I am coaching this 17 year old kid, has shot up about 4 inches in a year, is 6'4" and 140 pounds. He's got real long legs, okay mechanics, but he is all hands a feet, hasnt grown into his body yet. It seems that he has no strength, he can trot at a reasonable pace (he can do say 6 miles at 6:20, and a 7 minute mile pace run for 12 miles comforatble), but he struggles to get his wheels going(basically, any sort of repeat faster than 5 minute mile pace). The kid has got serious potential, I have yet to see him really open his stride, he runs basically from the knees down without moving his thighs. Any suggestions? Protein shakes? Weight ganner? I feel like he needs to strengthen his hip flexors and gluts to really get his stride going. Any good drills? weights? Any help is appreciated.