Less really can be more when it comes to exercise, scientists have discovered.
A new study found that about 20 minutes of high-interval training provided the same benefits of longer exercise sessions that focused on endurance training, and that the body can get as much benefit from a short but intensive burst of exercise than it can from ten hours of moderate training. 
This means that exercising does not have to be time consuming and can involve much less physical effort.
Scientists from McMaster University in Canada studied the benefits of "high intensity interval training", known as HIT. This technique involves running or cycling at almost maximum effort for a minute and then resting for a minute before repeating the process around 10 times.
HIT is "a time-efficient but safe alternative to traditional types of moderate long term exercise," they discovered.
In experiments, volunteers rode an exercise bike in stints lasting just 60 seconds while peddling hard enough to get close to their maximum heart rate.
Tests afterwards showed that their muscles had improved as much as if they had been involved in endurance training.
The study authors said it was not clear why HIT was so effective but it appeared to "stimulate many of the same cellular pathways" as traditional training regimes.
These men received the same benefits as they would have had they exercised at a lower intensity for one hour or more, leading researchers to say interval training "may represent an alternative to endurance training to improve metabolic health and reduce the risk for chronic diseases."
The findings also meant that a lack of free time was no longer an excuse for refusing to exercise, the author said.
Burn More fat With Less Effort
Several studies have confirmed that exercising in shorter bursts with rest periods in between burns more fat than exercising continuously for an entire session. This has been shown to be the case even when the session is not done at an extremely high intensity.
In one study, those who cycled for 40 minutes, alternating four-minute bursts at 90 percent effort with two minutes of rest, improved their cardiovascular fitness by 13 percent, and were able to burn 36 percent more fat than during a later hour-long moderate cycling session. 
Another study found that you can burn more fat exercising for just 20 minutes. 
In the trial, women either exercised for 20 minutes, alternating 8 seconds of sprinting on a bike with 12 seconds of exercising lightly, or exercised at a regular pace for 40 minutes. After exercising three times a week for 15 weeks, those who did the 20-minute, alternating routine lost three times as much fat as the other women.
The researchers believe this type of exercise works because it produces a unique metabolic response. Sprinting at intervals produces high levels of chemical compounds called catecholamines, which allow more fat to be burned from under your skin and within your muscles. The resulting increase in fat oxidation is thought to drive the increased weight loss.
Another benefit of interval training is that it cuts down on the amount of time needed to exercise, so an hour-long cardiovascular exercise can be replaced by 20-40 minutes of high-intensity interval training.
Exercise For Optimal Health
Exercise is one of the most powerful ways to gain optimal health. Regular physical activity helps to helps to combat the ongoing damage done to cells, tissues and organs that underlies many chronic conditions, and also boosts the immune system, helping to fight off colds and flu. Exercise also keeps insulin levels down, and elevated insulin levels are one of the primary reasons for many illnesses and for weight gain.
Research Paper Details:
 Little JP, et al. A practical model of low-volume high-intensity interval training induces mitochondrial biogenesis in human skeletal muscle: potential mechanisms. March 15, 2010 The Journal of Physiology, 588, 1011-1022.
 Talanian JL, et al. Two weeks of high-intensity aerobic interval training increases the capacity for fat oxidation during exercise in women. J Appl Physiol 102: 1439-1447, 2007.
 Trapp G, Chisholm DJ, Boutcher SH. Metabolic response of trained and untrained women during high-intensity intermittent cycle exercise. Am J Physiol Regul Integr Comp Physiol 293: R2370R2375, 2007.