Short on time? Try high intensity interval training!

By: Jared Ferguson Featuring: Joe Franco

Key Points

  • Most adults in the United States do not achieve the weekly recommended amount of physical activity due to “lack of time.”
  • If exercise is done at a relatively high intensity (defined by VO2max) less time is required to obtain the health benefits of physical activity.
  • High intensity interval training (HIIT) improves aerobic fitness and it improves body composition in overweight/obese individuals even in the absence of weight loss.
  • HIIT requires less time, but it is more physically demanding than steady state cardio.
  • If you are trying HIIT for the first time give the following a try:

o   1 – 2 sessions per week (performed on foot, a treadmill, or a stationary bike)

  • 5 minute warm-up
  • 4 – 6 intervals of 10 – 15 seconds each
  • 1 – 2 minutes of rest between intervals
  • 5 minute cool-down


I do not think anyone would argue that a healthy lifestyle should encompass both proper nutrition and plenty of physical activity. However, unless your job is physically demanding you most likely are not getting enough physical activity in each week. The following recommendations were pulled directly from the Centers for Disease Control and Prevention website.

“Adults need at least:

2 hours and 30 minutes (150 minutes) of moderate-intensity aerobic activity (i.e., brisk walking) every week and muscle-strengthening activities on 2 or more days a week that work all major muscle groups (legs, hips, back, abdomen, chest, shoulders, and arms).


1 hour and 15 minutes (75 minutes) of vigorous-intensity aerobic activity (i.e., jogging or running) every week and muscle-strengthening activities on 2 or more days a week that work all major muscle groups (legs, hips, back, abdomen, chest, shoulders, and arms).


An equivalent mix of moderate- and vigorous-intensity aerobic activity and muscle-strengthening activities on 2 or more days a week that work all major muscle groups (legs, hips, back, abdomen, chest, shoulders, and arms).”1

Roughly 21% of adults in the United States meet the recommendations listed above. Lack of time is one of the most common reasons given for not engaging in physical activity.2 If you noticed from the recommendations above less time is required to get the benefits of exercise when a person exercises at a high intensity.

Intensity is a relative term. I imagine that a Rocky montage enters the minds of individuals who do not exercise when they hear the words “high intensity.” What one person may perceive as being intense may not be considered intense to another. In strength training intensity refers to the percentage of a person’s 1 rep max. In other words high intensity strength training involves lifting relatively heavy weights. Intensity in aerobic exercise refers to percent of V02max which is the maximum amount of oxygen a person can consume and use during exercise. VO2max is accurately measured in a laboratory using a device that measures the gases you breathe in and out. You may have seen someone on TV or in movies running on a treadmill and breathing into a mask with long tubes. Moderate-intensity aerobic exercise is 40-60% VO2max while vigorous-intensity aerobic exercise is 60-85% VO2max.

The leading cause of death in the United States is heart disease.3 Physical activity can improve a person’s health and reduce the risk of heart disease as well as type 2 diabetes, stroke, depression and possible some cancers.1

How can you incorporate health improving exercise into your weekly routine when you have little time to spare? The answer may be high intensity interval training (HIIT). HIIT is performed at ≥ 85% VO2max and it is typically performed in 30 minutes or less. Intervals may be 6 seconds – 4 minutes with rest periods of 10 seconds to 5 minutes at 20-40% VO2max. Can you really exercise for less time and still get the health benefits as it relates to cardiovascular disease? The following paper may help answer this question. After I explore the research Joe Franco will give his insights and practical recommendations based on his 20+ years of experience as a fitness coach and personal trainer.

Title: Effects of high-intensity interval training on cardiometabolic health: a systematic review and meta-analysis of intervention studies.

Authors: Romeo B. Batacan Jr., Mitch J. Duncan, Vincent J. Dalbo, Patrick S. Tucker, Andrew S. Fenning

Type of Study: Systematic review and meta-analysis

Purpose: To assess the effects of HIIT on a wide range of cardiometabolic markers in adults.

Methods: For those who are not familiar with the types of studies that exist, systematic reviews and meta-analyses are studies of studies. You may have heard in the news that one study found a certain food to be harmful to a person’s health and later another study did not find that same food to be harmful. For example, eggs were thought to increase the risk of cardiovascular disease because of their cholesterol content. Then newer studies began to find eggs were not harmful to a person’s health. According to a recent meta-analysis, which included data from 7 studies, consuming eggs on a daily basis did not increase the risk of coronary heart disease.4 Systematic reviews and meta-analyses are at the top of the hierarchy of evidence meaning that they provide results that are more likely to be true. I will write an article on the types of studies and the hierarchy of evidence at a later date.

Now back to the HIIT study. Two reviewers searched PubMed for articles related to HIIT and the cardiometabolic markers of interest. Studies were included if intervals for HIIT were ≤ 4 minutes. Included studies were further assessed for quality, effect size, heterogeneity, and significance (if you are not familiar with these terms I will discuss them in another article). Studies were separated by the length of intervention. Short-term HIIT (ST-HIIT) studies were < 12 weeks while long-term HIIT (LT-HIIT) studies were ≥ 12 weeks. BMI was used to further separate the included studies into 3 groups: 1) normal, 2) overweight and 3) obese.

Results: A total of 65 studies were included and only 3 studies were considered to be high quality while 14 studies were graded as low quality. The rest of the studies were fair quality.

Most participants were 18 – 35 years old and some had medical conditions such as hypertension, type 2 diabetes, and cardiovascular disease. At the beginning of the studies participants were sedentary, active, moderately trained or well trained. The sample size ranged from 5 – 85 with an average of 14.4 subjects per study. Studies implemented a single HIIT session or multiple sessions over the course of 2 – 52 weeks. Participants performed HIIT by running on a treadmill, swimming or cycling.

