It is almost impossible to teach plyometrics and heart conditioning in this time frame. Pushing plyometrics too soon has caused injuries in our young athletes. The body wasn't designed to jump off and on 36' platforms without warning. The heart wasn't designed to withstand the high anaerobic bursts after spending the last three months on the couch. Conditioning the heart should be a well balanced program in order for the athlete to adhere to this program.
Coaches constantly push short training periods.
It cannot be safely done in this time frame. If you needlessly compress these training times, you damage your athletes future health. Recent studies have shown physical inactivity is at epidemic levels and sedentary life-style is skyrocketing. As I travel around this country, this appears to be prevalent in high schools, junior colleges and universities alike. I asked an athlete what he did in the off-season.