Metabolic rate: sports training has a significant effect on weight gain and weight loss

The effects sports and fitness training has on our metabolic rate and calorific needs

Metabolic rate basically refers to the energy that is released by the body.

Sports training can have a significant effect on metabolic rate – this can determine weight gain and weight loss. This is because it boosts calorie burning. This is a result of 1) doing the activity itself 2) the effects of a process known as ‘excess post oxygen consumption’ (EPOC) – of which more later – and 3) by creating a body whose constituent parts (specifically muscle) create an all day and every day increased calorie requirement (again of which more later).

Metabolic rate is comprised of:

  1. Total Daily Energy Expenditure (TDEE)
    This refers to all the energy we expend over a day
  2. Resting Metabolic Rate (RMR)
    60-75% of TDEE is used to maintain RMR. RMR includes all those ‘behind the scenes’ essential bodily functions, such as heart, lung and mental function, but does not account for calories burned when sleeping
  3. Thermic Effect of Feeding (TEF)
    Food provides us with energy, but the process of eating also requires energy. Around 10% of or TDEE is made up of this requirement
  4. Activity
    This may be a surprise but only 10-15% of our total daily energy expenditure comes from physical activity of any sort. However, this relatively small amount can have a huge effect on our body composition, i.e. how much fat we have and how many calories we need to optimally sustain ourselves and our sports/fitness training

How do you know how many calories you are burning during exercise?

When we exercise we increase our metabolic rate as our body boosts its energy output to meet demand. Calories measure the energy release from food (see box).

Research has provided the calorific requirements of numerous sports activities. It should be noted that although these figures are relatively accurate, they vary in regard to:

  1. Your weight. A heavier person will burn more calories, everything else being equal compared to a lighter one, simply because more energy is required to overcome the greater resistance.
  2. Your level of fitness. Someone who is fitter, for example, at rowing will be more ‘energy (and therefore calorie) efficient’ than someone who is less fit. This is why exercise intensity needs to be continually increased (progressively) if increased calorie burning is your objective, for example, in order to achieve a weight loss goal (or negative energy balance – of which more later).
  3. Atmospheric conditions. The body will burn more calories in hotter, humid conditions than in temperate ones. This is due to the energy required to maintain its cooling processes and reduce core temperature
  4. Body types. Certain people – particularly those with lean wiry frames (‘ectomorphs’) – tend to have faster metabolic rates, which can enhance calorie burning.
  5. Metabolic rate generally slows with age, sports and fitness training can do much to challenge this.

Table 1 displays the calories burned during various sport and fitness activities. It will be of use to athlete and coach in terms of calculating calorific expenditure

How to calculate metabolic rate

Following the steps below will enable you to gain an indication of the calorific value of your metabolic rate

Step 1 Calculate your RMR

 

Age: 18-30
Multiply your weight in Kg x 14.7 and add 496
31-60
Multiply your weight in Kg x 8.7 and add 829
Example: 65Kg Individual
65 x 14.7 + 496 = 1451.5 RMR
65 Kg Individual
65 x 8.7 + 829 = 1394.5 RMR

 

Step 2 Estimate your daily activity requirements in calories

Multiply your RMR by your daily activity level as indicated by one of the figures in the table below

 

Activity level Defined as
Not much Little or no physical activity RMR x 1.4
Moderate Some physical activity, perhaps at work or the odd weekly gym visit RMR x 1.7
Active Regular physical activity at work and or at the gym (three visits per week) RMR x 2.0

 

Examples:

25 year old weights 65Kg and has a moderate activity level – 1451.5 x 1.7 = 2466.7 Kcal

40 year old weighs 80Kg and has an active activity level – 1525 x 2.0 = 3050 Kcal

Adapted from Bean, A: The Complete Guide to Sports Nutrition

Excess post oxygen consumption (EPOC)

Sports and fitness training can increase metabolic rate by as much as 20%. This is due to EPOC. Unlike a car when the ignition is turned off, our body’s engine does not stop immediately after we have taken it for a run, row or performed a weights workout. The processes involved in producing the energy required for these and all other sports, fitness and general activity, take a while to slow down and return to base line levels. These processes include, the restocking of muscle fuel (notably a specific type of carbohydrate, known as glycogen) and the normalisation of lactate levels in our body. Lactate is used in energy creation at all times. Its levels increase with exercise. When we stop exercising it is still buzzing around inside us at a great rate. It needs time to slow down and in some circumstances be re-converted back to its original chemical format – and this all requires energy. Additionally, when we workout, particularly using weights, microscopic tears occur in our muscles and it is during the recovery period when these are repaired and our muscles grow stronger – again this requires energy. The more the intense the exercise the greater the EPOC.

