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Maximize Calorie Burn with Weight Intervals

Short, Hard Set Series Beats Traditional Weight Training

Intervals with weights work for weight loss!

We’ve often talked about aerobic interval training, but never about interval training using weights. Interval resistance training doesn’t exactly roll off the tongue; it requires a double take to get your mind around. Well, we’re going to talk about it now. An eye-opening study from Italy (University of Padova) compared the after-effects of high-intensity interval resistance training and traditional resistance training.

This will be the second month in a row that we’ve drawn attention to the inclusion of resistance training in government and other high profile weight control guidelines. Last month we took issue with a study which concluded that aerobic training alone is best for weight control (#349). This month we’ll give another reason why resistance training belongs in weight loss programs. What’s more, we’ll tell you about a time efficient form of resistance training that outdoes conventional multi-set training.

An often overlooked (or ignored) weight-control benefit of exercise is the added calorie burn long after the workout. Exercise physiologists call it excess post-exercise oxygen consumption (EPOC). The largest component of daily energy expenditure is resting energy expenditure (REE). About 60% of energy burn is REE—energy expended to keep the body going at rest—the other 40% comes from physical activity. Any increase in REE in response to exercise can have a major impact on weight control. A number of studies have been done on the after-effects of endurance training, but few on resistance training. 

“Resistance training acts in a substantially different way compared to endurance training,” the Italian researchers wrote in the November 24, 2012, Journal of Translational Medicine, “it increases muscle mass in the long term but also increases excess post-exercise oxygen consumption (EPOC).” Little, however, is known about the relative after-effects of different forms of resistance training. The aim of their study was to compare how traditional resistance training and high-intensity resistance interval training affect resting energy expenditure 22 hours after training—something that had apparently never been done before.

Antonio Paoli, Department of Biomedical Sciences, Physiological Laboratory, University of Padova, and colleagues from UP, two other universities in Italy, and one in Greece recruited 17 males (average age 28, 4-6 years of training experience) to participate in their clinical study. In two separated sessions, the participants did high-intensity interval resistance training (HIRT) and traditional resistance training (TT) protocols. Changes in resting energy expenditure (REE) and respiratory exchange ratio (RR) were measured for each protocol.

Participants randomly performed the HIRT or TT workout immediately after REE and RR were measured. After 22 hours the measurements were repeated. A week later the subjects switched protocols (HIRT did TT and vice versa) and were tested again. (The methods used to measure REE and RR were described in the study. 

In the HIRT protocol, a rest pause sequence was counted as one set. The one-set sequence was 6 repetitions, 20 seconds rest, 2-3 reps, 20 seconds rest, and 2-3 reps, with 2 minutes and 30 seconds rest between sets. All segments of each set were performed to failure. The leg press was done for 3 sets, and the bench press and lat pulldown were performed for 2 sets. The 7 sets took approximately 32 minutes, including warm up on a treadmill.

The traditional training (TT) program was 4 sets of the following exercises: bench press, lat pulldown, military press, biceps curl, triceps extension, leg press, led curl, and sit-up. Participants were told to do as many reps as possible in each set; the usual number of lifts before failure was 8 to 12 reps. Rest between sets was one minutes for single-joint exercises and two minutes for multiple-joint exercises. The eight exercises were performed for a total of 32 sets. The 32-set training session lasted approximately 62 minutes, including warm up.

The results are heartening. Hopefully, those who question the inclusion of resistance training—especially high-intensity—in weight loss programs are taking notice.

First, the total volume of work performed was significantly lower during the HIRT workout: HIRT volume totaled about 3872 Kg compared to 7835 Kg in TT. The TT load was twice the HIRT and took twice as long (62 min compared to 32). Nevertheless, HIRT increased resting energy expenditure (REE) more than TT. And how!

Both protocols significantly increased REE at 22 hours, but the increase was greater after HIRT. After TT, REE increased by 5%, from 1901 calories/day at baseline to 1999 at 22 hours. After HIRT, REE increased from 1910 calories at baseline to 2362 calories at 22 hours, an increase of 23%. The increase in calorie burn after high-intensity interval resistance training was 4.6 times greater than after traditional resistance training, 452 calories compared to 98 calories.  

