When I was in high school, I was a runner. I wasn't a jogger. I wasn't someone who just wore running shoes and running clothes. I was a runner. On an average day, I ran somewhere between ten and fifteen miles during my workout. I ran the half mile in a little under two minutes, the mile in under five, and my best time ever in a 5K was 17:15. That's three consecutive sub-six minute miles. Again I say, I was a runner.
It was clearly observable that I was a runner. My parents almost went broke trying to keep me fed, as I ate about 4000 calories a day. Our Tupperware got so little use that it dry rotted. A 10-pack of pork chops meant that my parents and little sister got one each, and I ate everything else. But even eating that much, I couldn't gain weight if I'd wanted to do so. I was a 6', 145 pound lean, mean running machine.
Looking at me with street clothes on, you wouldn't think that I was much in the way of strength, most probably would guess me to the arch-typical "98 pound weakling". But they were wrong. Dead wrong. Since I also pole vaulted, I really didn't want to gain much in the way of mass, I wanted strength instead. And strength is gained by muscle density, not muscle mass.
If you talk to a body building type, they'll tell you that muscle mass is developed by working out using high weight amounts and performing low repetitions. Muscle density, on the other hand, is developed by using low weight amounts and performing high repetition. As an example of this, find an older, skinny automotive mechanic and try to have a hand squeezing contest with him. He'll crush your hand like it's origami. Because for years, he's been using his hands thousands of times a day. When I occasionally went to the gym, I did seated calf raises with 450 pounds. The first 3 of my 5 sets of 15, I slapped the weights. That means that I threw them up so hard and fast that they lifted off my knees. When I did bench presses, I took the 45 pound bar and did at least 100 repetitions straight. Doesn't sound like much, until you try to do it. Finally, definition of muscle groups is developed by doing a multitude of different exercises, making sure not to overlook or overwork any area or areas. Exercise guys have a variety of ways to ensure this, but the goal is to make sure that you don't look like Arnold Schwarzenegger above the waist and Olive Oyl below the belt.
About this time, you're asking yourself, what in the world does this have to do with Christianity, or have I been suckered into reading a glory days bragging session? No, there is indeed a theological point to all this.
How does the Bible call a follower of Jesus most of the time? A disciple. One who follows the disciplines of becoming like their Master. 1 Timothy 4:7b tells us "... On the other hand, discipline yourselves for the purpose of godliness." (NASB) The disciplines of a disciple include but are not limited to prayer, reading the Bible, meditation (mulling over Scripture, not contemplating your navel), worship, service, fasting, solitude, submission, humility, confession, stewardship and charity.
Now, let's consider the muscle development rules with regard to discipleship. If you want strength in your Christian life, you need to do small things over and over and over and over and over and over and over (are you getting the point?) Conversely, if you perform large things on a rare basis, it might very well result in you getting a massive ego, that is, getting puffed up. Again, care must be taken to exercise all of the spiritual disciplines, or you might wind up being a disciple with massive arms of prayer and pencil legs of fasting.
To exercise my own discipline of confession, I am HORRIBLE at spiritual disciplines. But I am working on building up my spiritual muscles. I encourage you to do the same.