Fitness and Dementia

More than 5 million people in the U.S. are living with Alzheimer's disease, the most common form of dementia. There is no cure or prevention for Alzheimer's disease, despite all the research into its causes.

Now a new study spanning 46 years offers some tantalizing clues. Way back in 1968, researchers in Sweden enrolled 191 women 38-60 years old into a study of cardiovascular fitness, as measured by their capacity to exercise on a bicycle until they became so fatigued that they had to stop. Based on their workload achieved, they separated the women into "low", "medium" and "high" fitness groups. Then they followed the women for the next 44 years, looking for signs of dementia, among other health issues. Surprisingly, they found that compared to the "medium" fitness group, those in the "high" fitness group were 88% less likely to develop dementia. Among those who did develop dementia, high fitness delayed the time to onset of dementia by 5 years, compared to the medium fitness group.

A word of caution; these results show a correlation only; they do not prove that high fitness per se is what is reducing the risk of dementia. Perhaps the high fitness group also has a better diet, or just better genetics to begin with. Nevertheless, the results are intriguing, and may point the way to additional research to tease out the actual cause. Anything we can do to solve this baffling and debilitating disease would be welcome.

Exercise Can Turn Back Time on a Middle-Aged Heart

So... you didn't take care of your body when you were young, and now at middle age you're feeling out of shape and over the hill. You're motivated to make a lifestyle change if it would help, but will it actually do any good at this point?

The good news is that perhaps it will. According to a report in Circulation, just two years of high-intensity exercise improves heart health. In the study, sedentary middle-aged men (mean age 53 years) participated in either a moderate to high intensity aerobic exercise program for two years (the experimental group), or only non-aerobic exercise such as yoga or balance training (the control group). At the end of two years, those who had exercised showed signs of improved heart health, including improved oxygen uptake and a reduced stiffness of the left ventricle. It's as if the clock was turned back on the heart aging process.

Middle age may be the last time that one can improve heart function, however. According to an NPR article, the same improvement is not possible by the time one reaches seventy years of age. The time to get moving is now, not later.

Innate Fitness May Affect Cancer Risk

It's been known for several years now that being physically fit reduces a woman's risk of breast cancer. But how? Is there something about actively engaging in an exercise regimen that reduces risk, or is it just a function of being naturally fit (called "innate" fitness)? Or both?

To try to address this question, researchers took advantage of groups of rats that had been bred to be either genetically "fit" or genetically "not fit". The two populations were created over many generations by exercising rats on a treadmill; those that could run long distances were bred to other rats that also ran long distances; those that were poor exercisers were bred to other poor exercisers. Over time, the groups diverged in terms of innate fitness.

In recent experiments, then, female offspring of the "fit" and "not fit" groups were exposed to a known carcinogen. None of the rats in either group engaged in exercise after birth, so any differences between the two groups must be attributable to innate fitness, rather than exercise per se. The results were strikingly different - the incidence of breast cancer was reduced by more than 70% in the "fit" rats, compared to the "not fit" rats.

It's not known yet whether an active exercise regimen would reduce the risk of breast cancer in the "not fit" rats. Undoubtedly that will be tested next. But for now, the new information is that there's something about the metabolism of innately fit rats (and perhaps humans) that protects against breast cancer, even if they're not routinely exercising.

The researchers looked only at breast cancer as their measured endpoint in these experiments, but perhaps fitness affects the risks other cancers as well.

Workout Supplement Ingredient Banned

The Food and Drug Administration (FDA) issued a warning last week that several workout-booster and fat-burning products should be pulled from the market immediately because they contain an ingredient called DMAA (dimethylamylamine). The products, Jack3D (pronounced Jacked) and OxyElite Pro, are both marketed by USPlabs.

Back in 2011 the FDA sent letters to all 10 marketers of DMAA products, asking them to voluntarily stop marketing such products. All but USPlabs complied. The company continues to claim that the products are safe and legal.

According to the FDA, there have been 86 reports of health problems, including 5 deaths, among persons taking products containing DMAA. That does not prove that DMAA is dangerous, of course, and its not even the primary reason the FDA is asking that the products be removed from shelves. The FDA simply argues that DMAA does not fit the legal definition of a dietary supplement, and therefore it cannot be sold without prior FDA approval. I would agree; it's a drug. DMAA was actually developed by a pharmaceutical company in the 1940s and sold as a nasal decongestant until the 1980s. It stretches credulity a bit to suggest that it is a natural “supplement to the diet” when added to a workout-boosting product.

Exercise and the Flu Vaccine

Exercising immediately after receiving a flu vaccine enhances the effectiveness of the vaccine, according to researchers at Iowa State University. In the study, young adults who received the flu vaccine either participated in a mild-to-moderate exercise regimen for 90 minutes immediately after receiving the vaccine, or remained sedentary for 90 minutes. Participants who exercised immediately after receiving the vaccine showed a greater level of antibody production than students who remained sedentary. Presumably the higher level of antibody production would better protect the participants who exercised against the flu, but apparently that wasn’t specifically tested in this study. (The study has not yet been published in a peer-reviewed journal.)

