Rubuta ci gaba don wannan sakin layi - Magnussen ta fara aiki a matakin fitattu na wasan motsa jiki lokacin da ta lashe lambar yabo ta matasa ta Kanada a shekarar 1965. Da yake hawa zuwa babban matakin a shekara mai zuwa, an san ta da ƙwarewar motsa jiki ta kyauta, har ma an kwatanta ta da zakaran duniya Petra Burka. Ta ci gaba da tafiya sama a cikin martaba yayin da ta cancanci shiga gasar zakarun duniya.
a karo na farko a shekarar 1967 kuma ta lashe lambar farko ta Kanada a shekarar 1968. An aika ta zuwa gasar Olympics ta 1968 a Grenoble, Faransa, kuma ta kasance ta bakwai.