Pre-run Streching 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. 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 17970s), 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!

Reference: Gulati, M. et al., Heart Rate Response to Exercise Stress Testing in Asymptomatic Women: The St. James Women Take Heart Project. Circulation 122:130-137, 2010.

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.