Swim jammers look like bicycle shorts but you wear them in the water to make you sleeker and faster when you swim. In addition to swim jammers, goggles and snug-fitting swimcaps are standard gear for fitness and competitive swimmers. Only men wear jammers, which start at the waist and cover to just above the knees. Female swimmers might wear bodysuits that extend to their knees during competitions.
At the beginning of the 20th century, swimmers wore bulky woolen garments. Adolph Kiefer, a former Olympic swimming champion from the Berlin 1936 games, innovated and marketed lightweight and durable nylon suits in the 1950s. Lycra and spandex materials introduced later clung closely to the body, and suits got smaller and tighter. When manufacturers and swimmers realized that longer suits helped them move faster through the water, the trend toward smaller suits reversed, leading to full-body suits worn in the Beijing 2008 Olympics. The International Federation of Swimming, or FINA, banned full-body suits effective Jan. 1, 2010, so now elite male swimmers once again rely on suits that cover the body only below the waist.
Competition-quality swim jammers fit tightly and compress your body. Made out of hybrid materials including spandex, Lycra and some polyurethane, the suits help reduce your profile in the water. The smoother and sleeker your shape, the less resistance you encounter from the water as you move forward. According to USA Swimming, traditional swimsuit textiles cause friction in the water and slow you down, while the water-repelling qualities of polyurethane help make you "slippery." Following the Beijing Olympics, though, new regulations limit the amount of the material allowed in suits.
Younger male swimmers in the United States tend to prefer jammers in part because they are more modest, according to Swimming World. College-age athletes still wear the classic smaller swim briefs, but kids starting out might be hesitant to work out with so little coverage. The fitness-swimmer's versions of jammers are not as tight and sheer as competitive ones and the suits cover until just above the knees.
Swim jammers do not make elite swimmers out of average ones but they might shave a few fractions off swim intervals. Competitive suits cost more than workout suits and do not last long in chlorinated pools. When suits loosen, you lose the competitive edge.