yes he was. he was a runningback both in Joliet Catholic (although in some game he was an old school running FB) and at Purdue, although initially he was told by several other schools that he needs to put on some weight so he can become a fullback on collegiate level.
from buccaneers.com:
HIGH SCHOOL
Mike Alstott lettered in both football and baseball at Joliet Catholic Academy in Joliet, Illinois. As a junior, his football team won the state championship with a 14-0 record. Mike also threw the winning two point conversion in the championship game. He was a Parade football All-American and was recognized as Player of the Year by the Chicago Sun Times.
his stats were: seasons: 89-91 rushing yards: 3839 passing yards: 120 receiving yards: 346 total: 4305
you can see couple of his high school runs
here
COLLEGE
Was Purdue`s Most Valuable Player in each of last three seasons, the only player ever to accomplish that feat for Boilermakers. Statistics in 43 games included 3,635 rushing yards on 644 carries (5.6 avg.) with 39 touchdowns. Also caught 93 passes for 1,075 yards (11.6 avg.) with three scores. Finished as Purdue`s all-time leading rusher, surpassing Otis Armstrong. Also is school`s all-time leader in rushing TDs, total TDs and points. Is only Purdue player ever to accumulate over 2,500 rushing and 1,000 receiving yards. As a senior, finished 11th in Heisman Trophy balloting, was a Gannett All-America and was either a first or second-team All-Big 10 choice by all selectors. Rushed for a school-record 1,436 yards on 243 attempts (5.9 avg.) with 11 TDs. Established school records with eight straight 100-yard performances and nine overall for season. Caught 25 passes for 162 yards. In junior year, ran for 1,188 yards on 202 totes (5.9 avg.) with career-best 14 touchdowns, and had 23 receptions for 298 yards. Was first Purdue player in 18 years to rush for over 1,000 yards, averaging 108 yards per contest. 14 TDs tied school record set by Tony Butkovich (1943) and Leroy Keyes (1967). In sophomore season, credited with 816 rushing yards on 153 attempts (5.3 avg.) with 12 touchdowns. Also had career-best 30 catches for 407 yards with pair of scores. Was first Boilermaker sophomore in 48 years to be named team`s MVP. As a freshman, ran for 195 yards on 46 carries (4.2 avg.) with two TDs while also catching 15 passes for 208 yards with one score. Missed most of final two games after fracturing fibula versus Michigan State. Holds B.S. in business