A well-balanced fitness programme includes cardiovascular (aerobic) activity, strength and flexibility training. Aerobic training such as jogging is great for your heart and improving cardiovascular fitness, but does little for muscular strength, especially upper body. A certain amount of muscular strength and endurance is necessary for everyday activities such as lifting. Research has shown that resistance training to improve muscular fitness also improves bone density, metabolism and body composition. Group strength training classes are not new - they were offered in the early 1980s (mainly in the US), but as other classes, such as step and indoor cycling, took off resistance training classes dropped in popularity. Today, as more people understand that strength training helps to build lean muscle mass and develop a stronger, shapelier physique faster than a cardio workout, classes like body pump and sculpt bar have become very popular. Muscular fitness includes both muscular endurance and strength. Strength refers to the maximum amount of force that can be generated by a specific muscle or group of muscles. Endurance is the ability to exert less than maximal force for several repetitions. Both of these are developed by overloading the muscle through resistance, duration and frequency. This is accomplished by varying the amount of weight, amount of rest and sets of exercises in a strength training programme. In a body pump or sculpt bar class, the emphasis is on muscular endurance or high repetitions, so the amount of weight should be below an individual's maximum weight. The basic muscle actions are isometric, eccentric and concentric contractions. Isometric occurs when there's no joint movement, eccentric and concentric contractions occur when there is joint motion. Concentric occurs when the muscle is shortened and eccentric when the muscle is lengthened, like the lowering phase of a bicep curl. Research has shown individuals increased their muscle tone, bone density and metabolic rate after doing a strength training class such as body pump or sculpt bar twice a week for at least six weeks. As with any physical activity, correct technique and body alignment are important to avoid injury. The knee is one of the most vulnerable areas for injury, and when weight is added the risk is even greater. When doing squats (whether you are doing a strength training class or on your own), the knees should be about shoulder-width apart with the knees and toes facing forward. The weight bar should be in a comfortable position on the neck with the hands gripping the bar or the forearms resting on the bar. Heels should always remain on the floor and hips shouldn't drop below knee level. During lunges, the knee shouldn't be beyond the toes. The front leg should be perpendicular to the floor and the hip shouldn't drop below knee height. At first, it's best to reduce the weight and focus on technique. For upper body exercises performed in a standing position, the abs should be contracted and the rib cage lifted with the pelvis in a neutral position. It is critical not to sink into the lower back. Try not to use momentum in any of the exercises, such as swinging your arms or using your torso to lift a heavier weight. And make sure you complete the movements to a full range of motion without hyperextending (over-extending) your joints. This helps to maintain proper joint mobility. Finally, don't hold your breath when doing any of the exercises in these classes. Think about inhaling during the eccentric phase (lowering or lengthening) and exhaling during the concentric (shortening). These strength training classes are great for people who are new to weights or aren't sure of the proper techniques or exercises. Each class covers all the major muscle groups, like the legs, back and shoulders, and smaller muscles like biceps and triceps. A great way to add muscular strength and endurance to your fitness routine.