Because each machine works opposing muscle groups at the same time, the equipment eliminates the eccentric movement and is thus known as double-concentric. In conclusion, it's easy to see that circuit training equipment may very well be the best solution for those seeking a quick weight loss program. For those seeking to achieve a healthy weight quickly, hydraulic fitness equipment may be the best answer. Instead, it is designed to do two things only: burn fat and tone muscle. This may be due to eccentric contractions allowing greater force production in addition to less fiber recruitment, which means the fibers are stressed more and more damage occurs. The eccentric (negative) is what actually causes the vast majority of the muscle growth in resistance training. Instead, it is double-concentric. Examples would be pushing the bar away from you on a bench press, or lifting the bar towards your chin on a biceps curl. These are called the concentric and the eccentric Polyester FDY parts of the exercise, also commonly referred to as the 'positive' and 'negative'. Common sense dictates that working two separate and distinct (opposing) muscle groups at the same time is faster than working each muscle group individually. The concentric (positive), on the other hand, primarily tones the muscle. Another point to be made is that the eccentric part of the resistance training movement is the component that will lead to extensive muscle growth. Incidentally, the lack of any significant eccentric (negative) movement also means that the user will experience drastically reduced muscle soreness. When the bar is lowered away from the chin, that's an eccentric (negative) movement, again for the biceps. So what was an eccentric movement for the biceps (with free weights) has become another concentric movement for the triceps. The majority of hydraulic circuit training equipment does not have an eccentric movement. Each piece of equipment works opposing muscle groups. As an illustration, consider the user doing barbell curls with free weights (a constant resistance device). Because the machines are double-concentric, each total body workout takes less time. It will not return on it's own. Between work, family and other obligations most Americans are simply too busy for a diet and exercise program that doesn't produce fast results. In direct contrast, a circuit training Bicep/Tricep machine is designed so that when the user reaches the top of the movement the equipment must be pushed back down to the bottom of the movement. The micro-tears in the muscle fiber that are a direct result of eccentric training simply do not occur with double-concentric equipment. Examples would be lowering the bar on a bench press, or lowering the bar away from your chin on a biceps curl. When you engage in resistance training you create microscopic tears in the muscle. There are two movements in any resistance training (weight lifting) exercise. The eccentric (negative) part of the resistance training movement is defined as "Muscle action in which the muscle resists while it is forced to lengthen" (source: International Sports Sciences Association; 2001). This is true because most circuit training equipment is double-concentric. Why is that important? It's important because, being double-concentric, circuit training fitness equipment will never lead to huge, Arnold-like muscle growth. What does this mean to you? Eccentric contractions cause greater muscle damage and thus provide the stimulus to make your muscles grow and strengthen. In other words, there literally is no need for an eccentric movement. When the bar is curled up towards the chin, that's a concentric (positive) movement for the biceps.Often, people who are looking for the best weight loss program are also seeking easy weight loss. There's nothing wrong with that. The concentric (positive) part of the resistance training movement is defined as "Muscle action in which the muscle is shortening under its own power" (source: International Sports Sciences Association; 2001). These fibers repair and regenerate so that they are able to handle future bouts of similar work while experiencing less damage.