Trindade Thiago Barbosa, Neto Leônidas Oliveira, Pita José Claudino Neto, Tavares Vagner Deuel de Oliveira, Dantas Paulo Moreira Silva, Schoenfeld Brad J, Prestes Jonato
Graduation Program in Physical Education, Catholic University of Brasilia, Brasilia, Brazil.
Department of Arts, Federal University of Rio Grande do Norte, Natal, Brazil.
Front Physiol. 2020 Jul 7;11:769. doi: 10.3389/fphys.2020.00769. eCollection 2020.
Bilateral squat exercise is widely used in resistance training (RT) programs to increase lower limb strength and muscle mass, but this exercise does not result in significant hypertrophy of the hamstrings. It has been speculated that stretching between sets with a certain degree of tension results in muscle hypertrophy, while acute stretching could decrease performance during maximal contractions. This study investigated the acute effects of hamstring stretching before bilateral squatting on muscle thickness (MT), electromyography (EMG), and total training volume (TTV) on exercise performance. Fourteen resistance-trained young men, with ∼7.5 years of RT experience, performed the 10 repetition maximum (RM) for the barbell squat in two sessions (test-retest) separated by period after 48 h. Participants engaged in two resistance exercise conditions separated by a 1 week recovery interval: one session employed hamstrings stretching and the other did not include hamstrings stretching. Before and after each resistance exercise session, the thickness of the quadriceps muscles and biceps femoris long head were obtained by ultrasound imaging. Moreover, the EMG amplitudes for the quadriceps muscles, biceps femoris, and iliocostalis muscles were recorded during back squat performance. The TTV was also evaluated for each exercise session. A significant increase in MT was observed after every set in both conditions for the evaluated quadriceps muscles (all < 0.05), while for the biceps femoris, this effect was found only in the stretching condition ( < 0.05). EMG activity increased in the rectus femoris, vastus lateralis, and vastus medialis for the stretching condition. For the non-stretching condition, activity only increased in the vastus lateralis and medialis. There was no difference in EMG activity for the biceps femoris and iliocostalis in both conditions. Stretching the hamstrings immediately before each set of the back squat can be used to acutely increase biceps femoris thickness without impairing squat performance.
双侧深蹲练习在阻力训练（RT）项目中被广泛用于增强下肢力量和肌肉量，但该练习并不会使腘绳肌显著肥大。据推测，在组间进行一定程度张力的拉伸会导致肌肉肥大，而急性拉伸可能会降低最大收缩时的表现。本研究调查了双侧深蹲前腘绳肌拉伸对肌肉厚度（MT）、肌电图（EMG）以及运动表现的总训练量（TTV）的急性影响。14名有大约7.5年RT经验的受过阻力训练的年轻男性，在48小时后的时间段分隔的两个 session（重测）中进行杠铃深蹲的10次重复最大值（RM）测试。参与者在1周的恢复间隔后进行两种阻力运动条件：一个session进行腘绳肌拉伸，另一个不包括腘绳肌拉伸。在每次阻力运动session前后，通过超声成像获得股四头肌和股二头肌长头的厚度。此外，在进行后深蹲时记录股四头肌、股二头肌和髂肋肌的EMG幅度。还对每个运动session的TTV进行了评估。在两种条件下，对于所评估的股四头肌，每组后MT均显著增加（均P<0.05），而对于股二头肌，仅在拉伸条件下发现这种效果（P<0.05）。拉伸条件下，股直肌、股外侧肌和股内侧肌的EMG活动增加。对于非拉伸条件，仅股外侧肌和股内侧肌的活动增加。两种条件下股二头肌和髂肋肌的EMG活动没有差异。在每组后深蹲前立即拉伸腘绳肌可用于急性增加股二头肌厚度而不损害深蹲表现。
