HIIT workouts that make you exercise vigorously for 30 seconds and then rest for two minutes ‘do NOT improve your fitness’
- Study participants were divided into two HIIT groups on a six-week programme
- Pairing 30 seconds exercise and 120 seconds rest had no effect on fitness
- But 60 seconds work with 60 seconds rest did improve fitness, study shows
- The scientists added that heart rate must increase for benefits to be seen
If you thought 30 seconds of HIIT was enough, scientists say you’re wrong – unless your rest periods are very short.
Participants in a study were given a six-week programme involving high intensity training (HIIT) workouts.
Those doing 30 seconds of work with 120 seconds rest reaped no benefits at all despite their hard work.
The researchers stressed it is important to push your heart rate up to see beneficial changes in the body, which isn’t likely to occur if you are resting for a long time.
They found pairing 60 seconds of flat-out intense exercise with 60 seconds of rest boosted fitness.
Pairing one minute of intense HIIT exercise with one minute of rest can increase fitness, while 30 seconds exercise and 120 seconds rest has no benefit, researchers said
High intensity workouts (HIIT) have become popular because they can be done anywhere – no gym equipment is required.
It involves short bursts of exercise at maximum effort followed by a rest period.
HIIT is considered more effective than continuous cardio for weight loss because you end up exerting more energy in total.
The research team at Liverpool John Moores University (LJMU) wanted to investigate two HIIT timing methods they say are popular.
Twenty-six previously sedentary men and women were enrolled in the study and put into two groups.
They either took part in 60-second HIIT workouts, with 60 seconds rest, or ones that lasted just 30 seconds, with 120 seconds rest.
The workouts, three times a week, consisted of body weight exercises, such as squats, lunges and push ups.
Researchers checked the participants were adhering to the six-week programme through a mobile app and heart rate monitors.
They measured three parameters before and after the intervention: aerobic capacity, stiffness of arteries and body composition.
Body composition is used to assess how lean a person is based on how much muscle or fat they have in their body.
Aerobic capacity jumped in the 60-second HIIT group – but no difference was seen for participants who took part in 30-second workouts.
Aerobic capacity is measured as the highest amount of oxygen consumed during maximum exercise.
Generally, the higher aerobic capacity is, the higher the anaerobic threshold and the longer a person can exercise without fatigue – thus improving fitness.
Lead researcher Hannah Church, who studies sport and exercise science at LJMU, said: ‘In order for people to get the most out of HIIT, which may be the answer to the difficulties of paying for and getting to the gym, we need to get the timing right.
‘Our research showed just how important this is, because we found that 30 second intervals with 120 seconds of rest meant that participants’ heart rates didn’t stay up. 120 seconds is just too long to be resting for.’
Although there is no hard and fast rule, it is recommended you exercise within 55 to 85 per cent of your maximum heart rate for at least 20 minutes to reap benefits of exercise.
In general, the higher your heart rate during physical activity, the higher the exercise intensity – but physical level of fatigue should be taken into account.
Currently 40 per cent of people in the UK do not meet the Government’s physical activity guidelines of 150 minutes aerobic activity a week.
Lack of time is cited as the most common barrier, Ms Church said, but HIIT is time convenient and can be done in the living room.
The research is being presented today at The Physiological Society early career conference, Future Physiology 2019: Translating Cellular Mechanisms into Lifelong Health Strategies. It is not published or peer reviewed.