Science

Love, inside the brain, is a chemical cocktail of many different hormones. Oxytocin — which is often called the "love hormone" — is believed to be the most important of all. But it is nothing more than an ancient chain of nine amino acids, produced by all mammals, with similar molecules found in fish, reptiles and worms. It helps induce contractions in childbirth, which is how it got its name: From the Greek oxys (swift) and tokos (birth).  "There's nothing inherently social about oxytocin," said Sarah Winokur, a neuroscientist at the NYU Grossman School of Medicine. So how did oxytocin get its reputation for making love happen? Oxytocin, the wonder drug? In the 1990s, an Emory University research group experimented on prairie voles, a rodent species that forms long-term monogamous ...

There's a body of research going back at least 40 years, with scientists asking whether hormonal shifts in women influence strength, fatigue and recovery.  Over time, that research has filtered into gyms and social media, often simplified into rules like "take it easy during your period" or "push hard mid-cycle." The menstrual cycle is a monthly rhythm of hormones. During the month, two key hormones, estrogen and progesterone, rise and fall, shaping how many women feel, move and recover. Fitness professionals often divide the cycle into four stages:  Week one: during menstruation, also known as the bleeding phase or "period" Week two: days leading up to ovulation  Week three: after ovulation  Week four: before the next period begins And depending on where you are in your cycle, ...