Thoracic Outlet Syndrome (TOS) is a condition caused by compression of the nerves or blood vessels in the space between your collarbone and first rib — known as the thoracic outlet. One major contributor to this compression? The pectoralis (pec) muscles.
What Do the Pec Muscles Do?
Your pectoralis major and minor muscles help move your shoulder and arm. However, when they become tight or shortened (often due to posture, repetitive activities, or overuse), they can compress nearby nerves and blood vessels.
How Tight Pec Muscles Can Contribute to TOS:
• The pectoralis minor, located underneath the pectoralis major, attaches to the ribs and shoulder blade.
• When shortened, it can compress the brachial plexus (a network of nerves that controls arm movement) and the subclavian vessels.
• This leads to symptoms such as:
• Numbness or tingling down the arm
• Shoulder or neck pain
• Arm fatigue or weakness
• Swelling or discoloration in the arm or hand.
• Poor posture (e.g., rounded shoulders from desk work)
• Overtraining chest muscles
• Repetitive overhead activities
• Carrying heavy backpacks or bags
What Can Help:
• Manual therapy to release soft tissue tension
• Postural correction and ergonomics
• Stretching the pectoralis muscles (especially pectoralis minor)
• Strengthening opposing muscle groups (e.g., mid-back, rotator cuff)
• Kinesiology or physiotherapy for targeted rehab
When to See a Physiotherapist or Kinesiologist
If you’re experiencing arm numbness, weakness, or pain — especially if symptoms worsen with activity — a physiotherapist can help assess the cause and develop a personalized treatment plan.
Online book with us if you feel your pecs need some attention
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