A review of research suggests that women can optimise the outcome of resistance training based on their menstrual cycle. A researcher concludes that women’s outcomes are optimal if they train between the start of every cycle and ovulation.
A review article published in Sports Medicine concludes that women athletes can benefit optimally from carrying out resistance training between the start of their menstrual cycle and ovulation.
According to a researcher behind the study, this should influence how female athletes plan their resistance training, especially in sports for which margins in muscle strength determine the difference between winning and finishing fourth.
These marginal differences might result from how women organise resistance training based on their menstrual cycle.
“Serious athletes alternate between hard and light training. The benefits of resistance training can depend on where a woman is in her menstrual cycle, and women can improve training-related outcomes by up to 10% by coordinating the training in relation to the menstrual cycle. However, our review also indicates that more studies are needed to formulate clear recommendations,” explains Morten Hostrup, Associate Professor, Department of Nutrition, Exercise and Sports, University of Copenhagen.
Hormones fluctuate during the menstrual cycle
The menstrual cycle can be divided into three phases: luteal, early follicular and late follicular.
The luteal phase and the follicular phase each last about 14 days, with variation among women, and the late follicular phase ends with ovulation.
During the phases, the egg matures, with estrogen and progesterone playing major roles. These two hormones fluctuate throughout the menstrual cycle, with progesterone levels highest in the middle of the luteal phase and estrogen levels highest just before ovulation.
These hormones also influence other physiological processes apart from ovulation.
“Progesterone and estrogen influence muscle strength, mass and recovery. Maximising the benefits of resistance training possibly requires coordinating the training with the menstrual cycle,” says Morten Hostrup.
Studies on how the menstrual cycle affects resistance training
To elucidate this, Morten Hostrup and colleagues obtained data from six studies that examined whether and how women’s menstrual cycle affects how they benefit from resistance training.
They found that organising resistance training based on the menstrual cycle may give women additional benefit.
Women carrying out resistance training to optimise muscle mass and become stronger can maximise the effects in the early follicular phase compared with the late follicular phase and the luteal phase.
Morten Hostrup says that some of the studies reviewed suggest that periodising the resistance training based on the menstrual cycle instead of distributing it evenly can improve muscle strength by up to 10%.
Some of these studies even suggest that women who distribute their resistance training in the luteal phase rather than apportioning it throughout the cycle lose muscle strength and mass.
“Studies involving both humans and animals collectively suggest that resistance training in the early follicular phase positively affects the body’s protein balance, and the synthesis of new proteins exceeds the degradation associated with training. The net positive balance will affect muscle strength and mass,” explains Morten Hostrup.
Estrogen activates the reconstruction of muscle fibres
Hormones – and how they fluctuate – probably also affect the outcomes of resistance training in other ways.
Reconstruction of muscles after exercise requires specialised stem cells called satellite cells that repair the muscle cells.
Estrogen can activate these satellite cells, and the hypothesis is therefore that the higher estrogen levels in the follicular phase enable the muscles to be more easily repaired and reconstructed.
“This is another possible explanation for why women benefit more from resistance training in the follicular phase,” says Morten Hostrup.
Team Denmark research network aims to provide greater insight
Morten Hostrup says that few female athletes have been aware of this connection between the benefits of training and the menstrual cycle, but there has been greater focus on this in recent years.
A Team Denmark research network with support from the Novo Nordisk Foundation is investigating this and making recommendations based on the findings.
The network, with research groups from the University of Copenhagen, Aarhus University and the University of Southern Denmark, will also examine whether oral contraceptives influence resistance training outcomes, since oral contraceptives suppress fluctuation in estrogen and progesterone.
“We reviewed the current knowledge on how the menstrual cycle affects resistance training but also conclude that more high-quality studies are needed to elucidate this more thoroughly. In elite sports, marginal gains from slight changes may be decisive, and adapting training strategies according to women’s menstrual cycle may be worth examining further,” concludes Morten Hostrup.
