Marlene Habib is a full-time senior copy editor on the Copy Desk at CBC.ca. She's also a Can-Fit-Pro certified trainer who leads outdoor exercise classes.

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Video: CBC-TV's Maureen Taylor on interval training. (Runs 2:55)

In the repertoire of exercise naysayers, the claim "I don't have time to exercise" stands out even more than the burning desire to avoid the irksome rants of fitness crusaders like Richard Simmons. But that's no longer a valid excuse, according to new research that shows even short periods of activity can have big health benefits.

Alan Katz works out during his 20-minute circuit at his gym, Aug. 17, 2006, in Citrus Park, Fla. (Steve Nesius/Associated Press)

A report out of McMaster University in Hamilton suggests bona fide benefits to interval training (IT) – short bursts of movement alternated with slower activity. IT, with more and more studies backing its calorie-burning and performance-enhancing bonuses, is the trendy "it" word in fitness.

Athletes have long incorporated IT into their training to better their speed, power and performance, but what does IT mean to the average exerciser? Boosted muscle performance, for one, the Hamilton study suggests, allowing the body to better convert stored carbohydrates into energy and speed up calorie burning, and we can all relate to that. And alternating fast and slow movement during a workout – rather than just working out continuously at the same speed – can also keep an exerciser mentally psyched. Given that boredom is another popular excuse for forsaking exercise, there's a lot to be said about spicing up what can be a long and tedious treadmill walk or run, stationary bike ride or other workout.

As a fitness professional, I'm well aware that many people believe time isn't on their side. If kid duties aren't the downfall to developing an exercise habit, then it's work, social or other family obligations. Oh yes, don't forget the risk of breaking a nail or wrecking your hairdo, or being exposed to Simmons's screeches. There are no such excuses from the students in my outdoor boot camp classes, which are designed using interval training – like stop-and-go jogging and walking up a hill, combined with callisthenics like push-ups. Government worker Agnes, for one, got into the exercise habit well before her recent retirement, and Robin is a young mother of two whose personal time outside pushing baby carriages includes pumping iron and marathon training.

That's not to say interval workouts are the elixir to getting motivated to move. But IT adds to the training arsenal, and the following can help put a fitness plan incorporating the concept into focus:

Stop the stalling

The body is made to move. Without daily physical activity, everything slows down – metabolism, vigour for life, digestive and circulatory systems, even the mind. According to Can-Fit-Pro, the national fitness organization that certifies trainers, including myself, increased activity promotes health, longevity and quality of life. We need to move daily, preferably for at least an hour. But even 30 minutes of moderate-intensity activity over most days of the week helps the cardiovascular system, promoting heart and lung health. So commit now to get into the exercise habit – just like you take time to brush your teeth or go grocery shopping, schedule that hour just for yourself (whether it's at the gym, in the neighbourhood or at the local park). No time, you say? Canada's Physical Activity Guide to Healthy Active Living says you can get your fitness fix in bits through the day. So park the car 10 minutes away from work, walk to the office, take a 10-minute jaunt on your lunch, and head back to your car after work to meet that 30-minute cardio requirement.

Find your footing

Whether you're a seasoned or novice exerciser, interval training has a place in workouts. There's no one-size-fits-all program, though. Beginners, in particular, need to have a good handle on their health before starting exercise. Fitness trainers will assess a beginner – using the industry's Physical Activity Readiness Questionnaire (PAR-Q), which analyses heart, high blood pressure and other health – before putting anyone on a program. Anyone with health problems or concerns should consult a doctor before starting a program, although simple brisk walking is as safe – and effective – as any training method. Then you can look to getting entrenched in an exercise routine that slowly breaks you into interval training. For more advanced exercisers, especially those using continuous training and who have stalled in reaching their fitness goals, interval workouts can provide a boost.

