Physical fitness has always been important part of life. It is theorised that when people left a hunter-gatherer lifestyle and formed fixed communities based around agriculture that physical fitness levels declined. This is not to say that levels of physical labour decreased but that the type of work undertaken was not necessarily as conducive to a general level of fitness. As such, regimented fitness regimes were either invented or became more common. This was especially the case in classical civilisations such as Ancient Greece and Rome. In Greece especially physical fitness was considered to be an essential component of a healthy life and it was the norm for men to frequent a gymnasium. Physical fitness regimes were also considered to be of paramount importance in a nation's ability to train soldiers and field an effective military force. Partly for these reasons, organised fitness regimes have been in existence throughout known history and evidence of them can be found in many countries.
Cardiorespiratory fitness can be measured using VO2 max, a measure of the amount of oxygen the body can uptake and utilize.[15][16] Aerobic exercise, which improves cardiorespiratory fitness, involves movement that increases the heart rate to improve the body's oxygen consumption. This form of exercise is an important part of all training regiments ranging from professional athletes to the everyday person. Also, it helps increase stamina.

These types include cardiorespiratory endurance, which is how long or fast a person can perform an activity and how this impacts heart rate and oxygen consumption. Muscular strength, which is how much weight can be moved in relation to repetitions and muscular power, which is how much force can be generated during a given activity. There is also flexibility, how far a muscle group can be stretched or joint can be moved. Balance how long a particular position can be held with or without some type of activity being performed. Speed, how quickly an individual can move from one point to another. And body composition, the amount of fat on the body versus other tissues such as muscle, bones and skin.
Strength, cardiovascular endurance, balance, agility and flexibility should be the goals of any well-rounded fitness program. But how do you go about developing these skills? The key is variety. Don't spend all your time in the weight room or on the treadmill. Include different types of fitness training in your routine and you'll see better overall results in your exercise performance and how your body performs and feels in daily life.
Endurance is your ability to perform physical activity over time. You might be able to serve aces and hit winning forehands and backhands, but if your muscles cramp or you run out of energy after a few games, you won’t win any matches. You build endurance by exercising for longer periods without stopping, working at a slower speed than when you interval train. This type of exercise is usually aerobic, calling on your slow-twitch muscle fibers and burning more fat than glycogen, depending on the speed you work. The slower you work, the higher percentage of your calories burned comes from fat.
Weight-Bearing Exercise. You don't necessarily need to lift weights to build muscle and strength. Any weight-bearing activity that forces your body to work against gravity can make you stronger. This is especially true if you aren't used to exercising, because your muscles will be more challenged by activities than someone who is stronger and more experienced. Examples of weight-bearing exercises include:

Gymnasiums which would seem familiar today began to become increasingly common in the 19th Century. The industrial revolution had led to a more sedentary lifestyle for many people and there was an increased awareness that this had the potential to be harmful for health. This was a key motivating factor for the forming of a physical culture movement, especially in Europe and the USA. This movement advocated increased levels of physical fitness for men, women and children and sought to do so through various forms of indoor and outdoor activity, and education. In many ways it laid the foundations for modern fitness culture.[50] 

People who are physically fit are also healthier, are able to maintain their most optimum weight, and are also not prone to cardiac and other health problems. In order to maintain a relaxed state of mind, a person should be physically active. A person who is fit both physically and mentally is strong enough to face the ups and downs of life, and is not affected by drastic changes if they take place.