Understanding Cycle Syncing: Hormones and Your Workout

You’ve done this workout before. The route is familiar, the weights haven’t changed and you’ve slept reasonably well. Yet today everything feels harder.

Many women notice fluctuations in energy, strength, endurance, motivation and recovery throughout their menstrual cycle. This has fuelled growing interest in “cycle syncing” – the practice of adapting exercise according to hormonal changes across the month.

Supporters argue that training in harmony with your hormones can improve performance and recovery. Critics argue that the evidence is weak and the benefits overstated.

So what does the science actually say?

A Quick Tour of the Menstrual Cycle

The menstrual cycle is orchestrated primarily by two hormones: oestrogen and progesterone.

During menstruation, both hormones are relatively low. Some women experience fatigue, cramping, headaches or reduced energy, while others notice little change at all. During the follicular phase, which begins with menstruation and ends with ovulation, oestrogen gradually rises. Ovulation marks the release of an egg from the ovary and is typically associated with peak oestrogen levels.

Following ovulation, the luteal phase begins. Progesterone rises and remains elevated until the start of the next period. This is the phase during which many women experience symptoms such as bloating, breast tenderness, food cravings, disrupted sleep, mood changes or fatigue.

Not every woman experiences these symptoms, and those who do may experience them to very different degrees. However, these hormonal fluctuations can affect more than reproductive health alone. Oestrogen and progesterone also influence metabolism, body temperature, fluid regulation, appetite, muscle tissue and the way the body responds to exercise.

Person checking a fitness smartwatch on their wrist while sitting on an exercise mat.

Why Hormones Might Influence Exercise Performance

One of the most interesting areas of research is how hormones affect the way the body produces and uses energy during exercise.

Fuel, Fatigue and Glycogen

Carbohydrates eaten in the diet are stored as glycogen in the muscles and liver. Glycogen acts as a readily available fuel source during exercise, particularly during higher-intensity activities such as running, cycling, team sports and strength training.

Research suggests that higher levels of oestrogen may encourage the body to rely slightly more on fat as a fuel source and slightly less on carbohydrate during exercise. In theory, this may help preserve glycogen stores and delay fatigue during prolonged exercise.

Because glycogen is a limited fuel source, once stores become depleted, exercise often feels significantly harder and performance can decline. If the body is able to use a greater proportion of fat for energy, glycogen may be used more slowly, allowing those stores to last longer before being exhausted. This could potentially support endurance performance during longer-duration activities.

Conversely, during phases when oestrogen is lower, glycogen stores may be used more readily. This does not mean performance will inevitably decline, but it may help explain why some women report differences in endurance, energy levels or perceived effort at different points in their cycle.

The effect appears to be modest and varies considerably between individuals. Nutrition, fitness level and training status still have a much larger influence on performance.

Nevertheless, these physiological changes may help explain why the same workout can sometimes feel very different from one week to the next.

A woman sitting cross-legged on a yoga mat, enjoying a salad from a bowl while smiling. She is dressed in workout attire, with a glass of orange juice beside her and a tablet on the mat.

Recovery and Muscle Function

Oestrogen receptors are found within muscle tissue, leading researchers to investigate whether hormonal fluctuations influence strength and recovery.

Some studies suggest that higher oestrogen levels may reduce the amount of muscle damage that occurs during exercise. Others have explored whether rising oestrogen may improve the ability of muscle fibres to generate force.

These findings have led to the theory that strength, power and recovery may be slightly enhanced during certain phases of the cycle. However, research findings remain inconsistent and any differences appear small on average.

Connective Tissue and Injury Risk

Hormones do not only affect muscle. Researchers have also investigated their effects on tendons and ligaments.

Oestrogen appears to influence the production and turnover of collagen, the structural protein that gives connective tissues much of their strength and elasticity. This has led scientists to explore whether hormonal fluctuations could affect joint stability or injury risk throughout the menstrual cycle.

One area of particular interest has been anterior cruciate ligament (ACL) injuries, which are more common in female athletes than males. Some studies have suggested that injury risk may vary across the menstrual cycle, possibly due to hormonal effects on ligament properties and neuromuscular control.

However, findings remain inconsistent and no firm conclusions have been reached. At present, there is insufficient evidence to recommend modifying training specifically to reduce injury risk according to cycle phase.

A person lying on a yoga mat while using a foam roller for muscle relief or stretching.

Body Temperature and Endurance

Progesterone increases core body temperature by approximately 0.3-0.5°C during the luteal phase.

While this sounds insignificant, endurance performance can be sensitive to even small increases in body temperature, particularly during prolonged exercise or in hot environments.

This may partly explain why some women find endurance sessions feel more challenging during the latter part of their cycle despite no change in fitness.

Appetite and Energy Intake

Many women notice increased hunger and food cravings before their period. This is not simply a matter of willpower.

