Weight training is composed of three separate components. Free weights are physical training aids designed for use in isolating resistance to a muscle or muscle group, when the weight is not supported or otherwise connected to a machine, pulley, or lever. A barbell or dumbbells are classic examples of free weights. In contrast, a weight machine is a device in which the resistance created against the muscle is through mechanical means; the user is generally placed in a fixed position in relation to the equipment. The third component, calisthenics, is often overlooked as having a role in the development of muscular strength; calisthenics has both strength exercise components such as pushups and squats, as well as flexibility exercises that make the body more efficient and less prone to injury.
A comprehensive and effective weight training program will incorporate each of free weights, machine weights, and calisthenics. To understand how each discipline can be best employed, it is important to understand how training develops human muscles. Improved muscle strength is achieved through the principle of overload, which is the increase in the intensity required of a particular muscle, such as the bicep (upper arm), or a muscle grouping, such as the quadriceps (the thigh muscles). Overload can be achieved in three ways: through increased resistance, the increase in the amount of the weight to be lifted; by increasing the number of repetitions at which the weight will be lifted (for example, increasing the number of repetitions from seven times to ten times per set); and increasing the number of sets at a particular weight (as in two sets at 100 lb/45 kg to three sets at 100 lb/45 kg).
Once the basic principle of overload is understood as fundamental to strength training, factors for the training routine must each be tailored to the age, physical development, and capabilities of the athlete, in conjunction with the goals that the athlete seeks to achieve through increased strength. Those factors include: the amount of weight to be lifted; number of repetitions, and recovery time.
The amount of weight to be lifted in any given aspect of the weight training routine will be a factor; as a general rule, the body type of the athlete, including the ratio of fast-twitch to slow-twitch muscle fibers (fast-twitch athletes have a generally greater ability for explosive movement, including weightlifting)
The number of repetitions of any movement is important. The development of pure strength is generally achieved with fewer repetitions and greater weight; muscle endurance is heightened through lesser weights and greater repetitions.
The recovery time between each set is critical. When heavier weights are being used, the recovery time will be necessarily greater. The recovery time between each weight training session should be adhered to. The development of muscle strength requires a rest period for the repair of the muscle tissue. Weight training cannot be effective if conducted on a daily basis.
Free weights and machines are often contrasted in terms of whether one method of weight training is better than the other. Free weights and machines each represent the optimal weight training method for some, but not all, purposes. Free weights have advantages over machine training in a number of areas: they are more cost effective, more versatile, develop a broader range of physical skills, and may be used anywhere.
Free weights are more cost effective because a single set of barbells can be used in a wide range of training routines. Most machines are constructed for a limited series of movements. The simplicity of the free weight in contrast to a machine represents significant savings of cost and potential maintenance expense.
Free weights are a versatile training tool, as there are no built-in limits on how the weight can be deployed. If an athlete feels that a particular free weight program is becoming stale or that he or she is losing interest, the program can be entirely redesigned using the same equipment; machines do not permit such flexibility.
Free weights require more of the athlete in their use, as the entire body, including the central nervous system, must be engaged to produce balance and hand/eye coordination.
Once an athlete has become accustomed to free weight training, it may be used in any venue; machines are often more idiosyncratic, and each machine requires the athlete to become accustomed to the measures of resistance and ranges of motion.
The chief drawback of free weight usage is the greater risk of injury. Inherent in proper free weight training is the employment of good posture; poor form can lead to imbalances when the weights are lifted, which can result in injury. Further, the heavier the weights used in training, the more important a training partner or spotter becomes for the athlete.