Personal trainers are qualified instructors who maximise the effectiveness of exercise through knowledge of how the body and muscles work. However, often this aim becomes clouded in the nation that the only way to train is one that causes a so-called ‘good pain’. It is very easy to make someone sweat and have their muscles ache from fatigue, but it is hard to achieve the same while making sure they are exercising safely. It is particularly in larger classes and group sessions where there is no time to monitor each person and tailor exercises for individuals, that the pursuit of fatigue and exhaustion at the end of a workout often overrides any focus on the prevention of injury.