Any recommendations for a shoe my wife might want to wear for track work outs. Life long runner, 55 years old, just started working out with a group that does track workouts. A novice, but getting fit, workouts signaling a 5:55-6:05 mile time. Doing things like repeat 800s or 16/4/12/4/8/4 kinds of workouts. She wear a Clifton 9 - her favorite shoe. She has no interest in spikes, but wonders if it makes sense to try a lighter flat for those track days. Does she even need a different shoe at her level for track workouts? No interest in racing - a 5k here or there and maybe a time trial to see if she can break 6.