Energetic; vigorous — showing a lot of energy and actively engaging in activities (used as a na-adjective).
彼は精力的に新規事業に取り組んでいる。
He is energetically working on a new business venture.
精力的な活動のおかげで、売上が伸びた。
Thanks to energetic activities, sales increased.
高齢でも精力的に趣味を続ける人がいる。
There are people who energetically continue their hobbies even in old age.