Despite being one of the younger entrants, Alcántara improved two personal bests at the 2008 World Junior Championships in Athletics, jumping 14.25 m to take the triple jump gold medal and 6.41 m to earn herself the long jump bronze medal. She began to establish herself nationally in 2009 by winning the long jump at the Barrientos Memorial and placing third in the triple jump with a Central American and Caribbean junior record of 14.36 m (beating Mabel Gay's former mark). That year she entered senior international events, winning the long jump at the 2009 ALBA Games and placing sixth at the 2009 Central American and Caribbean Championships in Athletics. She also won the triple jump at the 2009 Pan American Junior Athletics Championships.