You can see how it is important to pay attention to details of a study. The results of a study that was performed in young, well trained males should be extrapolated and applied to older individuals with type 2 diabetes.

ST-HIIT did not have a significant effect on body mass, BMI, body fat % (BF%), heart rate (HR) or blood pressure (BP). Not enough studies were available to assess the effects of LT-HIIT on body mass in normal weight individuals. However, LT-HIIT was shown to have a small effect in reducing waist circumference and BF% in overweight/obese individuals despite a lack of weight loss. ST-HIIT and LT-HIIT greatly improved VO2max.

LT-HIIT had the greatest effect on VO2max in overweight/obese subjects. Unfortunately, heterogeneity was significant for overweight studies meaning that the studies’ methods were very different. When studies differ significantly there is an increased risk of producing biased results. You could still expect to see improvements in VO2max among overweight/obese individuals. The improvements may not be as great as what this study demonstrated. Also, the longer the HIIT session the greater the overweight/obese person’s VO2max improved.

LT-HIIT had a small effect on HR reducing it in overweight/obese individuals. ST-HIIT reduced diastolic blood pressure (DBP) in overweight/obese subjects with a medium effect overall. Systolic blood pressure (SBP) and DBP decreased by a small amount in overweight/obese in individuals that were subjected to LT-HIIT. However, once again there was significant heterogeneity among the studies.

FBG was improved by a small amount when ST-HIIT was prescribed to overweight/obese subjects. Other cardiometabolic markers including blood lipids, inflammatory markers (IL-6 and CRP), fasting insulin and HbA1c did not improve significantly with the use of either ST-HIIT or LT-HIIT.

The Takeaway: Performing HIIT for at least 12 weeks improves predictors of cardiovascular health, including waist circumference, body fat %, resting heart rate, systolic blood pressure, and diastolic blood pressure, in overweight/obese individuals. HIIT improves aerobic fitness as measured by VO2max in persons that are normal weight or overweight/obese. Furthermore, weight loss is not required to see improvements in waist circumference or body fat % as body composition can improve without losing weight.5

Joe Franco’s Insights and Recommendations:

We are always looking for the quick way to reach fitness goals and this of course applies to diet and exercise. Once interval training became popular and studied more we too in the fitness world have adopted it and we started applying it to those who want to get in better shape. The benefits as noted above are endless and quite encouraging if you think about it.

Personally, what I like most about HIIT cardio is the fact that you don’t have to spend as much time doing it as opposed to a steady state cardio at a sub maximum level for your heart rate.  Hence doing the HIIT cardio takes less time. However, it does take a lot more energy and intensity to perform it correctly. The issues that I have found are that people don’t do it properly. In real world if you were to do an all-out sprint like an Olympic hundred meter runner, do you really think you could perform 20 sprints in a row or more with the same intensity? I don’t think so. Performance starts to decrease therefore the effect of the actual workout is not as adequate. So in my experience I have found it is best to start off with a minimum amount of time for sprint intervals. I would prescribe a duration anywhere between 10 – 20 seconds because physiologically you cannot do a sprint for more than 15 seconds. Other energy sources come into play and we’re getting away from the initial idea.

In conclusion, one of the main benefits of HIIT is less time exercising which is something that the general public is always seeking. Not only are you burning calories during HIIT, but you will continue to burn calories throughout the day which does not happen with steady state cardio. Although the effort has to be there, when it comes to prescribed cardio I will learn what the person’s mentality is about and how driven they are and those factors will determine the frequency at which HIIT is performed. Too often people get psyched out because HIIT is just too darn hard if and when performed the correct way. I think 1 – 2 times a week is plenty for someone to start off with doing for 4 – 6 sprints lasting anywhere between 10 – 15 seconds. Recovery time between each sprint is up to the individual. Personally, I will prescribe anywhere from 1 – 2 minutes between each sprint so the person will be fully recovered for the next sprint.

Joe Franco’s Bio:

Joe has dedicated his life to health and fitness for the past 20 years, and has been involved in competitive bodybuilding since the 1980’s. During this time, Joe received his Bachelor Degree in Exercise Physiology from Temple University, and personal training certification through ACE. Joe’s personal training business, F.I.T. ( was started in 1996, and his competition prep ( for others began in 2000. Ever since then, Joe has work with 100’s of competitors and those who want to achieve the look! He coaches bodybuilders, figure and bikini competitors at all levels.


  1. Physical Activity. Centers for Disease Control and Prevention. Updated June 4, 2015.
  2. Overcoming Barriers to Physical Activity. Centers for Disease Control and Prevention. Updated February 16, 2001.
  3. Leading Causes of Death. Centers for Disease Control and Prevention. Updated October 16, 2016.
  4. Alexander DD, Miller PE, Vargas AJ, Weed DL, Cohen SS. Meta-analysis of Egg Consumption and Risk of Coronary Heart Disease and Stroke. J Am Coll Nutr. 2016 Nov-Dec;35(8):704-716. PubMed PMID: 27710205.
  5. Batacan RB Jr, Duncan MJ, Dalbo VJ, Tucker PS, Fenning AS. Effects of high-intensity interval training on cardiometabolic health: a systematic review and meta-analysis of intervention studies. Br J Sports Med. 2016 Oct 20. pii: bjsports-2015-095841. doi: 10.1136/bjsports-2015-095841. PubMed PMID: 27797726.