Neuromechanics Laboratory, University of Kansas, Lawrence, Kansas.
Neuromuscular Research Laboratory, Department of Exercise Science and Sport Science, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina.
Scand J Med Sci Sports. 2018 Nov;28(11):2310-2321. doi: 10.1111/sms.13256. Epub 2018 Jul 26.
Neuromuscular function in young overweight/obese (OF) children is not well described.
This study examined isometric and isokinetic leg extensor strength, muscle size (mCSA) and tissue composition as measured via echo intensity (mEI), and motor unit (MU) firing rates in normal weight (NW) and OF children aged 7-10 years.
Fourteen NW (eight girls and six boys, BMI: 15.8 ± 1.4 kg/m ) and 15 OF (10 girls and five boys, BMI: 20.8 ± 2.3 kg/m ) children volunteered to perform this study. Percentage body fat (%BF) was measured, and mCSA, mEI, and subcutaneous fat (sFAT) of the vastus lateralis (VL) was assessed. MU mean firing rates (MFRs) in relation to recruitment threshold (RT) of the VL were assessed during submaximal isometric contractions. Maximal isokinetic contractions were performed at 1.05 and 4.20 rad/s. The 95% confidence intervals (CI) from the statistical tests are presented.
The OF children had greater %BF (95% CI = -15.1 to -7.2), mCSA (95% CI = -4.1 to -1.2), mEI (95% CI = -22.3 to -5.9), and sFAT (95% CI = -0.5 to -0.1), greater rate of strength loss with increasing isokinetic velocities (95% CI = 0.4 to 5.4), and a smaller range of MFRs (95% CI = 0.007 to 7.136) at the steady torque than the NW children.
The OF children had poorer muscle tissue composition, greater velocity-related impairments in muscle strength, and a smaller range of MFRs at the targeted torque that may suggest altered MU recruitment strategies. Interventions in OF children should include exercises and recruit higher-threshold MUs, such as high-intensity resistance exercises.
本研究旨在比较 7-10 岁正常体重（NW）和超重/肥胖（OF）儿童的等长和等速伸膝肌力、肌肉横截面积（mCSA）和组织成分（通过回声强度[mEI]测量）以及运动单位（MU）放电率。
本研究招募了 14 名 NW（8 名女孩和 6 名男孩，BMI：15.8±1.4kg/m²）和 15 名 OF（10 名女孩和 5 名男孩，BMI：20.8±2.3kg/m²）儿童志愿者参与本研究。测量体脂百分比（%BF），评估股外侧肌（VL）的 mCSA、mEI 和皮下脂肪（sFAT）。在亚最大等长收缩期间，评估 VL 募集阈值（RT）与 MU 平均放电率（MFR）的关系。在 1.05 和 4.20rad/s 下进行最大等速收缩。统计检验的 95%置信区间（CI）如下。
OF 儿童的 %BF（95%CI=-15.1 至-7.2）、mCSA（95%CI=-4.1 至-1.2）、mEI（95%CI=-22.3 至-5.9）和 sFAT（95%CI=-0.5 至-0.1）更大，随着等速速度的增加，肌力下降的速度更快（95%CI=0.4 至 5.4），在目标转矩下 MU 放电率的范围更小（95%CI=0.007 至 7.136）。
OF 儿童的肌肉组织成分较差，肌肉力量与速度的相关性损伤更大，在目标转矩下 MU 放电率的范围更小，这可能表明 MU 募集策略发生了改变。OF 儿童的干预措施应包括高强度阻力运动等可以募集更高阈值 MU 的运动。
