This study verified how much performance damage can high-intensity efforts cause to FT shooting efficiency. Methods: A sample of 13 male amateur basketball players (19.9 ± 3.2 years; 76.7 ± 8.7 kg; 182 ± 10 cm) participated in the study on three non-consecutive days. A maximum progressive exercise test determined maximum heart rate (HRMax) during the first session. On the other two days (randomly assigned), athletes performed five bouts of basketball-related exercises, intense enough to raise HR to either 65% (S65) or 90% (S90) of HR Max , followed by two FT shots (totaling 10 FT). Results: FT performance was lower in S90 than in S65 (56.9% ± 18.9% vs 73.1% ± 12.5%, respectively; p = 0.026; ES = 1.01 -"large effect size"). Magnitude-based inference analysis considered shooting at S90 moderately disadvantageous and odds ratio analysis suggest that shooting FT at higher HR values represents an 11-fold chance to worsen performance (OR = 11.1; 95% CI = 1.79 to 68.9; p = 0.01). Conclusion: Basketball FT shooting efficiency is impaired after a bout of game-related high-intensity activity.