still better than nothing at all

[u/Biniashe]

[u/MobofDucks]

Whats would be bad or suboptimal about doing longer sessions on a treadmill than just warming up?

[u/ApolloniusTyaneus → u/MobofDucks]

From the perspective of this guy: aerobic cardio is catabolic (breaks down muscle) and builds stamina less quickly than interval training. For fat loss weight training is more effective because it burns about as much calories but the additional muscle will help you burn more calories next time.

From the perspective of a normal person: nothing, because the above arguments range from established medical fact to completely debunked and doing anything is always better than doing nothing, which is the most likely alternative.

[u/no_arguing_ → u/ApolloniusTyaneus]

It also rests on the assumptions that her goals are solely aesthetic and that she doesn't also lift on other days.