The mechanism whereby exercise enhances the effectiveness of the flu vaccine isn’t known yet. The study’s lead researcher speculates that by improving blood flow to some tissues, exercise may speed the delivery of the vaccine to the lymph nodes, where most antibody production takes place. But that remains to be tested.

So go ahead and exercise immediately after the flu shot if you want to: it appears to do more good than harm.

Semenya Takes the Silver Medal

After a slow start that had her running dead last at the 200-meter mark, Caster Semenya turned on the afterburners and blew past six other runners, placing second and earning the silver medal in the 800-meter event at the summer Olympic Games in London this month.

Ms. Semenya, as you may recall, was the young woman whose gender was questioned after winning the 800-meter event at the world championships in 2009. After her win she was hustled out of the stadium before she could even finish her victory lap. She was out of competition for nearly a year while the International Association of Athletics Federations (IAAF), international track and field’s governing body, “decided” whether she could compete as a woman. Ultimately the IAAF decided that she could compete, but the incident caused enormous embarrassment to the 18-year-old Semenya; embarrassment that could have been avoided if the IAAF had had a gender decision policy in place and made its gender determination before the event, not after.

Following her second-place finish at the Olympic Games, there have been rumors that Ms. Semenya might have deliberately held back, taking second place to avoid re-igniting a controversy had she won the gold. Really? If you had survived an embarrassment like Ms. Semenya’s and then trained hard for two years for the Olympic Games, would you be able to deliberately not go for the gold? Somehow I doubt it.

Ms. Semenya’s gender didn’t become an issue at these past Olympic Games. The Olympic Committee planned to rely on a test of testosterone levels, but said they would only test female athletes if the athlete’s performance was questioned. Neither the IAAF nor the Olympic Committee has a policy of screening all female athletes equally beforehand, in order to avoid publicly embarrassing athletes who ultimately are not allowed to compete as women.

Does Running Form Affect Running Injuries?

Competitive distance runners train hard, sometimes to the point of injury. Does a runner’s running form affect the likelihood of injury? In an interesting study just published online, researchers say yes – at least in terms of how the runner’s foot strikes the ground. The researchers analyzed data for mileage run, running pace, and injuries sustained by the members of Harvard University’s men’s and women’s distance running teams over a four-year period. They also videotaped each runner to determine their predominant “foot-strike style” – either heel-first or toe-first.

Nearly 3/4 of the group was injured each year. And when the researchers analyzed who was getting injured and what type of injuries were sustained, they found that the predominantly heel-strikers were twice as likely to suffer from repetitive stress injuries than were the predominantly toe-strikers. Interestingly, the type of shoe worn (well-padded versus minimal racing flats) didn’t seem to matter.

The researchers say they don’t know why the heel-strikers suffer more repetitive stress injuries, but they speculate that it may be because of a greater peak of impact energy when the heel strikes the ground first than when the toes strike first. And they’re not suggesting that heel-runners switch their running style unless they’re getting injured frequently, and then only if they’re willing to retrain slowly. After all, doing something unnatural and different could make matters worse.

Stretching and Exercise-Induced Muscle Soreness

Previously I reported that a U.S Track and Field Association study had indicated that stretching before exercise does not decrease the risk of running-related injuries (see "Pre-run Stretching Doesn't Prevent Injuries"). Now a review of 12 stretching-related studies reveals that stretching before exercise does not reduce perceived muscle soreness, either, in the days following exercise.

None of the studies of the effects of stretching on exercise-induced injury or soreness are considered scientifically ideal, however. Ideally, such studies would be randomized (subjects assigned randomly to either the stretch or no-stretch group) AND double-blind (neither the investigators nor the subjects would know which group each subject was in until the study was over). Unfortunately, subjects in exercise studies always know whether they are stretching or not, and therefore a double-blind study design is impossible! It’s conceivable that subject bias about the value of stretching affected the subjects’ judgment of their own post-exercise level of soreness. Until we have a truly objective measure of “soreness”, there’s no other way to conduct such studies. It’s the best we can do for now.

But from what we can tell so far, there’s no compelling evidence that stretching before exercise is either good or bad for you. Do it (or don’t do it) as you wish.

Reference: Henschke, N. and C.C. Lin. Stretching Before and After Exercise Does Not Reduce Delayed-onset Muscle Soreness. Br. J. Sports Med. 45:1249-1250, Dec. 2011.

Pre-run Stretching Doesn't Prevent Injuries

I reported last year on this blog that the U.S.A. Track & Field association (USATF) was recruiting runners for a study to try to determine whether pre-run stretching prevents running injuries (see "Stretching and Sports Injuries"). Coaches and trainers often recommend stretching before exercise, but whether it’s helpful, harmful, or neutral has remained essentially an untested hypothesis.

