The Bulgarian Bag ( / Български чувал), also known as the Bulgarian Training Bag (), is a crescent-shaped exercise equipment used in strength training, plyometric weight training, cardiovascular training, and general physical fitness. The bags are made of leather or canvas and filled with sand; they weigh from to and have flexible handles to allow for both upper and lower body training, and for building grip strength. History The Bulgarian Bag was invented by Ivan Ivanov at around 2005. Ivanov, a former Bulgarian Olympic athlete, was working as a U.S. Olympic wrestling coach at the Olympic training center in Marquette, Michigan, and was looking for a training tool that would allow his wrestlers to improve explosive actions and dynamic movements involved in pushing, twisting, swinging, pulling, bending, rotating, squatting, lunging, and throwing. Ivanov was inspired by the tradition of shepherds performing strength acts with sheep and goats on street fairs in his homeland, Bulgaria. The shepherds were often forced to carry lambs and weak sheep around their shoulders when they were wandering with their herds, and were showing off their strength at festivals. Ivanov based the design of his tool on the body of an ovine and saw its use as a modern interpretation of the old tradition. Although the Bulgarian Bag was initially designed for Olympic class wrestlers, it came to be adopted by fitness trainers and professional athletes for its ability to increase muscular endurance and make weight training more versatile. One of the first advocates of the Bulgarian Bag outside the Olympic wrestling circuit was fitness specialist and retired Navy SEAL Stephen Nave. Along with Ivan Ivanov they formed the International Bulgarian Bag Confederation to educate the public and offer advanced instruction to individual consumers, personal trainers and fitness establishments. Construction The exterior of Bulgarian Bags is made out of leather or heavy-duty canvas. The leather bags are handmade in Bulgaria and mostly constructed of goat skin. Because goat skin is finer in thickness and the follicles are shallow in the skin, there is less compromise in the strength of the hide when compared to other leathers. The interior is filled with individually wrapped and weighed sand packets and padded with wool to form a smooth rounded contour. Once filled, the main seam is closed using a heavy gauge soft nylon. The exterior of the bag consists of three kinds of handles and straps to allow for