Monday March 15 2010
The study did not compare intense activities to moderate ones
The secret of keeping fit is to “do less exercise”, says the Daily Express. The newspaper claims that new research shows that short bursts of intense activity are enough to keep most people fit, “blowing away the myth that staying in shape takes hours of dedication”.
The news is based on a small study in seven healthy men, comparing their fitness levels before and after a two-week programme of short cycling sessions. After the course of six sessions the researchers found the men had improved exercise performance and metabolism in their muscles.
However, this study did not compare this exercise regime with others, or look at any long-term benefits of exercise, such as any reduction in heart disease or obesity. This, and other limitations, means the research does not support the claims that short bursts of intensive exercise offer as much benefit as the officially recommended, more frequent, but less intensive exercise. Government guidelines suggest 30 minutes of moderate-intensity exercise taken five times a week.
Where did the story come from?
This study was carried out by Dr Jonathan Little and colleagues from McMaster University in Canada. The research was funded by the Natural Sciences and Engineering Research Council of Canada and individual researchers were supported by grants from various health research organisations. The study was published in the peer-reviewed Journal of Physiology.
Newspapers have reported on the study in some detail, but most fail to discuss the shortcomings of this small, non-comparative study. A few do report that the short-term changes assessed in this study, muscle metabolic capacity and functional performance, do not equate with long-term cardiovascular health. This is very preliminary evidence towards the reported theory that “less really can be more when it comes to exercise”.
What kind of research was this?
In this before-and-after experiment, seven men undertook six training sessions over a period of two weeks, with researchers comparing their performance and muscle health before the sessions with that seen after the training programme.
What did the research involve?
Seven healthy men were enrolled in this study. Their average age was 21, and they were reported to be healthy and “recreationally active” two or three times a week, although none were “engaged in a structured exercise training programme”. They were asked to maintain normal diet and routine levels of physical activity throughout the study but to refrain from any sporting activities beyond the exercise programme.
During each of their six exercise sessions (on Monday, Wednesday and Friday for two weeks), they did short bursts of high-intensity cycling. In each session they performed 8 to 12 repetitions of a one-minute burst at 100% of their individual maximum power output (as determined by previous tests), followed by a recovery period, which was 75 seconds of low-intensity cycling. The time commitment for each training session was around 30 minutes including warm-up and recovery.
Timed cycling trials were used to assess the participants’ exercise capacity 72 hours after the end of their final training session. Tissue samples were also taken from their “skeletal muscle”, the type of muscle tissue that powers movement and activities like running, walking and lifting. These tissue samples (taken from a muscle in the quadriceps) were assessed for their protein content and general metabolism and compared with a tissue sample taken prior to training.
Researchers used a statistical test called a “paired Student’s t-test” to compare the participants’ results after their training with their results prior to it. This is an appropriate statistical analysis method that takes into account the fact that this is a before-and-after study.
What were the basic results?
The researchers found that the time taken to complete the cycling trials improved by about 10% after training and that there was an increase in the average power during the trial. The activity of various enzymes in muscle cells also improved, as did the cells' protein content.
How did the researchers interpret the results?
The researchers say that the results of their study demonstrate that low volume HIT (high-intensity training) is a “potent stimulus for increasing skeletal muscle [energy releasing] capacity and improving exercise performance”. They also say that the results shed light on ways in which exercise training potentially promotes changes in the metabolism in skeletal muscle.
This small observational study has demonstrated an improvement in muscle health following low-volume, high-intensity training in seven healthy men. There are a number of points to keep in mind when considering the results of this research, including:
- The small sample size. The study included only seven men with an average age of 21. The researchers report that they were healthy and “recreationally active two or three times a week”, but that “none were engaged in a structured exercise training programme”. The results of the study cannot therefore be taken to represent the wider population, particularly older people.
- This study lacked a comparator group. While newspapers have reported that short bursts of high-intensity exercise are as effective as longer-term training is, the research featured no direct comparison between the two. Although the researchers say that their programme was “designed to be more practical and attainable for the general population”, they do not claim that their exercise programme was better than other types or durations of exercise.
- Given that the participants were all healthy, active young men, it is likely that they were doing other forms of activity and exercise outside of their experimental training programme. The Department of Health recommendations on physical activity say that activities of daily life, including walking, gardening and cleaning, can all count as forms of exercise.
- The Department of Health document At least five a week acknowledges that there is “growing support for the benefits of accumulating activity in shorter bouts of activity of 10 minutes or more, interspersed throughout the day”, and reports that equivalent total volumes of short activities have demonstrated positive effects similar to a single, long bout of activity. This particular study, although using a weak design, adds further evidence that low-volume, high-intensity training is good for muscles and their metabolism. However, how well it compares to other regimens is yet to be established.
- Research needs to establish how suitable short bursts of intensive exercise are for different groups of people, particularly older people or people with health problems like arthritis or high blood pressure.
These findings are interesting, but it remains to be seen whether the improvements in muscle metabolism and exercise performance observed in this study are the same as those seen with other levels of exercise. Furthermore, it remains to be seen whether they will translate into the longer-term health benefits (such as reductions in heart disease, strokes and obesity) that are associated with the levels of exercise recommended by the Department of Health.
While this type of research may suggest theoretical benefits to short bursts of intensive exercise, it does not change the fact that regular, moderate-intensity exercise is good for our health. The current recommendations of 30 minutes’ physical activity a day, five days a week, are based on rigorous reviewing of the evidence and discussion with experts.