2016 Hernandez made her senior debut in 2016 at the
City of Jesolo Trophy, where the U.S. team won the gold medal. Hernandez won the bronze medal in the all-around with a score of 58.550, behind two U.S. teammates, fellow first-year senior
Ragan Smith and
Gabby Douglas, the
2012 Olympic all-around champion. She also earned a silver medal on the vault behind
MyKayla Skinner and a gold medal on the balance beam, ahead of Smith and 2012 Olympian
Aly Raisman. In April, Hernandez competed at the
Pacific Rim Gymnastics Championships in
Everett, Washington along with Raisman, Smith, three-time world all-around champion
Simone Biles, and 2015 World Championships team member
Brenna Dowell. She contributed an all-around score of 59.800 toward the American team's first-place finish and placed third individually behind Biles and Raisman, but did not earn the all-around bronze medal because of a rule limiting medals to two gymnasts per country (Japan's
Nagi Kajita took bronze instead). Hernandez also qualified for the balance beam final, but
USA Gymnastics announced that she and Biles would not compete in event finals in order to rest them before the Olympics. In June, Hernandez competed at the
U.S. Classic on the uneven bars only, scoring 15.400 and placing fourth. Later that month, she competed on all four events at the
U.S. Championships. At the end of night one, she was tied for second place in the all-around with Raisman, behind Biles, with a score of 60.450. She finished the two-day competition in third all-around, behind Biles and Raisman. She placed third on uneven bars and balance beam and tied for third on floor exercise with
MyKayla Skinner. At the
Olympic trials in early July, Hernandez placed second in the all-around, behind Biles. She was named to the Olympic team alongside Biles, Douglas, Raisman, and
Madison Kocian. Hernandez had previously committed to the
University of Florida to compete on the
Florida Gators gymnastics team in the
NCAA. However, she decided to forgo NCAA eligibility and become a professional athlete on August 3, 2016, in the lead-up to the
Olympic Games.
Rio de Janeiro Olympics On August 7, Hernandez competed in the
qualification round at the
2016 Summer Olympics. She scored 15.200 on the vault, 15.366 on the balance beam, and 14.800 on the floor exercise, qualifying for the balance beam event final in second place. She posted the fourth highest score on floor, but she did not advance to the final due to the two-per-country rule, with teammates Biles and Raisman getting higher scores. Hernandez and the rest of the United States team, known as the
Final Five, won gold in the
team final. The Americans won every event, scoring a total of 184.897, more than eight points higher than second-place team Russia (176.688) and third-place team China (176.003). Hernandez was the first competitor on vault and floor exercise for the United States team.
Hiatus After the 2016 Olympics, Hernandez took a break from gymnastics to pursue media opportunities and rest her body. She appeared on the television show
Dancing with the Stars and won the competition. She continued appearing on television and in the media throughout the next four years, as a show host and voice actor as well as a celebrity guest. She returned to gymnastics training in October 2018, after two years off. Although Hernandez previously trained in New Jersey at MG Elite, for her comeback she chose to switch gymnastics clubs and train at Gym-Max in California with coaches Jenny Zhang and Howie Liang. She was invited to the national team training camp held November 15–18, 2019, after spectating at the U.S. Championships in August and speaking to team coordinator Tom Forster while there.
2020 In January 2020, Hernandez said that she was focusing on meets beginning in late May 2020: the
U.S. Classic,
U.S. Championships, and
U.S. Olympic Trials. As the February camp was a selection for spring international meets, Hernandez could not participate in competitions held in March and April 2020. According to team coordinator Tom Forster, Hernandez accepted an invitation to the April camp. On April 29, Hernandez's former coach
Maggie Haney was suspended by USA Gymnastics for eight years due to abusive conduct. Hernandez testified against Haney at the USA Gymnastics hearing, Haney publicly humiliated Hernandez for her weight, leading Hernandez to binge and purge. She also forced Hernandez to train and compete while injured. In 2020, Hernandez said that she still struggled with depression and
disordered eating that began due to Haney's abuse. Within the gymnastics community, Haney's suspension was seen as progress in the aftermath of the
USA Gymnastics sex abuse scandal.
2021 In February, Hernandez returned to elite gymnastics competition at the
2021 Winter Cup, competing on two events. Despite competing a downgraded floor routine, Hernandez managed to hit a clean beam routine to finish fifth on the event behind
Skye Blakely,
Jordan Chiles,
Sunisa Lee, and
Konnor McClain. Then at the
2021 U.S. Classic, she competed on the vault and balance beam, but she fell off the balance beam. In June, Hernandez was scheduled to compete at the 2021 U.S. Championships. However, she had to withdraw from the competition after hyperextending her left knee in balance beam warm-ups. She was not added to the national team, and she did not qualify to compete at the upcoming
Olympic Trials. She later shared that she had a
torn meniscus, a bone bruise, and a cyst. Hernandez participated in
Simone Biles'
Gold Over America Tour in the fall of 2021. She retired from competition in 2021. ==Television roles and media appearances==