Can Intervals Help With Weight Loss Post-Workout?

What is Excess Post-Exercise Oxygen Consumption (EPOC)?

As a cyclist, you’re no stranger to the exhilaration of the open road, the rhythm of the pedal strokes, and the pursuit of peak performance. But did you know that the benefits of your ride can extend beyond the road? In this toolbox article, we will learn more about excess post-exercise oxygen consumption (EPOC) and see if it’s a helpful tool for weight loss, or just a trendy fitness buzzword.


Climbing intervals

What is EPOC?

Excess Post-Exercise Oxygen Consumption (EPOC), often referred to as the “afterburn effect,” is a physiological phenomenon that describes the elevated oxygen consumption and energy expenditure that occurs after an exercise session has been completed. In other words, EPOC represents the additional amount of oxygen the body needs to return to its pre-exercise state and recover from the stress and energy demands of the workout.


Figure 1. Oxygen consumption during & after exercise. Notice the ‘Oxygen deficit’ at the start of exercise must be repaid following exercise as ‘EPOC’. Taken from Arney, et al., 2019.

 

EPOC occurs because exercise places various stresses on the body, including elevated heart rate, increased respiration, and the breakdown of energy substrates like fat & carbohydrates. After the exercise is completed, the body continues to consume oxygen at an elevated rate to:

  • Replenish oxygen stores within the body.
  • Clear accumulated metabolic byproducts
  • Restore the body to homeostasis, including body temperature, heart rate, and other physiological processes

EPOC results in additional calorie expenditure and can persist for a period of time, depending on factors like exercise intensity & duration. High-intensity and interval-based exercises are thought to produce a more pronounced and extended EPOC compared to lower-intensity, continuous exercise. We’ll review a 2016 study that investigated the role of exercise intensity & duration on the afterburn effect and see if EPOC can be a major contributor to fat loss and body composition changes.


Sprint interval training

What did they test?

Researchers wanted to understand how exercise type impacts EPOC and overall energy expenditure (EE). They compared 3 different types of exercise to a non-exercise control condition:

  • Steady State Exercise (SSE) – 30 min @ 80% maximum Heart Rate (HRmax). This would be analogous to a high zone 2 endurance ride.
  • High-Intensity Interval Exercise (HIE) – 4 x 4min @ 95% HRmax with 3 min active recovery between efforts. This would be similar to ‘Seiler 4 x 4 intervals’
  • Sprint Interval Exercise (SIE) –  6 x 30 sec ‘Wingate’ sprints with 4 min active recovery. Participants were encouraged to ride has hard as possible for each 30s sprint. I should point out that this type of exercise is certainly not easy, nor fun. In fact, SIE resulted in 3 participants failing to complete the study.

Who did they test?

Thirteen recreationally active men were recruited to participate, though only ten would complete the study. Compared to other cyclist-specific studies we’ve reviewed in the past with elite level cyclists, these participants are slightly less well trained:

  • Age: 24 +/- 4 years
  • Weight: 73.1 +/- 8.2 kg
  • Relative VO2max: 45.9 +/- 7.2 mL/kg/min

What did they find?

For 3 hours after exercise, cumulative EPOC & net energy expenditure were greater from sprint intervals than from steady state or high intensity intervals, suggesting that the “afterburn effect” from sprint training was greater than high-intensity intervals or steady state exercise.


Figure 2. Oxygen consumption (in L/min) against time (in minutes) for the 3 exercise conditions, relative to a non-exercise control. Notice that all 3 exercise types resulted in some EPOC, but Sprint Interval training (white squares) resulted in the greatest net amount of EPOC. Image taken from Tucker, et al., 2016.

 

As you might expect, oxygen consumption was greater during exercise for the steady state & high-intensity exercise conditions, compared to sprint training. There was no significant difference between SSE & HIE. In other words, the sprint interval exercise used the least amount of energy during exercise.

Interestingly, despite greater EPOC and EE following exercise in sprint exercise, steady state exercise still resulted in the greatest total oxygen consumed & net energy expended. There was also a trend for more oxygen consumed and greater energy use in steady state compared to high-intensity interval exercise, but it did not reach statistical significance. The results are well-summarized in the figure below:


<emFigure 3. Oxygen consumed during exercise (black) and after exercise – e.g. EPOC  (white) for the 3 different exercise conditions: steady state exercise (SSE), high-intensity interval exercise (HIE), and sprint interval exercise (SIE). Despite SIE having significantly more EPOC, SSE still resulted in the greatest total oxygen consumed. Image taken from Tucker, et al., 2016).

So… What’s the Verdict?

Sprint Interval training certainly does elicit a greater EPOC than both steady state exercise and high-intensity interval exercise. However, the exercise energy expenditure for sprint training, even with 6 maximal efforts, was significantly less than that for SSE and HIE. Also, the combined exercise + post exercise net energy expenditure was lowest for SIE, which suggests that EPOC following high-intensity interval and sprint interval training is unlikely to be the major contributor to fat loss and body composition changes.

Therefore, including some high-intensity and sprint intensity intervals can be a beneficial addition to your training and results in increased EPOC. However – based on the results of the study we reviewed today – there is still certainly an argument that continuous moderate-intensity exercise can increase your total energy expenditure, which is a major contributing factor to weight loss.

That’s all for this month! Stay safe, ride fast, and I’ll see you next time!

References

Arney, Blaine E. M.S., ACSM-EP; Foster, Carl Ph.D., FACSM, MAACVPR; Porcari, John Ph.D., FACSM, MAACVPR, ACSM-RCEP. EPOC: IS IT REAL? DOES IT MATTER?. ACSM’s Health & Fitness Journal 23(4):p 9-13, 7/8 2019.

 

Tucker WJ, Angadi SS, Gaesser GA. Excess Postexercise Oxygen Consumption After High-Intensity and Sprint Interval Exercise, and Continuous Steady-State Exercise. J Strength Cond Res. 2016 Nov;30(11):3090-3097.

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