Exercise when it feels optimal to you

Are you a morning lark or night owl? A lark is someone whose natural body clock is geared toward early rising. They are more productive early in the day, energetic early on and wake up generally with the sun (or before the sun, certainly, in the winter).

The night owl has a natural rhythm later in the day. They often stay up later and, for them, mornings can be more of a struggle.

I am a night owl. For example, I’m writing this column at 10 p.m., which is not uncommon for me. In fact, if I start reading a book — and I just started a rather trash novel, alternating my reading between history books and historical fiction — I might stay up until 1 or 2 in the morning. I have to be careful because most people like to get their day started much earlier than I do.

When it comes to exercise, I’ve often heard it’s better to get moving early in the morning. But as much as I try to do that, I fail.

A study, small and proactive, from the British Medical Journal shows that exercising in line with your individual chronological body clock might be best. So let’s dive in.

Researchers took 150 people ages 40-60 and had them start out with something called the Morningness-Eveningness Questionnaire. It’s been around since 1976, containing a series of questions that try to determine your circadian rhythm, or chronotype. Sample questions include:

• What time would you get up if you were entirely free to plan your day?

• If you got into bed at 11 p.m., how tired would you be?

• If you could choose work hours, what time would you begin?

Everyone in the study had one cardiovascular risk factor, such as high blood pressure, obesity, previous heart attack and so on, and none of them exercised. Some had a family history of heart disease — so it was what we call a selected population, more likely to get a heart attack.

Then everyone started to exercise. Half exercised at a time that matched their chronotype. If they were a lark, for example, they exercised between 8 and 11 a.m.; if they were an owl, their exercise was scheduled between 6 and 9 p.m.

The other half were assigned exercise times that were the opposite of their chronotype. Larks exercised at night and owls in the morning.

A little more information here on your chronotype: It is an internal timing mechanism in the brain that comes from your own master clock, the suprachiasmatic nucleus, located in a tiny region of the hypothalamus. It works on light signals from your eyes and uses that information to keep your internal body clock aligned with the 24-hour day.

It works in conjunction with something called peripheral oscillators, which are like little local clocks found in other parts of your body, like in your liver or muscles. They also follow rhythms, but they take cues from the master clock, along with things like eating and physical activity.

So, the suprachiasmatic nucleus sets the main schedule, and the peripheral oscillators sync up with it, making sure your whole body is in rhythm.

Now, back to those study participants. They were asked to exercise five times a week, doing supervised moderate-intensity aerobic exercise (brisk treadmill walking) that lasted 40 minutes each time. They did this for 12 weeks.

Blood pressure, heart rate variability, fasting blood sugar, maximal oxygen consumption during exercise, good cholesterol, bad cholesterol and sleep study were all measured before the start of the study, during the study and three days after it finished.

Everybody benefited from the exercise in one way or another. They were more fit, slept better and had better cholesterol, for the most part. But those who exercised based on their chronotype had large improvements in blood pressure, aerobic capacity and LDL cholesterol, and they had better sleep.

My spin: Exercise works better when you fit it to your internal body clock. Whether you’re a lark or an owl, exercise at a time that’s right for you. Stay well.