Trunk and Hip Muscle Activation during Yoga Poses in Untrained Individuals

Research Article

Ann Yoga Phys Ther. 2017; 2(4): 1033.

Trunk and Hip Muscle Activation during Yoga Poses in Untrained Individuals

Beazley DA, Patel S, Davis B, Vinson S and Bolgla LA*

Department of Physical Therapy, Augusta University, USA

*Corresponding author: Bolgla LA, Department of Physical Therapy, Augusta University, Augusta GA, USA

Received: August 23, 2017; Accepted: September 02, 2017; Published: September 19, 2017


Yoga has become a popular form of exercise for improving core strength and stability in individuals with Low Back Pain (LBP). Researchers have quantified muscle activation during core stabilization exercises, believing that exercises which require greater activation will benefit that needing improved core stabilization. Minimal attention has been directed toward muscle activation during yoga. The purpose of this study was to determine and compare the relative activation of core muscles during yoga to traditional back exercises. Surface Electro Myo Graphy (EMG) was used to quantify the relative activation of the Rectus Abdominis (RA), Abdominal Obliques (AO), Lumbar Extensors (LE), and Gluteus Maximus (GMX) during four yoga poses (Chair, High Plank, Upward-Facing Dog, and Dominant-Side Warrior 1). Data were expressed as 100% of a Maximum Voluntary Isometric Contraction (100% MVIC). Separate analyses of variance with repeated measures were used to compare muscle activity across each exercise. The sequentially rejective Bonferroni test was used for post hoc testing. EMG activity during the High Plank was moderate (28% MVIC) and high (44% MVIC) for the RA and AO, respectively. The AO had moderate (27% MVIC) activity during the Upward-Facing Dog. EMG activity during the Chair was moderate (38% MVIC) only for the LE. GMX activity was low (< 21% MVIC) during all the exercises. These findings suggest that certain yoga poses may be useful for improving core endurance and strength. Clinicians may use these data when developing and implementing an evidence-based core exercise program for individuals with LBP who prefer a yoga treatment strategy.

Keywords: Complementary medicine; Surface electromyography; Core stabilization


Classified as a Complementary and Alternative Medicine (CAM) mind-body therapy, the practice of yoga is growing in popularity in the United States. As such, yoga is being adopted in conventional physical therapy practice as an integral therapy [1]. The National Center for Complementary and Alternative Medicine defines CAM as a group of diverse medical and healthcare systems practices not presently considered part of conventional healthcare. CAM is commonly used as an adjunct intervention with conventional medicine and represents the synthesis of conventional practice and evidenced-based complementary medicine [2]. National survey trends of adult users of CAM illustrate that approximately 33.2% of adults aged 18 years and over have used one form of CAM in the last 12 months [1,2].

Yoga is a popular CAM intervention, with 34% of adults in 2016 likely to practice yoga within the next 12-month period. More than 15% (36.7 million) of adults in the US consistently practice yoga, an increase of over 16 million since 2012. Most importantly, 74% of those who engage in yoga are relatively new to the practice, becoming involved within the last five years. Significance is the emerging and growing use of yoga across ethnic dimensions. Non-Hispanic adults showed a 30% increase in use of yoga from 2002 to 2012; significant increases in use by Hispanic (5.1%) and African American (5.6%) adults has been reported as well [1].

Yoga is defined as “a combination of breathing exercises, physical postures, and meditation used to calm the nervous system and balance the body, mind, and spirit” [1]. Approximately 55% of physical therapists regularly use yoga as a common form of alternative strength training [3], which may reflect its adaptability for addressing various musculoskeletal problems [4]. The incorporation of lowintensity forms of exercise can be varied and scaled to age, medical complexity, and preference across all age and ethnic groups. The use of yoga suggests a positive relationship to the alleviation of chronic Low Back Pain (LBP) [5] and supports the premise that yoga brings balance and health to the physical, mental, emotional, and spiritual dimensions of an individual [6].

