The latest research published in PLOS One Journal (April 26, 2016) showed men who did one-minute of “all-out” exercise on bikes experienced significant improvements in cardiometabolic health measures despite exercising for significantly less time. The length of the study was 12-weeks and the sprint-interval training (SIT) group exercised for 1:00, using a 3×20 second protocol, while the moderate-intensity continuous training (MICT) group completed workouts consisting of 45-minutes of continuous cycling at ~70% HRmax. A 2-minute warm-up and 3-minute cool-down (using 50 watts as resistance) were used for both groups, resulting in 10- and 50-minute sessions for SIT and MICT, respectively.
According to Jenna Gillen, the lead investigator of the study, “the major novel finding from the present study was that 12-weeks of SIT in previously inactive men improved insulin sensitivity, cardiorespiratory fitness, and skeletal muscle mitochondrial content to the same extent as MICT, despite a five-fold lower exercise volume and training time commitment. SIT involved 1-minute of intense intermittent exercise, within a time commitment of 10-minutes per session, whereas MICT consisted of 50-minutes of continuous exercise at a moderate pace.”
There is truth in saying short duration, “all-out” training can improve health and fitness outcomes, just realize that you need to challenge yourself during the short bouts of intense exercise. Most importantly, be mindful that there are no quick fixes when it comes to health and fitness, if so, we would have less of an obesity epidemic on our hands in this country (a reported 69% of Americans are overweight or obese).
Previous research has shown that high intensity interval training (HIIT) improves aerobic and anaerobic capacity, lean muscle level, glucose tolerance, insulin sensitivity in addition to other health/fitness markers.
Researchers from the Division of Sport and Exercise Science at Abertay University in Dundee, Scotland and Leeds Trinity University in Leeds, UK demonstrated for the first time that HIIT needs to be “performed only twice a week to see major improvements in aerobic capacity, functional capacity and metabolic health in a middle-aged population.”
During middle age (defined as 35 to 58 years old), adults typically see an 8 percent drop in both VO2 max (aerobic capacity) and insulin sensitivity per decade. This study showed just 16 sessions of HIIT over an eight week period, with one or two days of rest between each sprint, offset these and other changes seen with aging. The participants in this study experienced a significant increase in VO2max of 8 percent (see Figure 1). Each training session consisted of 10 repeated 6-second all-out cycling efforts against 7.5% of body weight for males and 6.5% for females (on a Monark peak bike Model 894E).
Short duration HIIT continues to show impressive results in health and physical function compared to traditional, long duration, steady state exercise that most people continue to do. Adding in 1-2 days/week of HIIT would seem warranted as a result of this and other well-documented HIIT research.
Fitness fads come and go, but the resurgence of High Intensity Interval Training (HIIT) might be here to stay.
HIIT uses a combination of quick intervals of intense exercise and short recovery periods to increase your heart rate, burn fat and work muscles in a short amount of time. In fact, HIIT is becoming the go-to training method for many professional fitness instructors. The allure lies in the ability to complete an entire workout in less than 20 minutes and burn fat. In fact, this type of training burns more fat than a regular 45 minute cardio session since it keeps your heart rate up and gives your metabolic rate a boost.
Mike Volkin, creator of HIIT the Game, now on Kickstarter states “HIIT is just fun, it’s a fun way to mix up any routine and it can be done by just about anyone, and anywhere.”
A study performed at Laval University in Canada used two groups of participants. One group followed a 15-week program using HIIT while the other group performed only steady-state cardio for 20 weeks. The steady-state cardio group actually burned 15,000 calories more than the HIIT group. But, the HIIT group lost significantly more body fat. There are many scientific studies with similar results.
Aside from being quick and very effective at both burning fat and increasing metabolism, HIIT is appealing to many because no equipment is required. This training method uses bodyweight exercises so a workout can be done anywhere from a gym to a living room.
Another great aspect of high intensity interval training is variety. Everyone has complained that their workout routine gets boring and stale after a while, but with HIIT it doesn’t have to be that way. You can change things up and try something new every week if you want. Variety not only maintains enthusiasm during training but it will benefit the body immensely through a process called muscle confusion. Targeting a wide array of muscle groups and performing different exercises regularly is going produce results fast.
