12/20/2010 12:29 pm ET Updated May 25, 2011

What a Physician/Exercise Physiologist Looks for in a Personal Trainer

In the thick of the holidays, many of us find ourselves contemplating what to get for the person who is already loaded up with every gadget available to make a call, send a message, surf online, play a song or take a picture? Or, what do you ask for if you happen to be that person?

A common item on the wish list of fitness-conscious Angelenos is personal training sessions. It's a nice indulgence that also jump-starts progress on the inevitable New Year's resolution to lose weight and get fit.

The right trainer is a coach and teacher who can help you intensify your workouts safely. But, trainers don't come in one size that fits all. The wrong trainer could just be an expensive means to learn a workout routine that you'll tire of quickly. How do you know the difference?

That's the question I posed to Alexis Peraino, MD, a colleague of mine who also has a degree in exercise physiology. She selects the personal trainers to be included on our medical center's weight loss program referral list.

These are her tips:

Ask tough questions like you were interviewing them for a job. When you're meeting prospective trainers at gyms, you may be on their turf - but remember they are the ones on a job interview. Don't be afraid to grill them on their credentials and what kinds of clients they've worked with in the past. Know your own fitness goals - like losing weight or increasing muscle mass - and let that shape what kind of past work experience you'd like your trainer to have. Also, be honest about your limitations and old injuries. A good trainer can work around them, tailoring a workout to your specific needs. For example, if you have bad knees then lunges, a favorite exercise of many personal trainers, may be out for you. Ask what they can do instead. Don't forget the practical questions: Does their availability gel with yours? What's their cancellation policy? The best trainers will ask you questions, too, to determine your goals and fitness level.

Are they currently certified? Current credentials are more than just pretty certificates. They prove a trainer is committed to honing their skills and keeping up with the latest science and trends in fitness. The most prestigious credentialing bodies include American College of Sports Medicine, National Academy of Sports Medicine and the American Council on Exercise.

Optimize your training time to avoid injuries. Ideally, your trainer coaches you from warm up to cool down. In addition to pushing you to work at the highest levels of intensity you can manage, your trainer should also work with you on improving your flexibility. These steps are critical to avoiding injuries. This is time well spent in your workout. Trainers are there, in part, to help you avoid injury. There's little benefit to a high-intensity workout if it results in an injury that sidelines you for weeks or months. "No pain, no gain" shouldn't be your mantra, or your trainer's.

Does your trainer give you workout assignments between visits? To get all the exercise your body needs to achieve your goals, that's more workouts in a week than you can likely afford to do with a trainer at your side. The U.S. Department of Health and Human Services, the American Heart Association and the American College of Sports Medicine have recommend at least two, non-consecutive days weekly of resistance exercise such as weight lifting. Optimally, you squeeze in three or four of these workouts a week. That's why it's important to receive exercise "homework" to complete on your own. Your trainer should teach you exercises you'll continue to benefit from after you run out of sessions, and keep that in mind when developing routines with them. Will you run the stairs in the gym without your trainer? Who will toss that medicine ball to you when they're gone?

Trainers should be masters of many workout modalities. Boredom is the enemy of fitness. Find a trainer who is skilled in several exercise disciplines like weight training, pilates, yoga and martial arts so they can keep it fun and interesting.

Combine cardio and resistance training. Your workout should raise your heart rate and challenge your muscles. The trainer should combine cardio and resistance training to optimize your time at the gym. The calorie-burning power of cardio is often a priority for those who want to lose weight, but never underestimate the importance of building muscle. If you neglect your muscles while dropping weight, it's easy to lose lean body mass rather than fat. In addition, when your lean body mass decreases, so does your metabolic rate. Consider circuit training to combine the best of both types of exercise, or perhaps tackle some cardio on your own before or after a training session.

Beware of the trainer who sells exercise supplements. Often, hiring a trainer is a single step toward larger lifestyle changes. It's common to change diet or add in protein shakes or other supplements. Be wary of those trainers who focus on specific supplements, protein drinks or fat burners. If there was a "miracle" product or pill, I would be writing this blog about that instead. In addition, ethically, trainers should not give advice beyond the scope of their expertise. Before taking specific diet and nutrition advice that goes beyond old-fashioned common sense, find out if they have the education and training to back up that advice.

Don't be afraid to be picky about personal training. Working with a trainer is a worthwhile investment in improving your health - just also invest the time to find the right person. Also bear in mind the most expensive trainers aren't necessarily the best. Many will consider semi-private sessions so you can split the cost with a friend. Just be sure that friend's needs and goals are similar to yours.