For the study, the Greece-based research team divided a group of 20 21-year-old women into two even groups. One group practiced one weekly bout of concentric exercise for 30 minutes for eight weeks, and one group practiced one weekly bout of eccentric exercise for 30 minutes each week over the same time period. The specific exercise chosen was knee extension (a common exercise to increase quadriceps strength) and all of the exercises were performed on a piece of exercise equipment known as an isokinetic dynamometer.
The women were asked to perform 75 repetitions for each leg (five sets of 15 repetitions with a two-minute rest period between each set) either raising (concentric) or lowering (eccentric) the legs against the resistance provided by the dynamometer. The women were asked to move their legs against the maximum resistance they could bear (the researchers noted that the maximum declined with each successive set as the women’s legs fatigued).
Prior to the initial workout and after the eighth and final workout session, researchers drew blood samples and conducted other diagnostic tests such as calorimetry to assess resting energy expenditure. Then, the researchers compared the baseline results of these tests with the eighth-week results within each exercise group and across the two exercise groups.
They discovered that the women who participated in the concentric training regimen did NOT markedly improve their triglyceride levels, blood lipid levels, or their resting energy expenditure between baseline readings and the measurements taken at end of the study period. In fact, most readings were flat between the pre- and post-training measurements.
By contrast, the eccentric group saw triglycerides fall by 13%, total cholesterol by 10%, and LDL (bad) cholesterol by 16%. In addition, HDL (good) cholesterol rose by 9%, fat oxidation rose by 9% (i.e., they burned more body fat), and resting energy expenditure increased by 5%. These improvement levels are consistent with improvements achieved through more intensive exercise routines.
As the study authors concluded, “On the basis of the evidence derived from the current study, eccentric training markedly increased muscle strength and performance, REE (resting energy expenditure), and lipid oxidation as well as decreased insulin resistance and blood lipid profile. It is reported that only 30 minutes of eccentric exercise per week for 8 weeks was sufficient to improve human performance and health, rendering eccentric exercise a promising novel type of physical activity … The favorable effects of eccentric training, as evident in the present investigation, are probably equal to or even superior to classical modes of training, like resistance and aerobic exercise lasting for about an hour and performed three to five times per week.”
So, What’s the Big Deal?
Well, like we said before, many people find it challenging to stick with exercise programs that require three to five hours of weekly exercise. An eccentric exercise program may allow people to achieve similar benefits from 30 minutes of weekly exercise. As the study authors pointed out, “Taking into consideration that the current trend in overweight and obesity statistics has become epidemic, such enhanced energy expenditure and lipid oxidation levels during recovery from eccentric exercise could assist in body weight management issues.”
Good forms of eccentric exercise include bench stepping, downhill walking, and resistance training where the intensity of effort is stressed on the unwinding or lengthening motion rather than the shortening or concentrating motion. A certified fitness instructor at your local health club should be able to recommend specific exercises that involve eccentric movements.