Doing cardio before strength training reduces strength gains by depleting glycogen stores needed for maximal effort. Strength first, cardio after produces better outcomes — both for strength gains and for fat loss (cardio after taps fat stores more directly).
Why order matters
Strength training requires glycogen (stored carb in muscles). Pre-fatigue from cardio reduces weight you can lift, weight you can lift over time, and ultimate strength gains. Strength first uses fresh glycogen; cardio after taps fat in already-depleted state.
How to structure sessions
30-45 min strength training first. 15-30 min cardio after. Total session 60-75 min. Or separate days entirely if time permits.
If you currently do cardio first as warm-up, you're costing yourself strength gains. Switch order and observe.