by Duncan Larkin
The editor of Canadian Running raises some doubts.
by Duncan Larkin, Published Aug. 18, 2011, Updated Aug. 18, 2011 at 10:28 AM UTC
Once frowned upon, they are now ubiquitous.
Start your FREE subscription to Competitor Digital today!
Get our monthly digital magazine, weekly running content & exclusive offers delivered to your inbox.
© 2014 Competitor Group Inc. All Rights Reserved