Eccentric Cycling Doubles Fat Loss: 24 Obese Teens Lose -3.4kg ('-10%') Body Fat in 12-Wk W/Out Dieting Efforts

This is how ecc. cycling works + it also happens to show the bike used in the study!

Eccentric cycling? How does it even work? I admit that I was asking myself the very same thing when I hit on Valérie Julian's (2018) latest paper... until I found the video on the right and realized: it's just a modern day torture machine.

A torture machine that doubled the urgently needed fat loss in 24 obese adolescents, though, and hence probably is worth considering - not only, but also because the benefits of eccentric endurance training on fat mass "remain underexplored" (Julian 2018).
As the authors point out in the introduction to their paper, said lack of research is mostly due to several methodological:

"(a) the difficulty in isolating ECC and CON actions during typical everyday movements; (b) the rigorous methodology required to compare ECC and CON exercise in standardized experimental conditions of power output (ie, at the same mechanical power) or oxygen consumption (ie, at the same metabolic rate or oxygen consumption level, with mechanical power 3‐5 times higher during ECC cycling); and (c) specific ECC pedal ergometers have only acquired widespread usage in the last decade" (Julian 2018).

In obese adolescents, the study at hand is even the first to probe the impact of eccentric cycling. Now the question is: Why on earth would one even want to do that, i.e. cycling eccentrically? Well, here's the rationale: During #EccentricTraining, which forces your muscles to generate force by lengthening (developing tension to either decelerate movement or acting against gravity), your muscles are subjected to greater mechanical stress and respond with increased adaptational effects - that's at least the theory ;-)

Hold on, eccentric training is the thing you do for biceps curls, isn't it?

For most athletes eccentric training belongs into the realms of strength training and bodybuilding, though. To use it in endurance athletes and/or as "cardio" exercise to burn fat, is not exactly what people think aout when they hear about eccentric training. Few people know that there are at least three distinct types of ECC training, namely (a) #plyometricExercises (such as drop jumps, with contractions lasting milliseconds and producing thousands of watts of negative power), (b) classical ECC resistance exercises (protocols consisting of near maximal ECC contractions lasting few seconds, used to lift and lower weights), and (c) “continuous moderate load ECC exercises” as discussed by Hoppeler et al. in their 2016 paper in Frontiers of Physiology:

"This type of training has been characterizes as moderate load eccentric exercise. It has also been denoted RENEW (Resistance Exercise via Negative Eccentric Work by LaStayo et al., 2014). It is distinct from plyometric exercises (i.e., drop jumps) that impose muscle loads of several thousand Watts on muscles and tendons. It is also distinct from eccentric overload training whereby loads in a conventional strength training setting are increased in the eccentric phase of the movement to match concentric loads. Moderate load eccentric exercise (or RENEW) has been shown to be similarly effective as conventional strength training in increasing muscle strength and muscle volume.

Figure 1: Eccentric ergometer custom built for the Swiss National ski-team, capable of providing loads up to 2000 W. As shown, this ergometer can be used in a sitting and in a standing position (from Hoppeler 2014). You can see the machine that was used in the study at hand in the YouTube video at the top of this article.

However, as carried out at higher angular velocities of joint movement, it reduces joint loads. A hallmark of moderate load eccentric exercise is the fact that the energy requirements are typically 4-fold smaller than in concentric exercise of the same load. This makes moderate load eccentric exercise training the tool of choice in medical conditions with limitations in muscle energy supply. The use and effectiveness of moderate load eccentric exercise has been demonstrated mostly in small-scale studies for cardiorespiratory conditions, sarcopenia of old age, cancer, diabetes type 2, and neurological conditions. It has also been used effectively in the prevention and rehabilitation of injuries of the locomotor system, in particular the rehabilitation after anterior cruciate ligament surgery" (Hoppeler 2016).

As you can see in the video at the top of this article, as well as the photos from Hoppeler 2014 (Figure 1), a special motorized device is necessary to power this alternative training modality, which includes, next to cycling on special motorized ECC cycle ergometers, also downhill walking or running, and stepping exercises. As Juliann et al. point out, all four training modalities share one important characteristic: they lower the metabolic demand, compared with concentric training when performed at the same mechanical power (Peñailillo 2017).
Now, while this makes eccentric training "particularly suitable for patients with chronic pathologies, resulting in cardiac, respiratory, or muscular limitations to their exercise capacities" (Julian 2018), it is, indeed, not obvious why training less metabolically demanding would still promote greater fat loss than regular concentric training... Unless, however, you consider the energy demands of repairing muscle damage and the corresponding increase in resting energy expenditure, that is:

"Moreover, [eccentric training] modifies metabolic substrate use, increasing fat oxidation, and favors a postexercise decrease in blood lipid (which would participate in synthesize new cell membranes of injured muscles)" (Julian 2018 | my emphasis).

Thus, you will be getting more "calorie burning buck" for your bang... or, as the scientists phrase it:

"considering the similar or superior potential effects of ECC training on body composition and its lower metabolic demand, ECC training would be more efficient than CON training given the ratio of energy expenditure to net force or work production" (Julian 2018 | my emphasis).

