For many entrepreneurs, health and fitness isn't a personal "interest." Health and fitness play a major role in their success. They know that exercising at moderate intensity for 20 minutes can elevate your mood for up to 12 hours. That exercise can improve memory and cognitive skills.

That exercise can help you better manage stress, a small-business owner's constant companion.

Yep: Fitness and health matter.

But what happens when, say, a massive new project is going to put even greater constraints on your time? When, for a period of time, you know you won't be able to follow your normal routine -- but you want to hang on to as much of your current level of fitness as possible?

As anyone who has been in decent shape knows, having to start over sucks. So what is the least (or shortest) amount of training you can temporarily do while still staying fairly fit?  

That's the question a study published last month in Journal of Strength and Conditioning Research set out to answer. Researchers focused on three basic variables:

  • Frequency: How many days per week you work out
  • Intensity: How heavy, fast, or, um, intense is the workout
  • Volume: How many sets and reps, how many intervals, etc.

So how little is enough?

For cardiovascular endurance -- think VO2 max, the maximal volume of oxygen that can be inhaled and absorbed by a body -- two workout sessions per week allowed participants to maintain their V02 max for up to 15 weeks. (In fact, two workout sessions per week were basically as effective as four.)  

Keep in mind the intensity and volume of those sessions had to stay the same. So, yeah: You can work out fewer times, but when you do work out, you have to go just as long. And as hard.

The same held true when volume was decreased; cutting workouts by one-third to two-thirds the amount of time -- while maintaining intensity and days per week frequency -- allowed participants to maintain their VO2 max for 15 weeks.

Keep in mind, though, that VO2 max is just one measure of fitness. If you're training for a Gran Fondo, reducing the frequency of your rides while maintaining intensity and volume will limit the VO2 max decrease, but without sufficient frequency, your legs won't be able to handle the distance.

As Alex Hutchinson writes in this excellent review of the study, "Don't expect to run your best marathon after a few months of twice-a-week training: your legs, if nothing else, won't be able to handle it."

Now for the bad news. Participants who reduced the intensity of their workouts by a third, while still working out the same number of times per week and at the same volume, saw significant decreases in VO2 max and endurance. Participants who cut their workout intensity by two-thirds lost nearly all the gains they had made from training.

Bottom line? If you want to maintain your fitness for a period of time, you can work out less often. Or you can work out for shorter periods of time.

But you can't go easier. (Which is why studies show that one 23-minute HIIT workout per week is nearly as effective as three -- as long as that one workout kicks your ass.)

So don't fret that all will be lost if circumstances require you to step away from your normal exercise routine. You can work out less often. Or you can work out for shorter periods.

Just make sure that when you do work out, you go as hard as you typically do.

Because, as with most things, quality is the most important variable.