Changes in the respiratory exchange ratio for the two protocols were also telling. What was the difference and what does it mean?

The respiratory exchange ratio (RR) declined significantly more after HIRT than after TT. RR is the relationship of carbon dioxide exhaled to oxygen inhaled. When RR is close to 0.7 it means that the major energy source is fat, while a reading near 1.0 indicates that carbohydrate is the main source of energy. The RR for HIRT at 22 hours was 0.798 compared to 0.822 for TT at 22 hours, indicating a significantly greater fat burn following HIRT.

Importantly, the elevation in resting energy expenditure almost a full day after HIRT was greater than previously reported for other training protocols. REE after resistance training typically varies from 5% to 20%, according to the researchers.  

What’s the explanation for the extraordinary metabolic rate 22 hours after HIRT?

Paoli et al say the intensity of their weight interval protocol is the most likely explanation. Research has shown that intensity and duration of exercise are the key factors, but there is a major difference. Excess post-exercise oxygen consumption (EPOC) increases “exponentially” as a function of exercise intensity, whereas it increases “linearly” as a function of exercise duration. That would explain why weight training has been shown to require more energy and longer recovery than endurance training, according to the researchers.

“Many authors explain the basis for the greater increase in EPOC after more intense exercise as involving a perturbation of energy homeostasis,” Paoli et al wrote. High-intensity training traumatizes and unsettles the body more than other forms of exercise. “This consideration could help to explain the conflicting data between our study…and several others that reported more modest increases.”

“Our training protocol…was performed at a very high intensity,” they continued, “which can be demonstrated by the greater increase in maximal blood lactate levels and it is well know that lactate plays a role in the total increase of post exercise energy expenditure.” Blood lactate increased 5.1 after TT and 10.5 following HIRT. Again, a marked difference.

The rest-pause technique and longer duration of each set put the body into overdrive.

Increased hormonal response may also be a factor. “In fact, in response to exercise induced trauma an increase of metabolic hormonal concentration is seen (e.g., cortisol, catecholamine, and thyroid hormone) that could increase metabolism,” the researchers wrote. “More likely,” they continued, “increased protein re-synthesis due to post-exercise muscle damage is energy expensive…and could contribute to greater EPOC after high intensity resistance training.” Weight training breaks down muscle tissue and the body builds it back bigger and stronger. This takes time and energy.

Another weight control advantage of the HIRT protocol is the small time commitment and low volume. As noted, the high-intensity interval protocol took half the time of the tradition technique. People are likely to be more enthusiastic about doing 7 sets than 32 sets. That’s important in a time where a growing number of us are overweight or obese and the vast majority are couch potatoes.

“The shorter exercise time commitment may help to reduce one major barrier to exercise,” Paoli et al concluded.

A possible disadvantage is that the interval protocol may be beyond the capabilities of non-athletes, the Paoli team observed. “In this regard, we and others have demonstrated that it is possible, after a familiarization period, for previously untrained persons to successfully perform this kind of training—however it would be correct to exert appropriate caution when applying this protocol to overweight/obese subjects.”

Paoli et al concluded: “Our results suggest that high-intensity interval resistance training increases excess post exercise energy consumption to a significantly greater extent than traditional resistance training. This exercise methodology allows subjects to improve metabolism and at the same time, muscle mass and strength, all of which are promoted as beneficial by many [weight control] guidelines. In Western society leisure time is lacking and motivation to perform daily exercise is uncommon…In this situation a short intense training that enables elevation of basal metabolism whilst lowering RR (i.e. increase fat consumption at rest) may be an interesting and attractive alternative to more traditional and time consuming exercise…”

*  *  *

The effect of added muscle mass on resting metabolism can only be determined over time and not after a single workout. So the full effect of HIRT on metabolism and weight control is yet to be determined. The study discussed here last month (#349) showed that a combination of traditional aerobic and resistance training resulted in more overall and belly fat reduction than either alone. It appears that high-intensity interval weight training may be substantially more effective for weight control—with less time devoted to exercise.

The more we learn the better resistance training looks. More research is needed, but resistance training clearly belongs in weight control programs.

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