The Achilles tendon is the largest and strongest tendon in the body. It connects your calf muscles to your heel bone and is used when you walk, run, climb stairs, jump, and stand on your tiptoes. The Achilles tendon can withstand a lot of stress from running and jumping; however, it is also prone to injury/irritation due to overuse and poor healing patterns.
Achilles tendonitis or tendinopathy is usually not related to a specific injury/event. It often is an overuse type injury caused by repetitive stress to the tendon. A sudden increase in the amount or intensity of exercise/activities can lead to Achilles tendinopathy (i.e., doing too much too soon). Overtraining change in training surface (i.e., track running), lack of variation in training, poor choice in footwear and hill running can also lead to Achilles tendon issues.
Other biomechanical issues can also play a role. These include tight or weak calf muscles, poor control of foot muscles, problems with arch control, knee or hip issues/weakness and stiff ankle/foot joints. Achilles tendinopathy is more common in males than females, and is more prevalent in those over 30.
Symptoms of Achilles tendinopathy include pain and stiffness along the Achilles tendon in the morning, severe pain the day after exercising, and pain along the Achilles tendon or the back of the heel that gets worse with activity/exercise. You may also notice swelling or thickening of the tendon.