Question: "Should a Christian exercise? Is exercise something Christians should be focused on?"
Answer: As with many things in life, there are extremes in the area of exercise. Some people focus entirely on spirituality, to the neglect of their physical bodies. Others focus so much attention on the form and shape of their physical bodies that they neglect spiritual growth and maturity. Neither of these indicates a biblical balance. First Timothy 4:8 informs us, "For physical training is of some value, but godliness has value for all things, holding promise for both the present life and the life to come." Notice that the verse does not negate the need for exercise. Rather, it says that exercise is valuable, but it prioritizes exercise correctly by saying that godliness is of greater value.
The apostle Paul also mentions physical training in illustrating spiritual truth in 1 Corinthians 9:24-27. He equates the Christian life to a race we run to "get the prize." But the prize we seek is an eternal crown that will not tarnish or fade. In 2 Timothy 2:5, Paul says, "Similarly, if anyone competes as an athlete, he does not receive the victor's crown unless he competes according to the rules." Paul uses an athletic analogy again in 2 Timothy 4:7: "I have fought the good fight, I have finished the race, I have kept the faith." While the focus of these Scriptures is not physical exercise, the fact that Paul uses athletic terminology to teach us spiritual truths indicates that Paul viewed physical exercise, and even competition, in a positive light. We are both physical and spiritual beings. While the spiritual aspect of our being is, biblically speaking, more important, we are to neglect neither the spiritual or physical aspects of our health.
So, clearly, there is nothing wrong with a Christian exercising. In fact, the Bible is clear that we are to take good care of our bodies (1 Corinthians 6:19-20). At the same time, the Bible warns against vanity (1 Samuel 16:7; Proverbs 31:30; 1 Peter 3:3-4). Our goal in exercise should not be to improve the quality of our bodies so that other people will notice and admire us. Rather, the goal of exercising should be to improve our physical health so we will possess more physical energy that we can devote to spiritual goals.