Morning exercise initiates gene programmes in muscle cells, making them more effective and better capable of metabolising sugar and fat. Picture: 123RF/PAOLO DE SANTIS
Morning exercise initiates gene programmes in muscle cells, making them more effective and better capable of metabolising sugar and fat. Picture: 123RF/PAOLO DE SANTIS

Are you a sparrow or an owl when it comes to exercise? Do you wake each morning full of the joys of spring, even in the very dead of winter, to rush off enthusiastically to the gym or to pound your neighbourhood pavements on a run?

You’re a sparrow.

Do you battle grumpily to get going in the morning before you’ve downed at least one cup of coffee and can summon up enthusiasm for any exercise at all only much later?

You’re an owl.

There’s a long-held perception that sparrows do much better than owls at accruing health benefits from exercise.

Some research suggests that sparrows’ vigorous activity first thing in the morning is best for weight loss and other benefits, including overall fitness and cognition. And while most experts say that exercising later in the day, particularly at night, is better than not exercising at all, many advise against it. That’s based on the belief that late-night exercise interferes with restful sleep.

A new US and Danish study in the journal Cell Metabolism undermines those beliefs. The data builds on growing research into the effects of exercise on circadian rhythms, the body’s biological “clock”, no matter the time of day.

The authors say that health effects of exercise do differ depending on whether it’s in the morning or evening, but that doesn’t mean one is better than the other.

Their data shows that morning exercise initiates gene programmes in muscle cells, making them more effective and better capable of metabolising sugar and fat. That makes morning exercise especially helpful for those who are obese or have type 2 diabetes. (Both conditions are epidemic in SA, as they are in many other countries.)

Their study also shows a beneficial “global effect” of evening exercise by increasing whole-body energy expenditure for an extended period compared with morning exercise. That also benefits those with metabolic issues, the authors say.

Their study is in mice and thus cannot be generalised for all  humans. Humans have “more variation in their chronotypes than mice living in a laboratory”, as researchers point out.

The lead author, University of Copenhagen associate professor Jonas Thue Treebak from the Novo Nordisk Foundation Centre for Basic Metabolic Research, wants to extend studies to humans to identify if timed exercise really can be an effective treatment strategy for people with metabolic diseases.

Growing evidence supports benefits of a metabolic boost from exercise on weight loss but also on cognition, no matter the time of day. That’s one way of preventing declining cognitive function as the years go by, the experts say. That’s important as the incidence of dementia diseases continues to rise in SA and globally.

Zimbabwe sports physician Dr Austin Jeans is fully on board with that thinking and encourages his athletes and patients to exercise regularly any time of the day. Jeans returned from Brazil last week where he was a team doctor at the World Rugby Under 20 Trophy. 

Optimising the time of day when we do specific types of exercise could add huge value to the way we manage metabolic disease in conjunction with other important lifestyle factors.
Dr Austin Jeans

The circadian rhythm is “a complex system of body clocks linked to sleep patterns, light and dark cycles, and eating”, Jeans says. Mounting research shows that disruption of the body’s circadian machinery is “highly detrimental” to metabolism.

In animal experiments on mice and baboons, disruption of the body-clock machinery resulted in obesity and insulin resistance.

“That’s the basis for developing diabetes,” he says.

“In humans, the disruption through poor sleeping patterns or shift work can have similar deleterious effects on metabolism, thereby predisposing us to poor health as a consequence.”

Exercise can offset that as it has a significant influence on the function of our skeletal muscle clocks and can reset the circadian rhythm, Jeans says. In turn, this can offset the effects of disturbed sleep patterns.

Most studies into the timing of exercise have found that the effects of low-intensity training on muscle peak in the morning, and the effects of high-intensity exercise or strength-training exercise performance increases in the afternoon and evening, Jeans says.

The implication of all this research is “exciting and simple”, he says. “Optimising the time of day when we do specific types of exercise could add huge value to the way we manage metabolic disease in conjunction with other important lifestyle factors, such as good nutrition.”

And either way, we’ll boost brain function thanks to the global benefits of exercise. There’s nothing new to that idea.

In the 18th century, Scottish theologian Hugh Blair called exercise “the chief source of improvement of our faculties”.

Circadian rhythm

  • Every organism, from algae to zebra and humans, has a circadian rhythm that is popularly known as the body’s “clock”.
  • Human body clocks differ depending on “chronotype”, that is, whether they are sparrows or owls, and affect health and performance in body and mind.
  • The body clock is composed of genes and proteins that operate in a feedback loop.
  • The clock regulates the body’s timing of processes, such as eating, sleeping and temperature.
  • A “master clock” in the brain co-ordinates all the body clocks so they are in synch.