In the early days of the sport, swimmers would often prioritize high-volume training, meaning they would swim for much longer distances, however as time went on swimmers shifted from high-volume practices to higher-intensity training which was geared towards racing and their specialties.
A sprinter would swim shorter distances at a high intensity to mimic their races meanwhile a distance swimmer would swim longer distances on a pace to replicate their longer races.
Another huge difference with training nowadays is the creation of equipment to help swimmers focus on certain aspects of their stroke.
The kickboard which was invented in the 1940s helps swimmers focus on their kick and building power in their legs.
The pull buoy was invented in the 1960s which helps swimmers focus on their pull and building power in their arms.
The snorkel was invented in 1938 which helps swimmers build lung capacity.
Hand paddles were invented in the 18th century which helps swimmers build strength in their arms .
Swimming fins which were invented in 1940 which helps build strength in their legs.