Sedentary people who find the idea of fitting regular exercise sessions into their lives so difficult that they don't even try, may be interested to hear about a new study that found even regular short bursts of intense exercise, such as a short session of four to six 30-second high intensity sprints on an exercise bike every two days, showed a significant effect on the body's ability to metabolize sugars and could be an effective way to cut the risk of diabetes.
This was the conclusion of a study by professor James Timmons and a team of researchers from Heriot-Watt University in Edinburgh, Scotland, that is to be published in the journal BMC Endocrine Disorders.
Most people know that regular physical activity is a good way to cut the risk of developing heart disease and Type 2 diabetes, but knowing it and doing it are not the same, and many people feel they just don't have the time to do vigorous aerobic exercise for several hours week, as suggested by many of the current guidelines.
Timmons said that while these guidelines are worthwhile in principle, the fact many people don't follow them shows we need an alternative.
"Unfortunately, many people feel they simply don't have the time to follow current exercise guidelines. What we have found is that doing a few intense muscle exercises, each lasting only about 30 seconds, dramatically improves your metabolism in just two weeks," he said.
Timmons and colleagues investigated the effect of "high-intensity interval training" (HIT) on the metabolic performance of sixteen sedentary male volunteers aged from 19 to 23 years with an average BMI (body mass index) of 23.7.
This type of exercise has been shown to improve aerobic function, but its effect on insulin action and glycemic control has not been investigated, wrote the authors in their background information.
The volunteers did a total of 15 minutes of HIT exercise over two weeks, structured as 6 sessions where in each session they did 4 to 6 high intensity sprints of no more than 30 seconds on an exercise bike.
The researchers measured the volunteers' aerobic and metabolic performance before and after the training.
The results showed that:
After two weeks of HIT, many measures of metabolic performance improved.
For instance, the area under the blood glucose, insulin and non-esterified fatty acid or NEFA curves reduced by 12, 37 and 26 per cent respectively (all p<0.001).
Insulin sensitivity, as measured by the Cederholm index, improved by 23 per cent.
And, although the fasting blood insulin and glucose levels did not change, there was a tendency for fasting blood NEFA to go down after training.
Aerobic cycling performance improved by about 6 per cent (p<0.01).
The researchers concluded that:
"The efficacy of a high intensity exercise protocol, involving only ~250 kcal of work each week, to substantially improve insulin action in young sedentary subjects is remarkable."
" This novel time-efficient training paradigm can be used as a strategy to reduce metabolic risk factors in young and middle aged sedentary populations who otherwise would not adhere to time consuming traditional aerobic exercise regimes," they added.
The volunteers in this trial did high intensity sprints on exercise bikes, but the researchers said in principle any highly vigorous activity on a few days per week should have a similar protective effect on metabolism. As Timmons explained:
"This novel approach may help people to lead a healthier life, improve the future health of the population and save the health service millions of pounds simply by making it easier for people to find the time to exercise."
"Current guidelines, with regards to designing exercise regimes to yield the best health outcomes, may not be optimal and certainly require further discussion. The low volume, high intensity training utilized in our study substantially improved both insulin action and glucose clearance in otherwise sedentary young males and this indicates that we do not yet fully appreciate the traditional connection between exercise and diabetes," he added.
"Extremely short duration high intensity training substantially improves insulin action in young healthy males."
John A Babraj, Niels BJ Vollaard, Cameron Keast, Fergus M Guppy, Greg Cottrell and James A Timmons.
BMC Endocrine Disorders (in press).