Sports scientists have discovered two distinct EPOC phases:

EPOC phase 1

The most significant – in terms of calorie burning – occurs in the two to three hours after training. The less significant given the same criteria lasts up to 48 hours after training.

If you do not factor EPOC in to your calorie requirements you could experience muscle loss, lack of energy and a failure to obtain sufficient amounts of vitamins and minerals needed to optimally maintain bodily processes. Basically your body would be running ‘energy light’ – not getting enough fuel to optimally power it.

Table 1 Energy expenditure and exercise

Energy expenditure in calories per minute for selected activities against selected body weight (Kg)

 

Activity

Kg

59

62

65

68

71

74

77

80

Volleyball

 

3.0

3.1

3.3

3.4

3.6

3.7

3.9

4.0

Easy cycling

 

5.9

6.2

6.5

6.8

7.1

7.4

7.7

8.0

Tennis

 

6.4

6.8

7.1

7.4

7.7

8.1

8.4

8.7

Easy swimming

 

7.6

7.9

8.3

8.7

9.1

9.5

9.9

10.2

Running 8 min/mile pace

 

12.5

13.1

13.6

14.2

14.8

15.4

16.0

16.5

Weight and plyometric (jumping) training burn approximately 5-8 calories per minute dependent on body weight and exercise intensity

How can you specifically measure the amount of calories you burn during a workout?

As well as using the figures from table 1 (and other similar calculators that you can find on the net), you can use:

Calorie counters on heart rate monitors. However, they only provide an estimate of energy expenditure and are about 90% accurate.

Galvanic response. The 100% accurate method is to use devices that measure what’s known as galvanic skin response (basically electrical energy) produced by the body. These are worn usually on the upper arm and the information from them is downloaded. These devices are becoming increasingly available in the fitness and sports world – they were originally the preserve of cardiologists in the medical world.

As a sports or fitness participant you must factor in EPOC when calculating your calorie expenditure and metabolic needs, for the reasons mentioned, if you are to optimise your training.

Muscle as a calorie burner

It was mentioned that increased lean muscle mass can increase metabolic requirements. Muscle is very active body tissue, not only when it is firing to produce sports and fitness movements, but also when it is ‘sitting’ on your body. Research indicates that an additional 0.45Kg (1lb) of muscle burns about 35 calories a day. Now that does not sound a lot, but over 10 days that 0.45kg will have amounted to 350 calories, which is the equivalent of a half hour moderately paced run. So as with EPOC it is important to account for the effects that an increase in lean muscle can have on metabolic rate.

Note: women may not benefit to the same extent as men from increased lean muscle mass calorie burning. This may reflect their naturally higher levels of body fat – with the latter cancelling out the gains made by the former

Understanding food energy

A Kilocalorie (Kcal) represents the amount of energy needed to increase the temperature of 1Kg of water by 1 degree centigrade and is the unit commonly used to measure the energy released from food or burned in sports activities. As in this article, Kilocalories are often referred to simply as ‘calories’. Food packaging also gives energy release in kilojoules (kJ), the international standard for energy. To convert Kcal to kJ, multiply by 4.2 and to convert kJ to Kcal divide by 4.2.

The energy balance equation

In order to lose weight you need to create a ‘negative energy balance’ – that is, to consume fewer calories than you expend. In order to gain weight (and this could be your objective, if you want to increase muscle mass for a sport such as shot-putting), you need a ‘positive energy balance’ – that is, to consume more calories than you expend. And to maintain weight you need to create a ‘balanced energy balance’ – to consume a similar amount of calories to those expended.

As you’ll have realised, metabolic rate is a very important variable in terms of maintaining optimum physical condition and weight. As an athlete or fitness trainer, fully comprehending what effects your training routine is having on it will enable you to optimise your training returns. Failure to do so could result in impaired training response, illness and injury, due to insufficient calories and the optimum supply of nutrients required to maximise physical performance.

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