Obiena first took up pole vaulting when he was eight years old, but initially focused on hurdles. His father, Emerson Obiena served as his coach until he was 18 years old.[13] Obiena competed in the 100 and 400 meter hurdles events for his high school, Chiang Kai Shek College.[10] Unable to qualify for regional meets, he decided to return to pole vaulting when he was in his last years in high school, in a bid to secure a college scholarship.[13]
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In early 2014, Obiena was able to meet Ukrainian pole vaulter Sergey Bubka who was visiting the Philippines. Originally, he only intended to get an autograph from Bubka, but learned from him of an opportunity to train in Italy.[13] In the same year for three months, Obiena travelled to Italy to train under coach Vitaly Petrov in Formia, who also previously coached Bubka.[15] On July 20, 2014, at the PATAFA weekly relays held at the PhilSports Football and Athletics Stadium, Obiena broke the national record for pole vault by registering 5.01 meters. The previous record was 5.0 meters by Edward Lasquete at the 1992 Summer Olympics in Barcelona, Spain. The junior national record was also broken, since Obiena at that time was still 18 years old. The previous record was 4.31 meters set three years before.[15]
He later broke his own record several times in 2014 alone (5.05, 5.05, 5.15, 5.20, 5.21). By the time Obiena became ineligible for the national junior record, the record was 5.21 which Obiena set himself.[citation needed]
In the 2015 Southeast Asian Games, Obiena won a silver medal with a leap of 5.25 meters, then his personal record.[16]
Obiena won a gold medal in the 2016 Philippine National Games Finals in Lingayen, Pangasinan after breaking a new personal record (5.47 meters), despite problems with a broken pole.[citation needed]
Obiena won gold in the men's pole vault event at the 2019 Summer Universiade[17] setting a new national record of 5.76 meters. He secured a berth in the 2020 Summer Olympics by surpassing the qualifying standard by making a 5.81 meters height in a tournament in Chiara, Italy on September 3, 2019. The height was also a national record.[18]
The COVID-19 pandemic caused the postponement of the Olympics and travel restrictions imposed by countries in response to the health crisis posed logistical issues to Obiena's preparations. For most of 2020, Obiena spent his time training in Formia, Italy, and was unable to go back to the Philippines during the Christmas season. He trained under American conditioning coach James Michael Lafferty and Nutritionist Carol Lafferty; along with Brazilian Thiago Braz as his training partner.[19] Competing in the 2020 Summer Olympics in Tokyo, Obiena managed to advance to the final of the pole vault competition but failed to make the podium.[20]
Obiena set a then Asian record in pole vault when he lifted his best vault all the way to 5.93 meters at the International Golden Roof Challenge in Innsbruck, Austria on September 12, 2021. He won the tournament.[21] This record was later broken on July 25, 2022, when Obiena lifted his best vault all the way to 5.94 meters at the 2022 World Athletics Championships in Eugene, Oregon, United States. He won a bronze medal, becoming the first Filipino to win a medal in the tournament.[22]
In June 2023, Obiena cleared 6 meters for the first time at the Sparebanken Vest Bergen Jump Challenge in Norway also resetting the Asian record.[23] He was able to accomplish said feat due to shifting to a 20-step technique from the previous 18-steps approach.[24] He was then ranked world No. 2 in men's pole vault by the 2023 World Athletics Rankings, just behind Armand Duplantis.[25]
In November 2021, the Philippine Athletics Track and Field Association (PATAFA) publicly escalated an accounting dispute involving late payments to Obiena's coach, Vitaly Petrov. Petrov later denied there was any payment issue with Obiena.[30][31] Philippine Senators quickly came to Obiena's defense, calling unproven accusations "harassment" against an athlete considered a national treasure and passing a motion to recall the budget of the PSC. The Senators later approved the PSC budget with the condition that PATAFA will “rectify the grave injustice” done to Obiena's reputation. During congressional hearings, witnesses testified that PATAFA's payment system is broken.[32][33][34][35]
After an investigation by its Ethics Committee, the Philippine Olympic Committee (POC) declared PATAFA's president Philip Juico persona non grata for his role in the harassment of Obiena. The investigation of the POC's ethics committee concluded that Juico had harassed the athlete by making "malicious public accusations".[36][37]
On March 30, 2022, the Philippine Sports Commission announced that both parties reached an agreement during a mediation process. Obiena will be endorsed by PATAFA in any future competitions.[38]