Background

Many training providers, boot camps and other forms of training alike, inform us how effective their individual training programmes are in burning calories in comparison to others.  However, the number of calories an individual actually burns (i.e. energy expenditure) during a given workout will vary and depends on a number of factors:

1. Characteristics of the Exerciser: certain characteristics of the exerciser can affect the magnitude of the exercise response.  The basic pattern of the response is similar but the magnitude of the response may vary with the individual’s sex, age, and/or physiological status, such as health and training level.
   1. Weight: basically lighter people will burn fewer calories than heavier people.
   2. Body Composition: this is the percentage of muscle and fat that makes up an individual’s body; muscle burns calories and fat does not.
   3. Age: child, adolescent, adult or older adult.
   4. Health: health conditions (e.g. heart disease or diabetes) and recovery from illness and older age can affect the exercise response.
   5. Training Level: an individual’s current training level may impact on the exercise response.
   6. A person may also burn more calories if they are muscular and lean and have developed a high metabolism through consistent strength training.
2. Environmental: many physiological variables are affected by environmental conditions, most notably temperature, relative humidity (RH), and barometric pressure.  Normal responses typically occur at neutral conditions (20–29 °C [68–84 °F]; 50% RH; and 630–760 mmHg, respectively).  An individual’s normal exercise response can be affected by one or a combination of the following conditions inadequate sleep, illness, time last eaten, time last exercised and/or taking any prescription or non-prescription drugs or supplements.  If one or more of these conditions is met, the expected exercise response might not occur.
3. Metabolic Rate (MR): is the rate of energy metabolism, i.e. the number of calories required to keep your body functioning at rest.  Exercise, stress, fear and illnesses will increase your MR.  A person’s MR is relative to their body mass, age, weight, height and gender; it is widely regarded that men need more calories than women.  There are two formulae used to calculate MR, in [kcal/24hrs] for men and women respectively:
   1. Men: 66.47 + (13.7 * weight [kg]) + (5 * size [cm]) − (6.8 * age [years])
   2. Women: 655.1 + (9.6 * weight [kg]) + (1.8 * size [cm]) − (4.7 * age [years])
4. Modality (or mode): means the type of activity or the particular sport and is often classified by:
   1. The type of energy demand (aerobic versus anaerobic);
   2. The major muscle action (continuous and rhythmical (e.g. walking, cycling and swimming), dynamic resistance (e.g. jumping sprinting and weight lifting) or static); or
   3. A combination of the energy system and muscle action.
5. Intensity: is described as either maximal or sub-maximal:
   1. Maximal: this simply refers to the highest intensity, greatest load or longest duration an individual is capable of completing.
   2. Sub-maximal: this can be described in one of two ways:
   3.  Absolute Workload (Set Load): is a load that is known or is assumed to be below an individual’s maximum.  Using this method, if individuals vary in fitness then some will be challenged more than others.  Generally, those who are more fit in terms of the component being tested will be less challenged and so will score better than those who are less fit and more challenged.  The use of an absolute load allows for the ranking of individuals based on the results of a single exercise test and is therefore often used in physical fitness screenings or tests (i.e. press-ups).
   4. Relative Workload (Load Prorated to Each Individual): A load may be set at a percentage of an individual’s maximal heart rate, maximal ability to use oxygen, or maximal workload.  All individuals are therefore expected to be equally challenged by the same percentage of their maximal task. This should allow the same amount of time or number of repetitions to be completed by most, if not all, individuals.  If all individuals are equally motivated, they should all be able to perform the same total number of repetitions. Relative workloads are occasionally used in physical fitness testing but are more frequently used to describe exercises that are light, moderate, or heavy in intensity or to give guidelines for exercise prescription.
6. Duration: the length of time that muscular action continues.  Duration can be:
   1. Short: i.e. 1-3 seconds for an explosive action, such as a jump; or
   2. Long: i.e. 12 hours for a full triathlon and as a general rule:
   3.  The shorter the duration, the higher the intensity.
   4. The longer the duration, the lower the intensity.

It should be noted that sports psychology, aka motivation, plays an important role in the achievement of maximal, and also sub-maximal, levels of exercise.  Also, some of the best calorie burners are high intensity in nature, requiring some degree of aerobic or cardiovascular conditioning.  Some fitness professionals argue the more effort you put into a workout, the more calories you will burn during the workout.  However, this could just as easily be described as another form of exercise intensity.