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February 2010

Interval training improves fitness
Interval training helps heart failure
Interval training helps oxygen capacity
Dietary fat and strokes post-menopause
Whole grains lower diabetes risk
Lipoic acid inhibits breast cancer cells

Interval training improves fitness

Exercise recommendations have changed in the past few years. It appears that continuous moderate training (CMT) is not as beneficial for cardiovascular fitness as aerobic interval training (AIT). While this means brief intervals of more intense activity, it also means that the benefits of exercise for the heart can be achieved in less time per week.

Current recommendations are for two and a half hours of CMT every week, but with the new studies, that may change. Using AIT, it appears that more fitness is achieved with three weekly sessions of 25 minutes. This includes 4 periods of 4 minutes at higher intensity, with 3 minute breaks at lower intensity.

Specifically, during the aerobic interval you should reach 90 to 95 percent of your peak heart rate, and the lower intensity interval means being at 50 to 70 percent of your peak heart rate. To figure this out, an approximation of your peak heart rate is determined by subtracting your age from 220 and multiplying the result by 0.67 to 0.75. This may not be perfectly accurate, but without this estimate, you would otherwise need more complicated medical testing of maximal oxygen consumption to be more accurate.

Using myself as an example, I am 65, so I subtract that from 220, leaving 155. Two thirds to ¾ of that number suggests that my maximal heart rate is 104 to 116. This is only a guide, as it is influenced by temperature, humidity, time of day (a result of normal diurnal variation), and the duration of the exercise (partly due to changes in hydration during longer exercise sessions). However, using this calculation as a general guideline is valuable for exercise determinations.

During the more intense exercise you should be just a little out of breath (aerobic exercise levels means not getting out of breath, or being able to hold a conversation during the exercise, and this would be just a little more than that level). This does not mean that you should feel intensely stressed or exhausted by the workout, but it is not a casual walk or easy bicycle ride. (Interval training can cut exercise hours sharply. Cheng M, AP Health News, 25 February, 2010. )

Using this method, over a three-month study, subjects were able to improve their endurance, oxygen use, strength, and speed in less time per week than with the usual recommendations. The research suggests that this is beneficial not only in young, fit people, but also in the elderly and in people with a variety of health problems, including cardiovascular and pulmonary disorders (see the next articles). The researcher, Jan Helgerud, from the Norwegian University of Science and Technology, said that this method is “twice as effective as normal exercise.” (It is still true that any activity is better than none, and most people do not get nearly enough of any physical activity, even walking.)

Interval training helps heart failure

Researchers evaluated the effect of AIT on elderly patients (with an average age of 75) who had stable heart failure after a heart attack. Their heart failure was reflected in an average ejection fraction of 29 percent (the percent of the blood in the ventricle that is pumped out with each beat; normal is 55-70 percent). Most were stable using a combination of beta-blockers and ACE inhibitor medications.

The 27 patients were divided into three groups, the AIT group and MCT group exercising three times per week, and a control group just receiving standard exercise advice. (Wisløff U, et al., Superior cardiovascular effect of aerobic interval training versus moderate continuous training in heart failure patients: a randomized study. Circulation. 2007 Jun 19;115 (24):3086-94.)

After 12 weeks, peak oxygen use improved in the AIT group by 46 percent, compared with just 14 percent in the MCT group. In the AIT group only, heart muscle anatomy improved by 25 percent and ejection fraction improved by 35 percent.

For both exercise groups the quality of life improved, while there was no change in the control group. The researchers measured the blood flow in the brachial artery and found that improvement in endothelial function was better in the AIT group. They also measured mitochondrial function in the leg muscles, which increased only in the AIT group. This shows clearly that even in elderly patients, exercising with greater intensity, even if only for 25 minutes (4 minutes intense with 3 minutes less intense as a break) three times per week, can improve heart failure and other health measures.

Interval training helps oxygen capacity

In another study in 2007, researchers evaluated the effect of AIT on maximal oxygen uptake (VO2max). They followed 40 subjects for 8 weeks on four different exercise programs, including CMT and AIT, all done three times per week. One of the protocols included a different form of AIT (called 15/15), with 15 seconds of high intensity exercise (90-95 percent of maximal heart rate), then 15 seconds of “active resting” at 70 percent of maximal heart rate.

