With New Years approaching, it isn't truly a "New Years Resolution" without doing some cardio. What if I told you that all those hours of running or any other cardio were of minimal, if any, benefit including body fat loss? What if I told you the majority of the weight you would lose in the process was muscle mass? The muscle mass you lost doing cardio was the very muscle mass your body utilizes and to burn fat. What if I told you, that despite losing weight (muscle mass), you have actually increased your body fat percentage?
In the past, the thought was: "you just needed to move more, i.e. cardio to lose weight." Studies have shown we can be even more productive to engage in HIIE (High Intensity Intermittent Exercise) instead of cardio or SSE (Steady State Exercise).
To study the benefits of HIIE vs SSE, the International Journal of Obesity (2008) studied "The Effects of High-Intensity Intermittent Exercise Training On Fat Loss And Fasting Levels Of Young Women" .
The study followed 45 untrained women with a mean BMI of 23.2 kg and age of 20.2 years. Because these volunteers were untrained and unused to cycling, they typically ceased cycling before achieving a true VO2 max.
(Shape Sense provided an excellent description of VO2. VO2 (or oxygen consumption) is a measure of the volume of oxygen that is used by your body to convert the energy from the food you eat into the energy molecules, called adenosine triphosphate (ATP), that your body uses at the cellular level. VO2max (or maximal oxygen consumption) is simply the maximum possible VO2 that a given person can achieve. VO2 and VO2max are important in the context of exercise, because they are a measure of your body's ability to generate ATP, and ATP is the energy source that allows your muscles to continue working while you are exercising. Therefore, a VO2max measurement is ultimately a measure of your cardiorespiratory fitness level).
Thus, VO2 peak was accepted as an indicator of aerobic power. Venous blood samples were taken in the last 30 seconds of every stage of the test and at the end of the cool down. Heart rate (HR) was recorded at the end of each stage. Blood samples were centrifuged and frozen.
Subjects were randomly assigned to one of the three groups: HIIE (High Intensity Intermittent Exercise) vs SSE (Steady State Exercise) vs. control group (which did no exercise at all). HIIE and SSE groups underwent a 15-week exercise intervention.
For SSE training, subjects trained on a bike. They completed a 5-min warm-up at a comfortable workload after which everyone exercised at 60% VO2 peak. At the end of the conditioning phase, a 5-min cool down and stretching was completed. Subjects started the 15-week program exercising at this intensity for 10–20 min. The duration of the exercise was gradually increased to a maximum of 40 min of exercise per session. They supplied a record of their dietary intake at week 1 and 15 weeks later with no changes observed.
For the HIIE training protocol, each subject performed 8 sets of sprinting and 12 sets of turning the pedals over slowly (between 20 and 30 r.p.m.). The same cool down and stretching protocol as the SSE group was followed. At the beginning of the 15-week training period, subjects started with a resistance of 0.5 kg and worked as hard as they could during the sprinting phase. Subjects started with as little as 5 min in the conditioning phase and gradually increased work time to a maximum of 20 min. Once an individual could complete 20 min of intermittent sprinting at 0.5 kg, resistance was increased by increments of 0.5 kg. A decrease in the subject's HR at the current workload preceded by an increase in resistance. The women adapted to the training stimulus rapidly. By the end of 2 weeks (six exercise sessions), all women could complete the full 20 min of exercise. They supplied a record of their dietary intake at week 1 and 15 with no changes observed.
The CONTROL group was asked to maintain their current physical activity levels and dietary habits for the 15 weeks of the experimental period. They supplied a record of their dietary intake at week 1 and 15 weeks later with no changes applied.
Before the women started the study, there were no significant differences between the three groups on any measured variable.
The results after were the following:
HIIE group SSE group
Exercise Time 36 minutes per week 120 minutes per week
Body Fat loss decrease of 11% no fat loss
Lean Body Mass not significant gains lost lean muscle tissue
Heart Rate (mean) 168.6 bpm 155.7 bpm
Peak VO2 increased by 23.8% increased by 19.3%
Diet no changes were made no changes were made
Fasting Insulin 31% decrease 9% decrease
Leptin significant decrease no changes
Let's explain the results in detail.