Warming up to workouts

Never tackle a workout, especially an interval-based one that requires pushing your body to its limits, without warming up first. A warm-up simply pushes the blood carrying oxygen to your muscles, lubricating them so they're less at risk of getting pulled or injured. And the calm before the exercise storm also helps prepare you mentally for a full-force workout. A good warm-up can be as simple as a few minutes of brisk walk, slow cycling or even some jogging on the spot.

Play it safe

Need to squeeze into those trendy skinny jeans ASAP? Forget it. Making exercise a lifelong habit is more likely to happen if you start slowly, and build on the effort. The same goes for interval training. For training newcomers especially, watch that you don't overdo it. Set goals within your capability. Start slowly, for example, walk two minutes and then run two minutes, and keep that one-two punch up for about 10 minutes, gradually increasing intensity and slow-fast exercise time to work up to 20 minutes or beyond.

There's no limit

As appealing as the idea of getting your fitness fix in 20 minutes can be, don't be a naive exerciser. For most people, interval training should be incorporated into a balanced activity plan that includes these elements: endurance (cardiovascular), flexibility (stretching) and strength (weight or other resistance) training. There's still a place for those long continuous workouts, like walking on a treadmill for half an hour at a certain pace and incline. But try mixing things up, like throwing in a day or two of interval training for variety to relieve boredom – that will help you avoid getting in a rut where you don't see any change in your weight, body shape, stamina or strength. The body adapts to a repetitive routine, stalling results, so ideally, try to revamp your workouts every four to six weeks.

Getting up to speed

Tune into your "target heart rate," or THR. The term refers to how many beats per minute you should be elevating your heart rate to get cardiovascular and calorie-burning benefits. There are heart-rate charts and devices on treadmills, exercise bikes and other equipment that can relay that information to you, and tell you the range you're working in. But here's a simple formula to determine your THR zone: Take 220, minus your age, and then multiply that number by 65 per cent and then 80 per cent. Most people should aim to be in that 65 to 80 per cent range. For example, a 20-year-old's zone is 130 to 160 beats per minute, a 30-year-old's is 123 to 152; a 40-year-old's is 117 to 144; and a 50-year-old's is 110 to 136. To measure beats per minute, take your pulse (at the side of your neck and on your wrist), count 10 seconds, and multiply that by six. Interval training can get your heartbeat up to its zone range quicker than continuous training, and you may even go above that 80 per cent upper limit, which is fine for more conditioned exercisers.

The strain and pain

The beauty of interval training is that you're not placing continuous strain on your body, or one part of your body, for any length of time. Repeated pounding can cause repetitive strain injuries (RSI) – niggling aches and pains such as shin splints (lower leg pain) and plantar fasciitis (heel pain). Proper, supportive footwear and stretching after a workout – holding a stretch for each body part, especially the one being exercised most, for several seconds – can also reduce your RSI risk.

Cool it, will ya!

Just as a warm-up prepares your body for exercise, a cool-down gets it used to getting back in pre-exercise mode. Research suggests a proper cool-down – reducing the intensity of your workout when you're near the end of it – can be highly effective in preventing next-day soreness.

Be a sport

To some, hitting a gym or doing some other form of "formal" exercise isn't nearly as motivating or fun as playing sports. Hockey and soccer are examples of sports that are interval-based, demanding periods of high intensity and bursts of speed combined with slowed down activity. But don't attempt to play sports to get in shape. Rather, get in shape to play sports, to boost performance and prevent injuries – not to mention to build up the stamina to complete that hockey or soccer game.

Give it a rest

So now you're in the exercise swing of things. Bravo! But there can be such a thing as overdoing it. Exercise burnout is another well-used excuse to break the exercise habit. Rest days are just as important as working out days to achieving overall health and wellness. A good rule of thumb is to avoid exercising the same body part, in weight or other resistance training especially, two days in a row, because tiny muscle tears created during exertion need time to recover in order to develop. Cardio workouts CAN be done every day, but vary your training. That's where IT can be your best workout buddy.

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