Both the AIT and 15/15 groups showed improvement in VO2max by 7.2 and 5.5 percent, respectively. In addition, the stroke volume increased by 10 percent with either interval training program. Stroke volume is one measure of the strength of the cardiac muscle, referring to the total amount of blood pumped out with the beat – about 70 ml in a healthy male (while the ejection fraction is the percent of the blood in the ventricle that is pumped – normally 55-70 percent). (Helgerud J, et al., Aerobic high-intensity intervals improve VO2max more than moderate training. Med Sci Sports Exerc. 2007 Apr;39(4):665-71.) Previous concerns about more intense exercise in elderly people or patients with heart or lung disease now seem unwarranted.

Dietary fat and strokes post-menopause

Increasing amounts of dietary fat can increase the risk of strokes in post-menopausal women, according to a recent review of data on 87,230 subjects aged 50 to 79 in the Women’s Health Initiative. The data were reported at the recent meeting of the American Stroke Association.

Women who at the most fat (an average of 95 grams per day, or 855 calories of fat) were 44 percent more likely to have an atherosclerotic stroke (the most common kind) than those who ate the least fat (an average of 25 grams per day, or 225 calories). The women were followed for 7.6 years. Total fat and trans fat were both associated with the increased stroke risk. (Yaemsiri S, et al, Dietary fat intake and incidence of ischemic stroke in postmenopausal U.S. women: the Women's Health Initiative. ASA 2010; Abstract 79.)

This association does not relate to younger women, who have a lower risk of stroke than men of the same age, but this comparative risk relationship reverses after menopause.

Whole grains lower diabetes risk

A news release from the American Heart Association indicates that replacing refined grains (such as white rice and white flour) with whole grains can markedly reduce the risk of developing type 2 diabetes. Analyzing data from the Health Professionals Follow-up Study (39,765 men) and the Nurses’ Health Study (157,463 women), researchers were able to evaluate 3.3 million person-years of follow-up. This is a particularly large study population.

During that time, there were 10,507 incidents of type 2 diabetes. They found that people who ate five or more servings of white rice per week were 17 percent more likely to develop type 2 diabetes than those who ate less than one serving of white rice per month. However, those who ate two or more servings of brown rice per week were 11 percent less likely to develop diabetes than those who ate less than one serving of brown rice per month. (American Heart Association news release, March 3, 2010).

The researchers estimated that replacing 50 grams per day of white rice with the equivalent amount of brown rice would lower diabetes risk by 16 percent. They noted that if a variety of whole grains were consumed (such as whole wheat, oats, barley, corn, and millet), as opposed to just brown rice, the diabetes risk was lowered by 36 percent. This confirms the value of the suggestion to eat a wide variety of whole foods, including whole grains. The generally healthier Japanese, and other Asians and white-rice consuming cultures, could be even healthier if they switched to brown rice instead.

Lipoic acid inhibits breast cancer cells

Laboratory research on human breast cancer cells shows benefits from treating them with alpha lipoic acid (ALA). ALA is a natural dietary substance containing two sulfur atoms. It is known to help treat neuropathies from various causes, and as an antioxidant has gained attention in treating cancer patients, raising the level of the antioxidant enzyme, glutathione peroxidase.
In this study, cells in tissue culture were bathed in four different concentrations of ALA, along with their other nutrient media. Each level of ALA inhibited the growth of the cancer cells in a dose-dependent manner. (Na MH, et al., Effects of alpha-lipoic acid on cell proliferation and apoptosis in MDA-MB-231 human breast cells. Nutr Res Pract. 2009 Winter;3(4):265-71.)

In addition, two proteins and mRNA expression associated with cancer growth were also inhibited in a dose-dependent manner. ALA enhanced programmed cell death (apoptosis). Typical doses in humans range from 300 mg per day up to 1200 mg daily, the larger doses commonly used for neuropathy and for cancer patients.

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Information herein is not medical advice or direction. All material in this newsletter is provided for information only. Its contents should not be used to provide medical advice on individual problems. Consult a health care professional for medical or health advice.