Abstract
The benefits of eccentric (ECC) training on fat mass (FM) remain underexplored. We hypothesized that in obese adolescents, ECC cycling training is more efficient for decreasing whole‐body FM percentage compared to concentric (CON) performed at the same oxygen consumption (VO2). Twenty‐four adolescents aged 13.4 ± 1.3 years (BMI > 90th percentile) were randomized to ECC or CON. They 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, maximal incremental CON tests, strength tests, and blood samples were assessed pre‐ and post‐training. Whole‐body FM percentage decreased significantly after compared to pretraining in both groups, though to a larger extent in the ECC group (ECC: −10% vs CON: −4.2%, P < 0.05). Whole‐body lean mass (LM) percentage increased significantly in both groups after compared to pretraining, with a greater increase in the ECC group (ECC: 3.8% vs CON: 1.5%, P <0.05). The improvements in leg FM and LM percentages were greater in the ECC group (−6.5% and 3.0%, P = 0.01 and P < 0.01). Quadriceps isometric and isokinetic ECC strength increased significantly more in the ECC group (28.3% and 21.3%, P < 0.05). Both groups showed similar significant VO2peak improvement (ECC: 15.4% vs CON: 10.3%). The decrease in homeostasis model assessment of insulin resistance index was significant in the ECC group (−19.9%). In conclusion, although both ECC and CON cycling trainings are efficient to decrease FM, ECC induces greater FM reduction, strength gains, and insulin resistance improvements and represents an optimal modality to recommend for obese adolescents.
Highlights
Obesity, defined as excessive fat accumulation due to an imbalance between energy intake and energy expenditure, is a serious current public health challenge
Absolute whole‐body lean mass (LM) did not significantly change after training compared to pretraining in the ECC group (−1.0 ± 4.3), while it decreased in the CON (−1.8 ± 3.2) group (P < 0.05)
The improvements observed in our study after a 12‐week CON cycling training on whole‐body fat mass percentage (−4.2%), BMI (−5.4%), and VO2peak (10.9%) are fully in line with the literature, which has extensively demonstrated its beneficial impact in obese population.[2,3,31,32]
Summary
Obesity, defined as excessive fat accumulation due to an imbalance between energy intake and energy expenditure, is a serious current public health challenge. One of the physiological characteristics of ECC cycling is that it lowers metabolic demand, compared with CON cycling when performed at the same mechanical power ,5,6 due to the combination of a high muscle force with low energy cost (ie, low oxygen uptake ratio and V O2/power) This lower metabolic cost is mainly due to a lower level of extensor and flexor muscle activations and lesser muscle deoxygenation during ECC compared with CON cycling.[6] Eccentric training is suitable for patients with chronic pathologies, resulting in cardiac, respiratory, or muscular limitations to their exercise capacities.[4,7] one possible negative effect of ECC modality is exercise‐induced muscle damage (EIMD).[8] This causes temporary lesions on plasma membranes, contractile and non‐contractile proteins in response to overstretching,[8] and induces muscle weakness and delayed‐onset muscle soreness (DOMS), in untrained subjects and chronic disease populations. The repeated bout effect, which includes neural and structural adaptations, protects against muscle damages from subsequent ECC bouts.[9,10] an ECC cycling program can be achieved without undue DOMS provided a progressive ramping protocol is followed.[4,11]
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