Also known as exercise after burn, Excess Post-Exercise Oxygen Consumption (EPOC) relates to the amount of oxygen required and therefore the amount of energy expended (above resting values) after an exercise is completed.
As many personal trainers and fitness instructors have clients who exercise to burn calories and lose weight, this blog aims to show how different types of exercise and intensity can have an effect on EPOC.
OXYGEN REQUIREMENTS DURING AND AFTER EXERCISE
Taking part in a personal training session or other form of exercise will cause the blood vessels in the muscles to dilate and there will be a higher blood flow in order to increase the amount of oxygen available.
After exercise, the body requires more oxygen than usual, in order to metabolise the lactic acid produced, to replenish ATP, phosphocreatine and glycogen, and to replenish myoglobin with oxygen.
EPOC, therefore, represents the additional amount of oxygen needed by the body – above a client’s normal resting level – in order to return to the pre-exercise state.
The EPOC effect is most in evidence straight after exercise and it can take anything from 15 minutes to 48 hours for this process to be completed, depending on the intensity of the workout, the gender of the client (EPOC for women can be affected by their menstrual cycle) and their fitness levels.
BURNING ENERGY AFTER A WORKOUT
The body does not only burn calories during exercise; after any personal training session, fitness class or sporting activity, the person taking part will continue to burn energy for some time. However, the amount of energy and the length of time it burns can vary depending on the type of exercise carried out.
LONG SLOW DURATION EXERCISE VERSUS INTERVAL TRAINING
Imagine a personal trainer has two clients:
By running at a slow speed over a long duration, Runner 1 will be working at, say, 60% of their maximal heart rate, which corresponds to low intensity as far as the effect it will have on their cardiovascular system, their core body temperature, the amount of carbohydrate they need as fuel and the amount of oxygen they need to synthesise ATP – the creatine phosphate needed for their muscles to slide together and contract (see our blog on Energy expenditure during different exercise).
At the end of their run, they will only need to repay the oxygen debt to a small degree.
In contrast, Runner 2, who is combining short bursts of high-intensity sprinting with recovery intervals at slower speeds, will be pushing their heart rate up to 100%, requiring more oxygen and using increased amounts of ATP.
The EPOC – or oxygen debt – at the end of Runner 2’s workout will be much higher than that of Runner 1, even though they have spent less time on their workout.
So, if a personal trainer encourages a client to work at a higher intensity, they should expect a greater EPOC effect post workout. The body will be burning calories at a higher rate, it will increase the basal metabolic rate (see our blog on BMRs: Calories, body fat and burning energy) and afterwards the body will have a higher oxygen debt.
In short, Runner 1 will be burning energy at a higher rate for around 30 to 60 minutes after their steady session. Runner 2, meanwhile, will be burning energy at a much higher rate for several hours at least after their intensive interval training, which means anything they consume post workout will be broken down and used more quickly.
EPOC AFTER RESISTANCE TRAINING
Although there have not been many studies to look at EPOS after resistance training, there have been some findings that show that weight training can also elicit a EPOC response, which can have a bearing on weight management.
EPOC AND THE FITT PRINCIPLE
The effects of EPOS and the benefits of interval training can be seen in the FITT Principle (see our blog on Personal Training: The FITT Principle), which stands for Frequency, Intensity, Time and Type, and is used by many personal trainers to help clients train for a particular health or exercise goal.
EPOC AND WEIGHT LOSS
For personal trainers with clients who want to lose weight, it’s believed that a more intensive workout will help as they will increase the calories burned during the workout and also afterwards, because of the subsequent increase in EPOS.
While a personal trainer may want to encourage their clients to carry out interval training and work hard enough to get out of breath in order to increase the EPOC effect, fitness instructors should always bear in mind each individual’s fitness levels.
For a client with specific health issues or recovering from an injury, they may want to alternate walking and jogging, whereas an elite athlete can alternate a steady walk with a sprint. Both will target the EPOC response, just at different rates.