Lastly, even though HIIT workouts are short, usually 20 minutes, they actually improve endurance. HIIT works, if you’re skeptical, give it a try for a week and see how you feel, at the very least, it is a great plateau breaker of your current routine.
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A paper published by Gillen and Gibala tested the hypothesis that high-intensity interval training (HIIT) can be used as a time-efficient strategy to improve health and fitness. Their paper was basically a literature review of HIIT research studies that used 2, 6, 12-15 weeks of low-volume HIIT. They state that results of these types of studies show promising results but more research is still warranted.
“While the findings from these small pilot projects are intriguing, large-scale investigations with appropriate participant screening and monitoring are clearly warranted, including randomized clinical trials to directly compare low-volume HIIT versus traditional endurance training in a comprehensive manner, especially in those with, or at risk for, cardiometabolic disorders.”
Research has consistently demonstrated the positive use of HIIT to improve among other things, aerobic capacity, insulin sensitivity, muscle oxidative capacity, and exercise tolerance with as little as one to three sessions a week. Exercise sessions, typically, involve <10 minutes of hard “all-out” exercise followed by brief recovery periods coupled with a warm-up and cool-down that equates to, typically, <30 minute sessions.
Most governing bodies, like the CDC, WHO and Surgeon General, publish content stipulating 150-minutes of moderate-intensity (or 75-minutes of vigorous) exercise is needed to keep disease at bay. Is it time to alter some of these findings due to the abundance of HIIT research that has been published over the last four decades? There is now evidence that HIIT is as effective as traditional, longer duration, steady-state type exercise.
With the number one reported reason for not exercising typically being – “lack of time” – maybe <150 minutes of moderate or 75 minutes of vigorous exercise guidelines should soon be cut in half?; possibly getting more individuals to start/continue with an exercise routine using, at times, HIIT.
By understanding your body type, you can customize a workout program to be more effective than an “out of the box” workout program. Customizing a workout program based on your body type is surprisingly easy. Before you start developing a workout program you have to identify your body type (also called somatotype). There are three basics somatotypes; mesomorph, ectomorph, and endomorph. A mesomorphic body is ideal. They are the individuals who are athletic with a strong frame that can easily gain muscle while remaining quite lean. Ectomorphs are those with thin delicate frames that have a hard time gaining weight, have a fast metabolism and very lean muscle definition. Lastly, endomorphs are the heavier individuals that have a round shape who find it difficult to burn fat but can gain muscle mass easily.
If you are a mesomorph, lucky you! Since you can gain muscle mass fast your program has to include cardiovascular exercise to keep your body lean. Twenty five to thirty minutes of cardio 3 times a week is recommended. As for training, stay within 8-12 reps for each set with a 1 minute rest in between. Make sure to include a variety of exercises to continue to challenge your body, maintain muscle and improve strength as well as endurance.
Ectomorphs have to customize their fitness program to work against their natural thinness. To do so select short and intense exercises that target major muscle groups like the biceps, triceps, abdominals and hamstrings. This type of workout will help with muscle development. When doing any sort of weight or resistance training, train heavier and keep your repetitions within the 5-10 range. As for cardio, keep it to a minimum since burning fat is not needed. As for rest periods, 2 minute rests between sets are suggested. Since you will be doing more intense exercise you need additional time to recover.
Endomorphs on the other hand have to embrace cardio in order to burn fat and maintain a good body fat percentage. Do cardio as much as you can and be sure to change it up. Try swimming, running, HIIT, cycling and any other form of cardiovascular exercise that interests you. Aside from that you do need weight and resistance training. It is highly recommended that you do compound lifts and stick with 8-15 repetitions per set with 30 second of rest. Challenging major muscle groups will speed up your metabolism to help keep the excess body fat off.
The buzzword in the fitness industry this past year was definitely high-intensity interval training, also referred to as HIIT. HIIT reached the number one spot in the 2014 survey for exercise trends published by the American College of Sports Medicine (ACSM). According to one source, HIIT will end up at the number two spot for 2015 on that same ACSM list, replaced by body weight exercise as the new exercise trend. HIIT however is not a new to the spotlight, it has been around for more than a century. Some of the greatest runners in the world have used various forms of HIIT as part of their training. As early as 1912, the Finnish Olympic long-distance runner Hannes Kolehmainen was using interval training in his workouts (Billat 2001). Research has demonstrated that HIIT:
• Improves the performance of competitive athletes.
