"In modern tennis, the importance of the non-dominant arm has become fundamental for good shot execution." (Riccardo Piatti)
After analyzing a sample of 10 000 tennis players (amateurs of all types and talent levels) in 12 years, I can say more than 70% of people incorrectly use their non-dominant arm in the opening phase of their forehands. This leads to a chain of mistakes through the next phases and, ultimately, negatively affects the shot.
Through video analysis, we can see crucial key points of shot execution that can act as a step-by-step standard referral for all players.