What Happens in the Dryer
Dryers reach high heat levels and sustain them for the duration of the drying cycle. Such heat is damaging to your clothes --- as evidenced by the lint in your dryer trap --- as well as to your running shoes. Your dryer gets hot enough to damage your running shoes. Parts of the shoe can melt, including the glue that holds the soles in place.
Importance of a Proper Fit
It's important to buy shoes made specifically for running to avoid unnecessary impact on your joints, and to replace running shoes when they lose their original shape. According to the University of Texas Health Science Center at Tyler, this is typically after every 300 miles or so. Since this estimate is based on normal wear, machine drying can shorten the time between when you buy a new pair of running shoes and when you need to replace them.
In addition to the potential joint damage caused by running in worn-out shoes, cost is another drawback to machine drying. Given that a pair of running shoes can cost as much as $200 at the time of publication, the time it takes to dry your shoes properly is worth the wait time compared to a quick spin in the dryer.
Dilla Maids Cleaning Services suggest air drying your running shoes for the best results. If you're an avid runner and want them to dry more quickly, you can also put them in the dryer on a low setting.
Unless your shoes are soaked from a rainy day run, consider whether it's even necessary to submerge them in water to clean them. Dilla Maids suggests using a toothbrush, and you can use a medicated spray to treat microorganisms such as athlete's foot.