For many of us, running is one of the most accessible forms of exercise. It\u2019s free and you don\u2019t need equipment. But it is also one of the more likely to lead to injury.<\/p>\n\n\n\n
Studies of novice runners report around 18 injuries per 1,000 hours of running, which is more than double the rate experienced by more advanced runners. Most injuries seem to occur to the knee, ankle and lower leg, and are more likely to be \u201coveruse\u201d injuries, rather than acute muscle sprains.<\/p>\n\n\n\n
Overuse injuries tend to occur when a tissue is repeatedly loaded more than it can tolerate, without enough time to adapt.<\/p>\n\n\n\n
This might happen because running starts to feel easier before your body is actually ready to do more.<\/p>\n\n\n\n
So, what\u2019s going on? And does improving strength alongside fitness help prevent injuries?<\/p>\n\n\n\n
When you start running, your cardiovascular system adapts quite fast. Blood volume increases within days, your cells\u2019 mitochondria (which generate energy for exercise) can adapt in as little as two weeks, and the number of blood vessels in your muscle increases in around four weeks.<\/p>\n\n\n\n
As a result, aerobic fitness measurably improves within as little as two weeks, and runs that felt hard in week one can feel manageable by week four. This can make it very tempting to go further and faster.<\/p>\n\n\n\n
However, tendons and bones adapt on different scales and different timelines.<\/p>\n\n\n\n
Tendon adaptations, such as becoming stiffer and stronger, typically take at least 12 weeks of consistent (and fairly heavy) loading.<\/p>\n\n\n\n
Similarly, bone remodelling \u2013 which can make bones denser and able to withstand more impact \u2013 can take months, if not years.<\/p>\n\n\n\n
Muscles sit somewhere in between. They can grow fairly quickly (within three to four weeks), but running on its own doesn\u2019t do much to improve muscle strength or size.<\/p>\n\n\n\n
This is important because, when you run, the calf muscles and Achilles tendon handle forces of several times your body weight with every stride \u2013 but running may not actually strengthen these tissues.<\/p>\n\n\n\n
Basically, your heart and lungs adapt to running before your tendons and bones have caught up. This might explain why we see so many overuse injuries in runners.<\/p>\n\n\n\n