To test the hypothesis that pre-run stretching reduces the incidence of injuries to runners, the USATF recruited 2,729 runners, defined as persons who ran over 10 miles a week. Each runner was randomly assigned to either a “stretch” or a “no-stretch” group. “No-stretch” runners were instructed not to stretch before running even if they had been in the habit of doing so before. “Stretch” runners were instructed to follow a specific stretch routine before running. All runners were instructed to continue their normal running routine for three months and to report any injuries that caused them to stop running for at least three days.

The results of the study were released last month. Just over half of the runners complied with their assigned group protocol and successfully completed the three months of the study. The results - injury rates were precisely 16% in both groups. In other words, pre-run stretching had no effect on injury rates.

One intriguing finding was that runners who normally stretched before running but were assigned to the “no-stretch” group had a higher injury rate than those who normally didn’t stretch and were in the same group. One hypothesis is that just changing their routine (stopping stretching) may have been enough to predispose them to injury.

So if you’ve always stretched before you run and like doing it, by all means keep doing it. But if you haven’t been in the habit of stretching before running, don’t feel that you have to start.

Maximum Heart Rate for Women

Many serious exercisers pay close attention to their heart rates while exercising. That’s because they generally are advised to keep their heart rates within 65-85% of their maximum heart rate for a safe but relatively strenuous workout designed to improve aerobic capacity and endurance.

According to a formula for maximum heart rate that is now 40 years old (it was developed in the 1970s), your maximum heart rate should be around 220 beats per minute (bpm) minus your age. The formula is a population average, of course, and shouldn’t be taken as an absolute number for each individual. More importantly, the old formula was based solely on men subjects. Now a new study of over 5,000 healthy women indicates that a better population-based formula for women is:

Maximum Heart Rate for Women = 206 – (0.88 x age)

Admittedly the new formula has the disadvantage that it can’t be calculated in your head, but it’s easy enough to do with a calculator. And the difference may be significant: By the old formula, a 40-year-old’s 65-85% target range would have been 117-153 bpm. By the new formula, the target range for a 40-yr-old woman would be 111-145 bpm. Six to eight beats per minute might not sound like much, but over an hour’s workout it could make the difference between pushing yourself too far and getting discouraged, and just getting a good healthy workout.

The new study focused only on women subjects. Perhaps someone ought to confirm or revise the old formula for men, too!

Is Running Hard on Knees?

Runners are often told (usually by non-runners) that running is hard on their knees. According to commonly held belief, the constant pounding wears out or damages knee cartilage and leads to either knee injury or an increased likelihood of osteoarthritis later in life.

But the available scientific evidence suggests that running is not a risk factor for knee osteoarthritis, and may in fact keep you healthier later in life. In one study, runners were compared to age-matched non-runners over an 18-year period. There was no difference in the rate of development of osteoarthritis between the two groups. In another study, overall disability rates in runners increased at only one quarter of the rate seen in age-matched sedentary persons.

A major risk factor for knee osteoarthritis is not running per se; its having had a previous knee injury. That is why there is so much osteoarthritis among former N.F.L. football players and former soccer players. But if you’re a recreational runner and manage to stay injury-free, don’t worry about wearing out your knees – just keep running!

Stretching and Sports Injuries

Does stretching before exercise reduce the risk of sports injuries? Many coaches, trainers, and athletes swear that it does, but no one knows for sure because the critical experiment has never been done.

Now researchers are attempting to do the experiment. Sponsored by USA Track & Field (USATF), the researchers are currently enrolling people who run at least 10 miles per week. Participants must agree to be assigned randomly to either the "stretch" or the "no-stretch" group and to adhere to the study protocol for three months. Runners in both groups are expected to report their injuries during the study period.

Runners can apply to be participants at www.usatf.org/stretchStudy/. So far several thousand runners have signed up, though not all of them have completed the study protocol and submitted their reports. The results will be made public as soon as enough runners have completed the protocol for there to be a statistically significant difference between the groups, or when enough data has accumulated to show that there is no difference. Ultimately, up to 10,000 runners may be needed.

Runners, this is your golden opportunity to contribute to the advancement of science.

Exercising Your Head Cold

When you catch cold, should you continue your usual exercise routine or just stay at home and rest?

According to a pair of articles published about 10 years ago, maintaining your usual exercise regimen may be good for you when you have a cold, or at least it will do no harm. A typical head cold with a runny nose and sneezing does not affect lung function or exercise capacity. And although exercise doesn’t actually speed recovery time, people who continue to exercise during a head cold tend to report that they feel better than people who don't exercise. So the next time you catch a cold, go ahead and continue doing whatever exercise you enjoy doing.

References:
"Effect of rhinovirus-caused upper respiratory illness on pulmonary function test and exercise responses". Weidner TG et al. Med. Sci. Sports Exerc. 29:604-609, 1997.
"The effect of exercise training on the severity and duration of a viral upper respiratory illness". Weidner TG et al. Med. Sci. Sports Exerc. 30:1578-1583, 1998.