Problems in the Trapezius muscle are a major cause of neck and upper back pain. Although it is quite common to be told to relax the upper Trapezius and draw the shoulder blades down the back to avoid tension in the neck, many yoga practitioners do experience neck pain and tension, especially after vinyasa practices or from Pincha Mayurasana and handstands.
The Trapezius muscle is usually divided into two distinct parts, upper and lower, and the upper and lower portions are considered to act as antagonists to each other. The upper Traps also have an antagonistic relationship with the Biceps and the Latissimus Dorsi.
The upper Traps exert an upward pull at the shoulder, while the lower Traps, Biceps and Lats all pull downwards. An imbalance between these muscles is a common source of shoulder and neck pain. Vinyasa can affect the neck as follows:
Chaturanga has a tendency to strengthen and shorten the Biceps and Lats, creating tension in the upper Traps. Stronger chest muscles also create tension in the shoulder girdle, because the arm position promotes shortening of the Pectoral muscles and draws the shoulder girdle forwards, weakening the Traps and Rotator Cuff muscles. Weak Rotator Cuff muscles also create referred neck pain.
Sirsasana variations are a useful start to developing Trapezius and neck strength, as vinyasa on its own can lead to a weak, tight Trapezius, if Sirsasana, Pincha Mayurasana and Urdhva Vrksasana are not practised regularly to balance the shoulders with the chest.
Yogis who are not strong enough to do this should practice Urdhva Mukha Svanasana on the forearms regularly instead.
Leaning the feet against the wall in these asanas tends to take the work out of the shoulders and while it can be useful to balance against walls, when learning these asanas, keeping the feet against the wall does not strengthen the Trapezius and will prevent you from developing the necessary shoulder strength for balancing inversions, and muscle imbalance between the chest and shoulders becomes likely.
The sensation of a strained neck in Pincha Mayurasana can be from a tight upper Trapezius: Traps work very hard here and pull on the muscle attachments to the neck vertebrae.
If the lower Trapezius feels tight and sore in Pincha Mayurasana, loosening the upper Traps with strength training can be more helpful than stretching. Movements like shrugs are not usually taught in yoga and are sometimes the only way to loosen a tight neck.
More suggestions on strengthening the neck will be given in Neck Strengthening
Kendall, McCreary, Provance, 1993, Muscles, Testing and Function
Ellenbecker, De Carlo, DeRosa, 2009, Effective Functional Progressions in Sport Rehabilitation
Sharkey, 2008, The Concise book of Neuromuscular Therapy