This is the 9495th most frequent Japanese word.
精力
Vitality; energy.
In this sentence, '精力的に' means 'energetically,' referring to someone putting effort and enthusiasm into their work.
彼は精力的に仕事をしている。
He works energetically.
Here, '精力' refers to 'vigor or energy,' emphasizing the maintenance of physical vitality.
老人は精力を維持するために健康的な食事をしている。
The elderly maintain vigor through healthy eating.
In this example, '精力を集中させる' implies focusing one's mental or physical energy on a specific goal.