They're both great for muscles and health but remove the bone benefits of weight bearing activity. (flippingfifty.com)
During pregnancy, the babies need to get in optimal birth positions, and avoiding strenuous abdominal exercises, as well as doing weight bearing activity, can help make that possible. (twinloveconcierge.com)
Other endurance athletes such as cyclists and swimmers may be at even greater risk as they train just as hard and restrict calories to keep their weight down but without doing any of the weight bearing activity that runners do. (sciencedaily.com)