Three simple tests that busy entrepreneurs can use to gauge their strength, endurance

Several owners of small-businesses have understood the concept of diminishing returns: The idea is that, when other variables stay constant, at some point putting in additional time and effort results in increasingly smaller results.

Since resources are always limited, figuring out where to spend the entrepreneurial time so it delivers the best bang for the hour is critical.

The same premise extends to health and fitness. Many try to stay reasonably fit. Not just because it is good, but because exercise helps an individual perform better under stress. Can elevate mood for up to 12 hours. It can also make you a little smarter.

How "fit" is fit enough?

If you want to run a marathon, the definition of "fit" will differ from most. But if you want to compare yourself with other people and see where you currently stand -- and get a sense of where you would like to stand, here are three simple tests you can do at home.

Upper Body Strength

The American College of Sports Medicine recommends using a pushup test to assess upper body strength and endurance. To do pushups, start at the top, go down to the 90-degree mark, and push back up without locking out at the top. Women can do plank-version pushups or modified (from the knees) pushups.

However, research shows that men who could do 40 or more pushups were 96 percent less likely to experience a cardiovascular event than those who could only do 10 or fewer. In fact, pushup capacity was more strongly associated with reduced cardiovascular disease risk than aerobic capacity.

Lower Body Strength

To conduct this test, find a chair that, when you sit on it, puts your thighs at a 90-degree angle to your lower legs. Then put your hands on your hips, lower yourself until your butt grazes the chair, and then straighten back up. Do as many as you can.

Like many things, by increasing the number of squats, one can do is just a matter of time and effort: Do four or five sets of squats to failure three times a week, and in three weeks you'll definitely be stronger.

Squats can strengthen your lower body and core, improve your flexibility, and reduce your risk of injury.

Cardiovascular Fitness

This fitness is a little trickier, since there are a variety of ways to evaluate cardiovascular fitness. Stress tests. Exertion/heart rate tests. Another is VO2 max, the maximal volume of oxygen that can be inhaled and absorbed by a body.

Generally, the higher your VO2 max, the better your cardiovascular fitness within genetic reason.

One way to estimate VO2 max is to use a fitness calculator take a mile walk test.

There are a number of ways to improve your cardiovascular fitness. Walking and jogging can be seen as a great start.Cycling, rowing, elliptical training or if you want to double-dip and get some strength gains at the same time, consider doing HIIT workouts.