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Components of Fitness

In order to prescribe the ideal sets, reps and rests for your clients you must understand the components of fitness these variables relate to. This page provides you with all the clarity you'll need..

What is a ‘fitness component’


A fitness component is simply a way of identifying a certain part of a person’s fitness – essentially you are labelling a subset of changes that you want to occur as a component.  For example, if a client wants to be more flexible I’d work on the ‘flexibility’ component of their fitness.  Or, if a client wants to get stronger to compete in a power lifting event I’d work on the ‘strength’ component of their fitness. 

By having components we can analyse someone’s fitness and then focus on developing an area that will best help them meet their goals.  For example if a basketball player wanted to jump higher then as a trainer I’d look at developing explosive jumping power whilst maintaining the other components of their fitness – for example their aerobic fitness and their flexibility.  Another example may be a client who wants to lose weight, and has significant muscle wastage and low aerobic fitness.  So we might decide to work on the ‘hypertrophy’ and ‘aerobic fitness’ components to rebuild some of the wasted muscle and burn calories at the same time.

The fitness components, their definitions and examples are covered in the following table:


personal training speed


The ability to develop and maintain movement as quickly as possible for short durations


Sprinting 100 metres, jabbing in boxing, getting to a drop shot in tennis, escaping an unpleasant situation as quickly as possible


personal training power


The ability to produce maximal or near maximal force very quickly


Throwing a shot put, a left hook in boxing, serving in tennis, slam dunking in basketball, pushing an offensive personal away


personal training flexibility


The ability to move a muscle/tendon around a set of joints and maintain full range of movement (ROM) at those joints


Doing the splits, being able to turn easily when backing a car, reaching wide and low for a volley in tennis, stretching after a gym session


personal training balance and stability


The ability to maintain the centre of mass over the base of support


Not drifting during a jump shot in basketball, not falling over after a golf shot, not falling over when doing lunges or squats in the gym


personal training agility


The ability to change the body’s position quickly and precisely


Changing direction while dribbling a soccer ball, side stepping in rugby, swaying to avoid a punch in boxing


 personal training strength


Strength is the maximum force a person can exert on a given resistance for a set number of repetitions or set time 


Lifting a bed down a set of stairs, carrying six heavy shopping bags in from the car, climbing a rope ladder on an obstacle course, lifting very heavy weights in the gym


personal training bicep muscle


The ability to grow a muscle/group of muscles


Growing total muscle mass in the off-season for a rugby league front rower, building muscle size in the gym, building muscles that have wasted away over time due to a sedentary lifestyle

Muscular endurance



The ability to work a particular muscle or muscle group for longer periods at less than maximal effort


A small craft yachtsmen squatting in the boat for long periods, a snow boarder developing leg stamina for boarding, doing as many push ups as you can in a circuit class

Anaerobic fitness

personal training running race


The ability to sustain high intensity efforts for as long as possible


A 400 or  800 metre runner, a basketball player during several minutes of continuous play, any form of interval training

Aerobic fitness

personal training joggers


The ability to sustain exercise for extended periods of time using large amounts of muscle mass in cyclical (repeated) movement at low to moderate intensities


A 10km run, a triathlon, walking a track, cycling an hour home from work

It’s important to realise that fitness components exist on a continuum rather than as distinct areas as depicted in the previous table.  An obvious example of this concerns repetition ranges with resistance training.  Strength training is typically low repetition with very high loads, hypertrophy is typically high load resistance training for intermediate reps, and muscular endurance is typically high reps with lower loads.  Strength training for example doesn’t ‘stop’ as soon as you do more than 6 reps for example, the training just becomes predominantly hypertrophy training.

In the same vein if I went for a long distance jog I’d primarily be training the aerobic fitness component, but while out on the jog I might get chased by an angry dog causing me to increase my speed considerably to avoid getting bitten.  This would mean that for a short period of time I’d predominantly be working the components of speed and/or anaerobic fitness before returning to training the aerobic fitness component as I reduced my speed when the dangerous dog passed.

What we have done in the exercise sciences is to define fitness components and attach training guidelines to each component.  These training guidelines are known simply as the ideal ‘FITT’ (frequency, intensity, time and type) variables that we must manage to affect the component we want to change or maintain. 

The application of the FITT variables for the different fitness components is covered in more depth in the exercise prescription pages at ptdirect.


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