Research suggests that energy expenditure rises slightly during the luteal phase, meaning the body may genuinely require more energy. Hormonal changes also influence appetite-regulating hormones and food preferences.

This may help explain why some women feel hungrier, crave certain foods or struggle more with recovery at particular points in their cycle. If energy intake does not keep pace with these changing physiological demands, workouts may feel harder and recovery slower despite no change in training volume or fitness.

Can Exercise Performance Actually Change Across the Cycle?

This is where the science becomes less clear.

While there are plausible physiological reasons why hormonal fluctuations could influence exercise performance, demonstrating this consistently in research studies has proven difficult.

Studies examining strength, endurance, power output and recovery have produced mixed results. Some report small advantages during particular phases of the cycle, while others find little or no meaningful difference.

Recent reviews of the evidence suggest that any average differences in strength, endurance or power output across the menstrual cycle are generally small. However, averages can sometimes hide important individual differences.

Some women consistently notice predictable changes in performance, recovery or motivation throughout their cycle. Others notice almost none. This variability may help explain why research findings are often contradictory.

A training strategy that feels transformative for one woman may make little difference to another.

The Rise of Cycle Syncing

Cycle syncing refers to adjusting training according to different phases of the menstrual cycle.

The concept is simple: train harder when hormones may support performance and recovery, and reduce training intensity when symptoms are more prominent. It is an appealing idea and, for some women, may feel intuitive.

However, current evidence does not strongly support rigid cycle-based training programmes for all women.

There is currently insufficient evidence to say that every woman should perform strength training during one phase, cardio during another and recovery sessions during a third.

The research simply is not strong enough.

This does not mean hormonal changes are irrelevant. Many women notice predictable patterns in energy, recovery, motivation, appetite or exercise enjoyment throughout their cycle. Recognising those patterns will provide better guidance on training decisions.

What About Hormonal Contraception?

Much of the research discussed so far relates to women who experience natural hormonal fluctuations throughout the menstrual cycle.

Hormonal contraceptives alter these fluctuations to varying degrees.

Combined oral contraceptive pills suppress ovulation and provide synthetic hormones, creating a more stable hormonal environment than a natural cycle. Hormonal implants, injections and coils can produce different hormonal patterns depending on the method used.

As a result, women using hormonal contraception may experience fewer cyclical changes in energy, recovery or performance. Others may continue to notice fluctuations despite using contraception.

Current evidence suggests that hormonal contraceptives have little overall effect on athletic performance for most women. Any differences in strength, endurance or aerobic fitness appear small and are unlikely to be meaningful for most recreational exercisers.

However, responses remain highly individual. Some women feel better on hormonal contraception, while others notice changes in mood, energy, recovery or training enjoyment.

What About Perimenopause and Menopause?

As oestrogen levels decline, women gradually lose muscle mass and bone density at a faster rate than before. Muscle is metabolically active tissue that helps maintain strength, mobility and physical function. As muscle mass declines, maintaining strength becomes increasingly important.

For this reason, resistance training often becomes a higher priority during midlife and beyond. Strength training helps preserve muscle mass, maintain bone strength and support long-term physical independence.

Many women also notice changes in body composition during perimenopause, particularly an increase in abdominal fat. Hormonal changes influence where fat is stored, while age-related muscle loss can reduce overall energy expenditure. Regular strength training can help counteract some of these changes.

Sleep disruption, hot flushes and fatigue can also affect recovery and exercise tolerance. During these periods, training plans may need greater flexibility, with more emphasis on recovery, adequate protein intake and consistency rather than continually increasing training volume or intensity.

Unlike cycle syncing, where the evidence for structured training adjustments remains limited, there is strong evidence that resistance training becomes increasingly important during and after menopause.

A group of older adults performing resistance band exercises in a park, with a focus on a woman in a blue tank top engaging her upper body.

So, Should You Change How You Train?

The menstrual cycle can influence exercise performance, recovery, appetite, body temperature and energy levels. There are plausible physiological reasons for these effects, and many women recognise clear patterns throughout their cycle.

However, the size of these effects varies enormously between individuals.

Current evidence does not support rigid cycle-based training for every woman, and women do not need to organise every workout around their hormones in order to be healthy, fit or successful.

Understanding your cycle can be a useful tool. It may help explain why certain workouts feel easier, harder, more enjoyable or more fatiguing at different times of the month.

However, understanding your cycle is not a prerequisite for good health, fitness or performance. Many women achieve remarkable athletic success without adjusting their training around hormonal fluctuations.

The fundamentals still matter most: consistent training, adequate recovery, sufficient nutrition and long-term adherence. The best training plan remains the one that works for your body, not somebody else’s spreadsheet.

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Information and other content provided in these blogs should not be construed as medical advice and should not be considered a substitute for professional medical expertise. If you have any medical concerns, you should consult with your health care provider.