The Physiology of Sun Salutation (Surya amaskar) Peeyush Bhargava M.D, ABIHM www.vedic-healing.comIntroduction:Sun Salutation or Surya Namaskar (SN) is a classic yoga exercise consisting of 12 asanaspreformed sequentially, and synchronized with breathing. It is considered acomprehensive and ideal practice for physical and spiritual wellbeing. SN is performed asa prayer to the Sun, ideally at sunrise and in open air, facing east . It has aerobic anddynamic components, and has been shown to improve strength, body composition, andgeneral body endurance [2,3]. Performing 6-8 rounds will achieve the energy expenditureof light exercise intensity, and a 10 minute practice may improve cardio-respiratoryfitness in unfit or sedentary individuals [4, 5].
We attempted to identify the skeletal muscles involved in SN by visualizing F-18 FDGhypermetabolism on PET/CT imaging. F-18 FDG PET/CT imaging is the standard ofclinical care in patients with malignancies . Typically, 10 mCi of F-18 FDG is injectedIV and whole body PET/CT images are acquired 60 minutes later. Cancer cells havehigher rate of glucose utilization and so cancerous lesions are identified on the images asfoci of increased uptake or hypermetabolism. Patients have to fast for at least 6-8 hrs andare asked to avoid physical exertion 24 hrs before to after the scan . Artifactual skeletalmuscle uptake is frequently seen on the images and correlates well with physical activityduring the uptake period . PET imaging has been used to study skeletal muscle glucosemetabolism [9, 10].After the intravenous administration of 8.7 mCi of F-18 FDG a healthy male volunteerperformed 15 rounds of SN in 45 minutes. These were performed at a moderate pace of30-45 seconds per cycle, and in sets of five cycles with intermittent rest. He thenunderwent whole body PET/CT imaging on Siemens Biograph PET/CT scanner. ThePET images were acquired at 3 min per bed position, in 3D mode, from the top of thehead to the tips of the toes. Corresponding CT images were acquired at a low dose, andwithout any oral or intravenous contrast. CT based attenuation correction was applied andimages were reconstructed and interpreted in three orthogonal planes.
Figure 1: Anterior (A) and left lateral view (B) of the whole body FDG PET/CT imagesshowing intense uptake in bilateral shoulders and anterior abdominal muscles (arrows).Physiologic uptake is seen in the brain, liver, kidneys, and the urinary bladder.
The images show most intense skeletal muscle uptake in both shoulders and anteriorabdominal muscles (Figure 1). It is clear that with most intense uptake in these regions onPET/CT imaging after performance of 15 rounds, practice of SN will exercisepredominantly the shoulders and the anterior abdominal muscles. The fused PET/CTimages (Figure 2) localize the uptake to the following individual muscles bilaterally:deltoid, infraspinatus, triceps, serratus anterior, rectus abdominis, and tibialis anterior.Physiologic uptake is seen in the brain, the lymphoid tissue and vocal cords in the neck,liver and myocardium, and intense activity is seen from renal excretion of the tracer inthe kidneys, ureter, and the urinary bladder.Figure 2: Fused PET/CT images localize FDG uptake to deltoid and infraspinatus (arrowand arrow head respectively in A); triceps and serratus anterior muscles (arrow and arrowhead respectively in B); rectus abdominis in C, and tibialis anterior muscles in D.
Sun salutation has been well described in the yogic literature , but a recent search ofmodern scientific literature revealed only 7 articles when “sun salutation” was used as thesearch word and only 4 articles when “surya namaskar” was used for search.The twelve steps involved in this exercise are well described in several papers usingillustrations [1, 2,3]. These steps involve alternate flexion and extension of the spine inassociation with inspiration and expiration, respectively. This can be expected to be seenon PET/CT imaging as increased uptake in the anterior abdominal muscles (flexion) andthe paraspinal muscles of the back (extension). We found more intense uptake in therectus abdominis muscle, as compared to the paraspinal extensors. This is in contrast withSinha et al who showed that the backward bending poses have greater oxygen demand .Several SN steps involve weight bearing in the shoulders and arm extension to push upthe body weight. These are seen as increased uptake in the deltoid, infraspinatus, triceps,and serratus anterior muscles. Flexion and extension at the hip joint was not seen asincreased uptake in any muscles. Dorsiflexion at the ankle is seen as intense uptake inbilateral tibialis anterior muscles. This case study identifies the skeletal muscles involvedin SN, seen as increased uptake of F-18 FDG on PET/CT imaging. A baseline restingwhole body FDG PET/CT scan without the intervention of SN could make this reportmore convincing, but was avoided for the reason of limiting radiation exposure from anadditional radio-isotope injection and CT imaging study. It does not address the questionsabout how exercising these specific muscles bring about the known health benefits, butshows that imaging of F-18 FDG using PET/CT is a viable method in identifying musclerecruitment during yoga exercises.
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