As I began working as a personal trainer I found it a bit surprising that there were people who were willing to pay me for guiding them through a workout. I would even be hired by people who were already in relative good shape. Working out seemed to be so intuitive to me, I was involved in sports and fitness ever since I was in high school. Erroneously, I thought that exercise was equally intuitive to everyone.
Expertise and Knowledge
Exercise is not intuitive to most people. Common generalizations about application of exercise and exercise program design are often wrong. Grabbing an exercise program from magazine or a book might not be the best option. All clients are different and therefore they all respond differently to exercises. A skilled personal trainer will accurately asses a client and design a program that best matches the client's physical capacity and help the client achieve his/her goal most efficiently.
For example, I have been working with a client who is in his early fifties. He is an avid tennis player. Therefore, the program reflected his need to improve as an athlete. The exercise program first focused on his weaknesses. As his balance and stability improved we included exercises often found in football strengthening program. According to generalizations, heavy dead-lifts and push-presses might be incorrect exercises for someone in his early fifties. Yet with prudent planning he was able to perform these exercises while avoiding any dangers (and dominating the tennis courts).
On the other hand, I have worked with competitive young athletes whose performance on the court/field was decreasing because their bodies might not have been properly progressed to the exercises they were performing. Most of them believed that in order to improve their speed and explosiveness they needed to perform plyometrics. This is true and often suggested to young athletes. However, in this case, the athletes were not properly prepared for plyometrics and benefited far more from stability and balance exercises in the first three weeks, after which plyometrics were implemented.
Another good example is a client who I have worked with who wanted to loose weight. So she focused on cardio, since common knowledge says that cardio is the superior form of weight loss exercise. Excessive running caused her severe knee pain. As a result, she ran less and began to put on weight again. When I started working with her, I focused on strengthening and balancing her hips. Her workouts were challenging, but far less stressful to her system. Taking the stress caused by running away appeared to help her loose some weight alone (cortisol, stress induced hormone, will make you FAT)! Six weeks later she was running again and several months after that she ran a marathon. Of course, as she resumed running and included a strength routine in her regiment she began to loose weight.
The main point is that exercises can be easy learned. There are hundreds of magazines and websites where anyone can look up exercise for specific goal (i.e. weight loss, toning, and sport specific). However the correct design of an effective exercise program requires skill, experience, and understanding of a client's physical capacity.
Efficiency
According to literature, program design is number one reason why consumers hire a personal trainer. Most of consumers who can afford a personal trainer are successful people and, as a consequence, are very busy. Busy people do not want to go to gym and plan what they are going to do. These consumers want to get in and out of the gym as quickly as possible yet still feel like their time was productive. In fact, many of my clients often "turn off" their brain while they workout. They simply do what they are told. Often these clients forget what exercises they did about five minutes ago.
The last thing busy successful people want to do in the gym is to think and plan. They do that all day long, workout to them is most often a retreat from daily grind of thinking and planning. Moreover, if they were to plan a workout as thoroughly as I would they would need resources (like magazines and websites) and time to plan. It therefore makes complete sense to delegate that responsibility to a personal trainer. If my clients were to calculate their hourly wage (most of them do not work for hourly wage) it would be between $60 and -$200 an hour. If they would spend an hour a week planning a workout (reading magazines articles, searching for websites, learning the exercises, writing down exercises, logging weights) they would end up ripping themselves off.
Motivation
I recently got a chance to appreciate being trained as I bartered some session with a Pilates instructor. I am sure that I could figure out Pilates exercise if I have looked them up, given my fitness experience. However, I doubt that I would maintain the same level of focus had I not been guided through these exercise by a certified instructor. The fact that there was someone standing over me and CARED what I did made me work just that much harder and focus on the task. Human feedback is extremely powerful. This is obviously clear in realm of sports where playing on the home field is a great advantage.
Working with a personal trainer also makes people feel more committed and more compliant to their fitness goals. Clients know that they are responsible for their work and that a personal trainer will hold them to that responsibility. Consequently, the client and his/her personal trainer form a bond, a professional relationship so to speak. Psychologists often claim that such a relationship can be therapeutic. Naturally, overcoming a daunting task, like getting into shape, is far easier when there is someone else that cares.
Furthermore, as clients become fit and healthier they inevitably feel happier. A common observation I made is that clients that do achieve their set fitness goals often tell me how other domains in their life have changed. They often take bolder career choices, are more confident in their interpersonal relationships and so on. It would appear that positive health/fitness changes have a truly synergistic effect.
Accountability
Another clear advantage of working with a personal trainer is accountability. It is less likely that you will skip a training session when you have a scheduled appointment. This is especially true when a personal trainer has a 24 hour cancellation policy, and most of us do strictly enforce it.
Conclusion
In sum, hiring a personal trainer has clear advantages to working out alone. A personal trainer will plan an efficient workout based on his extensive knowledge. Personal trainer will also keep a client motivated by forming a team with the client and therefore keep him/her accountable for the work.
A personal trainer is, on the other hand, a very expensive investment. In fact, I do not think that it is a service for everyone. However, if the previously described factors are important, it is an investment that will pay dividends many times over.