Sprint intervals:
One reason people give for not engaging in exercise is they do not have the time. Well if time is your main limiting factor sprint intervals is the perfect ticket for you.
A currently equaling pressing issue for many people is lack of extra funds so they can not afford to join a gym. Then sprint interval training is the perfect ticket for you.
Sprint training will save you immense time and money – no driving 10-40 minutes to the gym (time and financial cost), no gym membership.
You simply need an open area of anywhere from 50-200 meters long. A nice uphill grass slope is one great choice, but not the only one. If you don’t like sprinting in the rain or snow you can easily use a stairwell of any building (you only need about a 5 flights of stairs to get a great workout). Even a parking lot, sidewalk (but don’t plow down the strollers), or side street can provide an avenue for your sprint intervals.
The science:
The reality is any form of sprint training will be good for you. Some people point out, just look at sprinters physiques. The problem with that argument is was in the sprinting that make them look that way, or they are sprinters because they have that type of physique (lean and muscular).
But there are a series of scientific papers that point out the efficiency of sprint intervals.
Burgomaster et. al., 2005 used 4-7 ‘all out’ 30 second sprints (which are painful I can tell you from experience) followed by 4 minutes of recovery performed every second day for a two week period (total of 6 sessions). In sum total the subjects performed approximately 15 minutes of exercise over the 2 week period.
Results:
Citrate synthase increased by 38%, resting muscle glycogen levels increased by 28%. More importantly cycling endurance at 80% of Vo2 peak was significantly improved compared to the control group (26 +/- 5 minutes for the control group, 51 +/- 11 minutes for the sprint training group). Hence, endurance performance doubled in 2 weeks. The authors point out the increase in citrate synthase seen with 15 minutes of work is similar to what is observed with more traditional endurance paradigms of 6-7 days a week of an hour or more of moderate level aerobic exercise (65% of Vo2 max).
A followup study by Gibala et. al., in 2006 found similar results. In this study they directly compared the above sprinting paradigm training done for 2 weeks versus 90-120 minutes of continuous cycling at 65% of Vo2 max over the same two week period in young active men (university students that already did recreational exercise 2-3 times a week, e.g. jogging, cycling, etc). The total time commitment for the two groups was 2.5 hours (including recovery periods – with only 15 minutes of actual exercise) for the sprint training versus 10.5 hours for the endurance based training.
Results:
Both groups improved their endurance ability in a 750 kJ cycling test, and there were no statistical difference between the two groups (the sprint group improved 10.1% and the endurance group 7.5%). Mean power output was in the range of 212 to 234 Watt range for the approximate 1 hour of cycling (which just to give you a baseline is the wattage a serious but not top age group athlete would push for the entire ironman leg of the bike portion - 5-6 hours). Additionally, muscle buffering capacity and glycogen content increased similarly in both groups (with the un-statistical overall advantage trending to the sprint group).
Bottom line in a direct comparison in already active young men the sprint training which required 4 times less time produced equal level of aerobic improvements.
But there is a cost to sprint intervals:
It saves you time and money – but they are somewhat painful. Not only can your muscles hurt but also a more visceral hurt in the guts that can occur with serious physical exertion. You have to teach yourself to tolerate this discomfort. It is not going to kill you – it will make you stronger 
Another very popular form of interval training is called Tabata intervals. Tabata intervals consist of 20 sec of sprints (be it rowing machine, bicycle, sprints, or stairs) followed by 10 seconds of rest intervals (which will even save more time since you have less resting period – but you pay in higher overall level of pain). I will save the discussion about these intervals for another time – but feel free to try them out.
Get ready for the new year with a new resolution to improve your fitness and health. Sprint intervals might be one answer for you.
Tags: save money, save time, sprint intervals, training
