1Department of Exercise and Sport Science, Human Performance Lab, University of Mary Hardin-Baylor, Belton, Texas, USA.
J Strength Cond Res. 2012 Mar;26(3):599-607. doi: 10.1519/JSC.0b013e318242f92d.
Extracellular signal-regulated kinase (ERK) 1/2 signaling has been shown to be increased after heavy resistance exercise and suggested to play a role in the hypertrophic adaptations that are known to occur with training. However, the role that ERK1/2 may play in response to lower intensities of resistance exercise is unknown. Therefore, the purpose of this study was to determine the effects of resistance exercise intensity on ERK1/2 activity in human skeletal muscle. Twelve recreationally active men completed separate bouts of single-legged resistance exercise with 8-10 repetitions (reps) at 80-85% 1 repetition maximum (1RM) (85%) and 18-20 reps at 60-65% 1RM (65%) in a randomized crossover fashion. For both resistance exercise sessions, vastus lateralis biopsies and blood draws were taken immediately before exercise (PRE) and at 30 minutes (30MPST), 2 hours (2HRPST), and 6 hours (6HRPST) post exercise, with an additional blood draw occurring immediately after exercise (POST). The phosphorylated levels of pIGF-1R, pMEK1, pERK1/2, and activated Elk-1 were assessed by phosphoELISA, and serum insulin-like growth factor 1 (IGF-1) was assessed via enzyme-linked immunosorbent assay. Statistical analyses used a 2 × 4 (muscle responses) and 2 × 5 (serum responses) multivariate analysis of variance on delta values from baseline (p < 0.05). Both exercise intensities significantly increased the activity of insulin-like growth factor 1 receptor (IGF-1R), mitogen-activated protein kinase 1, ERK1/2, and Elk-1, with peak activity occurring at 2HRPST (p < 0.001). However, 65% resulted in a preferential increase in IGF-1R and Elk-1 activation when compared with 85% (p < 0.05). No differences were observed for serum IGF-1 levels regardless of intensity and time. These findings demonstrate that resistance exercise upregulates ERK1/2 signaling in a manner that does not appear to be preferentially dependent on exercise intensity.
细胞外信号调节激酶 (ERK) 1/2 信号在大强度抗阻运动后增加，提示其在训练引起的肥大适应中发挥作用。然而，ERK1/2 在低强度抗阻运动中的作用尚不清楚。因此，本研究旨在确定抗阻运动强度对人体骨骼肌 ERK1/2 活性的影响。12 名有规律运动的男性以随机交叉方式分别进行单腿抗阻运动，强度分别为 80-85% 1 次最大重复次数 (1RM) (85%) 和 60-65% 1RM (65%) 的 8-10 次重复 (REPS) 和 18-20 次重复。对于两种抗阻运动，股外侧肌活检和血液样本分别在运动前 (PRE) 以及运动后 30 分钟 (30MPST)、2 小时 (2HRPST) 和 6 小时 (6HRPST) 时采集，并在运动后即刻 (POST) 进行额外的血液采集。通过磷酸化酶联免疫吸附试验 (ELISA) 检测 pIGF-1R、pMEK1、pERK1/2 和激活 Elk-1 的磷酸化水平，并通过酶联免疫吸附试验 (ELISA) 检测血清胰岛素样生长因子 1 (IGF-1)。统计分析采用基线 (p < 0.05) 时的 2 × 4（肌肉反应）和 2 × 5（血清反应）多元方差分析。两种运动强度均显著增加了胰岛素样生长因子 1 受体 (IGF-1R)、丝裂原激活蛋白激酶 1、ERK1/2 和 Elk-1 的活性，最大活性出现在 2HRPST (p < 0.001)。然而，与 85%相比，65%的运动强度更优先地增加 IGF-1R 和 Elk-1 的激活 (p < 0.05)。无论强度和时间如何，血清 IGF-1 水平均无差异。这些发现表明，抗阻运动以一种似乎不依赖于运动强度的方式上调 ERK1/2 信号。