Exercise Time: The SSE group worked out 84 extra minutes or 4x longer each week as the HIIE group!
Body Fat Loss: The HIIE saw an average of 11% loss. The SSE group had NO fat loss! It is remarkable that this very activity lead to no fat loss for the SSE group.
Lean Body Mass: The SSE group lost lean muscle tissue. This will lead to lower RMR (Resting Metabolic Rate) which will compromise the body's ability to burn fat when not working out. The HIIE did not gain or lose but stayed the same. Thus, they maintained their RMR.
Heart Rate (mean): Both groups elevated their heart rates but the HIIE elevated it's heartrate greater thus creating stronger heart.
Peak VO2: A VO2 Peak or (max measurement) is a measure of your cardiorespiratory fitness level. SSE increased it's VO2 by 19.3% and the HIIE increased it by 23.8%. I was talking to a member about this study. She said, "I don't want to lose my stamina. If I do not do cardio, how will I ever keep up with my children?" Since the VO2 is a measure of how efficiently you use oxygen, the HIIE group showed a 4% increase in Peak VO2 over the SSE. Don't forget, the HIIE did absolutely no steady state cardio and did the workouts in a fraction of the time. It took the SSE group 84 extra minutes of cardio per week and they still came up short for VO2 levels.
Diet: Absolutely no changes were made during the 15-week study. Participants kept a food journal tracking what they ate to ensure a quality study.
Fasting Insulin: Fasting insulin shows your body's blood sugar in the morning. Studies have shown that exercise can help lower your fasting blood sugar. While the SSE lowered their fasting insulin by 9%, the HIIE lowered it by 31%!
Leptin: Leptin is a hormone that plays a crucial role in appetite and weight control. The SSE group had no changes in leptin levels causing the SSE group to become hungrier. Because the SSE group did not increase the sympathetic nervous system activity, they had an inability to burn fat and showed no body fat loss. The HIIE group had a significant decrease in leptin levels causing the woman to become less hungry. Because the HIIE did increase the sympathetic nervous system activity, they had the ability to burn fat and showed 11% body fat loss!
The major finding of this study was that both HIIE and SSE significantly increased VO2 peak, but only HIIE resulted in a significant loss in total and body fat%. Both exercise protocols decreased fasting insulin levels; however, the effect was significantly greater in HIIE compared to the control grop and the SSE group. Fat loss induced by HIIE was achieved with half the time commitment, but with a similar energy expenditure to that of SSE.
In conclusion, 20 min of HIIE, performed three times per week for 15 weeks compared to the same frequency of 40 min of SSE exercise was associated with significant greater reductions in fasting insulin and total body fat.
The International Journal of Obesity weren't the only group to investigate SSE vs. HIIE.
In 2009, a study conducted by researchers at Queensland University of Technology in Australia showed that participants who engaged in steady-state cardio five times a week for 12 weeks lost an average of 7 pounds. Unfortunately, the 7-pound loss is the law of averages. While a couple of participants saw success in losing weight, nearly half of the participants lost less than 2 pounds total. Keep in mind, we learned from above, the majority of the weight lost is most likely muscle mass and not body fat loss.
A 2011 study presented at the American College of Sports Medicine Annual Meeting showed that just 2 weeks of HIIE training improves your aerobic capacity as much as 6 to 8 weeks of SSE training.
What are you to do?
Stop doing Steady State Cardio! While you may see studies showing the benefits of Steady State Cardio, those studies are not comparing to High Intensity Interval Exercise. When going head to head, study after study show HIIE with significantly greater improvements in fat loss, fasting insulin, and leptin all in 75% of the time! With HIIE sprinting is harder and more challenging, you will start seeing results both aesthetically and with your blood work! Start doing HIIE workouts such as sprints outside, on the treadmill, or even the stationary bike to see your fat loss. By doing sprints, you will be sprinting towards success with your New Years Resolution goal.
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