Dear Doctor: Those electric scooters that you can rent by the hour have come to our city, and our son, who is almost 18, wants to start riding one to school. My husband thinks it’s OK, but all I see are the different ways he can get hurt. Am I overreacting?

Dear Reader: It may seem like you’re asking a question about transportation, but the rapid spread of motorized scooters has been accompanied by a rising number of injuries to both riders and pedestrians. Here in Los Angeles, we’re at one of the epicenters of the electric scooter phenomenon. That means local emergency rooms and medical practices, ours included, are now seeing a spike in scooter-related injuries, many of them serious.

For anyone not familiar with the concept, several companies now offer electric scooters on a ride-share model. Since last spring, thousands of these rentable scooters have become available in an estimated 90 towns and cities across the country. They have a 15-to-37-mile range on a full charge and can go 15 to 30 mph. All it takes to get started is a credit card, a driver’s license and a smartphone to download the app. Although most companies require riders to be at least 18 years old and to wear a helmet, those rules are mostly self-enforced.

Doctors are now treating scooter-related injuries that are typically associated with vehicular collisions. These range from serious scrapes and cuts that require stitches, to broken wrists, ribs, collarbones, shoulders and noses. Riders who ignore the helmet rule risk head trauma that can leave lasting brain damage. Injuries to pedestrians are not uncommon. Several scooter-related deaths have been reported.

Electric scooters are so new that the tracking of accidents and injuries has not yet begun at either the state or federal level. Scooter companies, meanwhile, have declined to share their data. Emergency medicine departments in some cities, startled by the surge of injuries, have begun keeping their own statistics. An analysis by Consumer Reports found that at least 1,500 people nationwide have been injured in crashes related to electric scooters since late 2017, when the scooters first began to appear. Not all hospitals or law enforcement agencies track scooter accidents yet, so these numbers are certainly low.

Earlier this year, colleagues at UCLA conducted a study into the extent of electric scooter injuries. Among their findings: 80 percent of the injuries they tallied resulted from falls, 11 percent from collisions with objects and 9 percent from collisions with cars, bikes or other scooters. About 40 percent of riders who got hurt suffered head injuries, 32 percent had breaks or fractures, and the rest got away with just cuts, sprains or bruises. When the researchers spent seven hours watching riders at a busy intersection, they found that a stunning 94 percent of riders weren’t wearing helmets.

Because electric scooters are nimble, affordable and, let’s face it, fun, in many cases they’re being approached more as toys than as motor vehicles. If your son does decide to try electric scooter transportation, please make sure he understands the risks, becomes fully educated about best riding practices, and that he always -- and this is non-negotiable -- wears a helmet.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10880 Wilshire Blvd., Suite 1450, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)

Dear Doctor: My kids say you’re not supposed to admit it, but I hate to exercise. Running a mile once or twice a week is really the most I can manage. Should I even bother?

Dear Reader: In a word, yes. While it would be great if you enjoyed exercising enough to do more of it more often, intriguing new research suggests that when it comes to physical activity, every little bit helps. In fact, a study conducted on mice at the University of Texas Southwestern Medical Center in Dallas found that just one workout kept the nerve cells in the brain that play a role in metabolism activated for up to two days. The takeaway of that research, which was published in December, is that these neurons respond to even a small amount of activity.

The study focused on two types of neurons, which are part of a brain circuit found in humans as well as in mice. These two neuron types, when activated, have very different jobs. One plays a role in lowering glucose levels, muting appetite and revving up the metabolism. The other neuron type does pretty much the opposite -- it ramps up appetite and puts the brakes on metabolism.

Researchers found that a single vigorous workout amplified the activity of the first neuron type -- that’s the one that reduces appetite, lowers glucose and causes energy output to increase -- for up to two days. At the same time, it suppressed the effects of the second neuron type -- the one associated with an increase in hunger and a downshift in metabolic rate -- for the same amount of time. While this is good news for people like you who prefer a more modest exercise schedule, the study also contained an incentive to be even more active: It turns out that these changes to neural activity lasted even longer in people who exercised more often.