In conjunction with increasing the energetic demands for muscle repair, eccentric training will - as previously highlighted - also provide a(n allegedly) more pronounced stimulus to skeletal muscle adaptation. Hence, it is not totally surprising that the body fat levels of the subjects were not the only parameter the scientists measured that improved more in the ECC vs. CON group.
Speaking of which, said subjects were twenty‐four adolescents aged 13.4 ± 1.3 years (BMI > 90th percentile), who were randomized to ECC or CON.

All subjects performed three cyclo‐ergometer sessions per week (30 min per session) for 12 weeks: two habituation, 5 at 50% VO2peak, and 5 at 70% VO2peak. 

Anthropometric measurements, body composition (using DXA), maximal incremental CON tests, strength tests, and blood samples were assessed pre‐ and post‐training. About the training protocol, the scientists write:

Figure 3: Study design (Julian 2018)

"The training program consisted of three phases. Phase 1 involved 2 weeks of habituation (ie, progressive increase in exercise intensity and session length) in order to protect subjects from DOMS. During the first sessions, a load corresponding to 20% VO2Peak was imposed, with exercise duration gradually increased by 10‐minute increments up to 30 minutes. Once the exercise duration reached 30 minutes, the exercise intensity ramped up progressively by 10% until achieving 50% VO2Peak.

Phase 2 consisted of 45‐minute sessions with a 10‐minute warm‐up on CON cycle ergometers at 30% VO2Peak then 30 minutes ECC or CON cycling at 50% VO2Peak, and a 5‐minute cool down. Phase 3 consisted of 45‐minute sessions with a 10‐minute warm‐up on CON ergocycles at 30% VO2Peak, 30 minutes ECC or CON cycling at 70% VO2Peak, and a 5‐minute cool down.

Patients were asked for a rating of their perceived exertion (RPE) during each exercise. During the whole 12‐week training, the duration of the session and loads was not increased if participants suffered from DOMS, as indicated by scores >3 on a visual analogic scale (0‐10 scale) or when the rating of the perceived exertion (RPE) of the session was >13 according to BORG (6‐20 scale)" (Julian 2018).

As highlighted as early as in the headline of this SuppVersity article, the analysis of the data the scientists generated with the protocol that is illustrated in Figure 3 yielded a quite astonishing result: The young, obese subjects reduced their body fat percentage by -10% while the subjects in the concentric training group lost only -4.2% (P < 0.05 | note: those are relative values, you can see the absolute changes in body fat percentage over the bars in Figure 4).

Figure 4: Changes in body composition and central parameters of glucose management (calculated based on Julian 2018 | the values for the body fat % and lean mass % differ because I didn't calculate them as the relative change in a parameter that is already expressed relative to the total body weight; I simply subtracted them -subjects went from 31% to 27% BF).

What the headline doesn't tell you, though, is that the increases in whole‐body lean mass (LM) percentage, as small as they were, was also significantly higher in the ECC compared to the CON group (ECC: 3.8% vs CON: 1.5%, P <0.05) - a result that seems to confirm the superior adaptive stimulus of ECC vs. CON training.

The large effect sizes shall not go unmentioned, either

By now, you'll probably not be surprised that the improvement in leg FM and LM percentages were greater in the ECC group (−6.5% and 3.0%, P = 0.01 and P < 0.01 | note: that's the difference between the relative values; the absolute changes were -1kg and -0.8kg), as well and came with significantly elevated increases in quadriceps strength in the ECC group (28.3% and 21.3%, P < 0.05).

Figure 5: Three of the changes in body composition were 'large' - that's something you don't see in every study.

Now, this is great, but let's be honest: Being strong and diabetic is a bummer, so the -19% reduction in HOMA-IR that occurred in the absence of significant differences in VO2peak improvement (ECC: 15.4% vs CON: 10.3%) may be the most important improvement the scientists observed in their 12-week study. And who knows if the subjects had eaten more protein (0.9g/kg is clearly not enough for optimal body composition changes in adolescents) the subjects would probably not just have seen relative gains in lean mass (lean mass:body weight), but actual gains.

Speaking of which, it is probably worth mentioning that the effect sizes for the lean leg mass and the reduction in leg fat were all 'large' (ES 1.07, 0.66, and 0.95, respectively). A 'large' effect (ES 0.85) was also observed for the reduction in waist circumference the scientists do not even report in the abstract to their study (see Figure 5 for an overview of 'large' effects).
References:

• Hoppeler, Hans. Eccentric Exercise: physiology and application in sport and rehabilitation. Routledge, 2014.
• Hoppeler, Hans. "Moderate load eccentric exercise; a distinct novel training modality." Frontiers in physiology 7 (2016): 483.
• Julian V, Thivel D, Miguet M, et al. Eccentric cycling is more efficient in reducing fat mass than concentric cycling in adolescents with obesity. Scand J Med Sci Sports. (2018): Ahead of print.
• Peñailillo, Luis, Anthony J. Blazevich, and Kazunori Nosaka. "Factors contributing to lower metabolic demand of eccentric compared with concentric cycling." Journal of Applied Physiology 123.4 (2017): 884-893.
• Phillips, Stuart M. "Higher Dietary Protein During Weight Loss: Muscle Sparing?." Obesity 26.5 (2018): 789-789.