In training the desired result dictates the mode of exercise. Some folks want to have a beach body, while others have a more functional or competitive motivation. Most agree that what you train at is what you get better at. (Lifting weights has minimal benefits for running a 5K) With minor disagreements it is generally thought that lifting very heavy objects 1-6x produces strength, lifting heavy 8-12x makes one stronger but also bigger and 15+ is for endurance. Obviously the actual weight needed depends on a person's individual strength (doing fifteen presses with ten pounds may be a heavy work out for a tiny, sixty year old woman, but next to nothing for a twenty year old athlete). There has to be some work involved to accrue benefits. (by analogy a baby's book on Jesus is not going to be the recommended material to embrace to grow in knowledge of the Lord for a 'churched' adult)
Someone who wants to get very strong, therefore tends to train in the lower range. Body builders go for the middle range. Obviously there are other factors (nutrition and sleep) but generally this is what you will usually be told. A repetition is one movement. A set is an isolated bundle of repetitions. (Repetitions done in sequence without resting in between, once a set is complete then one rests) The volume is the number of total repetitions times the number of sets (e.g. 3x5 or 2x12). Intensity has to do with how hard the person is working (compared to maximum effort). High intensity leaves you winded, heart pounding and shaking. Frequency has to do with how often each week someone is engaged in training.
Intensity can not be sustained over long periods of time. No one can lift their maximum poundage more than once or twice. An increase in duration requires a decrease in intensity. Many advocate mixing things up so that on a regular basis you mix high intensity with moderate intensity. It gives the body time to rest and the central nervous system needs some down time as well. There is a limit on what you can do. There is also an optimal range for improvement. So the question of efficiency enters the equation. How to get the most result with the least amount of time is a practical question.
Some years ago I read an article in a running magazine titled World's Fittest Fat Man (or something to that effect). It detailed, with photos, a pretty amazing case of a man who looked obese, yet ran consistently long distances and was involved in very demanding marathon races. The question was, how could someone running so far on a regular basis look like this? The answer was 'conservation of energy.' In other words, he did not move much the rest of the day and his calorie intake exceeded his daily energy output. Anyone trying to lose weight by 'running' has had the moment after a "long run" (for me it was an eight miler) when they do the math and realize that the last exhausting hour was worth one snickers bar. It is devastating to learn that you (a normal person with a normal life) just cannot burn off enough calories exercising to be able to eat anything you want. So what about spirituality?
In spiritual disciplines, we also have some high intensity and low intensity options. We must make choices based on our natural preferences (it is hard to stick with something you hate doing), the goals (sometimes unpleasant things are required to become what we want), and the needs we are addressing (in response to the call of God and the cries of others). Just as a normal guy cannot walk in the gym, hoist a hundred pounds over his head for two dozen repetitions and repeat that for five sets, so a normal person cannot just enter into a mystical communion with Christ and illicit all manner of visions and spiritual blessings. That is not how it works.
Long periods of intense, focused prayer are exhausting, mentally and emotionally, as well as exhilarating (just like exercise). However, most of us need to build slowly and brief moments of intense are more likely our limit. And in addition to that, like the "fat fittest man" we need to remember that the rest of the day matters. An hour of power to start the day needs to be supplemented by moments of low key prayer and meditation. However, snatching a minute here and a minute there needs a foundation of more extensive focused discipline. [that is if you want to grow spiritually]
You cannot spend thirty minutes reading the Bible and praying and then spend your day forgetting about God. You have to be kind and generous, have a listening heart and practice service all day long. Sometimes we are not on-task, we are not consciously aware of God, but that does not matter as much IF we are living a life consistent with our prayers/spiritual disciplines.
Most of us cannot schedule hours and hours of exercise each day, and many of us could not sustain such a rigorous schedule if we could; our bodies would break down (and relationships would suffer, as would work, etc.). However, if your schedule does not allow for more than ten minutes twice a week, you cannot get healthy and strong. Likewise with the spiritual disciplines. For most of us it requires a daily effort. Some "moderate" exercise daily (thirty minutes) is the base. So, likewise, a daily regiment of prayer (meditation and listening, too) is needed. If we have set a time(s) each day to do this, then perhaps once or twice a week we can hone in for the more "intense" prayer.
One disclaimer, unlike physical improvements, spiritual growth is harder to discern and measure. One can see a belly disappear, or recognize that six months ago I had trouble lifting 100 pounds and today I can lift 150 ten times. With spiritual advancement it is not always observable (although others tend to be able to see it). Here is where the analogy breaks down. The spiritual is about union with God in Christ (not self perfection). Obviously growth is part of the deal (one will know more and be better) but it is not the goal. God is. So I hope the analogy is not creating confusion. We continue later...