• Improves health outcomes for recreational exercisers.
• Provides the same benefits of endurance training but with fewer workouts covering less time.
One thing you can bank on, HIIT gets results, when done correctly. HIIT is one of the most effective means of improving cardiorespiratory and metabolic function in both athletes and recreational exercisers. HIIT involves repeated short-to-long bouts of high-intensity exercise (90-100% VO2max) interspersed with recovery periods. The term HIIT can be used to
describe protocols in which the training stimulus is near maximal effort or the target intensity is between 80 and 100% of maximal heart rate. HIIT typically involves repeated short bouts of exercise (<45 seconds) to long bouts (2-4 minutes) of high-intensity exercise interspersed with recovery periods. Traditional high volume aerobic exercise training has been shown to reduce cardiovascular and metabolic disease risk but involves a significant investment of time. Extremely low volume HIIT has been shown to produce improvements to aerobic function.
Humpreys and Holman credit the famous German coach Woldemar Gerschler, as the person who formalized a structured system of interval training back in the 1930’s. Exercise Physiologists Fox and Matthews have identified the following five variables that need to be adjusted individually for each athlete during a HIIT session:
-Rate and distance of the work interval.
-Number of repetitions and sets during each training session.
-Duration of the rest, recovery or relief interval.
-Type of activity during the rest interval.
-Frequency of training per week.
The following list includes just a few of the many research studies that have been published looking at various health and fitness benefits of HIIT.
A 2011 study presented at the ACSM annual meeting showed 2 weeks of HIIT improved aerobic capacity as much as 6-8 weeks of traditional endurance training.
A 2006 study found after doing 8 weeks if HIIT subjects could bike twice as long when they started the study while maintaining the same pace.
Researchers from Canada’s McMaster University looked at the effects of interval exercise on VO2max. Training was performed on a stationary cycle ergometer for three days each week. The program began with four intervals lasting 30 seconds each, separated by a 4-minute rest period. By the seventh week the number of intervals had increased to ten, while the rest intervals were gradually reduced to 2.5 min. VO2max increased by 9%, demonstrating that significant gains in VO2max could be achieved from exercise of a relatively short duration.
A group of researchers from Japan’s National Institute of Fitness and Sport found a high-intensity intermittent training program achieved bigger gains in VO2max than a program of steady cycling. Active male subjects were assigned to one of two groups, each training 5 days per week for 6 weeks. One group followed a training program involving 60-minutes of moderate intensity exercise (@70% VO2max), totaling 5 hours per week. The average improvement in VO2max in this group was 9%. Training sessions involving the other group consisted of eight all-out work bouts, each lasting 20 seconds followed by 10 seconds of rest (Tabata et al., 1997). This group cycled for a total of only 20 minutes per week, but their VO2max still improved significantly by 15%.
A study from the University of New South Wales in Australia, found women lost an average of 10.5% of their fat mass after just 15-weeks on a 3x/wk program using 20 minute workouts consisting of 8 second sprints (on a stationary bike) followed by 12 seconds of passive recovery = 60 total sprints. Subjects in a control group lost considerably less fat doing traditional endurance exercise despite spending roughly 400% more time pedaling.
Billat, L.V (2001). Interval training for performance: A scientific and empirical practice. Special recommendations for middle-and long-distance running. Part I: aerobic interval training. Sports Medicine, 31(1): 13-31.
Research has consistently shown that high intensity interval training (HIIT) is not only time-efficient but also very effective in improving health and fitness. The duration used for some of the early HIIT research may have utilized brief work periods (like 20 seconds) but the intensity level used to get results was extremely high (i.e. 170% VO2 max).
In 2010 Martin Gibala, PhD and colleagues from McMaster University took HIIT research to the next level, showing significant results could be obtained by using a lower intensity during the interval stages. His group used a protocol that involved 8-12 one-minute sprints on a bike with 75 seconds of recovery in between the sprints, 3 times week for 2 weeks. The intensity used during each work stage was about 100% of peak power output (an average output of about 350 Watts).
