Running at around two and half feet a second helps a “car clutch” calf muscle work more efficiently than when we walk briskly.
This helps the muscle to release more momentum-boosting energy and increase stamina. US researchers used ultrasound images to scan the muscles of people walking and running on a treadmill.
This revealed how the medial gastrocnemius muscle attached to the Achilles tendon adjusted as they walked and ran at various speeds.
Muscles work too inefficiently to speed walk so the body turns to running
The North Carolina State University team found the calf muscle engages as we move and the Achilles – the long tendon down the back of the lower leg – “springs into action”.
Writing in the journal Proceedings Of The National Academy Of Sciences, Dr Gregory Sawicki said: “Muscles work too inefficiently to speed walk so the body turns to running in order to increase efficiency.”