Recently i was asked "how do you do intervals"? as in, with what piece of equipment. This question assumes that doing intervals is a good thing to do - we've touched on this before. It doesn't matter what your sport or activity is: interval training, or timed piece of intense work followed by a time piece of recovery, is a good supplement to any activity program, whether you go for walks in the park, play squash or weight train.
Interval Types: there are a bunch of ways to do intervals, and you can look on the web to find ones you trust for your preferred activity. The most common way to do intervals though is on or with some stationary piece of equipment, like a stationary bike, treadmill, rower, stepper, elliptical whatever, where the intensity can be adjusted.
You don't *need* to have this equipment: you can do intervals running or on a bike or in a boat or wherever.
One reason people prefer stationary equipment for this kind of training is that they don't have to focus on anything life threatening like traffic or waterfalls when they're going flat out. One great piece of low cost equipment that travels well for interval work is a jump rope. You can pace doing fast/high intensity intervals, with more relaxed recovery intervals. My fave rope is by U.S. maker Lifelines.
There's another couple of reasons a stationary thing can be useful: control over measures that a real environment can screw up. For instance, an interval, can be easily optimized with a machine where you can safely set things like cadence (how many times you pedal a minute for instance) and intensity (the gearing on a bike or the elevation and speed on a treadmill). All this work is usually gated relative to a percentage of your maximum heart rate or target zones (one set of calcs here - note that max heart rates can actually be sport specific: you may see a different max on a bike than when running, so actually doing a test for that thing can be a GOOD IDEA. saying that, when starting out, the basic calcs can help get you in the zone. Chat with your GP if you have concerns about stressing your heart.)
How to adjust these parameters for an effective interval set is a nicely researched sports science issue, and can be divied up into two categories: fitness interval work (one ref) that is simply pushing up a heart rate for a period (slow walk to fast enough walk to get heart rate elevated for a period) and performance interval work - where you're training for a higher level of performance improvement, and are pushing your heart rate harder. The rationale in each case is the same: improving capacity; improving health
A few types follow.
If you are just starting out a fitness routine, just once in awhile upping your intensity (go faster, go up a steep hill) for a period, and then bringing it back down, and going back up for 6-8 times is really great. Lots of warm up lots of cool down. Good! If you feel yourself huffing and puffing a bit (not so you'll keel over) that's excellent. Old running rule of thumb: can you still keep up a conversation while you're upping the pace? if not, bring it down a bit. The point is to plan out a workout and say i'm going to push for X intervals for Y minutes of intensity followed by Z minutes of recovery. Three hard effort followed by three minutes of recovery is great. Check your pulse at your neck for ten seconds after that first hard effort: how fast is your heart? what % of Max is it? that will let you know if you need to push a little harder to get to that zone for more intensity benefits (check with your doctor if this is ok for you).
In the area of performance protocols, one of the most discussed interval protocols, and one that i've used a lot is a stationary bike one known as the Tabata protocol. It very specifically says that you have to warm up (this is critical in all interval work), then you do 20 secs of HARD activity such that you are in a high gear but are able to maintain 90RPM. Then you stop for 10 secs. Like dead stop. You do 8 of these intervals. This was a significant study to show that you did not have to do a LOT of intervals to get max benefit (Clarence Bass covers the study in more detail and as well as a comparison of this protocol with another)
The critical thing about these intervals is the cadence. I've heard a lot of folks say they're doing tabatas when all they're doing is 20secs of "hard" work with 10 secs of rest. They're missing the cadence piece. This is the measure of hardness, as it were, and also a measure of whether or not you're able to keep up that intensity evenly for that period.
Why is this important? The goal of the protocol was to find out what was more efficient for developing increased VO2max - or volume of oxygen consumed. More is better. The protocol compared two groups: one with a 30 hard/60 recovery ride vs the 20hard/10 dead stop. Remember that the more oxygen you can get into the blood the better fat burner you are, too. When huffing and puffing, or simply able to take in better volumes of O2, you're providing what the blood needs to oxidize fat - to convert it to energy. Interval training - these bouts of pushing yourself a bit, followed by recovery, are a great way to improve your VO2max. Not only is it good for your heart, it's good for that fat burning and lean muscle growth.
This is not to say that other non-tabata intervals are not useful: this protocol was specifically designed to optimize training for improved VO2max. The 30/60 also had benefit, but not as much in the same period for that one effect. The 20/10 was also superior for burning subcutaneous fat, but the 30/60, i think, burned more calories.
As said there are loads of interval programs out there. The nice folks at cycleops who make devices you can fit to your bike to convert it to a stationary trainer, have several great videos on interval workouts for bikes. My fave is a hills workout where heart rate is used as a way to determine what gear to use: find a gear that will let you get to X% max of your heart rate when pedaling with Y cadence. (i usually just write the workout down and follow it while listening to a soundtrack or audio book rather than watch the video of 6 other people on trainers. Tho this vid of a race track is kinda interesting.)
Here the intervals in one part of the set are ten minutes of one minute at 60-65rpm with a 75-80% HRM followed by lighter gears for a minute of recovery. This is HARD. Make sure your doctor says you can do this kind of training before you try it. Another part of the set has five minutes slogging in the 50-55RPM with a 70HRM, followed by five minutes of light gear recovery. Look around for protocols that feel right for you. Just consider the source of who's recommending a particular approach and why, and also remember that any interval work needs to be preceded by a good 10 mins of warm up and an equal cool down. There's a great article just about the use of heart rate monitoring in cycling, too, at cycling performance tips.
You'll notice that one important piece of kit for intervals is a heart rate monitor. If you're in the gym, many machines have these built in. You may however want to think about investing in one yourself. As i've said before, in the UK, the best place i've found is
Another kind of interval training that has been supported by good science is performed with a kettlebell (more on kettlebells here) - again the training is to improve VO2max, and its inventor has a few critiques of the tabata protocol, too, all based on some good science. This one is *very* intense. I mention it only because it's the one interval workout i've found specifically designed for something other than a stationary gym machine, where the exercise with a free weight means that you're working your core and a whole lot of other muscles. I mention it just in passing, but an important thing to note is that, once again, cadence is key to the protocol, not just time of interval and weight (like selecting a gear) used.
So, wrapping up on intervals, i've talked elsewhere about their benefits for fat burning; this has just touched on benefits for VO2max and your heart health. Bottom line, adding some interval work to your health program is a Good Thing for a rich variety of health benefits.