Baritello Omar, Khajooei Mina, Engel Tilman, Kopinski Stephan, Quarmby Andrew, Mueller Steffen, Mayer Frank
1Clinical Exercise Science, Department Sports and Health Science Medicine, University Outpatient Clinic Potsdam, University of Potsdam, Am Neuen Palais 10, House 12, 14469 Potsdam, Germany.
2Computer Science and Therapy Science, Trier University of Applied Science, Schneidershof, 54293 Trier, Germany.
BMC Sports Sci Med Rehabil. 2020 Mar 26;12:21. doi: 10.1186/s13102-020-00168-x. eCollection 2020.
Recent shoulder injury prevention programs have utilized resistance exercises combined with different forms of instability, with the goal of eliciting functional adaptations and thereby reducing the risk of injury. However, it is still unknown how an unstable weight mass (UWM) affects the muscular activity of the shoulder stabilizers. Aim of the study was to assess neuromuscular activity of dynamic shoulder stabilizers under four conditions of stable and UWM during three shoulder exercises. It was hypothesized that a combined condition of weight with UWM would elicit greater activation due to the increased stabilization demand.
Sixteen participants (7 m/9 f) were included in this cross-sectional study and prepared with an EMG-setup for the: Mm. upper/lower trapezius (U.TA/L.TA), lateral deltoid (DE), latissimus dorsi (LD), serratus anterior (SA) and pectoralis major (PE). A maximal voluntary isometric contraction test (MVIC; 5 s.) was performed on an isokinetic dynamometer. Next, internal/external rotation (In/Ex), abduction/adduction (Ab/Ad) and diagonal flexion/extension (F/E) exercises (5 reps.) were performed with four custom-made-pipes representing different exercise conditions. First, the empty-pipe (P; 0.5 kg) and then, randomly ordered, water-filled-pipe (PW; 1 kg), weight-pipe (PG; 4.5 kg) and weight + water-filled-pipe (PWG; 4.5 kg), while EMG was recorded. Raw root-mean-square values (RMS) were normalized to MVIC (%MVIC). Differences between conditions for RMS%MVIC, scapular stabilizer (: U.TA/L.TA; U.TA/SA) and contraction (: concentric/eccentric) ratios were analyzed (paired t-test; ≤ 0.05; Bonferroni adjusted α = 0.008).
PWG showed significantly greater muscle activity for all exercises and all muscles except for PE compared to P and PW. Condition PG elicited muscular activity comparable to PWG ( > 0.008) with significantly lower activation of L.TA and SA in the In/Ex rotation. The ratio was significantly higher in PWG compared to P and PW. No significant differences were found for the ratio in all exercises and for all muscles.
Higher weight generated greater muscle activation whereas an UWM raised the neuromuscular activity, increasing the stabilization demands. Especially in the In/Ex rotation, an UWM increased the RMS%MVIC and ratio. This might improve training effects in shoulder prevention and rehabilitation programs.
近期的肩部损伤预防计划采用了阻力训练与不同形式的不稳定训练相结合的方式，目的是引发功能适应性变化，从而降低受伤风险。然而，尚不清楚不稳定重量块（UWM）如何影响肩部稳定肌的肌肉活动。本研究的目的是评估在三种肩部运动的稳定和UWM四种条件下动态肩部稳定肌的神经肌肉活动。研究假设，由于稳定需求增加，重量与UWM相结合的条件会引发更大的激活。
16名参与者（7名男性/9名女性）纳入本横断面研究，并使用肌电图设备对以下肌肉进行准备：上/下斜方肌（U.TA/L.TA）、三角肌外侧头（DE）、背阔肌（LD）、前锯肌（SA）和胸大肌（PE）。在等速测力计上进行最大自主等长收缩测试（MVIC；5秒）。接下来，使用代表不同运动条件的四根定制管道进行内/外旋转（In/Ex）、外展/内收（Ab/Ad）和对角屈伸（F/E）运动（5次重复）。首先是空管道（P；0.5千克），然后随机顺序进行注水管道（PW；1千克）、配重管道（PG；4.5千克）和配重+注水管道（PWG；4.5千克），同时记录肌电图。原始均方根值（RMS）以MVIC（%MVIC）进行标准化。分析RMS%MVIC、肩胛稳定肌（：U.TA/L.TA；U.TA/SA）和收缩（：向心/离心）比率在不同条件之间的差异（配对t检验；≤0.05；Bonferroni校正α = 0.008）。
与P和PW相比，PWG在所有运动和除PE外的所有肌肉中均显示出显著更大的肌肉活动。条件PG引发的肌肉活动与PWG相当（>0.008），但在In/Ex旋转中L.TA和SA的激活显著较低。PWG中的比率与P和PW相比显著更高。在所有运动和所有肌肉的比率中未发现显著差异。
更高的重量产生更大的肌肉激活，而UWM提高了神经肌肉活动，增加了稳定需求。特别是在In/Ex旋转中UWM增加了RMS%MVIC和比率。这可能会改善肩部预防和康复计划的训练效果。
