During the past 30 years, exercise physiologist Tom Holland has completed more than 60 marathons, 25 triathlons and several ultramarathons stretching as far as 50 miles. Although the 50-year-old has asked a lot of his body, he has not endured a single significant injury since he separated his shoulder playing football in high school. Avoiding injury is vital to staying active and independent as we age—and even to avoiding physical therapy, which could easily cost $100 per session. So Bottom Line Personal asked Holland to share his secrets for remaining injury-free despite being ­extremely active…

I listen to my body. I don’t subscribe to the saying “No pain, no gain.” If I feel an unusual twinge or tweak while I’m exercising, I stop what I’m doing. If I felt something was really wrong in the middle of a marathon, I’d take myself out (thankfully, it has never happened). Pushing through pain is how small ­issues become major injuries.

That doesn’t mean I get to skip my workout whenever something seems off. It just means that I switch my focus to a different part of my body. If the twinge was in my knee, for example, I do upper-body exercises that day instead.

I do a little of many things rather than a lot of one thing. I love running. I could happily run every day. I’m less a fan of swimming and biking, but I took up triathlons anyway—because excessive focus on one activity puts great stress on certain body parts while leaving others underdeveloped, increasing the odds of injury.

A balanced fitness plan includes ­upper- and lower-body work and addresses all five components of fitness…

Cardiovascular endurance: Activities that get the heart rate up and keep it up for at least several minutes, such as jogging, swimming and biking.

Muscle endurance: Using a muscle continuously over an extended period, such as holding a plank position or ascending long staircases without pausing.

Muscle strength: Such as lifting weights.

Body composition: Making sure, through diet and exercise, that you develop and maintain a healthy balance of fat and muscle.

Flexibility: Such as from stretching, yoga or Pilates.

You can incorporate all of the above without spending hours a day exercising—just don’t do the same thing every day!

I begin very s­lowly with unfamiliar exercises and activities. The risk for injury is greatest when we try new things. We don’t yet know the proper forms and techniques…and our bodies aren’t yet used to performing the necessary actions.

The first few times I try something, I set aside my ego and keep the reps slow and the difficulty low. There have been times when I’ve lifted so little weight at the gym that people have asked me if something is wrong. Better that my pride gets hurt than my body.

I’m extremely cautious about group fitness classes. Fitness classes tend to be designed to be challenging for the strongest people in the class—which can leave novices at risk for injury as they struggle to keep up. Many instructors do not closely monitor participants’ technique, either—they just shout encouragement from the front of the room. Even yoga can be dangerous for novices. I have a number of friends who sustained injuries in yoga class that could have been avoided with better oversight from the instructor.

Fitness classes can be socially fun and great motivators—I myself take some. But before trying any new class, I confirm that it’s appropriate for someone at my level…and I ask the instructor to keep a close eye on my form. If I find that I can’t keep up during the class, I don’t try to—in fitness classes, ego gets people injured.

I’m always working on my balance. Falls cause injuries. Preventing falls requires maintaining your ability to keep your balance, which naturally declines with age from loss of muscle strength and joint flexibility and changes in the inner ear.

Incorporating balance exercises into your day is as simple as standing on one foot while you brush your teeth, put on your socks or ride an elevator.

For even better balance, add to your workouts an exercise called a ­single-leg floor touch. Stand with your feet hip-width apart. Lift your right foot off the floor, raising the leg behind you, and hinge forward at the waist until your torso is parallel with the floor. As you do so, lightly touch the floor with your right hand. (You should bend your left leg as you do this—this is not a stretching exercise.) Balance for a few seconds in that position, return to start, then repeat for a total of 10 reps. If needed for balance, hold your left arm out to the side or grasp something sturdy. Then switch sides, and do 10 reps with your left leg raised and left hand touching the floor.

I don’t do exercises that often cause injuries. I don’t do straight-leg lifts—an exercise where you lie flat on your back and lift your fully extended legs. These put too much strain on the lower back. I don’t do upright rows, where a barbell (or pair of dumbbells) is lifted repeatedly from waist height to collarbone height with the hands facing inward toward the body in an overhand grip. These put too much stress on the shoulders. And I don’t do behind-the-neck lat pull-downs, where a bar attached to weights by a cable is pulled down until it is behind the neck. This also puts excessive stress on the shoulders. (Lat pull-downs are safe when the bar is pulled down to a position in front of the head.)

I do lateral training. The most common exercise equipment includes treadmills, ellipticals, stationary bikes and stair climbers. The most common outdoor exercises include jogging and biking. What do all of these have in common? They all feature forward-only or forward-and-back movement, not side to side. That’s one reason why seemingly fit people often get hurt when they play basketball, tennis or touch football for the first time in a while—these sports require rapid side-to-side movement, which their exercise routines have not prepared them to do.

I include side-to-side, or “lateral,” ­exercises in my workouts. A lateral elliptical machine, which many gyms now have, is one way to do this. You also can train laterally with simple lateral lunges—stand with your feet shoulder width apart…take a big side step to your right, leaving your left foot where it is…bend your right knee until your right thigh is almost parallel with the floor, keeping your left leg straight, your right knee approximately above your right foot, and both feet pointed forward. Return to standing without repositioning your left foot, then repeat to the left, and do 10 lunges on each side.