Last year, I had two sophomores during XC who have been training year round since the summer before their freshman year join the wrestling team. I initially wasn't too thrilled because it meant two less people in indoor track, but they were very serious about it. Both of them had low 18 minute 5Ks, so they were prospectively good but not anything special.
One of them was so thin it was scary; he was 5'3 and mentioned that he was struggling to break 100lbs. His ribs were fairly visible, and at times it looked like he was starving. The other had a bit of excess fat on him, but it wasn't anything extreme; he definitely looked like he could lose 10lbs though.
Track season comes, and they take their shirts off for the first time; The skinny 5'3 guy in just the offseason put on what must've been a good 10lbs of muscle; He was just as lean as before, but at a much healthier weight. The other guy gained some muscle, but became a LOT leaner. He in fact looked more ripped than the skinny guy that was previously struggling to gain weight. A lot of the other kids on the team noticed them and were all saying, "What happened?"
Initially, it didn't look like they gained much fitness, but it didn't look like they lost any. This was good though, as they had not been running for a while. Three weeks in, they both run their first mile time trials: 5:03 and 5:05, the bigger guy outkicking the smaller guy by a bit. I was surprised at how well they did because it was for both of them their first season without any base training, but it wasn't over yet; the end of the season was even better. The skinny guy had a huge breakout and ran 4:42, while the other guy still improved a lot and ran 4:50, both becoming some of the fastest runners on the team.
I always made my team do strength training because I believed it would benefit them, but I never thought it could impact them to this degree; it certainly didn't match anything I've ever seen in a coaching book. Thoughts?