Archived from my FB page from Dec 30, 2016
In my friend Charynn McCurdy's pursuit of physical fitness, one of the less well understood aspects of training is often characterized as "aerobic training". This is a bit misleading, in a couple of ways.
First, aerobic activities are basically any physical action that is performed at a sufficiently brisk pace as to induce a temporary anaerobic condition in the person doing it. In reality, "aerobic training" consists of training yourself to continue functioning at an accelerated pace of activity in a condition of the body being unable to input sufficient oxygen into the bloodstream to relieve the anaerobic condition. Aerobic training induces a shortage of oxygen in the bloodstream so that you can train to work in that condition.
Second, weight lifting is an excellent form of aerobic training. You just have to use lighter weights than you ordinarily would, and perform the chosen lifts at an accelerated pace and for extra reps/set. This is an excellent way to break up your strength training routine occasionally.
Mostly, and most of the time as well, people focus on treadmills, elliptical machines, stationary bicycles and the like for their usual endurance training while in the gym. The primary purpose of which is to elevate your heart rate and air exchange rate, while sustaining a moderate level of muscle stress over as many of the large muscle groups as are involved in the activity, for as long a time period as reasonably possible. There is always the old stand-by, going outside for a walk or a run, but this is frequently difficult for sailors aboard ship.
I'm going to stick to the treadmill here, but do try out the other machines available to you as you can.
As with weight lifting, you want to discover your initial performance parameters, but instead of "how much can you lift?", you want to find out "how far can you walk in how much time?". A reasonable starting point might be a pace of 3 mph for 20 minutes, which would equal 1 mile walked in that amount of time. Don't be disappointed if you can't do this the first time you try. It seems easy (and it is, really), but most of us have no idea of just how little physical endurance we actually have. We can remember doing (insert some memory of past athletics here) back in high school (or wherever) and don't realize just how transitory a skill set physical endurance actually is. Rule of thumb here; every day you don't endurance train, you lose the gains of a day you did.
Once you can do 20 minutes at 3 mph, increase the pace to 3.1 mph and see how many minutes it takes you to reach 1 mile. Increase the pace gradually over each training session in an effort to build yourself up to 3.5 mph, which is about as fast as you can walk.
There is a transition from walking to running on a treadmill that isn't as noticeable when running outside on a track or path. It's harder to maintain your balance within the relatively narrow confines of a treadmill's rails than people appreciate. One of the fundamental training lessons running coaches impart is how to run forward, and not up-and-down or side-to-side during your stride. You're going to have to teach yourself how to do this, or you won't have much success as a runner generally and especially on a machine.
Watch people running; see how many of them have their heads bouncing up and down rather than maintaining an even distance above the ground. Those last ones are the good runners. What worked for me was to put my hands on the rails and jog along (maybe 3.7 or 3.8 mph) and feel what stride motions in my legs and hips resulted in the least amount of movement of my elbows (both laterally and vertically) while maintaining that pace. Then figure out how to make that combination of hip and leg motions your regular running stride. As you up the pace, recheck your stride for excess upward or lateral motion and focus on making the necessary stride movement corrections. It is called endurance TRAINING, after all.
You don't want to spend more than 20 minutes a day endurance training (as a distinct segment of your overall fitness routine), but you do want to train to complete at least 1 mile each session. As with weight strength training, you can vary the pace, distance, and time (if you can run 1 mile in 6 minutes, you can theoretically run 3 miles in 18 minutes - if you actually do that, congratulations, you're an average line Marine grunt; CNO will be so proud) (yes, that is indeed a 10 mph pace - you're gonna be a while getting there). The point of this is to train yourself to a degree of physical capability that is likely to exceed the requirements of your normal duty day (or just life its own self). This reduces the effects of exertion on you generally, and makes you capable of doing more for longer on the hopefully rare occasion when that may be the difference between you living or dying (or only just hearing harsh language from some bystanding CPO).
On the days when you simply don't have the time to do anything but one form of training, choose endurance training over anything else, as physical endurance is what is most necessary over the broadest range of activities you can find yourself confronted with.