Gorgey Ashraf S, Goldsmith Jacob A, Khalil Refka E, Liu Xin-Hua, Pan Jiangping, Cardozo Christopher, Adler Robert A
Spinal Cord Injury and Disorders Service, Central Virginia VA Health Care System, Hunter Holmes McGuire VA Medical Center, Richmond, VA, USA.
Physical Medicine and Rehabilitation, Virginia Commonwealth University, Richmond, VA, USA.
Eur J Appl Physiol. 2023 Mar;123(3):479-493. doi: 10.1007/s00421-022-05069-0. Epub 2022 Oct 28.
The purpose of the study was to identify potential predictors of muscle hypertrophy responsiveness following neuromuscular electrical stimulation resistance training (NMES-RT) in persons with chronic spinal cord injury (SCI). Data for twenty individuals with motor complete SCI who completed twice weekly NMES-RT lasting 12-16 weeks as part of their participation in one of two separate clinical trials were pooled and retrospectively analyzed. Magnetic resonance imaging (MRI) was used to measure muscle cross-sectional area (CSA) of the whole thigh and knee extensor muscle before and after NMES-RT. Muscle biopsies and fasting biomarkers were also measured. Following the completion of the respective NMES-RT trials, participants were classified into either high-responders (n = 8; muscle CSA > 20%) or low-responders (n = 12; muscle CSA < 20%) based on whole thigh muscle CSA hypertrophy. Whole thigh muscle and knee extensors CSAs were significantly greater (P < 0.0001) in high-responders (29 ± 7% and 47 ± 15%, respectively) compared to low-responders (12 ± 3% and 19 ± 6%, respectively). There were no differences in total caloric intake or macronutrient intake between groups. Extensor spasticity was lower in the high-responders compared to the low-responders as was the dosage of baclofen. Prior to the intervention, the high-responders had greater body mass compared to the low-responders with SCI (87.8 ± 13.7 vs. 70.4 ± 15.8 kg; P = 0.012), body mass index (BMI: 27.6 ± 2.7 vs. 22.9 ± 6.0 kg/m; P = 0.04), as well as greater percentage in whole body and regional fat mass (P < 0.05). Furthermore, high-responders had a 69% greater increase (P = 0.086) in total Akt protein expression than low-responders. High-responders also exhibited reduced circulating IGF-1 with a concomitant increase in IGFBP-3. Exploratory analyses revealed upregulation of mRNAs for muscle hypertrophy markers [IRS-1, Akt, mTOR] and downregulation of protein degradation markers [myostatin, MurF-1, and PDK4] in the high-responders compared to low-responders. The findings indicate that body composition, spasticity, baclofen usage, and multiple signaling pathways (anabolic and catabolic) are involved in the differential muscle hypertrophy response to NMES-RT in persons with chronic SCI.
本研究的目的是确定慢性脊髓损伤（SCI）患者在接受神经肌肉电刺激抗阻训练（NMES-RT）后肌肉肥大反应的潜在预测因素。将20例运动完全性SCI患者的数据进行汇总并进行回顾性分析，这些患者作为两项独立临床试验之一的参与者，每周进行两次NMES-RT，持续12 - 16周。在NMES-RT前后，使用磁共振成像（MRI）测量整个大腿和股四头肌的肌肉横截面积（CSA）。还测量了肌肉活检和空腹生物标志物。在各自的NMES-RT试验完成后，根据整个大腿肌肉CSA肥大情况，将参与者分为高反应者（n = 8；肌肉CSA增加>20%）或低反应者（n = 12；肌肉CSA增加<20%）。与低反应者（分别为12±3%和19±6%）相比，高反应者的整个大腿肌肉和股四头肌CSA显著更大（P < 0.0001，分别为29±7%和47±15%）。两组之间的总热量摄入或宏量营养素摄入量没有差异。与低反应者相比，高反应者的伸肌痉挛程度更低，巴氯芬剂量也更低。在干预前，高反应者的体重比SCI低反应者更大（87.8±13.7 vs. 70.4±15.8 kg；P = 0.012），体重指数（BMI：27.6±2.7 vs. 22.9±6.0 kg/m²；P = 0.04），以及全身和局部脂肪量百分比更高（P < 0.05）。此外，高反应者的总Akt蛋白表达增加幅度比低反应者大69%（P = 0.086）。高反应者还表现出循环IGF-1减少，同时IGFBP-3增加。探索性分析显示，与低反应者相比，高反应者中肌肉肥大标志物[IRS-1、Akt、mTOR]的mRNA上调，而蛋白质降解标志物[肌生长抑制素、MurF-1和PDK4]的mRNA下调。研究结果表明，身体组成、痉挛、巴氯芬使用情况以及多种信号通路（合成代谢和分解代谢）参与了慢性SCI患者对NMES-RT的不同肌肉肥大反应。