The “secret” to why HIIT is so effective is unclear. However, the study by Gibala and co-workers also provides insight into the molecular signals that regulate muscle adaptation to interval training.
It appears that HIIT stimulates many of the same cellular pathways that are responsible for the beneficial effects we associate with endurance training.
The great thing about a well-designed HIIT training session is that it can be fast but yet effective in producing health benefits. Here are a few examples of HIIT that I used in a recent workout. This template can be adapted for your needs depending on your fitness level and goals. The first interval example was performed on a stationary cycle using a 1:3 work-to-rest ratio while the second example was performed on an erg (Concept 2 rowing machine) using a 1:2 work-to-rest ratio. Try this type of protocol using other modalities that may fit your needs like running or other cardio equipment like an elliptical machine or treadmill.
The key take away is that the duration should be short and the intensity should be high. Use this type of HIIT protocol 1-3 times a week. The higher the intensity, the higher the excess-post oxygen consumption (epoc). EPOC is a “measurably increased rate of oxygen intake following strenuous activity intended to erase the body’s oxygen deficit.” In recovery, oxygen is used in the processes that restore your body to a resting state. It is possible to expend a few hundred extra calories (depending on body weight and intensity of the workout) over the course of 24 hours or more following strenuous exercise.
Example of HIIT Bike Protocol
20 seconds of all-out work (300-700 Watts) >100 rpm
1:00 recovery (<50 rpm)
Repeat x 3 then cool-down
Example of HIIT Rowing Protocol
2:00 Easy Rowing (damping set at 4-5, 20-25 spm)
30 seconds of all out work (damping set at 4-5 and >30 spm)
Repeat x 3 and cool-down
Jonathan P Little, Adeel S Safdar, Geoffrey P Wilkin, Mark a Tarnopolsky, and Martin J Gibala (2010). A practical model of low-volume high-intensity interval training induces mitochondrial biogenesis in human skeletal muscle: potential mechanisms. The Journal of Physiology,DOI: 10.1113/jphysiol.2009.181743
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There are many effective high intensity interval training (HIIT) protocols that have been used by exercise physiologist and researchers over the years. One such interval protocol (10-20-30) was tested and published in the Journal of Physiology by two researchers from Copenhagen. Researchers, Gunnarsson and Bangsbo, had very promising results on a group of moderately trained runners who used this particular protocol. The study compared training results on a control group and an interval group using the 10-20-30 protocol. The 10-20-30 training concept consisted of a standardized ∼1.2 km warm-up at a low intensity followed by 3–4 × 5 minute running interspersed by 2 minutes of rest. Each 5-minute running period consisted of five consecutive 1 minute intervals divided into 30, 20, and 10 seconds at an intensity corresponding to <30%, <60%, and 90–100% of their maximal intensity, respectively.
Study results showed the 10-20-30 group, significantly reduced systolic blood pressure by 5 ± 2 mmHg, and total and low-density lipoprotein (LDL) cholesterol was significantly lowered by 0.5 ± 0.2 and 0.4 ± 0.1 mmol/l, respectively. No changes were observed in control group. The study also showed that interval training with short 10-second near-maximal bouts can improve performance and V̇O2max despite a ∼50% reduction in training volume. In addition, the 10-20-30 training regime lowered resting systolic blood pressure and blood cholesterol, suggesting a beneficial training effect on the health profile of trained individuals.
Following the 7-week study the runners experienced an average increase in their VO2max of 4% (mean 52 ml/kg/min. VO2max) and improved running times in a 1,500-m and a 5-km run by 21 and 48 seconds, respectively. Four weeks prior to as well as before and after the intervention period each subject (n = 18) underwent a series of tests that included: (1) a treadmill test to determine V̇O2max and maximal aerobic speed, (2) a 1,500-m run, and (3) a 5-km run.
This type of training protocol suggest that adding 1:00 intervals using the 10-20-30 protocol to your current training routine would be ideal not only for runners but the general population as well. It would be prudent to try this only after a solid aerobic conditioning base is established.