What is "Fitness"?

"Quality" has been defined as "Fitness for use". What might be "Quality" for a fish-camp might not be quality in a mansion.

It also ties together the idea that "Fitness" is related to expectations of future use.

The body of a man delivering barrels of beer the old fashioned way will be exposed to different use than a surgeon who specializes in eye surgery who will have different requirements than a marathon runner or a long-distance swimmer or a man caring for his disabled spouse.

To improve your "fitness" you need to have a general concept of the demands that future events might put on your body.

It is convenient to divide various aspects of "fitness" into groupings that can be addressed (improved) in specific and focused ways. The dividing is more of a convenience than a biological fact.

Here is a common set of "groupings":

• Strength
• Endurance
• Balance
• Flexibility
• Response time
• Precision

Strength

Strength is the ability to generate force. Depending on the task, various muscle-groups will be activated to generate that force.

Lifting weights (or body-weight exercises) are the most common ways to build strength.

Important caveat: Lifting free-weights also has in impact on balance and flexibility. For example, squats require that you maintain your balance and for first-timers they require that you extend your glutes and front quads more than you would for most normal, everyday tasks. Just because an exercise is considered a "strength" or "endurance" or "balance" exercise does not mean that they don't impact other aspects of fitness.

Endurance

Endurance is "how long can you sustain a particular activity".

It is strongly linked to heart, circulatory and lung function.

Physiologists talk about fast-twitch muscles and slow-twitch muscles. Endurance is usually driven by the slow-twitch muscles. 

Another perspective is that the strength muscles are like the breast meat of a chicken. It is not very vascular but depends on the reserves of oxygen and carbs stored in the muscle...like a battery that is depleted and then recharged via a trickle charger. The endurance muscles are much more richly supplied with blood (oxygen) because they are expected to run steady-state for long periods of time. On a chicken, that would be the legs and thighs which are dark-meat.

Pretty much any movement will improve heart-circulatory-lung function, so in a sense all exercises positively impact endurance.

Since heart-disease is huge killer of Americans (and a factor in Erectile Dysfunction), endurance exercises will likely have a greater impact on your quality-of-life than the exercises aimed at the other facets of fitness.

Balance

Balance sounds like a simple thing but it is an activity that integrates many functions.

To balance, you must sense that you are falling out-of-balance (inner-ears, visual cues, pressure on bottom of foot or other places where your body is touching solids)

To restore your balance, you must activate appropriate muscle-groups with appropriate levels of force in near-real-time. So there are sensing, processing, strength and modulation functions that must be integrated to "balance".

Flexibility

Flexibility also plays into "balance". If you don't have good flexibility it is easy to panic and to over-react when you feel yourself tipping over.

Toddlers are very flexible. Quicksilver can squat down, flat-footed and touch her butt to the ground. We lose flexibility as we age as connective tissue cross-links our muscle fibers but much of that flexibility can be regained via stretching exercises.

Response time

Our brains make adjustments based on its perception of how quickly it can activate our muscles. It needs frequent "calibration runs" to keep its lead-time tables up-to-date. Without fresh data, our brains cannot figure out how much to lead-the-duck or how to efficiently coordinate various muscle groups' contributions.

A consequence is that we might over-react when we slip on a bit of ice and wrench our back even if we avoid the fall.

A simple game of catch where you and your sweetheart toss a tennis ball or a light-weight medicine ball is a great way to supply that calibration data. It will also improve your balance.

Precision

Precision is threading a needle, shooting a target, swatting a fly or making a drawing with a pencil.

In general, we have more precision in the low-and-mid range of our muscle strength so having "extra" muscle is an aid to precision.

In general, we have more precision when we are not fatigued so having more endurance than required for a task is an aid to precision.

There is a high degree of command-and-control between brain and muscle-groups when doing precise tasks. Even to the point of making the most delicate adjustments between heart-beats.