Physical fitness includes having a strong heart, powerful muscles, balance and agility, muscular endurance and speed and quickness. To improve your fitness in these areas, you'll need to create different workouts by varying the intensities at which you perform your exercises, such as using more resistance to build strength, and working at higher speeds for short durations to build speed. For many people, basic fitness includes your ability to perform physical activity with a sound cardio, strength and endurance base.
To exercise, work, do daily chores and play sports, you’ll need varying levels of cardiorespiratory capacity and stamina, muscle strength and endurance, footwork skills and speed. Training for one type of fitness often requires different types of exercises than training for another type of fitness. For example, strength training uses heavy weights and slower muscle movements than sprint training, which is performed with little resistance and high-speed muscle movements. These different types of fitness workouts recruit different muscle fibers and burn different amounts of fat and glycogen. It's best to focus on strength and endurance exercise during a sport off-season, and work on speed and recovery during the preseason and in season.
Physical activity boosts the immune system. This is dependent on the concentration of endogenous factors (such as sex hormones, metabolic hormones and growth hormones), body temperature, blood flow, hydration status and body position.[37] Physical activity has shown to increase the levels of natural killer (NK) cells, NK T cells, macrophages, neutrophils and eosinophils, complements, cytokines, antibodies and T cytotoxic cells.[38][39] However, the mechanism linking physical activity to immune system is not fully understood.
Bioelectrical Impedance - This test measures body composition. Using either a hand-held or at-home scale, a slight electrical signal is sent through either the hands or feet. Body fat percentage is estimated based on the speed in which the signal passes through body tissues. According to the American Council on Exercise (ACE) men with a body fat percentage of 14-17% and women with a body fat percentage of 21-24% are considered to be in the 'fitness' category.
Possibly one of the most important parts of fitness training is flexibility and mobility. Flexibility is the ability of your muscles to stretch, and mobility is being able to move your joints and tissues through their full range of motion. Both are important to athletic performance and for avoiding injury. Muscles and joints that are flexible and mobile — as well as strong — are much less susceptible to sprains and other injuries.
New (July 2011) guidelines in the United Kingdom include the following points: The intensity at which we exercise is key, and light activity such as strolling and housework is unlikely to have much positive impact on the health of most people. For aerobic exercise to be beneficial it must raise your heartbeat and make you sweat. The more exercise you do, the better. Everyone should do a minimum of 150 minutes a week of moderate-intensity aerobic exercise but that really is the minimum for health benefits. If you can go beyond 150 minutes, you’ll gain even more health benefits. Sedentary time (time spent sitting down to watch TV, use a computer, read or listen to music) is bad for your health, even for those who are achieving 150 minutes of exercise a week. These guidelines, are now much more in line with those used in the US, also include recommendations for muscle-building and bone strengthening activities such as lifting weights and yoga.
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.
A comprehensive fitness program tailored to an individual typically focuses on one or more specific skills,[7] and on age-[8] or health-related needs such as bone health.[9] Many sources[10] also cite mental, social and emotional health as an important part of overall fitness. This is often presented in textbooks as a triangle made up of three points, which represent physical, emotional, and mental fitness. Physical fitness can also prevent or treat many chronic health conditions brought on by unhealthy lifestyle or aging.[11] Working out can also help some people sleep better and possibly alleviate some mood disorders in certain individuals.[12] 

To get in top physical shape, you’ll need to work on three different areas of cardiorespiratory fitness. Capacity is the amount of work you can do, such as how fast you can perform a sprint or dash. Stamina refers to how long you can exercise. For example, a sprinter is faster than a marathon runner, but probably can’t run as long or as far as the marathoner. Anaerobic conditioning helps you work at very high intensities and helps you recover more quickly afterward. For example, many basketball players have no problem making fast breaks down the court, but afterward, you see them grabbing their knees, gasping for breath as they try to recover. Interval training consists of many high-intensity bursts of activity, each followed by a recovery period. These recovery periods, which occur many times during an interval workout, help you improve your ability to catch your breath after a point or play and recover for the start of the next one.
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There are different categories or types of physical fitness training. Each corresponds to a defined purpose or fitness goal such as the development and improvement of one or more of the five dimensions of physical fitness, or for participation in a particular type of sports and rehabilitation through physical training, among others. Note that the different types of training also correspond to the different categories or types of exercises.

Before the industrial revolution, fitness was defined as the capacity to carry out the day’s activities without undue fatigue. However, with automation and changes in lifestyles physical fitness is now considered a measure of the body's ability to function efficiently and effectively in work and leisure activities, to be healthy, to resist hypokinetic diseases, and to meet emergency situations.[4]

After your workout, perform static stretches, holding each stretch for 30 seconds or more. Static stretches help the muscle fibers relax after being stressed. Post-workout stretching can help you recover more quickly, and it may also slightly reduce the soreness that can occur for a few days after a strenuous workout. Examples of static stretches include:
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.
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.
^ Colbert LH, Visser M, Simonsick EM, Tracy RP, Newman AB, Kritchevsky SB, Pahor M, Taaffe DR, Brach J, Rubin S, Harris TB (July 2004). "Physical activity, exercise, and inflammatory markers in older adults: findings from the Health, Aging and Body Composition Study". Journal of the American Geriatrics Society. 52 (7): 1098–104. doi:10.1111/j.1532-5415.2004.52307.x. PMID 15209647.

Studies have shown that physical activity can improve mental health and well-being.[45][46]This improvement is due to an increase in blood flow to the brain and the release of hormones. Being physically fit and working out on a consistent and constant basis can positively impact one's mental health and bring about several other benefits, such as the following.[47]

Sam Ashe-Edmunds has been writing and lecturing for decades. He has worked in the corporate and nonprofit arenas as a C-Suite executive, serving on several nonprofit boards. He is an internationally traveled sport science writer and lecturer. He has been published in print publications such as Entrepreneur, Tennis, SI for Kids, Chicago Tribune, Sacramento Bee, and on websites such, SmartyCents and Youthletic. Edmunds has a bachelor's degree in journalism.
The Physical Activity Guidelines for Americans were created by the Office of Disease Prevention and Health Promotion. This publication recommends that all adults should avoid inactivity to promote good health mentally and physically. For substantial health benefits, adults should participate in at least 150 minutes a week of moderate-intensity, or 75 minutes a week of vigorous-intensity aerobic physical activity, or an equivalent combination of moderate- and vigorous-intensity aerobic activity. Aerobic activity should be performed in episodes of at least 10 minutes, and preferably, it should be spread throughout the week.
Eccentric training is another type of physical fitness training centered on improving eccentric muscle contraction. As a backgrounder, this type of muscle contraction occurs when the muscle elongates or lengthens from the influence of an opposing force. The contraction happens explicitly when a muscle gives in or goes with the flow or direction of an opposing force.
Many of the activities you do to build strength will also help your balance. Balance is partly a matter of developing your small stabilizer muscles that provide support and keep you steady. Free weight exercises, such as lunges and deadlifts, will help strengthen the stabilizer muscles. Even better, include some single-leg exercises, such as single-leg deadlifts and pistol squats, in your strength-training routine.