Strength

Strength, defined, is the capacity to exert force against a resistance in one effort--like the heave ho in a tug of war or the snatch, clean and jerk in Olympic weight lifting. But anytime we are resisting gravity we are using our strength, which is pretty much all the time. We use strength to get out of bed, take a step and do laundry. Our bones and muscles rise to whatever task we give them over time. Without a job to do, they will go into early retirement.  Sometimes our lives have strength training built right in to them, and we don't need to do much more except balance out the muscles, and release the fascia. Sometimes our lives are very passive and it requires more effort to keep our bodies humming as we might  like. Even for individuals with no performance goals, informed strength training a couple of times a week helps to stabilize weak joints, improve posture and reduce back discomfort, aid balance, minimize bone loss and risk of fractures, increase flexibility and boost metabolism, and ultimately improve ease of movement.

Stamina

From the latin root stamen, the pollen bearing part of a plant, stamina is the ability to sustain effort over a period of time. It is interchangeable with endurance, which means to remain “dur” (hard) or to last.
Stamina refers both to cardio-vascular fitness and a level of muscular strength. Some have none, some have lots. Cycling, running or walking briskly up hills tests the stamina in your legs. Increasing the grade/speed ups the ante. Rock climbing or Capoeira truly challenge your upper body, but carrying home heavy packages, shoveling dirt, and swimming can place sufficient demands to get your heart pumping and blood flowing to those working muscles as needed. About 150 minutes of moderate activity a week gives your heart the love that lasts.

Flexibility

We wow at gumby like maneuvers, but hyper-mobility can compromise joint stability and lead to injury. Flexibility balanced with strength enables joints to move through their full range of motion securely and muscles to function more effectively and efficiently.
 Flexibility assists healthy posture by reducing tension in the muscles that cross joints. Regular flexibility training reduces the stress in working muscles and maintains the synovial fluid that keeps your joints moving freely. Some people are naturally more flexible than others, but everybody can improve what they've got with a little consistent practice.