"Gotta get the Core"!  Whether you are at a cross fit class, spin class or Mile High, everyone is all about hitting he core these days.  When the weather is cold we are all thinks about so=umber bodies but there is more to "core work" than just looking good. Your coreactually made up of a bunch of abdominal muscles that are important for poster and balance as well as for the wash board look. 
The problem with abdominals, they atrophy very quickly when they aren't being used.  A study in Germanywas recently published in Medicine & Science in Sports & Exercise, looked at the affects of bed rest on the abdominal muscles as well as the effectiveness of exercise.  This study consisted of 24 healthy males that agreed to participate in a strict 60 day bed rest protocol.  They were randomly assigned to one of the three experimental groups.  The first group performed resistive vibration exercise, second group performed only resistive exercise and the third group did not perform any exercise as a control group.  An ultrasound of each of the muscles (transverse abdominals, internal oblique, erector spinal, multifidus) were taken to examine the atrophy changes over the first 14 days.  The exercised were performed 3 days a week for the entire study.  All participants also had ultrasounds taken on day 26, 40 and 52.  
The two groups that performed exercise 3 days a week had a slower rate of atrophy than the non-exercise group even though they were all on bed rest.  There was. Not a difference between the vibration group and the regular group.  What does this mean for you?  Everyday you are not working on your abdominal strength, you are actually losing some muscle mass.  Abdominal exercises are great for runners in New York because we should be engaging them on the subway, sitting at work and walking,  If you are able to encore orate abdominal strengthening into those activities you will make your running form so much stronger.
Any abdominal work that is dynamic, meaning you are moving, is better than static because running is dynamic!  Pilates is a great way to start.  Incorporating balance or abdominal engagement when lifting weights is also a great option.  
Belay, D., Gast, U., Felsenberg, D.  Exercise and Transversus Abdominis Muscle Atrophy father 60 days of Bed Rest.  Medicine & Science in Sports & Exercise.  August 2016.  238-245.