With the long safety elastic you work on strength but you work in the water! Many do not know that this is the reason why more and more teams are using these bands as a tool to strengthen the swimmer's stroke more effectively (compared to weight lifting). It has now been proven that the developed force is applied much more effectively if it has been increased by working THE SAME GESTURE that I will then go on to perform in the sport that I practice. So swimming against the resistance of a rubber band is the best, most efficient and also the only way to develop the power of the stroke. It is important to underline the presence of a cord inside the elastic which prevents, in case of breakage, the return of the elastic towards the two ends, thus avoiding any possible trauma or accident