Yoga incorporates core strengthening and stabilization exercises considered important for the treatment of non-specific LBP [5]. This core comprises the lumbar spine, pelvis, and hip, as well as the ligaments and muscles that control their movement [7]. Core stabilization refers to the ability of the core musculature to control the position and motion of the trunk over the pelvis and lower extremities during movement [8]. The importance of core stabilization has led to substantial evidence quantifying the relative Electro Myo Graphy (EMG) activity of core muscles during therapeutic exercise [9-14]. These studies were based on the premise that exercises which require greater EMG activity will result in increased muscle strength [15].

To date, limited data exist regarding the relative EMG activity of core muscles during yoga poses. Ni and colleagues are the only researchers who have examined such EMG activity during yoga practice. They reported differences in muscle activation during various poses performed by trained yoga practitioners [16]. They also found that muscle activation varied per practitioner skill level [17]. A limitation of these studies was the use of experienced subjects. With respect to physical therapy practice, patients who use yoga for rehabilitation purposes most likely have limited, if any, prior experience. Because skill level can influence muscle activity, additional studies are needed to examine EMG activity in untrained individuals. Therefore, the primary purpose of this study was to determine the relative EMG activity of core muscles during yoga poses in individuals with minimal yoga experience. The secondary purpose was to compare core activation during yoga to back exercises commonly prescribed for individuals with LBP. Our study was based on the null hypothesis that no differences would exist in core muscle activation during the chosen yoga poses and when compared to traditional back exercises.



Thirty individuals with minimal experience with yoga participated (15 females, mean age 24.7 + 2.1 y, mass 71.6 + 13.0 kg, height 1.7 + 0.1 m). A convenience sample was recruited from the greater Central Savannah River Area. Inclusion criteria included healthy subjects between the age of 18 and 40 years with less than four weeks of yoga experience. Additionally, subjects had no history of spine or upper/ lower extremity surgery. None had incurred any significant spine or lower extremity injury in the past two years. The investigators explained the benefits and risks of this study to all participants, who then signed an informed consent document approved by the Georgia Regents University (now Augusta University) Institutional Review Board.


Following the informed consent process, all subjects completed a warm-up session that consisted of gentle stretching exercises for the trunk extensors and rotators, hamstrings, quadriceps, and calf muscles. Subjects performed each stretch three times with a 15-second hold. Next, an investigator instructed each subject in the following yoga poses: Chair, High Plank (Plank), Upward-Facing Dog (Dog), and Dominant-Side Warrior 1 (Warrior) [16]. Based on our clinical experience, we chose these poses because they emulated those typically used for the rehabilitation of individuals with pathologies like LBP [18]. For the Chair pose (Figure 1), subjects were instructed to stand and flex the knees 45 degrees (as if to sit in a chair) while keeping their backs straight, upper extremities overhead, and palms facing inward. Stance width was standardized using a “fist-width” measure (Figure 2). For this purpose, subjects placed both hands in a closed-fist position with a side-by-side orientation. An investigator measured the distance from the most ulnar side of the head of the 5th metacarpal on each hand to the nearest 1/10th of a centimeter. This exercise was chosen to emulate a static position to facilitate core stabilization during a stand-to-sit transfer. For the Plank (Figure 3), subjects assumed a full push-up position. This exercise was chosen since it has been prescribed to improve trunk endurance. For the Dog, subjects assumed a prone position and then extended their spines (Figure 4). This exercise was chosen because of its similarity to the McKenzie extension exercise. For the Warrior (Figure 5), subjects lunged toward the same side as the dominant hand. Care was taken to ensure that subjects kept their shoulders, trunks, and non-dominantside lower extremities facing forward. Stance width was standardized as the distance equal to the lower limb length of the dominant hand side. Subjects lunged to the position where the tibia on the dominant hand side was vertical to the floor. This exercise was chosen to facilitate core stabilization during a frontal plane movement.