In a study published in the May 2008 issue of the Journal of Strength and Conditioning Research, three researchers compared the physical performance and cardiovascular load during heavy resistance circuit training (HRC) and traditional passive rest strength training. Over the course of three weeks, the researchers tested 10 healthy subjects who had an average age of 26 and had previous strength training experience. Through their research, they concluded that HRC increased the participants' heart rate and, therefore, can be an effective training strategy for strength and cardiovascular exercise.

Jay Dawes, the education director for the National Strength and Conditioning Association, says circuit training can have both cardiovascular and strength benefits. He says trainers can combine exercises in many ways to achieve a desired outcome, something that some club owners and personal trainers are doing by offering boot camps.

Many fitness facilities are already catering to time-pressed members by offering shorter classes and compact circuits. The Muscatine Community YMCA in Muscatine, IA, offers 35-minute and 45-minute classes during the lunch hour and invested in specialized resistance training equipment to help its members get an effective, yet brief total-body workout, says Andy Brabson, exercise area director and head personal trainer for the Y.

The Salt Fork YMCA in Marshall, MO, recently opened a fully staffed youth circuit area called the Fit Zone with eight pieces of circuit training equipment, cardio exercise stations and Wii Fit consoles. Franco's Athletic Club in Mandeville, LA, offers a fluid interval training (FIT) circuit for members, while the Sports Center at Chelsea Piers in New York designed cardio/strength classes incorporating sprints, kettlebell exercises and abdominal work.

The personal trainers at the 65,000-square-foot Telos club in Dallas also train their clients anaerobically. Everett Aaberg, co-owner, says cardio and strength shouldn't be viewed as two separate modalities because many studies have shown that circuit training can elicit a response similar to cardio exercise.

“Research has shown that similar, if not identical, cardio benefits can be obtained doing circuit-style resistance training workouts,” he says.

Bryant, however, says that the oxygen consumption will be higher with cardio exercise and will provide a stronger stimulus for improving cardiac function. Although circuit training provides some cardiovascular benefits, it shouldn't be viewed as a replacement to regular cardio exercise, he says.

William Kraemer, a kinesiology professor at the University of Connecticut, isn't sold on a one-size-fits-all approach to exercise. His research shows that exercisers should vary their intensity on different days of the week to work different muscle groups. He says everyone is looking to get everything out of one workout, and a workout like that simply doesn't exist.

“You need different workouts to do different things,” he says. “You can't find one tool in a box to do everything.”

The Fountain of Youth

By fitting in time for a workout, Americans can not only improve their cardiovascular conditioning, but they can also potentially lengthen their lives. A study released earlier this year by the AHA found that exercise can reduce death rates in both African-American and Caucasian men.

The study, which included more than 15,000 male veterans, investigated exercise capacity as an indicator of mortality by using a treadmill test and dividing the subjects into four categories: low fit, moderately fit, highly fit and very highly fit. The researchers followed the veterans for about 7 1/2 years and recorded their death rates.

The men who rated at the high end of the spectrum — the very highly fit — had a 70 percent lower risk of death than those in the low-fit category. Men who were in the highly fit category had half the risk of death compared to those who were considered low fit.

“Our findings show that the risk of death is cut in half with an exercise capacity that can easily be achieved by a brisk walk of about 30 minutes per session five to six days per week,” Kokkinos says in the report.

Another study showed similar results. Stanford University researchers found that running reduces the risk of not only heart disease but also of cancer and neurological diseases. In Stanford's study of a runner's club, the researchers found that middle-aged runners were half as likely to die over a 20-year period as middle-aged non-runners. In the experimental running group, 15 percent of the runners had died compared with 34 percent in the non-running control group.

Bryant says he is not surprised by the findings of the two studies because of the strong evidence that cardio exercise can lower the risk of hypertension, diabetes, stroke, metabolic syndrome and certain types of cancers.

“It's largely a result of helping to reduce the risk for developing a lot of chronic diseases, which can shorten one's life span,” he says. “Cardiovascular exercise can also help to prevent weight gain and falls, all of the things we know are not conducive to longevity.”

Health clubs can leverage this research by educating seniors about the health benefits of exercise. By helping Americans make exercise a part of their daily lives, club owners can help their members have more vibrant golden years, Bryant says.

“Through exercise, they can not only add years to their life,” he says, “but life to their years.”

Studies Show Benefits of Cardio Exercise

• Exercise is good for the brain. In a study using mice, researchers discovered that by doing cardio, the mice could actually regenerate brain cells and add gray and white matter to their brain.

  “Mice that do aerobic activity defy everything we have ever done,” says Wayne Wescott of the South Shore YMCA, Quincy, MA. “It can reverse the signs of aging.”

  Other research shows evidence that cardio exercise improves cognitive functioning — especially in older adults — as well as reduces depression and enhances mood, says Cedric Bryant of the American Council on Exercise.

• Cardio can turn back the clock. Research has shown that cardiovascular exercise not only can increase a person's longevity, but it can also reverse signs of aging. One study published in the British Journal of Sports Medicine concluded that by maintaining aerobic fitness through middle age and beyond, a person can delay aging by up to 12 years. A person can also stay independent longer when they become older. Bryant says the old saying of “use it or lose it” is definitely true when it comes to cardiovascular exercise. By exercising, an older adult can maintain a better level of functioning and delay aging-related disabilities.

• Flexibility training may not affect performance or prevent injuries. The fitness industry has had a long-standing debate about whether or not exercisers should stretch before, after or during a cardiovascular workout. Holden MacRae, a professor in natural science at Pepperdine University, induced muscle soreness in the subjects through a 20-minute step test and then measured their range of motion and their overall performance through the sudden reach test, the vertical hop and the stair climb. MacRae did not uncover any performance gains in subjects who did no post-workout stretching, took walks or did post-exercise flexibility training exercises.

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