Comparison of Muscle Activity in Three Single-Joint, Hip Extension Exercises in Resistance-Trained Women

摘要

The aim of the study was to compare neuromuscular activation in the gluteus maximus, the biceps femoris and the erector spinae from the Romanian deadlift, the 45-degree Roman chair back extension and the seated machine back extension. Fifteen resistance-trained females performed three repetitions with 6-RM loading in all exercises in a randomized and counterbalanced order. The activation in the whole movement as well as its lower and upper parts were analyzed. The results showed that the Romanian deadlift and the Roman chair back extension activated the gluteus maximus more than the seated machine back extension (94-140%, p < 0.01). For the biceps femoris the Roman chair elicited higher activation compared to both the Romanian deadlift and the seated machine back extension (71-174%). Further, the Romanian deadlift activated the biceps femoris more compared to the seated machine back extension (61%, p < 0.01). The analyses of the different parts of the movement showed that the Roman chair produced higher levels of activation in the upper part for both the gluteus maximus and the biceps femoris, compared to the other exercises. There were no differences in activation of the erector spinae between the three exercises (p = 1.00). In conclusion, both the Roman deadlift and the Roman chair back extension would be preferable to the seated machine back extension in regards to gluteus maximus activation. The Roman chair was superior in activating the biceps femoris compared to the two other exercises. All three exercises are appropriate selections for activating the lower back muscles. For overall lower limb activation, the Roman chair was the best exercise.Key points In general, the Roman chair back extension lead to superior muscle activation compared to the Romanian deadlift and the seated machine back extensionThe seated machine back extension showed the lowest gluteus and hamstring activationAll three exercises are appropriate selections for activating the lower back musclesThe differences in muscle activation are most likely caused by biomechanical differences. Key words: Gluteus maximus, biceps femoris, erector spinae, muscle activationIntroductionStrong hip and back extensors are considered important for sport-specific activity, daily tasks, and injury prevention (Contreras et al., 2016; Lariviere et al., 2010; Neto et al., 2020). Although several single-joint exercises are used to train the hip- and back extensors, little is known about the differences in how they activate the muscles. Single-joint hip extension exercise can be performed in several ways to target both the hip and the back extensors, typically using free weights (e.g. Romanian deadlift, Good mornings), machines (e.g. seated back extension), or a Roman chair. Although the movement is similar, these exercises are biomechanically different (Contreras et al., 2013). Contreras et al. (2013) compared the Good morning exercise, the 45-degree Roman chair back extension and the horizontal Roman chair back extension. The hip extension torque-pattern varied between the three exercises. The Good morning elicits the greatest torque in the lower part of the motion while the horizontal Roman chair exercise produces a peak in the upper part. In contrast, the 45-degree Roman chair back extension produces maximum torque in the middle of the motion. Importantly, in this exercise there is less change in the moment arm, creating a considerable amount of torque in both ends of the range of motion (338 Nm), resulting in less variation in torque. These differences in torque production would most likely affect muscle activation differently for both the whole movement, and the different parts of the movement. Alternatively, the seated back/hip extension machine transfers the load from the apparatus to the back through an upper back pad placed on the shoulder blades throughout the movement, keeping the moment arm and torque similar in all phases of the motion. However, performing the hip extension in a seated position with flexed knees and hip could be sub-optimal for activation of the different hip extensors (Kwon and Lee, 2013; Worrell et al., 2001).Most studies examining the neuromuscular activation of the hip and back extensors have compared single-joint hip extensor exercises to either multi-joint exercises or knee flexor exercises (Delgado et al., 2019; Ebben, 2009; Lee et al., 2018; McAllister et al., 2014; McCurdy et al., 2018), but two of them also compared different single-joint, hip extensor exercises (Ebben, 2009; McAllister et al., 2014). McAllister et al. (2014) reported similar activation of the erector spinae, the biceps femoris and the gluteus medius in trained men performing 1 repetition at 85% of 1-RM in the Romanian deadlift and the Good morning exercise. Ebben et al. (2009) reported similar findings when they compared hamstring activation among athletes performing two repetitions, at 6-RM loading, in the Stiff-leg deadlift and the Good morning ex