Could One Workout a Week Be as Effective as Training Three Times a Week?

Exercise Research: A randomized controlled trial investigated whether one workout a week could be as effective as three weekly workouts

Finding time to exercise can be challenging, especially during midlife when work, family commitments, and other responsibilities often leave little free time. Some people also become less active because of joint pain, osteoporosis, injuries, or other health conditions that make regular exercise more difficult.

Obesity has become a major global health concern. According to the World Health Organization, one in eight people worldwide were living with obesity in 2022. Since 1990, adult obesity rates have more than doubled, while adolescent obesity has quadrupled.

These rising numbers have increased interest in practical, time-efficient ways to improve health and reduce body fat.

Current physical activity guidelines recommend spreading exercise across the week, but many people struggle to fit in several workouts. This has led researchers to investigate an important question: if the total amount of exercise stays the same, does it really matter whether you complete it all in one session or spread it across multiple days?

What Did the Researchers Investigate?

The researchers wanted to find out whether completing the same amount of weekly exercise in one longer workout could produce similar health benefits to spreading the exercise across three shorter workouts.

The study included 315 adults with excess belly fat, a condition known medically as central obesity. Participants had an average age of 48.2 years and were randomly assigned to one of three groups for 16 weeks.

The once-weekly group completed all 75 minutes of HIIT during a single weekly visit. Rather than exercising continuously for 75 minutes, participants completed three 25-minute HIIT bouts separated by 15 to 30 minutes of rest, together with a warm-up and cool-down.

The three-times-weekly group completed one 25-minute HIIT bout during each visit, also with a warm-up and cool-down. A third group acted as the control group and received general health education but did not participate in the supervised exercise program.

The researchers measured body weight, body mass index (BMI), total body fat mass, body fat percentage, lean mass, waist circumference, and cardiorespiratory fitness before and after the intervention to compare the effects of the different exercise schedules.

What Is High-Intensity Interval Training (HIIT)?

High-intensity interval training (HIIT) is a form of exercise that alternates short periods of vigorous activity with brief recovery periods. It can be incorporated into many forms of exercise, including walking, running, cycling, swimming, and rowing, although the participants in this study completed supervised HIIT sessions on a treadmill.

HIIT is designed to raise your heart rate for short bursts, followed by slower exercise or rest before repeating the cycle.

Both exercise groups performed the same total amount of weekly exercise (75 minutes). One group completed all 75 minutes in a single weekly session, while the other spread the same amount of exercise across three shorter workouts.

What Did the Study Find?

Both exercise groups completed the same total exercise time each week, but one group completed it during a single weekly visit while the other spread it across three 25-minute workouts.

After 16 weeks, both exercise groups showed significant improvements in body fat, waist circumference, and cardiorespiratory fitness compared with the control group. The researchers found no significant differences between the one-workout group and the three-workout group for these main outcomes. This suggests that completing the same amount of weekly HIIT in one session produced similar overall benefits.

The improvements in body weight, body mass index (BMI) and waist circumference were also similar in both exercise groups. Although participants who completed one weekly workout exercised less frequently, they achieved comparable reductions in these measures to those who exercised three times a week.

The researchers also assessed several cardiometabolic health markers, including blood pressure and blood test results. However, there were no significant differences between the one-workout and three-workout groups for most of these measures after 16 weeks.

Importantly, participants completed the exercise program safely, and no serious exercise-related adverse events were reported.

Overall, the findings suggest that when the total amount of weekly high-intensity interval training is the same, completing it in one longer session may provide similar improvements in body composition, waist circumference and cardiorespiratory fitness as spreading the exercise across three shorter workouts.

What Could This Mean for You?

These findings suggest that the total amount of exercise you do each week may be more important than how often you exercise, at least for certain measures of body composition and fitness.

For people who struggle to fit several workouts into a busy schedule, completing one longer session each week may be a practical alternative to exercising several times a week. This could be particularly relevant during midlife, when work, family commitments and other responsibilities often make regular exercise more challenging.

For some people living with obesity or type 2 diabetes, exercise may also be combined with prescription GLP-1 medications as part of a comprehensive weight management plan. While these medications can support weight loss and improve blood sugar control, maintaining regular physical activity remains important for preserving muscle mass, supporting cardiovascular health, and promoting long-term success.

However, it is important to remember that this study investigated supervised high-intensity interval training (HIIT) performed on a treadmill. 

The findings do not necessarily apply to every type of exercise, and they do not suggest that exercising less is always better. The participants in both exercise groups completed the same total amount of weekly exercise, with only the frequency differing.

Study Limitations

This study has several limitations that should be considered when interpreting the findings. 

It included 315 adults aged 18 to 60 years with an average age of 48.2 years and central obesity. The results may therefore not apply to older adults, people with a healthy weight, or those with metabolic conditions such as type 2 diabetes.

The study investigated supervised high-intensity interval training (HIIT) performed on a treadmill over a period of 16 weeks. It is therefore unclear whether similar results would be achieved with other forms of exercise, different training intensities, or over a longer period of time.

The study was designed primarily to compare each HIIT group with the control group. It was not powered to determine conclusively whether once-weekly and three-times-weekly HIIT were equivalent. Although the three-times-weekly group generally showed larger numerical improvements in body weight, body fat, waist circumference, and cardiorespiratory fitness, these differences were not statistically significant when the two exercise groups were compared directly.

Finally, although the findings suggest that completing the same amount of weekly HIIT in one longer session may provide similar benefits to spreading it across three shorter sessions, the researchers concluded that further studies are needed to determine whether these findings can be applied to other populations and exercise programs.

Lillepin Takeaway

One 75-minute HIIT session per week may provide similar improvements in body composition and fitness as three 25-minute weekly sessions. For people who struggle to fit several workouts into a busy schedule, this approach could offer a practical, time-efficient way to stay active.

However, because this study investigated supervised treadmill-based HIIT, further research is needed to determine whether similar results can be achieved with other forms of exercise and in different populations.