The Effectiveness of Shooting and Sprint Training Variations on Shooting Improvement for 13-15 Year Old Soccer Players In Proceedings of the 3rd Yogyakarta International Seminar on Health, Physical Education, and Sport Science in conjunction with the 2nd Conference on Interdisciplinary Approach in Sports YISHPESS and CoIS - Volume 1, 115-120, 2019 , Yogyakarta, Indonesia