Although the rotator cuff muscles are susceptible to fatigue, shoulder fatigue studies reporting torque decline during intermittent tasks are relatively uncommon in the literature. A previous modification to the three-compartment controller (3CC) fatigue model incorporated a rest recovery multiplier (3CC-r model) to represent augmented blood flow to muscle during rest intervals (Looft et al., 2018). A rest recovery value of r = 15 was optimal for ankle, knee, and elbow joint regions, whereas r = 30 was better for hand/grip muscles. However, shoulder torque decline data was unavailable in the literature for comparison. Thus, the purpose of this study was to collect fatigue data for two different intermittent, isometric shoulder flexion fatiguing tasks and assess the 3CC-r model with r = 15 or 30 compared to the original 3CC model. Twenty healthy participants (9 M) completed two fatigue tasks: 50% maximum voluntary contraction (MVC) with 50% duty cycle (DC) and 70% MVC with 70% DC. MVCs were assessed at discrete time points (1, 3, 5, 10, and 15 min) until endurance time (MET). Mean observed percent torque decline (%TD) for the two tasks were compared to three model estimates: 3CC-r (using r = 15 and r = 30) and 3CC. Using these data, we confirmed that the addition of a rest multiplier (r = 15 somewhat better than r = 30) substantially improved predictions of shoulder fatigue using a previously validated analytical fatigue model (3CC). The relatively large reduction in model errors over the original model suggests the importance of representing augmented recovery during rest periods.

尽管肩袖肌肉容易疲劳，但报告间歇性任务期间扭矩下降的肩部疲劳研究在文献中相对罕见。之前对三室控制器 (3CC) 疲劳模型的修改纳入了休息恢复乘数（3CC-r 模型），以表示休息间隔期间流向肌肉的血流量增加（Looft 等人，2018）。对于踝关节、膝关节和肘关节区域，r = 15 的休息恢复值是最佳的，而对于手/握力肌肉来说，r = 30 则更好。然而，文献中没有肩部扭矩下降数据可供比较。因此，本研究的目的是收集两种不同间歇性、等长肩屈曲疲劳任务的疲劳数据，并与原始 3CC 模型相比，评估 r = 15 或 30 的 3CC-r 模型。 20 名健康参与者 (9 M) 完成了两项疲劳任务：50% 最大自主收缩 (MVC) 和 50% 占空比 (DC) 以及 70% MVC 和 70% DC。在离散时间点（1、3、5、10 和 15 分钟）评估 MVC，直至耐力时间 (MET)。将这两项任务观察到的平均扭矩下降百分比 (%TD) 与三个模型估计值进行比较：3CC-r（使用 r = 15 和 r = 30）和 3CC。使用这些数据，我们确认，使用先前验证的分析疲劳模型 (3CC)，添加休息乘数（r = 15 比 r = 30 稍好）可显着改善肩部疲劳的预测。与原始模型相比，模型误差相对大幅减少表明了在休息期间表示增强恢复的重要性。