A training corset is generally a corset used in body modification. A training corset may be used for orthopedic reasons (such as to correct a crooked spine) or for cosmetic reasons (to achieve a smaller waistline, commonly called tightlacing).
In addition, the term "training corset" may simply refer to a corset which is used to acclimate the body prior to wearing a full corset as an everyday undergarment, or to any corset worn by somebody undertaking training (achieving a desired body shape).
Corsets may be worn for orthopedic reasons, such as correcting a crooked spine or straightening the back and shoulders.
No structural features distinguish a modern waist training corset from a corset worn as an external garment for special occasions. Training corsets are always made from strong fabric (or leather) and with relatively inflexible boning (not all corsets are strong enough to mold a body). A training corset is designed to be used every day, and will probably be hidden under clothing, so it is likely that practical aspects (comfort, ease of laundering, etc.) will have been stressed in its construction over aesthetic ones.
Any style of corset can be used for waist training, although some styles are more popular and suitable than others. However, as the corsets necessary to maintain a body modification are no less rigid than those first worn to achieve the modification, there is no effective structural difference between corsets worn during training and those worn once the desired body shape is achieved. The term "training corset" can, therefore, be used for any corset worn by somebody undertaking training.
A training corset is also an alternative name for a discipline corset or bondage corset. A bondage corset is used as a tool for punishment. It is constructed to place severe limitations on the wearer's movements. A bondage corset generally extends to just above the knees, and is constructed to be laced very tightly. These corsets are often designed to be worn for long periods of time, e.g. overnight and during sleep.
During earlier times, in which a corset was an everyday item of apparel, a training corset in the sense of body modification was not used. Girls began to wear corsets as part of their transition into womenhood, in the same way modern girls begin wearing bras at the onset of puberty.
It was primarily in the 17th century when corsets were used to noticeably reduce a woman's waist in order to achieve a fashionable hourglass figure. The corset was laced progressively tighter, forcing the floating ribs upward and compressing the soft tissue at the waist. This could lead to many negative health ramifications, including difficulty breathing, problems with digestion, and permanent deformity.
The actual prevalence of this practice is difficult to ascertain. It was most likely practiced by only a small portion of the corset-wearing population.