A new study is challenging how and when people work out, suggesting that the clock on the wall may matter less than the clock inside the body. Researchers say aligning exercise with natural body rhythms could significantly improve heart health, sleep quality, and metabolic outcomes, especially for people already at risk of cardiovascular disease.

The findings point to a simple but powerful idea: the best time to exercise may be different for everyone, and forcing workouts at the wrong time of day could limit results.

Improvements in fitness

Some 134 people in their 40s and 50s in Pakistan took part in the study.

None were super fit and had at least one heart risk factor, such as high blood pressure or being overweight.

They were asked to do supervised, brisk-walking exercise sessions on a treadmill for 40 minutes a day, five times a week for three months.

Based on questionnaires, 70 were classed as morning larks and 64 were night owls.

Some did their exercises at times to match their body clock chronotype, the natural predisposition to morning or evening alertness, while others did the opposite.

Both groups showed improvements in fitness.

But matching exercise with chronotype produced larger health gains in blood pressure, aerobic capacity, metabolic markers and sleep quality.

Your internal body clock affects sleep wake patterns and hormone and energy levels across the day, which in turn could influence exercise performance and adherence, explain the researchers.

Social jetlag

The study authors say the findings suggest a "one-size fits-all" approach to exercise timing is less than ideal.

A mismatch between biological and social schedules or "social jetlag" has been linked to increased heart risk.

Night owls can be at greater risk of this, they add, meaning they should not force early morning exercise routines.

Some gyms now stay open all hours, night and day.

Hugh Hanley, Personal Training and Fitness Director at PureGym, says Monday and Tuesday evenings are typical peak busy times but, increasingly, people are spreading out the hours they train.

"One thing we have noticed over the last few years is people are actually prioritising their health more, bringing in more flexibility."

He says the key to staying fit is consistency, creating a habit of movement, building it into your lifestyle.

"Doing it regularly is better than one or two blasts."

"We see a lot of the time that people set too big a goal initially. We'd always rather they break it into small bite-sized goals that are achievable."

The trend at the moment, he says, is strength training. "We're seeing a big rise... across all generations. The younger generation are definitely prioritising strength training, but even the older demographic."

Dr Rajiv Sankaranarayanan of the British Cardiovascular Society, which co-owns the journal the work is published in, said the findings supported a shift towards workouts to suit body clocks, but proposed more studies to confirm this.

Dr Nina Rzechorzek, an expert in body rhythms at the University of Cambridge, said while timing may be one factor worth considering, getting enough regular exercise mattered most.

Doing a mix of exercise is helpful, evidence suggests, with the NHS recommending strengthening activities at least two days a week and vigorous cardio exercise for at least 75 minutes.

Ready to hit the gym morning or night? Strength training exercises, such as wall squats or holding the plank position, are among the best ways to lower blood pressure.

These isometric exercises are designed to build strength without moving muscles or joints.

Wall squats involve putting your back against a wall and lowering down into a sitting position using your hips until the thighs are parallel to the ground.

The plank involves holding a position similar to a push up for an extended period to work core abdominal muscles as well as the back, shoulders, arms and glutes.