shown to have lower blood glucose levels and lower carbohydrate usage during prolonged submaximal exercise than a control group. Another trial documented an increase in free fatty acids with exercise in association with these lower blood glucose levels. This trial also found an increase in the growth hormone response to exercise, possibly as a result of direct stimulation by the oestrogen component of the Pill.

Such findings suggest that the OCP may facilitate carbohydrate sparing during prolonged exercise, thus delaying time to exhaustion. An alternative interpretation, however, is that the increase in free fatty acid utilisation is a compensatory response to a decreased glucose release, suggesting that, even with increased free fatty acid availability, endurance performance might be negatively affected.

In summary, the pros and cons of OCP use for female athletes and sportswomen may be set out as follows, with the benefits appearing to outweigh the costs:


  • Highly effective, convenient and reversible;

  • Provides a source of oestrogen for athletes without periods, decreasing their risk of stress fractures and osteoporosis;

  • May decrease menstrual blood loss, which reduces the risk of iron-deficiency anaemia;

  • Reduces painful period cramps;

  • May decrease premenstrual symptoms (eg mood swings, nausea, headaches) which could have a negative impact on training and competition;

  • Can be used to manipulate the menstrual cycle for important events and travel;

  • Associated with a decreased risk of cancers of the ovary and uterus;

  • No known long-term effect on fertility.


  • Possibility of breakthrough bleeding, fluid retention, weight gain, breast tenderness and headaches (although these usually settle within a few months and can be controlled by changing to a different OCP);

  • No protection from sexually transmitted diseases;

  • Associated with a small increased risk of breast cancer in women using OCPs for more than 10 years without having children;

  • Possibility of decreased VO2max/endurance performance.

The conflicting results found in the scientific literature are often difficult to interpret, given the known differences in such variables as Pill dosages and formulation, menstrual history, duration of OCP use, age at which subjects were exposed to OCP, and outcome measurements. Nevertheless, there are individual variations in response to OCP use and these should be taken into account and monitored. Female athletes should be counselled about the range of potential benefits and disadvantages in order to make informed decisions based on their individual circumstances.


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