Both interval training and moderate-intensity continuous training (MOD) reduce body fat percentage, according to a recent review published in the British Journal of Sports Medicine. Interval training, however, offers a 28.5% greater reduction in total absolute fat mass.
“Interval training may elicit greater weight loss even if the energy expenditure obtained during the interval training is lower or equal to that during MOD,” wrote the authors, led by Ricardo Borges Viana, Faculty of Physical Education and Dance, Federal University of Goiás, Goiânia, Goiás, Brazil. “This may be due to greater resting energy expenditure and fat utilization immediately following interval training exercise.”
Interval training is comparable to MOD but takes less time to perform. The two primary reasons why some people quit exercising are lack of time and lack of results, which interval training could address.
By definition, continuous training, including MOD, results in 55% to 70% of the maximal heart rate (HRmax) or oxygen consumption (VO2) equal to 40% to 60% of maximum VO2 (VO2max).
Interval training is defined as bursts of effort punctuated by recovery periods, or breaks. The two most popular forms of interval training are high-intensity interval training (HIIT) and sprint interval training (SIT). Specifically, HIIT requires “near maximal” efforts performed at a heart rate ≥ 80% of the HRmax or the equivalent as expressed as a function of the VO2 max. In comparison, SITs are even more intense.
Many different types of interval training exist, but it remains to be elucidated what type (HIIT/SIT vs MOD) could result in maximal weight loss. To this end, Viana and colleagues performed a systematic review of 41 studies, of which 5 were excluded for lack of data, and included the remaining 36 in a separate meta-analysis to compare the effects of HIIT or SIT with MOD on adiposity in a pooled sample of 1,115 participants.
To illustrate how much more efficient interval training may be compared with MOD protocols, the investigators broke down total body fat percentage reduction per minute by exercise time. Specifically, MOD led to a reduction of 0.0026% per minute whereas HIIT led to a reduction of 0.0050% per minute and SIT to a reduction of 0.0067% per minute.
The investigators hypothesized that many factors could influence the effects of interval training on absolute fat mass, including: exercise supervision; walking, running, or jogging as the exercise of choice; age (< 30 years); intervention duration; and quality of study.
Vigorous exercise may bring about a more profound increase in skeletal muscle oxidative capacity, as well as sympathoadrenal stimulation. Therefore, the authors suggested that protocols that depend on the glycolytic system may result in greater body fat reduction.
With respect to SIT, the greater reductions in fat loss vs MOD could be secondary to heightened post-exercise fat oxidation, which has been linked to glycogen depletion.
It should be noted that interval training isn’t for everyone and carries a higher risk of discomfort, injury, or cardiac distress.
“In general, our findings suggest that the ‘signal in the noise’ is the similar effects of interval training and MOD on total body fat percentage (%) management and the superiority of interval training for total absolute fat mass (kg) reduction,” concluded the authors. “Yet that these effects can be produced in a ‘time-efficient’ manner when using interval training.”
The great thing about HIIT workouts is that there is no end to the variations you can try. Whether you want to incorporate weights, running, or do a routine that requires no equipment but yourself, there’s a workout for you. Here’s one that you can do in your living room:
- 40 squat jumps
- 20 push-ups
- 30 jumping jacks
- 10 tricep dips
- 10 burpees
- 30-second plank
Do not rest between each exercise, and repeat this circuit three times, with a 1-minute rest between circuits.
Here’s another HIIT circuit you can incorporate into any running routine. It will take approximately 12 minutes and can be done on a treadmill or outdoors:
- 30-second sprint
- 40-second brisk walk
Repeat this circuit 10 times in a row, with no rest. The point is to perform at 95% to 100% intensity during the sprints.
Remember that when done correctly, HIIT can boost your metabolic rate for up to 48 hours after your routine. HIIT is quick, convenient, and requires minimal to no equipment. So, if you want to get more out of your workout, and see less fat quickly, try to incorporate these HIIT routines into your regular exercise sessions.