Speaking of frequency, would you be willing to take on just 10 to 15 minutes of exercise per day? Although exercise classes and gym sessions are typically measured in hours, emerging research is showing that short bouts of exercise -- as long as they are done daily -- can yield rewards. A study conducted at Pennington Biomedical Research Center in Louisiana found that sedentary women who walked briskly for just 72 minutes per week -- that’s about 10 minutes each day -- had similar improvement to heart strength and general fitness as did the group that walked almost twice as long.

Another study found that as long as it included at least 60 seconds of high-intensity exercise, a 10-minute workout yielded similar benefits to 45 minutes of steady jogging. And for those who take the long view, numerous studies have associated regular exercise with a lower risk of early death.

When it comes to building on your current level of activity, are there any sports or games you enjoyed in the past and would consider doing again? It doesn’t have to be the same thing every day. Even a 10-minute game of tag with your kids a few times a week will get you moving. Think creatively, and we’re sure you’ll land on a solution. And in the meantime, please do keep running.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10880 Wilshire Blvd., Suite 1450, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)

Dear Doctor: I heard that getting more potassium will help with high blood pressure. Is that really true? I love salty food, and I really don’t want to give up my chips and popcorn.

Dear Reader: The conversation about blood pressure focuses far more on salt -- or the sodium it contains -- than it does on potassium. That’s because salt is so readily available. It’s a potent flavor enhancer that finds its way into virtually all processed and prepared foods. This makes it easy to blow the daily sodium budget without adding even a grain of it yourself.

The maximum recommended amount of sodium for healthy adults is 2,300 milligrams per day. For certain groups, such as those with hypertension, diabetes, heart disease, chronic kidney disease and adults 51 or older, the maximum drops to no more than 1,500 milligrams per day. In reality, our average daily sodium intake is a whopping 3,746 milligrams per day.

Potassium recommendations are similarly ignored. The most recent research shows the average American adult consumes about 2,000 milligrams of potassium per day. That’s less than half the recommended 4,700 milligrams per day. The result is most of us are not getting the ratio of potassium to sodium that the dietary guidelines recommend, which is twice as much potassium as sodium. In fact, studies show that sodium consumption often significantly outpaces potassium in the American diet.

This imbalance is a problem because sodium and potassium are inextricably linked. To understand why, we need to nerd out a bit. Potassium and sodium are electrolytes, which means they carry a tiny electrical charge. Our cells use this to create a molecular pump. When the pump brings potassium into a cell and pushes sodium out, it creates a kind of chemical battery. The output of these batteries plays a role in nerve function and muscle health, including the heart. Sodium and potassium are also vital to kidney function and bone health, and to blood and fluid balance, which helps regulate blood pressure.

When we overdo it with sodium, our bodies compensate by getting rid of it in urine. But this starts a cascade of events that lead to a loss of potassium and an influx of water, which results in a net increase in blood volume. Not only does that adversely affect blood pressure, the lack of potassium can cause electrical signals in the body to get disrupted. That interferes with the proper functioning of nerves and muscles, including the heart.

By following current United States dietary guidelines, we achieve the potassium-to-sodium ratio mentioned earlier, which is 2-to-1. Newer research leans toward ratios of 5-to-1 and higher. Unfortunately, most Americans miss even the more modest target by wide margins. Not only is that bad news for the vital functions we just discussed, but a new study published earlier this year also found that adults who took in more sodium than potassium increased their risk of stroke by 47 percent.

We understand your love of salt, but it’s quite possible it has put you into potassium debt. Our advice is that not only should you make adding potassium-rich foods to your diet a priority, you should also reduce sodium. For a useful list of potassium-rich foods, visit health.gov/dietaryguidelines/dga2005/document/pdf/Appendix_B.pdf.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10880 Wilshire Blvd., Suite 1450, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)