In 1995, Lenard was named one of Vogue magazine's Top 55 Personal Trainers. It's part of overall fitness. If all other things are equal, a stronger athlete will win out over a weaker athlete. Also, a repetitive movement pattern, as in a sport, might leave you with a lot of imbalances in your body. And that can lead to joint,tendon, and muscle imbalances.
Weight training helps to balance out the body.
At first it would be best to learn just a few exercises, and then to master those movements. Ideally, these would be exercises geared towards running and the imbalances that occur with runners. So maybe one exercise for quadriceps, one for hamstrings, one for chest, one for upper back, one for abs and one for lower back. That's enough to start with - a handful of things they feel they can really master, rather than trying to learn twenty new things in the first day. An off-season program might include weights three times per week, and really focus on getting a good strength base.