Frenn set world bests in the outdoor and indoor weight throws, won two medals in the Pan American Games and competed in the 1972 Summer Olympics.

[4] He improved rapidly, placing sixth at the 1962 NCAA championships with 169 ft 7 in (51.69 m);[5] in that meet, he represented Abilene Christian University, a school he only briefly attended.

[4] Frenn suffered an injury in April 1964 and lost his best form;[3] he returned to the NCAA championships, this time throwing for Long Beach State, but again only placed sixth.

[6] By 1967, the outdoor 56-lb weight throw had become an obscure event; it rarely featured in meets, had only been contested once at the AAU national championships after 1959, and the International Amateur Athletic Federation didn't ratify official world records in it.

[20] In the hammer, Frenn placed second in the AAU meet for the third consecutive year; despite throwing 227 ft 2 in (69.24 m), he still lost to Gage by a foot and three inches.

[6] Nevertheless, Track & Field News ranked him the #1 hammer thrower in the United States for the first time, ahead of Connolly and Gage.

[26] At the 1971 Pan American Games in Cali he won silver in the hammer with a throw of 65.68 m (215 ft 5+3⁄4 in), losing to Hall by only six and a half inches.

[7] He remained a top weight thrower, however; between 1970 and 1977 he won six indoor national titles, only missing out in 1974 (when he was the best American but lost to France's Jacques Accambray)[31] and in 1976, when he was a close second behind Larry Hart.

[38] In 1982 he helped his friend Tom Waddell promote the inaugural Gay Olympics in San Francisco and carried the torch into the stadium during the opening ceremonies;[39] he also competed in the meet, winning gold in the hammer throw.