▲It's easy to get carried away when you start working out with a PT. You might think you actually need a lot of supplements to achieve your goals. You don't. Start by eating a balanced diet instead!

▲A PT won't take away your aches and pains and turn you into a fitness model overnight. You should have reasonable expectations about what you're going to achieve with a few sessions.

▲Unfortunately not all PTs have actual training experience. In most countries all you need to become a PT is to take a short course and get a certificate.

▲You might have some health problems that may have an impact on your objectives or hinder your progress. Any pathology should be addressed by a physician, not a personal trainer.

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Sometimes you need more than just a few PT sessions to go through life. A PT won't be your life mentor, their job is to get you in shape, that's all.

▲Many PTs are able to advise you on how to eat better, but they won't be able to prescribe you a custom diet for your specific needs.

▲Do you share details of your personal life with your accountant? It's exactly the same with your PT. A PT's job is to train you, not to be your best friend.

▲You actually need to have some muscle mass before you reduce your body fat percentage to a level that'll allow you to have a "defined" look.

▲A PT has to deal with people, and that requires good communication and interpersonal skills. Some might need a bit of calibration when it comes to the approach they use to deal with some clients.

▲You will find overqualified PTs with dozens of certificates, but who actually have little or no experience training by themselves or with clients. Don't judge a PT by their diplomas.

▲Sometimes PTs will have you do all sorts of exotic exercises. While some might be useful, others are simply different versions of tried and tested movements. They just look cooler.

▲If your PT puts you on a treadmill for 20 minutes and then follows it up with a few weight machines, maybe it's time for you to reflect on how you're spending your hard-earned money.

▲Your PT will most likely give you a training session and just tell you to eat healthier foods. But eating well is a life-changing habit that you need to take up if you want to see results.

▲Although it's possible to lose weight fast, to do so in a healthy and sustainable way will take time. If you're hoping a few PT sessions will cut it, you'll be disappointed.

▲If PTs earned a penny for every time a client told them this, they'd all be rich by now. If it was that easy, we would constantly be surrounded by big, muscular people.

▲Body weight might not be the best measurement of results. Your body weight will fluctuate daily depending on water and glycogen levels in the muscles.

▲Feeling sore does not necessarily mean you had a good workout, nor does sweating buckets.

▲It's true that some PTs simply use cookie-cutter routines for every client. These might or might not work for you.

▲Many PTs are extremely competent but they don't know everything—nobody does. So don't expect to be trained by a walking fitness encyclopedia.

▲Cheating on your diet? Not sleeping properly? Your PT will be able to tell if you're slacking.

▲They all have different training methodologies. Some might or might not be the best to help you achieve your goals.

▲Sleep is of utmost important when it comes to regulating your metabolism, losing body fat, and gaining muscle.

▲A PT will likely try to sell you more sessions. It's their business and how they make money so don't take it personally if sometimes they sound like sales reps.

▲A few PT sessions won't be enough for you to gain muscle. You'll have to train hard, eat well, and rest properly.

▲Some of your PT's clients might have your dream body, but that doesn't mean their bodies are just a product of your PT's training methods. Some might even be on performance enhancing drugs, such as anabolic steroids.

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Most PTs love working with unfit people to help them transform their lives. Their job is essentially about helping people, so don't wait until you're fit enough to book a PT session if you feel you'd benefit from it.

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We all need a little motivation, and that's what leads many of us to book PT sessions. Some PTs do this very well, but others are more concerned about you enjoying your session and booking another one.

▲The latest celebrity diet might not work for you. Remember, if being in good shape was easy, everyone would look and feel great.

▲Many personal trainers can help you address minor injuries, but full-on rehabilitation should be handled by a physical therapist or other similar professional.

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From losing weight to gaining muscle, personal trainers can help you to get in shape and achieve your goals. But just like any other profession, there are trade secrets that they don't want clients to know. Click through the gallery and get to know what PTs are hiding from you.