Muscles most affected by breast cancer and its treatment.

The skeletal muscles most affected by breast cancer and its treatment are:

  • pectoralis major:
  • serratus anterior
  • coraco-brachialis
  • trapezius.

(Don’t forget that chemo and radio-therapy affect the heart (cardiac) muscle. )

Why? and What to look for?

Pectoralis major:  The pec major suffers a lot.  Even conservative surgery leaves scars.  During wound healing, a protective arm position is logically adopted.  This may last for some weeks, leading to loss of muscle tone in the pectoral of the affected side. This muscle is frequently burnt by radiation.  Burn scars are deep and inelastic – the muscle loses stretchiness.   If an implant reconstruction has been performed, the expander and/or implant will likely be below the pectoral muscle.  This puts the muscle fibers under tension, leading the shoulder drop and poor arm abduction, extension and external rotation (difficulty taking arm back, outwards and palm up).
Serratus anterior: Watch for radiation burns (radio placement tattoos are often seen just around S.anterior digitations, on the side of the chest, below the armpit).  Often this muscle also suffers from the protective arm position post-surgery.  Poor shoulder position weakens S.anterior because the insertion fibers are under tension (sunken chest/rounded back posture). In re-constructed women, this muscle may be used for Serratus-flap reconstruction.  If this is the case, full arm rotation can probably never be re-established.  Watch for pain under the armpit and at the mid shoulder blade area.
Coraco-brachialis:  Usually loses elasticity due to inward rotation and adduction of the arm  (arm is pulled in towards the body, and rotated so that the back of the hand faces the front).  Majorly affected by axilliary web syndrome, or cording. Watch for pain in the inner arm, in the soft fleshy part, about two finger-widths down from the armpit).
Trapezius:  The trap is majorly affected by shoulder drop and poor posture post-therapy. Also, weakened S.anterior and P.major muscles mean the trap is unsupported.  Muscles work in pairs, that is, when one pulls the other gives.  If the pec is pulling down and forward, the upper fibers of the trap are being stretched.  After a while, they will get annoyed and pull back.  Then, watch for neck and shoulder pain, including headaches.
The shoulder capsule is frequently scarred as a result of radiation burns.
This list is not exhaustive. Each case is unique.  I have chosen to high-light these four major muscles because they are the ones that most often need rehabilitation.
Here are some oft-used postures, modified for yoga therapy for breast cancer.
Dvipâda-pitam or half-bridge pose:  Lying on the back, with legs bent and feet hip-width apart, heels towards buttocks without using the hands to adjust position.  Arms by the sides, palms down. Inhale, raise hips and lower back, at the same time, rotating the arms so that the palms face the ceiling (watch limitations).  Watch out for rotation from the elbow, protecting the shoulder joint.  If this is the case, advise that the student lift the forearm off the floor, bending the elbow, and while rotating the arm, see if she can place the back of the hand on the floor.

Dvipada-pitam or Half-bridge pose.
Dvipada-pitam or Half-bridge pose.

Virabhadrâsana or Warrior pose:  Stand, feet together at the back of your mat.  Turn your right foot out about 45º.  Step forward with the left.  Arms down by the side, back of the hand facing towards the front.  Exhale.  Inhale as the knee bends, and at the same time, rotate the palms forward and out, opening the chest and separating the arms from the trunk.  Exhaling, return to starting position.  Repeat six times.  Optionally, include 1-6 breaths in the warrior pose, holding static, deep breath, awareness chest and shoulderblades.
Warrior pose
Warrior pose – modified

Let us yog. Om.