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Low motivation, lack of energy, general gloom. If you are a premenopausal woman, you probably know the feeling all too well.

But have you ever wondered how hormone levels (a common reason for the grouch within) affect your physical performance and whether you might tailor workouts to fit a specific phase of the cycle?

If so, our experts have a tip or two for you.

First off, the menstrual cycle is divided into two main phases:

The follicular, low-hormone, phase (Days 1-14), which starts on the first day of the period; and the luteal, high-hormone, phase (Days 15-28), which starts with ovulation.

Though the actual period often gets a bad rap, the follicular phase is when you generally have more energy, says Stacy Sims, an environmental exercise physiologist and nutrition scientist in the Bay Area and co-founder of Osmo Nutrition .

“We are more like men in the follicular/low-hormone phase,” Sims says. “In this phase, it’s great to do high-intensity work, try to set PRs, push yourself harder.”

The only time in this phase when women — at least those with heavy flow — might feel less powerful is the third day of the menstrual period, says May Blanchard, chief of OB/GYN at the University of Maryland School of Medicine.

“That’s when we might do a blood count to see if levels are pushing the border of anemia,” she says. (Anemia is when the red blood cell count drops, creating fatigue and weakness.)

In that case, iron supplementation might be in order, Blanchard says. But this only applies to women who have heavy periods and are feeling low-energy.

Another issue for athletic women during the menstrual period is management on a practical level.

For example, for women who compete in endurance races that last many hours, such as ironman triathlons – where and when to use the restroom and where and how to store supplies?

“The logistics of it can be very challenging,” says Debi Bernardes, a longtime Washington area triathlete and tri coach.

But aside from these concerns, the follicular phase is the bomb, so to speak.

With female sex hormone levels low, the level of testosterone (even though much lower in women than men) stays the same — meaning that the relative level of testosterone is higher, says Kathleen Casto, an elite runner and PhD student at Emory University in the field of social neuroendocrinology (the relationship between hormones and behavior).

“And we know that testosterone can be beneficial for sports performance,” Casto says.

Which brings us to the many women who use birth control.

The pill “controls the hormonal milieu,” Casto says. With the pill, female hormone levels stay steady throughout the month.

Is there a downside?

Possibly, Casto says. It dulls the valleys, yes, but it also dulls the peaks. In other words, the testosterone level never goes up in relation to progesterone and estrogen.

For those who are not on the pill, the second half of the month, the luteal phase, is marked by high female hormone levels.

“In the mid-late luteal phase — five to seven days before your period starts — this is where women feel progressively worse – progesterone and estrogen interplay to cause a bit of metabolic mayhem,” Sims says.

For example, a woman’s core temperature goes up (causing a feeling of overheating); carbohydrate stores are not easily accessed (making it much harder to hit high-intensity intervals); and moodiness occurs.

“In this phase, it’s better to do more steady-state-endurance-focused work, body-weight or lighter resistance training,” Sims says.

Other ways she suggests to best manage this “mayhem” phase:

● Eat 10 grams of protein before and 20 grams within 30 minutes after exercise;

● Have carbs (e.g. energy chews) readily available if you have to race or participate in high-intensity intervals;

● Ensure electrolyte intake since you have a greater chance of hyponatremia (low sodium) in this phase;

● Take up to five grams of branched-amino acids (leucine, isoleucine and valine, three important amino acids found in eggs and meat) before exercise;

● Drink four to six ounces of cold tart cherry juice 30 minutes before bed for better sleep.

For elite athletes Sims helps train, she also increases magnesium, white willow bark, zinc and turmeric to “push back against the inflammation and fluid shifts caused by estrogen and progesterone.”

“Fluid shifts” is another, kinder way of referring to bloating.

This is a lot to digest — quite literally. Is it really that important?

It depends on what you are trying to achieve, Sims says. If you’re trying to set a personal record or increase power, then yes. But for general fitness, then it’s not critical, she says.

“Just be aware that it is your physiology, not your fitness, that can affect your performance across the monthly cycle.”

Bernardes agrees, and says, “Sometimes it calls for rethinking the rate of recovery.”

Dare we say it? A day off.

Casto agrees: “Sometimes you just have to go easy on yourself.” But she adds that not all women (even those who are not on birth control) feel changes throughout the cycle.

“It’s important to remember that there is no such thing as a normal menstrual cycle,” Casto says. “There is a lot of variability both physiologically and psychologically.”

But if you are in the affected category, then there may be a benefit to exercising despite feeling bloated and moody: endorphins — a chemical compound that is associated with euphoria. It’s not a cure, but it can help push back pain, bloating and the inner grouch.

Says Blanchard, “If you can push yourself to do something, it can make you feel better.”

Boston is a fitness trainer and freelance writer. She can be found at www.gabriellaboston.com.